CHEMISTRY, MINERALOGY fyc-, 6fC- PUBLISHED BY THE SOCIETY OF ARTS, MANUFACTURES, AND COMMERCE. PLATES AND WOOD CUTS. 1810—1843. ONLY ONE HUNDRED COPIES SELECTED. ’ ; i . V TABLE UF CONTENTS Alabaster, etching and cleaning — Moore Analysis of organic products, improved apparatus — Cooper Anatomical preparation — Goad by Annatto, East Indian Arsenic, separation — Marsh Galvanic test for — Morton Beer, apparatus for clearing in ferment — Dickinson Blow-pipe, Hydraulic — Rofe ■■■ — , Hydro-Pneumatic — Tilley ■ ■ — , Oxy-Hydrogeu — Gurney , improved — Daniels by Maugham , improved safety chamber to ditto — Wilkinson — — , safe tube — Hemming Boilers, steam, preventing earthy crust — Bedford Calico Printers’ Mordant — Davis Capillary tubes in metal, subdividing — Roberts ring — Wilkinson Chromate of Iron — Dr. Hibbert Chronometer, oil for — Wilkinson Cock, stop, for transferring corrosive gases — Griffiths Colours, Enamel — Wynn Copper, puiification — Thompson Dry-rot prevention — Carey Electrical machine-heater — Brown Electro-magnetic apparatus — Marsh Ditto, improved — Sturgeon Galvanic battery — Smee Geological model — Taylor Glass staining and gilding — Wynn Glaze for porcelain, improved — Rose Ditto for common red earthenware — Meigh Glue, bone — Macqueen Gold, purification — Thompson Hydrometer glass for spirits — Stokes Ditto for saline solutions — Cooper Ink, writing — Dr. Bostock Iron, improvements in — Booker Iron Magnet — Knight Lamp, steam safety — Dr. Clanny Lamp, Miner’s safe — Roberts Lamp, ditto — Newman Lamp, ditto — Bursill Ley Soda for Dyers — Cameron Light, instantaneous — Jackson Lime juice, on preserving — Bagnold Lime juice, on preparing — Bagnold Linseed Oil, purification — Cogau Mahogany, method of seasoning — Calendar Marble, Irish — Dombrain Melting pots — Marshall Ditto, improved — AiSstey Ditto, for iron and steel — Smith Mill-stones, Tuscan — Reveley Opium, British Palm Oil, improved bleaching — Cameron Paste from Potatoes Percussion tubes for cannon — Marsh Photogenic Paper, preparation — Cowper Polishing powder for Opticians, &c. — Ross Porcelain glaze, improved — Rose Potatoes, immersion in ammmiiacal water — Webster Prussian Blue — Thompson Smoke, or suffocating vapours, apparatus to breathe in — Roberts Smoke, plan for consnming— Chapman Sprats, extracts from — Stiles Stucco, Mortar — Way Tanning, by Larch bark Tests for acids, alkalies, compound salts — — Griffiths Ditto for ditto — Marsh Thermometer case, marine — Jamieson Ditto for corrosive liquids — Jowett 't itanium in Butterfield iron works— Glynn Varnish, Copal — Parley , colourless Lac — Field Ditto, ditto — Luning Varnishing, art of — Neil , boiling oil— Neil Vegetable Mediacl Extracts, method of preparing — Houlton Ditto, juices prepared — Bentley Voltatypes by plumbago— v Mur ray Watches, neutralizing magnetism in works — Abraham Water, instrument for samples (rom depth* — Dr. Danbeny Wine, Raisin — Aikin. CHEMISTRY. No. I. INSTRUMENT FOR TAKING A SAMPLE OF WATER FROM CONSIDERABLE DEPTHS. The Thanks of the Society were voted to Charles Dau- beny , M.D. F.R.S. M.R.I.A., #*c., Professor of Chemistry and Botany in the University of Oxford , for his Instrument for Draiving up Water from Depths in the Sea , and for collecting the Air which it may give out during the Process. The instrument now submitted to the inspection of the Society was exhibited, in a less perfect form than its present one, to the Mechanical Section of the British Association, at their Meeting* at Bristol, in 1836; but, as no written account of it was at that time given, and as the efficacy of the contrivance has since been in some mea- sure put to the test by a trial of it made off Margate, in water of fifty feet in depth, I have felt, in consequence, desirous of laying before the Society of Arts the following brief statement with respect to its object and con- struction. The instrument itself was executed under my own im- 4 CHEMISTRY. mediate superintendence, but the idea of it was first sug- gested by perusing the description given by M. Arago of one having the same object, which had been designed by M. Biot, for the use of the navigators of the French discovery ship, the Bonite. As the general plan of this latter contrivance is similar to that of my own, I will, in the first place, offer a trans- lation of the account therein given of it, as one which is in the main applicable to both, and I will afterwards merely subjoin a statement of the differences that appear to exist between the two. M. Biot employs a hollow glass cylinder, closed at one extremity by a solid plate of metal, which thus forms a bucket, and this is provided with a handle, having a cord attached to it, in order that it may be lowered at pleasure to the required depth in the sea. This bucket being open, and freely admitting the water surrounding it, descends through the different beds of the sea without sustaining injury from the pressure. When it has reached the required depth, a cord, which is attached to its lower extremity, is pulled, and the vessel is in this manner turned upside down. This second cord is then made use of for drawing up the apparatus ; and, in order to prevent the risk of its becoming entangled with the former one, it is kept at the further end of the ship. Now this glass cylinder possesses a double bottom, the one being fixed, the other movable. The movable bottom, fitting the interior of the cylinder like the piston of an air-pump, descends merely by its own weight when the bucket is inverted ; and at the same moment the bottom fixes to a small hole furnished with a valve, which opens inwards by the pressure of the surrounding CHEMISTRY. 5 water, and allows tlie latter to enter into tlie space left empty by the descent of the piston. When the latter has descended, and the space within the cylinder has become filled, the valve at bottom closes by its own spring, and the enclosed water is thus kept apart from that sur- rounding it until it arrives at the surface. But if this water contain compressed air, no force w T ill counteract its expansive tendency on being brought to the surface ; for, so soon as the pressure of the water from without is taken off, the gas must either escape or burst the apparatus. To guard against this, a free exit must be provided for all possible expansion, both of the water and the air. For this purpose the fixed bottom is perforated by a lateral canal, leading to a gas bladder, which has been, in the first instance, filled with water, then emptied, and lastly, just before sinking the apparatus, squeezed together. The bladder will receive all the air, which the water, on approaching the surface, may disengage ; and if any be given out, will return more or less inflated. Then, by closing the stop-cocks with which the canal is pro- vided, the gas may be separated from the vessel which contains the water, its volume measured, and the enclosed air analysed ; after which, what still remains in the water may be examined, as likewise may any other substance which the water holds in solution. Such is the instrument which was intrusted to the commander of the ship Bonite ; and it now only remains for me to state the differences existing between it, and the one which I now submit to Society, constructed by myself. 1st. The cylinder of my instrument is made of brass, c CHEMISTRY. which I conceive to be preferable, on the score of economy, to glass, on account of the labour requisite for grinding the latter with sufficient accuracy to allow of the piston moving in it air-tight. The only necessary precaution is that of cleansing the interior of the cylinder im- mediately after each time of using it. 2d. There are no valves in it like those which M. Biot appears to have adopted, the exclusion of the ex- ternal water being effected by means of the conical stopper attached to the piston, which drops down upon the aperture so as to close it, when, upon inverting the instrument, the piston is made to descend. 3d. In my instrument, no bladder to receive the com- pressed gas is required, a sufficient quantity of the air for examination being collected within the little brass receiver resting upon that aperture in the vessel, which, in its inverted position, stands uppermost. The re- mainder, if any, of the air would escape through the small holes perforated in the lower surface of the receiver, which, also, would allow of the water entering to fill the vacuum occasioned by the descent of the piston ; although, from their minuteness, they would admit of scarcely any sensible intermixture during the interval spent in draw- ing up the vessel, between the water within and that surrounding the cylinder, even if the two fluids w r ere exactly equal in point of density. But, as in point of fact, the fluid within the cylinder will be the more dense, there will always be a sufficient tendency outwards to prevent any water from flowing into the vessel. The air collected in the little receiver attached may readily be transferred into any appropriate vessel when the cylinder is brought to the surface, by opening the CHEMISTRY. 7 attached stop-cock, whilst the apparatus is standing- im- mersed in a tub of water. Upon the whole, if I rightly understand M. Biot’s contrivance (of which, however, 1 know of no descrip- tion more detailed than the one I have cpioted from the Annuaire), it appears to me, that my own contrivance may be regarded as preferable to it on the ground of greater simplicity, and, consequently, greater cheapness ; and that it may, therefore, be found worthy of the at- tention of this Society as likely to afford the means of accomplishing a desideratum in the science of hydro- graphy long acknowledged to exist, inasmuch as the contrivances by which hitherto sea water has been drawn from great depths, are considered by the best judges very faulty in their construction, and incapable of afford- ing trustworthy results. Such, at least, was the opinion expressed by Dr. Marcet after examining those instruments that had been invented for the purpose up to the period of the year 1819, the date of the paper in the Philosophical Trans- actions in which he has discussed their several merits ; and such more recently was the opinion of M. Arago, on which, in the article alluded to, he grounds his re- commendation of the instrument of M. Biot* of which my own professes to be a modification. 8 CHEMISTRY Fi or until 3^- gallons of turpentine, J s ^* n &y> mixed and strained, will produce about five gallons and a half. 8 lbs. of the best gum anime, j 2 gallons of clarified oil, l boiled as usual, 3^ gallons of turpentine, mixed, and strained hot, and put into the former pot of African gum-varnish. Put two pots of this anime-varnish to one of copal ; it will dry quicker and harder than the best body copal, and will polish very soon, but not wear either so well or so long'. Quick-drying Body Copal Varnish for Coaches, fie. 8 ibs. of the best African copal,' 2 gallons of clarified oil, ^ lb. of dried sugar of lead, 3^ gallons of turpentine, boiled till stringy, and mixed and strained. 8 lbs. of fine gum anime, 2 gallons of clarified oil, \ lb. of white copperas, 3i gallons of turpentine, * boiled as before, ) to be mixed, and strained while hot into the other pot. These two pots mixed together will dry in six hours in CHEMISTRY. 63 winter, and in four in summer : it is very useful for varnishing old work on dark colours, &c. Best Pale Carriage Varnish. 8 lbs. 2d sorted African copal, 2^ gallons of clarified oil, } boiled till very stringy. 5 lb. of dried copperas, ^ lb. of litharge, 51 gallons of turpentine, ■ strained, &c. I j 8 lbs. of 2d sorted gum anime, 2^ gallons of clarified oil, ^ lb. of dried sugar of lead, ^ lb. of litharge, 5jt gallons of turpentine, mix this to the first while hot. This varnish will dry hard, if well boiled, in four hours in summer, and in six in winter. As its name denotes, this is intended for the varnishing of the wheels, springs, and carriage parts of coaches, chaises, &c. ; also, it is that description of varnish which is generally sold to and used by house-painters, decorators, &c., as, from its drying quality and strong gloss, it suits their general purposes well. Second Carriage Varnish. 8 lbs. of 2d sorted gum anime, 2f gallons of fine clarified oil, 5^ gallons of turpentine, ^ lb. of litharge, \ lb. of dried sugar of lead, lb. of dried copperas, boiled and mixed as before. When three runs are poured into the boiling-pot, and the regular proportion of driers put in, and well boiled, this 64 CHEMISTRY. varnish will dry hard and firm in four hours in winter, and in two in summer: it is principally intended for varnishing dark carriage-work or black japan, and is also used by house-painters for dark work. Wainscot Varnish. 8 lbs. of 2d sorted gum anime, ' 3 gallons of clarified oil, i lb. of litharge, A- lb. of dried copperas, i lb. of dried sugar of lead, 5 \ gallons of turpentine, to be all well boiled until it strings very strong, and then mixed and strained. N.B. Where large quantities are required, it will always be found best to boil off the three runs in the boiling-pot. This varnish is principally intended for house- painters, grainers, builders, and japanners : it will dry in two hours in summer, and in four in winter. Mahogany varnish is either made with the same pro- portions, with a little darker gum ; otherwise it is wainscot varnish, with a small portion of gold size. Japanners ’ Gold Size . It is most proper to make gold size in iron pots, as, from the great heat and the quantity of driers required, copper pots are too thin and ductile ; they would soon become quite burned at the bottom. Therefore, to make forty gallons of gold size, put ten gallons of oil into the set iron pot, Fig. 1, make a good fire under it, and boil it for two hours ; then introduce seven pounds of dry red lead, seven pounds of litharge, and three pounds of cop- peras, by sprinkling in a little at a time; let the oil keep boiling all the time, not in too great a heat, or it will perhaps run over. During the time of putting in the CHEMISTRY. 65 driers, keep stirring them from the bottom of the pot ; for should they settle in a mass, before the oil has gradually taken them up, it will darken the gold size ; therefore, keep constantly stirring, and have the large iron ladle ready to cool it down, if it should appear to rise too high ; have also at hand an empty pot — the copper boiling-pot will do — into which immediately ladle part of the boiling- oil, if it cannot otherwise be kept in the pot, while the assistant is either choking or damping the fire with wet sifted ashes, of which there always ought to be a wheel- barrowful at hand, in case of an accident; but of which there need not be any fear, if due precaution is observed. It is better to be a little under the heat than above it, particularly by those who are not experienced makers ; it will only require a little longer boiling, to make up for the deficiency of heat. When the oil has boiled about three hours from the beginning, and the driers are all in, fuse in the gum-pot ten pounds of gum anime; and during the time of fusing, heat two gallons of raw linseed-oil in the copper-pouring jack, by placing it on the plate of the gum-furnace. After the oil has been poured to the gum, and as soon as, on examination, it appears boiled clear, take the gum-pot from the fire ; let it cool for a few minutes, then pour it into the oil in the set-pot. Wash out the gum-pot, and proceed with another run in the same way. When both runs of gum are in the set-pot, there are altogether fourteen gallons of oil, twenty pounds of gum, and seventeen pounds of driers; increase and keep up a regular fire in the front of the furnace, that it may be drawn out in a moment, if it should be necessary. The gold size will soon throw up a frothy head on the surface, which must be kept down by constantly plying with the VOL. XLTX. F 66 CHEMIST ItY. ladle when it is likely to rise within four inches of the pot- edge. In about five hours from the beginning of the oil boiling, it will become stringy; but the boiling must con- tinue until it hangs to the ladle, appears quite stringy, yet drops in lumps. When tried upon the glass, if it feels sticky and strings strongly, then it is boiled enough. D raw out the fire, sprinkle it with plenty of water; leave not a spark of fire in the varnish-house — not even a lighted pipe of tobacco. While the maker is cooling down the pot, let the assistant have ready at the door thirty gallons of turpentine, fill the pouring-pot ready, and have all the doors open. Endeavour to cool it as fast as possible, as it will require at the least one hour and a quarter after the fire has been put out before it will be ready to mix, because the pot being iron, and very thick, and set in bricks, causes the gold size to hold heat a long time, therefore it is difficult to describe exactly at what time to mix the turpentine ; for, observe, that if the oil and gum is not sufficiently boiled, the gold size will per- haps not dry quick enough ; and if it should, on the other hand, be too strongly boiled before it is cold enough to mix, even though the fire be out, it may become what is termed coagulated or slimy, and is so much concentrated that its particles will not open with the turpentine, and the whole becomes completely lost ; so that it is better to err on the safe side, and stop the boiling in time. When the mixing commences, continue the pouring without in- termission, until all the froth at the surface disappears, never stirring it until the turpentine is all in. If pouring in the turpentine has commenced while it was too hot, there will be a great loss of turpentine by evaporation ; but that will not injure the quality of the gold size. Place the carrying-tin close to the side of the pot. CHEMISTRY. G7 lay on the tin ladle, and strain off as quickly as possible. When all the gold size is out, pour into the set-pot about three gallons of turpentine-washings, and with the swish wash down the pot as quick as possible; and if the pot is still so hot as to evaporate the turpentine, ladle it out into the washings again, and pour in about three gallons of raw linseed-oil; and with a palette-knife scrape it all round, washing and cleaning it down with a rag until it is quite cleansed all round; then ladle out the oil, and wipe it completely clean and dry. The gold size ought to dry in from fifteen to twenty-five minutes, and in fourteen days it is ready for use. Experienced makers can make gold size that will dry in five minutes, but that requires great practice. Black Japan ( the best ) Is made after the manner of the gold size. Put six gal- lons of raw linseed-oil into the set-pot ; boil it with a very slow fire. Have a ten-gallon cast-iron pot, with two handles or ears ; this pot will fit into the plate of the boiling furnace Fig. 2 ; into which put ten pounds of Egyptian asphaltum, and make a good fire in the fur- nace : it will require a good regular fire all the time of fusion. There ought to be an iron cover exactly to fit the fusing-pot; and also a pair of pot-books for lifting it from the fire for sometimes, if the pot is thin and the fire too brisk, it requires lifting from the fire a few minutes to moderate the heat. During the time the asphaltum is fusing, have two gallons of oil getting hot to mix it with as soon as it is sufficiently melted. After it is oiled, leave it on the fire about ten minutes ; then either lift it by the pot-hooks, and pour it into the set-pot, or otherwise empty it with a ladle; whichever way it is emptied, leave 68 CM EM 1ST 11Y. the stones, &c. at the bottom. Carry it out of doors, and with a handful of hay or straw clear it out, and after- wards wash it out with turpentine-washings, and dry it with a rag. Proceed and finish three more separate runs like the first, until there are four runs in the set-pot, that is, forty pounds of asphaltum and fourteen gallons of raw linseed-oil; then introduce exactly the same driers as for the gold size, and in the same manner. Keep a regular, but moderate fire, so that the boiling continues at a mo- derate heat for four hours from the last run being poured in the set-pot; then draw, and put out the fire for that day. Next morning, as soon as it can be brought to a boil, try it upon a bit of glass ; if it but strings strongly, it will not do : it must be boiled so strong, that when a piece is pinched from off the glass, after it has been left to cool, it will roll in a hard pill between the finger and thumb. When it forms hard, and scarcely sticks to the fingers, it is then boiled enough. Put out the fire, as di- rected before. Leave it one hour and a half before mixing - . When cold enough, mix it with thirty gallons, at least, of turpentine, and strain it. If it is too thick when cold, heat and introduce as much turpentine as will bring it to a proper consistency. The japan will dry in six hours in summer, and eight in winter. It is principally intended for and used by coach-makers, japanners, painters, &c., and should be kept at least six months before it is used. Another Black Japan Is made by putting into the set-pot forty-eight pounds of Naples, or any other of the foreign asphaltums (except the Egyptian); as soon as it is melted, pour in ten gal- lons of raw linseed-oil. Keep a moderate fire, and fuse eight pounds of dark gum anime in the gum-pot; mix it CHEMISTRY. 69 with two gallons of hot oil, and pour it into the set-pot. Afterwards fuse ten pounds of dark, or sea-amber, in the ten-gallon iron pot; keep stirring it while fusing; and whenever it appears to be over-heated, and rising too high in the pot, lift it from the fire for a few minutes. When it appears completely fused, pour in two gallons of hot oil, and pour it into the set-pot; continue the boiling for three hours longer, and during that time introduce the same quantity of driers as before directed; draw out the fire, and let it remain until morning; then boil it until it rolls hard, as before directed : leave it to cool, and afterwards mix with turpentine. This japan will appear in colour like the other ; but when applied on work, it will dry more hard, compact, and glossy, and will not rub down or polish so soon as the other, which is occasioned by the toughness and durability of the amber. Pale Amber Varnish. Fuse six pounds of fine-picked, very pale transparent amber in the gum-pot, and pour in two gallons of hot clarified oil. Boil it until it strings very strong. Mix with four gallons of turpentine. This will be as fine as body copal, will work very free, and flow well upon any work it is applied to ; it becomes very hard, and is the most durable of all varnishes ; it is very excellent to mix in copal varnishes, to give them a hard and durable qua- lity. Observe, amber varnish will always require a long time before it is ready for polishing. Best Brunswick Black. In an iron pot, over a slow fire, boil forty-five pounds of foreign asphaltum for at least six hours, and during the same time boil in another iron pot six gallons of oil which 70 CHEMISTRY. has been previously boiled ; during the boiling of the six gallons introduce six pounds of litharge gradually, and boil until it feels stringy between the fingers ; then ladle or pour it into the pot containing the boiling asphaltum. Let both boil until, upon trial, it will roll into hard pills ; then let it cool, and mix it with twenty-five gallons of turpentine, or until it is of a proper consistence. Iron-work Black. Put forty-eight pounds of foreign asphaltum into an iron pot, and boil for four hours; during the first two hours introduce seven pounds of red lead, seven pounds of litharge, three pounds of dried copperas, and ten gallons of boiled oil; add one eight-pound run of dark gum, with two gallons of hot oil. After pouring the oil and gum, continue the boiling two hours, or until it will roll into hard pills like japan. When cool, thin it off with thirty gallons of turpentine, or until it is of a proper consist- ence. This varnish is intended for blacking the iron- work of coaches and other carriages, Sic. A cheap Brunswick Black. Put twenty-eight pounds of common black pitch, and twenty-eight pounds of common asphaltum made from gas-tar, into an iron pot ; boil both for eight or ten hours, which will evaporate the gas and moisture ; let it stand all night, and early next morning, as soon as it boils, put in eight gallons of boiled oil ; then introduce gradually ten pounds of red lead, and ten pounds of litharge, and boil for three hours, or until it will roll very hard. When ready for mixing, introduce twenty gallons of turpentine or more, until of a proper consistence. This is intended for engineers, founders, ironmongers. Sic . ; it will dry in half an hour, or less, if properly boiled. CHEMISTRY. 71 Another cheap Brunsivick Black. Put twenty-eight pounds of common pitch and twenty- eight pound of gas-asphaltum into an iron pot; boil these for eight or nine hours; leave it until next morning; then bring it to a simmer, and gradually introduce seven pounds of red lead and seven pounds of litharge, and continue it at a low heat while the oil is got ready. Put five gallons of boiled oil into the ten-gallon iron pot, and boil it until it will blaze inside the pot when a lighted paper is held over it. As soon as it will catch fire, carry it out into the yard, put a ladle into the burning oil, and move it gently from the bottom. In about ten minutes from its catching fire, have the iron cover ready, and boldly, but deliber- ately, step forward and clap on the cover, taking care to fit it so tight to the pot, that it will extinguish the flame in a moment, which if it does not, lift the cover and try a second time, while the assistant throws the carpet over the cover, and holds it close for a minute ; if that does not put out the flame, pour in cold boiled oil, of which there ought always to be two gallons in the pour- ing-jack ready at hand; then it will be easily extinguished by raising the cover. Continue setting it on fire and ex- tinguishing it after the space of three or four minutes, until, when a little is poured into a mussel-shell and cooled, it looks as thick as treacle; it is then strong burnt oil. Before it is cool, ladle it into the asphaltum, and boil the whole for two hours, or until it will roll hard. When sufficiently cool, pour in twenty gallons of turpentine or more, until of a proper consistence. When this is pro- perly managed, it may be made to dry in ten minutes. Flock Gold Size. Put twelve gallons of linseed-oil into the iron set-pot; 72 Cll EM 1ST K Y. as soon as it has boiled two hours, introduce gradually twelve pounds of litharge. Continue the boiling very moderately for six hours; let it remain until next morn- ing ; then bring it to simmer, and run ten pounds of gum anime and two gallons of oil. When these two runs of gum are poured into the iron pot, put in seven pounds of Burgundy pitch, which soon melt, and continue the boil- ing, and keep ladling it down, as before directed for the best gold size ; boil it moderately strong, but not over strong; and when proper, mix it with thirty gallons of turpentine, or more if required; but recollect, this should be left a little thicker and stronger than japanner’s gold size. This is intended for and used by paper-stainers to lay their flock on, and ought to dry slowly in one hour. Bronzing Gold Size Is nothing more than japanner’s gold size kept till very bright and tough from age, and then heated up and mixed with one gallon of very old carriage-varnish to nine gal- lons of gold size. This is used by paper-stainers for laying on bronze and also gold ; and likewise by writers, grainers, japanners, gilders, &c. Recollect, that the greater the proportion of carriage- varnish, the slower it will dry. Some paper-stainers like it to dry quicker than others ; and writers and grainers like it to dry quicker than gilders and japanners. Axioms observed in the making of Copal Varnishes. The more minutely the gum is run, or fused, the greater the quantity, and the stronger the produce. The more regular and longer the boiling of the oil and gum together is continued, the more fluid or free the varnish will extend on whatever it is applied. When the mixture CHEMISTRY. 73 of oil and gum is too suddenly brought to string by too strong a heat, the varnish requires more than its just pro- portion of turpentine to thin it, whereby its oily and gummy quality is reduced, which renders it less durable ; neither will it flow so well in laying on. The greater proportion of oil there is used in varnishes, the less they are liable to crack, because the tougher and softer they are. Increase the proportion of gum in varnishes the thicker the stratum, and the firmer they will set solid, and dry quick. When varnishes are quite new made, and must be sent out for use before they are of sufficient age, they must always be left thicker than if they were to be kept the proper age, as some of the annexed experiments will prove. Exp. I. Of two well-got-up pannels, painted with patent yel- low, I varnished the first with good body varnish twelve months old, the second pannel was varnished with body of the like quality only one month old. After both pannels were dry, on examining the first it was excellent ; but that varnished with the new-made looked poor, flat, and sleepy, as it is termed. Exp. II. Of two pannels, both prepared and flatted down, the first I varnished with gold size, and the second with japan ; both had only been made one month. The gold size dried in half an hour, and the japan in ten hours and twenty minutes. I then put both pannels into an empty drawer, where they remained for eight months. I then tried the same gold size and japan on two fresh pannels prepared exactly as the first, when l found the gold size much thicker, yet much paler, and it now dried in four- teen minutes; the japan also dried now in seven hours. 74 CHEMISTRY. Exp. III. That varnish made from African copal alone possesses the most elasticity and transparency, may be proved by the following facts. Three prepared pannels of a very pale straw-colour were all varnished in one day : the first with fine body varnish made from very pale gum anime ; the second with fine body varnish made from one half anime and one half African copal ; the third pannel was done with varnish made entirely from fine African copal. These three varnishes were all made with the greatest nicety for the experiment ; all equal in their proportions and ages, having been all made in one day. At the time of var- nishing the three pannels, the varnishes were all eight months old. I filled three vials, one with each sort, and could discover no difference in the colour, either when held near to the eye or at a distance. Upon moving the vials, and turning them, the third, containing the African copal, appeared the most elastic. All the three pannels dried about the same time — eight hours. I hung them all three where they were exposed to sun, wind, and rain, for one month. I then examined them, and could per- ceive little if any difference in colour. I left them for another month, when, on examination, the first, made from anime, was the darkest, and that from the copal the palest. I then polished all three ; the first polished very easily, the second not quite so easy, and the third was very difficult to polish, appeared very soft and clammy, but when completed was by far the palest and most trans- parent. I left them upon a roof exposed to the weather for three months, when I flatted them down a little, and varnished them afresh. In ten days after, I polished them, when the third, varnished with the African copal, was by far the palest, and looked like plate-glass. CHEMISTRY. 75 Exp. IV. — That too much Driers in Varnish render it opaque, and unfit for delicate Colours. One day I varnished two pannels, got up and glazed with a very rich crimson lake. No. 1 was varnished with body varnish, made entirely from African copal, without any driers whatever, either in the clarified oil or boiling. No. 2 was varnished with “body” of the same gum, age, and proportion, but with a small quantity of dried sugar of lead and dried white copperas. The pannel No. 1 dried in nine hours, and remained tacky for five hours more; the pannel No. 2 dried in seven hours without a tack. In a day after, both pannels were flatted down and varnished, and repeated until each pannel had four coats of varnish ; the varnish was eight months old, and each dried in the same space of time. I hung both up for a month, and then polished them, and examined them with a microscope, when the pannel No. I appeared quite clear in colour, solid, and brilliant, like plate-glass ; but No. 2 had changed a little in colour, inclining to purple, and in the varnish were almost imperceptible opaque points. I kept these two pannels for two years afterwards ; when I examined them, there appeared no decay in No. 1, but in No. 2 the driers were perceptible on the surface with the naked eye. Exp. V. — That moist Driers boiled in Varnish cause it to run in Pin-holes. To eight gallons of very fine African copal, during the boiling, I introduced half a pound of undried copperas and half a pound of undried sugar of lead. After the varnish had stood to settle for eight months, I varnished with it a pale patent yellow pannel; it floated very well, set and looked well for four hours, when it began to dry 76 CHEMISTRY. off in small pin-holes completely over the surface, some of the holes as large as the head of a pin. It dried off in seven hours without any tack. Exp. VI. — That the greater the Quantity of Driers and Acid, the larger the Pin-holes. I emptied six gallons out of the jar containing the last-named varnishes, then I varnished another pannel out of the two gallons remaining in the jar: the pannels dried in the same time, but went off not only into pin-holes, but into large blotches all over. Exp. VII. — That Particles either of Oil or cold Turpentine in the Varnish will create Pin-holes and Blemishes. To one gallon of body varnish, nine months old, which had been tried and found to be excellent, I introduced a quarter of an ounce of water and a quarter of an ounce of linseed-oil. I heated and mixed all together, and poured it into a jar, and let it stand for three months, when I varnished two pannels, one yellow and the other light green ; four hours after, when I examined them, they were about half dry, and beginning to run into pin-holes and round empty holes. I examined them with a micro- scope, and found a particle of oil hanging to the lower edge of every circle, and the small particles of water had evaporated ; the surface appeared as if dotted with the points of as many bristles. I repeated this experiment several times, but. with always the same results. Exp. VIII. — That Copperas does not combine with Varnish , but only hardens it. Three pounds very fine African copal, one gallon of clarified oil, and two ounces of dried copperas, were mixed CHEMISTRY. 77 off with two gallons of turpentine, which, after being- strained, had been put by in an open-mouthed jar for eight months ; I then poured off all the varnish, not quite to the bottoms. I afterwards well washed the sediment left at the bottom of the jar with two quarts of warm turpen- tine, which I filtered through some very fine cambric- muslin, and afterwards dried the copperas in the sun ; it still weighed two ounces, and appeared like what it nearly was, powder of zinc. Exp. IX . — That Sugar of Lead does combine with Varnish. With the same quantity and quality of gum oil and turpentine I made three gallons of copal varnish, intro- ducing two ounces of dried sugar of lead during the boil- ing. I put it in a jar for eight months. I then poured off all the varnish, and washed out the sediment with half a gallon of warm turpentine, filtered as before. I dried the residuum left on the muslin, which only weighed seven drachms, and appeared of a pearly lead colour, so that the varnish had absorbed the remainder. This varnish was very good, and dried well. Exp. X. — That Turpentine improves by Age. 3 lbs. of fine African gum-copal with one gallon of clarified oil were boiled without any driers, and thinned with two gallons of turpentine which had been kept in an open leaden cistern for upwards of two years, until it had become thickened and appeared like oil. After being mixed off and strained and set to settle only two days, I tried it on several pannels of different colours, when it dried hard, firm, and brilliant, without any tack, in less than eight hours. 1 kept the remainder of this varnish for 78 CHEMISTRY. twelve months, when it became too thick to use. I poured it into the gum-pot, brought it near to a boiling heat, and poured to it half a gallon of the same old turpentine, and set it aside for two days, when I varnished three fresh pannels of three different colours, which had been pre- viously twice varnished ; they all dried firm and free from tack in less than five hours, and had every appear- ance of fine cabinet varnish. These three pannels were afterwards laid on the roof of a shed for twelve months, and, when polished, looked solid and brilliant, and the colours were less changed than any I ever saw in the same time. Exp. XI. — That Varnish improves hy Heat. Very recently I had a brick erection (two feet high by four feet wide) built all round the warehouse, with an air- furnace at one end, whereby the heat and smoke were conveyed inside a large flue in the brick-work from one end to the other, where it joined into a chimney-shaft. This brick erection was covered with foot-tiles laid in composition, and over the foot-tiles was laid a bed one inch thick of fine sand sifted. Upon this sand were set the varnish-cisterns, four feet by three, and three feet deep, made of inch-and-quarter boards, and lined with lead. When these cisterns were filled up, each held 150 gallons, and a regular fire was kept up in the furnace every other day. During the time the fire was kept up, the varnish in the cisterns expanded to such a degree, that it rose two inches in the cistern nearest the furnace. During the time of its expansion it gave out a sickly smell of gas, turpentine, and moist air; but as soon as the furnace begins to cool gradually, the acid, moisture, and driers, descend to the bottoms of the cisterns, while the CHEMISTRY. 79 varnish on the surface attracts fresh oxygen from the air of the warehouse ; so that, by alternately heating and cooling the varnish in this manner for four months, it ac- quired all the properties and qualities equal to varnish which has been kept without heat for twelve months. I have repeatedly tried the experiment, and always found it answer. Exp. XII. — That all Copal or Oil Varnishes require Age before they ought to be used. I have frequently filled up several cisterns of varnish, each containing 150 gallons. When they have stood one month, I have varnished a pannel with varnish from the surface of each, when I have found every one of the pannels dry firm in regular time, and have no appearance of pin- holes whatever. On the same day I have taken out fifty gallons of varnish from each cistern. I then, out of the cisterns, which had 100 gallons left in each, varnished a pannel. I found all these dry in the same time as the first, but every pannel was either more or less sleepy or steamy, and appeared as if a fine mist had carried off the glossiness. After taking out forty gallons more from each cistern, there were only sixty gallons left in each. I then var- nished a panel from each cistern ; none of them dried so soon by two hours, and every pannel was opaque and full of pin-holes. I repeated the same experiment from different cisterns of varnish many times, at various periods from the varnishes being made, from one month’s age to twelve, and have invariably found that the varnish within fifteen inches of the surface is more perfect and sooner ready for use than that beneath it, and that the varnish towards the bottom of all cisterns requires time 80 CHEMISTRY. and the action of warm air to cause the moisture, acid, and driers, to settle before the varnish is fit to use. Concluding Observations. N.B. All body varnishes are intended and ought to have 11 lbs. of gum to each gallon of varnish, when the varnish is strained off and cold ; but as the thinning up, or quantity of turpentine required to bring it to its proper consistence, depends very much upon the degree of boiling it has undergone, therefore, when the gum and oil have not been strongly boiled, it requires less turpentine to thin it up; whereas, when the gum and oil are very strongly boiled together, a pot of twenty gallons will require perhaps three gallons above the regular proportionate quantity ; and if mixing the turpentine is commenced too soon, and the pot not sufficiently cool, there will be frequently above a gallon and a half of turpentine lost by evapo- ration. All carriage, wainscot, mahogany, &c. varnish ought to have full one pound of gum for each gallon when strained and cold ; and should one pot require more than its proportion of turpentine, the following pot can easily be left not quite so strong boiled, then it will require less turpentine to thin it up. Gold sizes, whether pale or dark, ought to have full half a pound of good gum to each gallon when it is finished ; and best black japan to have half a pound of good gum, or upwards, besides the quantity of asphaltum. The foregoing proportions I have found to answer best in general ; but, recollect, if the gum either be of such inferior quality that it will not properly fuse, or if it should, through inexperience or neglect, not be properly fused, however good the quality, the produce will be both inferior CHEMISTRY. 81 and deficient. And I am perfectly convinced, from forty years’ experience, that the greatest and most essential art belonging to the business of varnish-making consists in the management and regulation of the fire in the gum- furnace, so that the gum, from the beginning of its soften- ing in the gum-pot, and during the whole time of its fusion, shall be so managed, according to the nature and quality of that particular sort, particularly in increasing the heat, that it shall carry up and out of the pot all or as much of the gas and acid as is possible, which is the most difficult for an inexperienced person to under- stand, and, indeed, very few think about it. Every varnish-maker, during the time his furnaces are at work, ought always to have his assistant at hand, whether he is wanted or not ; and when any thing is to be done quickly, such as lifting a pot from the fire, pour- ing, or any thing that requires two persons, never do any thing in a hurry or flutter, but always be cool, collected, and firm ; and to insure against accidents, be prepared to 4 meet them deliberately. A nervous or timorous person is unfit either for a maker or assistant, and the greatest number of accidents occur either through hurry, fear, or drunkenness. Fine Mastic or Picture Varnish. Put 5 lbs. of fine picked gum-mastic into a new four- gallon tin bottle ; get ready 2 lbs. of glass bruised as small as barley; wash it several times; afterwards dry it per- fectly, and put it into the bottle with two gallons of tur- pentine that has settled some time ; put a piece of soft leather under the bung, lay the tin on a sack upon the counter, table, or any thing that stands solid; begin to agitate the tin, smartly rolling it backward and forward, VOL. XL1X. G 82 Cli EM1STRY. causing the gum, glass, and turpentine, to work like a barrel-churn for at least four hours, when the varnish may be emptied out into anything sufficiently clean, and large enough to hold it. If the gum is not all dissolved, return the whole into the bottle and agitate as before, until all the gum is dissolved, then strain it through fine thin muslin into a clean tin bottle; leave it uncorked, so that the air can get in, but no dust ; let it stand for nine months at least before it is used, for the longer it is kept the tougher it will be, and less liable to chill or bloom. To prevent mastic-varnish from chilling, boil a quart of river-sand with two ounces of pearl-ashes, afterwards wash the sand three or four times with hot water, straining it each time ; put the sand on a soup-plate to dry in an oven, and when it is of a good heat, pour half a pint of hot sand into each gallon of varnish, and shake it well for five minutes ; it will soon settle and carry down the moisture of the gum and turpentine, which is the general cause of mastic-varnish chilling on paintings. Common Mastic Varnish. Put as much gum-mastic, unpicked, into the gum-pot as may be required, and to every lbs. of gum pour in one gallon of cold turpentine ; set the pot over a very moderate fire, and stir it with the stirrer; be careful, when the steam of the turpentine rises near the mouth of the pot, to cover it with the carpet, and carry it out of doors, as the least steam will catch fire : a few minutes low heat will perfectly dissolve 8 lbs. of gum, which will, with four gallons of turpentine, produce, when strained, four and a half gallons of varnish, to which add, while yet hot, five pints of pale turpentine varnish, which im- proves the body and hardness of the mastic-varnish. CHEMISTRY. 83 Another cheap Varnish for Paper-hangings. Put into the gum-pot 10 lbs. of gum cat’s-eye, with four gallons of turpentine, and at a low heat dissolve it like the mastic ; then strain it into a cistern or tin. After having washed out the gum-pot and wiped it clean, dis- solve 5 lbs. of unpicked gum-mastic in two gallons of turpentine, and strain it warm into the cat’s-eye varnish. After washing and wiping out the gum-pot as before, dissolve 10 lbs. of good white frankincense with four gallons of turpentine ; strain it, and, while hot, mix this to the two former products ; stir them together, take a little out in a saucer, and if too thick, thin it with tur- pentine until of a proper consistence: when boiled, it may be used, but it is better for age. This may be made excellent at the cost of 10s. per gallon. Crystal Varnish May be made either in the varnish-house, drawing-room, or parlour. Procure a bottle of Canada balsam, which can be had at any druggist’s ; draw out the cork, and set the bottle of balsam at a little distance from the fire, turning it round several times until the heat has thinned it ; then have something that will hold as much as double the quantity of balsam, carry the balsam from the fire, and, while fluid, mix it with the same quantity of good turpentine, and shake them together, until they are well incorporated : in a few days the varnish is fit for use, particularly if it is poured into a half-gallon glass or stone-bottle, and kept in a gentle warmth. This varnish is used for maps, prints, charts, drawings, paper orna- ments, &c. ; and when required to be made upon a larger scale, requires only warming the balsam to mix with the turpentine. 84 CHEMISTRY. White hard Spirit- of -wine Varnish. Put 5 lbs. of gum sandarach into a four-gallon tin bottle, with two gallons of spirits of wine, 60 over proof, and agitate it until dissolved, exactly as directed for the best mastic-varnish, recollecting, if washed glass is used, that it is convenient to dip the bottle containing the gum and spirits into a copperful of hot water every ten minutes, the bottle to be immersed only two minutes at a time, it will greatly assist the dissolving of the gum ; but, above all, be careful to keep a firm hold over the cork of the bottle, otherwise the rarefaction will drive the cork out with the force of a shot, and perhaps set fire to the place. The bottle, every time it is heated, ought to be carried away from the fire, then ease the cork a little, to allow the rarefied air to escape, then drive it tight, and continue the agitation in this manner until all the gum i§ O O properly dissolved, which is easily known by having an empty tin can to pour the varnish into, until near the last, which pour into a gallon measure; and if the gum is not all dissolved, return the whole into the four-gallon tin, and continue the agitation until it is ready to be strained, when every thing ought to be quite ready, and perfectly clean and dry, as oily tins, funnels, strainers, or any thing damp, or even cold weather, will chill and spoil the varnish. After it is strained off, put into the varnish one quart of very pale turpentine varnish, and shake and mix the two well together. Keep spirit-varnishes well corked : they are fit to use the day after being made. Brown hard Spirit- Varnish Is made by putting into a bottle 3 lbs. of gum sandarach with 2 lbs. of shell-lac, and two gallons of spirits of wine, 60 over proof; proceed exactly as before directed for the CH EMTSTRY. 85 white hard varnish, or by agitating it when cold, which requires about four hours’ time, without any danger of fire ; whereas making any spirit-varnish by heat is always attended with danger. No spirit-varnish ought to be made either near a fire or by candle-light. When the brown hard is strained, add one quart of turpentine varnish, and shake and mix it well ; next day it is fit for use. Gold Lacker. Put into a clean four-gallon tin, 1 lb. of ground tur- meric, H ounce of powdered gamboge, 3^ lbs. powdered gum sandarach, f lb. of shell-lac, and two gallons of spirits of wine. After being agitated, dissolved, and strained, add one pint of turpentine varnish, well mixed. Red Spirit Lacker. 2 gallons of spirits of wine, 1 lb. of dragon’s blood, 3 lbs. of Spanish annato, 3 \ lbs. gum sandarach, 2 pints of turpentine. Made exactly as the yellow gold lacker. Pale Brass Lacker. 2 gallons of spirits of wine, 3 ounces of Cape aloes, cut small, ] lb. of fine pale shell-lac, 1 ounce gamboge, cut small. No turpentine varnish. Made exactly as before ; but observe, that those who make lackers frequently want some pale and some darker, and sometimes inclining more to the particular tint of some of the component ingredients. Therefore, if a four-ounce 86 CHEMISTRY. vial of a strong solution of each ingredient be prepared, there can be at any time produced a lacker of any tint required. Having so far given plain and particular directions, it will be” very easy for the operator to modify, or make any intermediate proportion or alteration, according to his judgment or inclination. INDEX TO THE FOREGOING PAPER. Directions for building or procuring proper Premises .... Page 34 On the Fixtures and movable Utensils necessary 35 Directions for erecting the Furnaces, with References to the Plates . . 37 Boiling-Furnace, No. 1 > No - 2 38 ' > No. 3 Gum-Pot, description of Boiling-Pot, ditto Copper Ladles, minute Instructions relating to Pouring- Jacks, Pots, &c Directions for clarifying Oil for Varnish Instructions for making Varnish on the smallest scale with the fewest Utensils General Observations and Precautions to be observed in making Varnishes On Copal, its different sorts and qualities Gum Anime, its qualities and uses Amber, ditto ditto Sandarach and Mastic Gum Cat’s-eye ^ On the Choice of "Linseed-Oil 5^ On Essential Oil, or Spirits of Turpentine On the Choice of Driers used in Varnishes White Copperas, its uses Litharge, ditto Asphaltum ^ How to make Copal Varnishes for fine Paintings, &c 58 Artists’ Virgin Copal CHEMISTRY. 87 Cabinet Varnish Page CO Best Body Copal Varnish for Coaclimakers, &c ib. Recipe for causing it to dry quickly Cl Effects of using Driers, injurious ib. Common Body Varnish G2 Quick-drying Body Copal ib. Best pale Carriage Varnish G3 Second Carriage Varnish ib. Wainscot Varnish G4 Japanners’ Gold Size ib. Black Japan (the best) G7 Another Black Japan G8 Pale Amber Varnish G9 Best Brunswick Black ib. Iron- work Black 70 Cheap Brunswick Black ib. Another Brunswick Black 71 Flock Gold Size ib. Bronzing Gold Size 72 Axioms and particularly useful Observations ib. Experiments proving the following important facts — I. That Age is most beneficial to Varnishes 73 II. The experiment varied ib. III. That Varnish made from African Copal is most elastic and transparent 74 IV. That too much Driers render Varnish unfit for delicate Colours 75 V. That moist Driers boiled in Varnish cause it to run in Pin-holes ib. VI. That the greater the quantity the larger the Pin-holes . . . 7C VII. That Particles of Oil or cold Turpentine will create Blemishes ib. VIII. That Copperas does not combine with Varnish ib. IX. That Sugar of Lead does combine with Varnish 77 X. That Turpentine improves by Age ib. XI. That Varnish improves by Heat 73 XII. That all Copal or Oil Varnishes require Age 79 Concluding Observations 80 Fine Magtic or Picture Varnish 81 Common Mastic Varnish . 82 Cheap Mastic for Paper-hangings 83 Crystal Varnish ib. White hard Spirit-of-wine Varnish 84 Brown hard Spirit-of-wine Varnish ib. Gold Lacker 85 Red Spirit Lacker . . . . ’ ib. Pale Brass Lacker ib. Concluding Remark 88 88 C1I EMISTRY. No. II. PREVENTING THE ADHESION OF EARTHY CRUST TO THE INNER SURFACE OF STEAM-BOILERS. The J'lianks of the Society were voted to Mr. James Bedford, of Leeds, for his Communication on this subject. Almost all natural waters hold in solution both car- bonate and sulphate of lime, two earthy salts, of which the former is thrown down by bringing the water to a boiling heat, and the latter by evaporation. On this ac- count it is, that if the inside of a steam-engine boiler be examined after having been in use for a few days, it will be found to contain muddy water, and an earthy crust will be seen adhering to the iron plates of which the vessel is formed. The rate at which this crust is deposited de- pends on the hardness of the water employed, that is, on the proportion of the above-mentioned earthy salts which it contains. This crust is a much worse conductor of heat than iron is, and, therefore, a boiler lined with it, even to the thickness of the tenth of an inch, possesses the following defects. The water which it contains is not so soon brought up to the boiling point, and a greater quantity of fuel is required to produce a given quantity of steam, because a larger proportion of the heat given out during its burning is carried up the chimney and lost. It becomes, therefore, necessary, from time to time, to remove this crust, which is usually done by a hammer CHEMISTRY. 89 and chisel ; but this operation not only incurs a waste of time, but the boiler is often seriously injured, and ren- dered leaky by means of it. It has been found, if a few potatoes are thrown into the boiler when it is again filled, after having been cleaned out, that the formation of crust is sensibly retarded, and that the adhesion of it to the sides of the boiler is greatly weakened, so as to allow of its being detached more speedily, and with much less hazard. Another method of producing the same effect has been pointed out to the Society, by Mr. James Bedford, of Leeds, druggist. He put into a large steam-boiler be- tween two and three gallons of sperm oil foots ; and found that, after eight weeks constant use, the deposit of crust was very small compared to what it used to be from the same water alone, and also that the crust could be cleared off by means of a common stiff broom. The application of oily matters for this purpose, though original on the part of Mr. Bedford, is not absolutely new ; for the Society have been informed by one of their members, that he has known an iron boiler using Thames water preserved in constant use for seventeen years by cleaning it often, and smearing the inside with oil or tallow after each cleaning. The Society, however, have reason to believe that neither of the above methods are in common use, and have, therefore, directed this short statement to be pub- lished for the benefit of those whom it may concern. 90 CHEMISTRY. No. III. HYDRAULIC BLOW-PIPE. The Large Silver Medal was presented to Mr. J. Rofe, 11 , Bernard Street, Russell Square, Civil En- gineer, for his Hydraulic Blow-pipe. The following Communication on the subject has been received from the Candidate. Previous to explaining the mechanism of the improved blow-pipe and gas-holder, it may be allowable shortly to notice some of the hydraulic blow-pipes at present in most common use, in order to shew wherein this new one surpasses them in ease and elegance of application. The principal claim which hydraulic blow-pipes have for pre- ference, is the saving of labour ; but in both Tilley’s and Toft’s the operator has to force the air into the blow-pipe ; and although, it is true, it is only at intervals, still the same quantity of air must be forced into the vessel as would be breathed through a common mouth blow-pipe in any given time during which the action on the flame is kept up. Pepys’s air-holder (which is the basis of this new apparatus) requires still more labour, when used as a blow-pipe, than either Tilley’s or Toft’s, as the water can only be poured into the funnel in successive portions ; and unless this is done by an assistant, it must very much distract the attention of the operator ; added to which, when the water has forced the air or gas out of the vessel, it must be emptied again before it can be used, which is both a troublesome and laborious operation. CHEMISTRY. 91 Having said thus much, I will proceed to explain the different parts of the improved blow-pipe. This consists of two cylindrical vessels connected by three pipes, and turning on an axis at M. From the lower part of the upper vessel A, at d, a pipe proceeds nearly to the bottom of the lower vessel B, where it terminates with a valve opening downwards; and in like manner a pipe proceeds from the top of the lower vessel at e, nearly to the top of the upper vessel, where it is closed with a valve opening upwards. A pipe,/, furnished with a valve at each end, 92 CHEMISTRY. connects the two vessels A and B ; the valves being so placed as to open into the two vessels. From this it is evident that the two valves in the upper vessel, whether it is A or B, will always be closed, and that, on the con- trary, the valves in the lower vessel will be open. The weight of the valves must always exceed the weight of the column of water acting against them or tending to open them. At the external ends of the vessels A and B a stop-cock must be placed. From the centre of the pipe f a pipe must pass through the axis, or the pipe may form the axis on which the apparatus turns; to this is to be attached a stop-cock with the blow-pipe nozle, as shewn in the section. To put the apparatus in action, open the stop-cock of the blow-pipe and shut that of the lower vessel, and through the upper stop-cock pour water into the upper vessel, which will flow through it into the lower vessel. When the lower vessel is full, the apparatus is ready for use, and no more water need be used for months — in fact, not until the water gets offensive from keeping. Before using the blow-pipe, it is necessary to turn the apparatus on its axis, so that the full vessel should be uppermost, and then the pressure of the water in the upper vessel forces the air through the pipe^/to the blow- pipe; and as the water descends into the lower vessel, the air enters the upper vessel through the stop-cock at the top. When the lower vessel is full of water, again turn it on the axis, and the blow-pipe is again ready for action; so that, by the simple operation of turning the apparatus, which need not interrupt any experiment half a minute, this becomes nearly a perpetually acting blow -pipe. Should it be required to use the apparatus as a gas- holder, let the upper vessel be full of water, and attach CHEMISTRY. 93 the pipe from the retort to the stop-cock of the upper vessel; then open the stop-cock of the blow-pipe, and as the gas is generated it will accumulate in the upper vessel, the water from which will descend into the lower vessel, the air escaping through the blow-pipe orifice. To use the gas either in the blow-pipe, or to transfer it to other vessels, it will only be necessary to reverse the position of the vessels, and proceed as in the case of common air ; or if to transfer it to other vessels, detach the nozle of the blow-pipe and screw on a flexible tube, the end of which being placed under the shelf of the pneumatic trough, the gas may be received into any vessel which may be desired. In making an apparatus for my own use, I should prefer stop-cocks at o o and s s to the valves shewn on the pipes in the drawing, as being easier to get to if out of order, &c. ; but as, from the number of cocks to open and shut, it would be rather more complicated in its use, I have constructed my model with valves. Should cocks be substituted for valves, the two upper ones would always be shut, and the two lower ones always open. Should this apparatus meet with the approbation of the Society of Arts, I shall conceive it a great honour conferred upon Yours, &c. &c. A. Aikin, Esq. J. Rofe, Civil Engineer . Secretary, Sfc. Sfc. C HEM IS TRY. No. I. MINER’S SAFE-LAMP. The Silver Medal was voted to Mr. J. Newman y 122 Regent Street, for his Improvement on Sir H. Davy s Safe-Lamp for Miners ; one of which has been placed in the Society’s Repository . The safe-lamp for the use of miners, invented by Sir H. Davy, consists of an oil lamp, the flame of which is con- lined within a cylindrical cage of wire gauze, about five inches and a half high, and one inch and a half in diameter. The iron wire of which the gauze is made is about a sixtieth of an inch thick, and the meshes or spaces between the wires are as nearly squares as the process of manufacture will allow ; the sides of these squares being equal to the diameter of the wire, or thirty in an inch. When the lamp is lighted, and is placed in common air, that portion which occupies the upper part of the cage becomes heated by the flame : those particles which, to- gether with the vapour of the oil, constitute the flame, being the hottest, rise, on account of their diminished specific gravity, through the upper end of the cage, and CHEMISTRY. 57 are replaced by a current of cooler, and therefore heavier, particles, which enters through the meshes that are below the flame ; while those on a level with the flame are pro- bably almost inactive. The flame is confined to the part above the wick, because the heated vapour of the oil, being lighter than the air, cannot mingle with that which has not yet arrived at the wick. If the air which enters the lamp contains inflammable gas in certain proportions, the flame of the wick will be sensibly enlarged in consecpience of the combustion of the inflammable gas : under these circumstances, it might be expected that the combustion would extend in all direc- tions, and that the space within the cage below the wick, as well as that above it, would be filled with flame ; this, however, is not the case, provided the cage is of a proper height ; the hotter the upper part of the cage becomes, the more rapid is the escape of the burnt vapour, and the cold current that sets in through the lower meshes of the cage, flows so swiftly, that, before its particles have be- come heated to the point of combustion, they have risen above the level of the wick. If the proportion of inflammable gas which enters the lamp be increased, the whole upper part of the wire cage becomes filled with flame, and the wire itself at length becomes red hot ; still, however, the lamp may be safely placed in an explosive atmosphere, because the wire, though red hot, is still cool enough, comparatively speaking, to lower the temperature of the inflamed particles, while pass- ing through the meshes of the wire gauze, to such a degree as to prevent them from setting fire to the combustible particles on the outside of the lamp. This is owing to the great rapidity with which iron cools, the heat which it is continually receiving from the inflamed gas being 68 CHEMISTRY. thrown off* so quickly by radiation, as to be unable to accumulate, under ordinary circumstances, to a hazardous degree. But it is evident that this depends on a certain pro- portion between the volume of the flame in the cage and the thickness of the wire, as well as the size of the meshes. The volume of the flame depends, of course, on the size of the cage within which it is contained ; therefore, by contracting the diameter of the cage and of the meshes, and increasing the size of the wire, we increase the safety of the lamp. In so doing, however, we diminish the supply of air, so that the lamp burns with a smoky flame and diminished light ; and, of this diminished light, a large proportion is intercepted by the thick wire of which the gauze is made. On the other hand, by increasing the diameter of the cage and of the meshes, and diminish- ing that of the wire, we place the lamp in the most favourable condition for giving light, but, at the same time, proportionably diminish its safety. The measure- ments already given of the cage, the meshes, and the wire, are those which were considered by Sir H. Davy, after re- peated experiments, as most satisfactorily conciliating the greatest quantity of light with perfect safety. But, since such a lamp, in its ordinary state, does not give as much light as a naked candle does of the size commonly used by miners, some lamp-makers have been tempted to improve the light by using finer wire, not being aware (from ignorance of the principles on which the instrument was constructed) that they were thus materially impairing its only merit — security; for, when the wire becomes white hot, it is not only capable of allowing the inflam- mable particles within the cage to pass out in a state of combustion, but is also capable of firing the mixture of CHEMISTRY. 59 inflammable gas and atmospheric air on the outside of the cage. The wire gauze made at Newcastle, as directed by Sir H. Davy, is very strong and safe ; but much of that manufactured in London for the finer kinds of sieves has been used for miners’ lamps. Such lamps are very unsafe, both on account of the thinness of the wire, and its great liability to be displaced by slight accidents, whereby some of the meshes become enlarged to a very dangerous degree. But an objection has recently been taken to the use of the miners’ lamp, even when constructed according to the directions of Sir H. Davy, it being found, when placed in certain circumstances (which probably, however, never occur in practice), that its safety is no longer to be de- pended on. These circumstances are as follows : The lamp, when lighted, is to be exposed to an oblique jet of coal gas, so as to fill the upper part of the cage with flame, and is to be kept in this position till the wire becomes red hot. The jet of gas being now turned off, the lamp is to be moved briskly for an instant, so as to fill the whole interior of the cage with atmospheric air, which may easily be done without cooling down the wire in any considerable degree ; the jet of coal gas is then to be directed on it as before, and when the first portions have entered and mixed with the common air previously there, an explosive mixture is formed, and is set fire to by the flame of the lamp. The mechanical effect of the explosion is to disperse on every side the particles of gas while in a state of combustion, driving them through the meshes with such great rapidity, that the wire, though scarcely red hot, has not time to cool them down during their passage; they enter the external air, therefore, still blaz- CHEMISTRY. 60 ing, and set tire to the jet of coal gas as it issues from the pipe. Even lamps made under Sir H. Davy’s directions, of single cylinders of twilled wire gauze, have been found not to be safe in the circumstances above described. The object of Mr. Newman has been to render the Davy lamp safe in the above-mentioned circumstances. For this purpose, the cylinder or cage of the common safe-lamp is surrounded with an outer cylinder, made of the same kind of wire gauze as the inner one* : the length of the outer cylinder is a little less than the inner one, and the distance between them is such as just to allow the outer to slide up and down over the inner cylinder without rubbing or touching; and, for further security, the top of each cylinder is made of two layers of wire gauze, with a small interval between them. The position of the outer cylin- der is usually that represented in the figure, so that its lower margin is nearly on a level with the point of the flame, leaving a cavity at top, about an inch in height, between the tops of the two cylinders. Thus, the outer cylinder does not intercept any of the direct rays from the lamp, but only some of the oblique ones. When this lamp is placed in the circumstances which render the common Davy lamp unsafe, as above described, explosion takes place in the inner cylinder, and sometimes a lambent flame makes its appearance for an instant in the space between the sides of the two cylinders, and for a longer time in the cavity above the top of the inner one, but in no instance, in the experiments tried, either by Mr. Newman or by a Committee of the Society, could the * Sir H. Davy himself has stated, in a manuscript note attached to the copy of his tract “ On the Fire-damp of Coal-mines,” in the Society’s library, that, “ for greater security, double wire cylinders might be used.” CHEMISTRY. 61 flame be made to pass through both cylinders, or even through the lower part of the inner* cylinder only, the external jet of gas never having been set fire to. This is evidently owing to the increase of cooling surface obtained by the use of two cylinders instead of one, to there being a clear though small space between them, in order to prevent the communication of heat by contact from the inner to the outer cylinder, and, perhaps, in some degree also, to the increased obstruction offered by the outer cylinder to the escape of the inflamed gas. A repetition of the experiment was made with another lamp of the same construction as the last, and differing only in the size of the wire, which, being thinner, increased in the same proportion the size of the apertures. In this lamp it was found, that when the upper part of the inner cage was filled with flame, the wire, in consecpience of its thinness, became heated to a bright red, and then, when explosion was brought about, the flame passed through both cylinders, and set fire to the coal gas on the outside ; thus shewing that the thickness of the wire which was recommended by Sir H. Davy, cannot, even with double cylinders, be safely dispensed with. The following are the practical details of the con- struction of Mr. Newman’s lamp, as shewn in the annexed figures, a a, fig. 1, is the inner cylinder of wire gauze, and b b is the outer one. Fig. 2 is a plan with the top sectioned off to shew the cylinders a and b. A lensf c * The reason why it is not necessary to protect the lower part of the cage by double gauze is, that, as the supply of fresh air is continually enter- ing through this part, the wire here remains nearly cold, while a few inches above it is red hot. •f- A lens on the outside of the cylinder , and unconnected with it , was first applied to the safe-lamp by Mr. Newman, in November 1817, and, in the spring of the following year, twelve lamps on this construction were sent by him to Newcastle. 62 CHEMISTRY. directs a larger portion of light towards the workman ; it is cut to the shape shewn in fig. 3, and is jointed on to one of the three wires ddd, and snaps by a hook within another wire, so as to be held very near to the inner cylinder. The bottom of the outer cylinder b is bound by wire on a metal ring that fits close on to the inner cylin- der a , only easy enough to slide up or down : the distance between the two being only three-sixteenths of an inch. The top of this outer cylinder is closed by a double disk CHEMISTRY. 63 of wire gauze, the rim of which is first turned upwards, as shewn at b , in fig. 4, whilst the rim of the cylinder is turned in and downwards on it ; this then receives a second bend inwards, as shewn in fig. 5. The top of the inner cylinder is turned outwards, then covered by a disk of wire, the rim of which is folded in under it, as shewn at a, fig. 4, this is again bent downwards, as at a, fig. 5 ; by this means the top of the inner cylinder is made to fit close to the outer one, with only room to slide. The 4- bottom of the inner cylinder is fitted tight into the ring ee, fig. 4, by which it is screwed to the lamp, and is secured there by a thin piece of tube/, forced very tight in. In this gauze the warp-wires are 27 £ to the inch, CHEMISTRY. 64 whilst tliose of the shoot are 30 to the inch, giving 825 apertures to the square inch. The wires are rather smaller than the spaces, consequently, they are a little less than ^ of an inch thick, and the spaces are larger than ^ of an inch, in the same degree. The outer cylinder is made by wrapping the margins over, as shewn at b , in fig. 6, taking care to keep all the extra thickness on the outside, that its inside may fit well on to the inner cylinder. But the inner cylinder must not be so joined ; it has to fit well into the brass ring at bottom of the outer cylinder ; it must therefore have no projection outwards, nor must the place of junction pro- ject inwards, lest it should receive any extra heat from the flame : it is therefore se'cured by lacing, as shewn, magnified, in fig. 7 ; but, previous to lacing, the two outer wires, as h and l, fig. 8, of each margin are to he laced or bound together, which effectually prevents them from being pulled out. mm, fig. 7, is the wire that hinds one margin, and nn the opposite one ; oo is the third wire, that laces the margins toge- ther, and completes the cy- linder, thus rendering it im- possible for any common ac- cident to tear the seam asun- der. Care must be taken in adapting the edges of the wire gauze previous to lacing them together, that they are CHEMISTRY. 65 perfectly similar, so that the two rows of meshes thus brought in contact are not what would be adjacent in the uncut gauze, but alternate ones. In other words, if a piece of gauze were cut, and the edges w r ere required to be laced together, one wire must first be cut off one of the edges to make it fit for the operation. The three lacings all slope the same way, and the middle one, whilst it takes hold of the opposite marginal wires, at the same time takes hold of the outer lacings, their folds meeting in alternate spaces, the most suitable to be so laced. The forming of these cylinders with the care just described, is quite requisite to ensure complete strength, toughness, and soundness, so that no apertures should be formed or left, that can, by rough usage, become larger than those of the gauze. In this gauze the longitudinal, or warp-wires, are deeply bent up and down, while the shoot-wires are also bent sufficiently to prevent any of the wires from changing their places ; a circumstance which, in addition to the gauze being woven with great truth, removes all danger of any of the perforations becoming larger by use, an accident which might destroy the safety of the instrument. There is nothing new in the burner and oil vessel, but a section of them is added in fig. 4 to shew their con- struction. The disk g of the wick-holder drops into the seat //, there being a gap through which the tube i of the trimming wire passes: the ring j is then screwed in and secures it. VOL. LI. F CHEMISTRY. GG No. II. SEPARATION OF ARSENIC. The Large Gold Medal was presented to Mr. James Marsh, of the Royal Arsenal, Woolwich, for his Method of separating Small Quantities of Arsenic front Substances with which it may have been mixed. Notwithstanding the improved methods that have of late been invented of detecting the presence of small quantites of arsenic in the food, in the contents of the stomach, and mixed with various other animal and vege- table matters, a process was still wanting for separating it expeditiously and commodiously, and presenting it in a pure unequivocal form for examination by the appropriate tests. Such a process should be capable of detecting- arsenic not only in its usual state of white arsenic or arsenious acid, but likewise in that of arsenic acid and of all the compound salts formed by the union of either of these acids with alkaline substances. It ought, also, to ex- hibit the arsenic in its reguline or metallic state, free from the ambiguity which is sometimes caused by the use of carbonaceous reducing fluxes. It appeared to me, that these objects might be attained by presenting to the arsenic hydrogen gas in its nascent state : the first action of which would be to deoxygenate the arsenic ; and the next, to combine with the arsenic, thus deoxygenated, into the well-known gas called arsenuretted hydrogen. Being thus brought to the gaseous state, the arsenic would spontaneously (so to speak) separate itself from the liquor CHEMISTRY. 07 in which it was before dissolved, and might be collected for examination by means of any common gas apparatus ; thus avoiding the trouble, difficulty, and ambiguity of clarification and other processes whereby liquors, suspected of containing arsenic, are prepared for the exhibition of the usual tests, or of evaporation and deflagration which are sometimes had recourse to in order to separate the arsenic from the organic substances with which it may have been mixed. I had the satisfaction of finding, on trial, that my anticipations were realised ; and that I was thus able, not only to separate very minute quantities of arsenic from gruel, soup, porter, coffee, and other alimentary liquors, hut that, by continuing the process a sufficient length of time, I could eliminate the whole of the arsenic in the state of arsenuretted hydrogen, either pure or, at most, only mixed with an excess of hydrogen. If this gas be set fire to as it issues from the end of a jet of fine bore into the common air, the hydrogen, as the more combustible ingredient, will burn first, and will produce aqueous vapour, while the arsenic will be de- posited either in the metallic state, or in that of arsenious acid, according as it is exposed partially or freely to the air. The former condition is brought about by holding a piece of cold window glass opposite to and in contact with the flame, when a thin metallic film will be immediately deposited on its surface ; and the latter, by receiving the flame within a glass tube open at both ends, which, in half a minute, will be found to be dimmed by a white pul- verulent sublimate of arsenious acid. By directing the flame obliquely within side of the tube, it strikes against the glass and deposits the arsenic partly in the metallic state. In this case, if the tube, while still warm, be held 08 CHEMISTRY. to tlie nose, that peculiar odour, somewhat resembling garlic, which is one of the characteristic tests of arsenic, will he perceived. Arsenuretted hydrogen itself has pre- cisely the same odour, but considerable caution should be used in smelling to it, as every cubic inch contains about a quarter of a grain of arsenic. The requisite apparatus is as simple as possible ; being a glass tube open at both ends, and about three-quarters of an inch in its internal diameter. It is bent into the form of a syphon ( aa , fig. 1), the shorter leg being about five inches, and the longer about eight inches in length. A stop-cock ending in a jet of fine bore, passes tightly through a hole made in the axis of a soft and sound cork, CHEMISTRY. 69 which fits air-tight into the opening’ of the lower bend of the tube, and may be further secured, if requisite, by a little common turpentine lute. To fix the apparatus, when in use, in an upright position, a hole is made in the wooden block c for the reception of the lower part of the pillar d, and a groove is cut in the top of the same block to receive the bend of the tube a a. Two elastic slips e e, cut from the neck of a common bottle of India rubber, keep the tube firm in its place. The matter to be submitted to examination, and sup- posed to contain arsenic, if not in the fluid state, such as pastry, pudding, or bread, &c., must be boiled with two or three fluid ounces of clean water, for a sufficient length of time. The mixture so obtained must then be thrown on a filter to separate the more solid parts : thick soup, or the contents of the stomach, may be diluted with water and also filtered ; but water-gruel, wine, spirits, or any kind of malt liquor and such like, or tea, coffee, cocoa, &c., can be operated on without any previous process. When the apparatus is to be used, a bit of glass rod, about an inch long, is to be dropped into the shorter leg, and this is to be followed by a piece of clean sheet zinc, about an inch and a half long and half an inch wide, bent double, so that it will run down the tube till it is stopped by the piece of glass rod first put in. The stopcock and jet are now to be inserted, and the handle is to be turned so as to leave the cock open. The fluid to be examined, having been previously mixed with from a drachm and a half to three drachms of dilute sulphuric acid (1 acid and 7 water), is to be poured into the long leg, till it stands in the short one about a quarter of an inch below the bottom of the cork. Bubbles of gas will soon be seen 70 CHEMISTRY. to rise from the zinc, which are pure hydrogen if no arsenic be present ; but, if the liquor holds arsenic in any form in solution, the gas will be arsenuretted hydrogen. The first portions are to be allowed to escape, in order that they may carry with them the small quantity of common air left in the apparatus ; after which the cock is to be closed, and the gas will be found to accumulate in the shorter leg, driving the fluid up the longer one, till the liquor has descended in the short leg below the piece of zinc, when all further production of gas will cease. There is thus obtained a portion of gas subject to the pressure of a column of fluid of from seven to eight inches high : when, therefore, the stop-cock is opened, the gas will be propelled with some force through the jet, and, on igniting it as it issues (which must be done quickly by an assistant), and then holding horizontally a piece of crown or window-glass ( f ’ fig. 1) over it, in such a manner as to retard slightly the combustion, the arsenic (if any be present) will be found deposited in the metallic state on the glass ; the oxygen of the atmos- phere being employed in oxydizing the hydrogen only during the process. If no arsenic be present, then the jet of the flame as it issues has a very different appearance ; and, although the glass becomes dulled in the first instance by the deposition of the newly formed water, yet such is the heat produced, that in a few seconds it becomes perfectly clear, and frequently flies to pieces. If the object be to obtain the arsenic in the form of arsenious acid, or white arsenic, then a glass tube, from a quarter to half an inch in diameter (or according to the size of the jet of flame), and eight or ten inches in length, is to be held vertically over the burning jet of gas, in such a manner that the gas may undergo perfect com- CHEMISTRY. 71 bustion, and that the arsenic combined with it may become sufficiently oxydized ; the tube will thus, with proper care, become lined with arsenious acid in pro- portion to the quantity originally contained in the mixture. When the glass tube is held at an angle of about forty-five degrees over the jet of flame, three very good indications of the presence of arsenic may be obtained at one operation ; viz. metallic arsenic will be found de- posited in the tube at the part nearest where the flame impinges, — white arsenic or arsenious acid at a short distance from it, — and the garlic smell can be readily detected at either end of the tube in which the experiment has been made. As the gas produced during the operation is con- sumed, the acid mixture falls into the short limb of the tube, and is thus again brought into contact with the zinc, in consequence of which a fresh supply is soon obtained. This gas, if submitted to either of the pro- cesses before described, will give fresh indications of the presence of the arsenic which the mixture may have originally contained ; and it will be easily perceived that the process may be repeated as often as may be required, at the will of the operator, till no further proofs can be obtained. When certain mixed or compound liquors are operated on in this apparatus, a great quantity of froth is thrown up into the tube, which may cause a little embarrassment by choking the jet. I have found this effect to take place most with the contents of the stomach, with wine, porter, tea, coffee, or soup, and, indeed, with all muci- laginous and albuminous mixtures. The means I adopt to prevent this effect from taking place, or, at least, for CHEMISTRY. 72 checking it in a great measure, is to grease or oil the interior of the short limb of the apparatus before intro- ducing the substance to be examined, or to put a few drops of alcohol or sweet-oil on its surface previously to introducing the stopcock and its appendages. I have, however, found, if the tube be ever so full of froth in the first instance, that, in an hour or two, if left to itself, the bubbles burst, and the interior of the tube becomes clear without at all affecting the results. In cases where only a small quantity of the matter to be examined can be obtained, I have found a great convenience in using the small glass bucket (<7, fig. 2). Under such circumstances, the bent glas3 tube may be filled up to within an inch of the short end with common water, so as to allow room for the glass bucket, which must be attached to the cork, &c. by means of a little platina wire ; a bit or two of zinc is to be dropped into the bucket, with a small portion of the matter to be examined, and three or four drops of diluted sulphuric acid (acid 2, water 14) ; and the whole is then to be introduced into the mouth of the short limb of the tube. The production of gas under this arrangement is much slower, and, of course, requires more time to fill the tube, than in the former case ; but the mode of operating is pre- cisely the same. Indeed, it is of great advantage, when the quantity of arsenic present is very minute, not to allow the hydrogen to be evolved too quickly, in order to give it time to take up the arsenic. A slender glass funnel will be found of service when as much as a table-spoonful, or even a tea-spoonful of matter, can be obtained for examination. In this case, the tube is to be partly filled with common water, leaving a sufficient space for the substance to be ex- CHEMISTRY. 73 amined ; a piece of zinc is to be suspended from the cork by a thread or wire, so as to bang in the axis of the tube ; and the fluid to be operated on, having previously been mixed with dilute sulphuric acid, is then to be poured through the funnel carefully, so as to surround the zinc, avoiding, as far as possible, to mix it with the water below, and the stopcock and its appendages are to be replaced in the mouth of the tube ; the production of the gas then goes on as before stated, and the mode of mani- pulating with it is exactly the same as described in the foregoing part of this paper. It will be necessary for me, in this place, to explain the methods I employ after each operation, to determine the integrity of the instrument, so as to satisfy myself that no arsenic remains adhering to the inside of the tube, or to the cork and its appendages, before I employ it for another operation. After washing the apparatus with clean water, a piece of zinc may be dropped in, and the tube filled to within half an inch of the top of the short limb ; two drachms of diluted sulphuric acid are then poured in, and the stop- cock and cork secured in its place ; hydrogen gas will in this case, as before, be liberated, and fill the tube. If the gas as it issues from the jet be then inflamed, and a piece of window glass be held over it as before described, and any arsenic remains, it will be rendered evident by being deposited on the glass ; if so, this operation must be repeated till the glass remains perfectly clean, after having been exposed to the action of the gas. When I have had an opportunity of working with so large a quantity of mixture as from two to four pints (imperial measure), I then have employed the instrument (tig. 3), which is, indeed, but a slight modification of one 74 CHEMISTRY. of the instantaneous light apparatuses, now so well known and used for obtaining fire by the aid of a stream of hydrogen gas thrown on spongy platinum. It will, there- fore, be of importance only for me to describe the alter- ation which I make when I employ it for the purpose of detecting arsenic. In the first place, I must observe, that the outer vessel a, which I use, holds full four pints, and that the jet of the stopcock is vertical, and its orifice is twice or three times larger than in the in- strument as generally made for sale, and also that there is a thread or wire attached to the cork of the stopcock b, for suspending a piece of zinc c, within the bell-glass With an instrument of this description, I have ope- rated on one grain of arsenic in twenty-eight thousand grains of water (or four imperial pints), and have ob- tained, therefrom, upwards of one hundred distinct me- tallic arsenical crusts. CHEMISTRY. 75 Similar results have been obtained with perfect success from three pints of very thick soup, the same quantity of port wine, porter, gruel, tea, coffee, &c. &c. It must, however, be understood, that the process was allowed to proceed but slowly, and that it required several days before the mixture used ceased to give indication of the presence of arsenic, and, also, a much larger portion of zinc and sulphuric acid was employed from time to time, than when working with the small bent tube apparatus, in consequence of the large quantity of matter operated on under this arrangement. With the small apparatus, I have obtained distinct metallic crusts, when operating on so small a quantity as one drop of Fowler’s solution of arsenic, which only con- tains one-120th part of a grain. The presence of arsenic in artificial orpiment and re- algar, in Scheele’s green, and in the sulphuret of antimony, may be readily shewn by this process, when not more than half a grain of any of those compounds is em- ployed. In conclusion, I beg to remark, that although the in- struments I have now finished describing, are the form I prefer to all that I have employed, yet it must be per- fectly evident to any one, that many very simple ar- rangements might be contrived. Indeed, I may say unequivocally, that there is no town or village in which sulphuric acid and zinc can be obtained, but every house would furnish to the ingenious experimentalist ample means for his purpose ; for, a two-ounce phial, with a cork and piece of tobacco-pipe, or a bladder, with the same arrangement fixed to its mouth, might, in cases of ex- treme necessity, be employed with success, as I have re- peatedly done for this purpose. 7(i CHEMISTRY. The only ambiguity that can possibly arise in the mode of operating above described, arises from the cir- cumstance, that some samples of the zinc of commerce themselves contain arsenic; and such, when acted on by dilute sulphuric acid, give out arsenuretted hydrogen. It is, therefore, necessary for the operator to be certain of the purity of the zinc which he employs, and this is easily done by putting a bit of it into the apparatus, with only some dilute sulphuric acid ; the gas thus obtained is to be set fire to as it issues from the jet ; and if no metallic film is deposited on the bit of fiat glass, and no white sub- limate within the opeu tube, the zinc may be regarded as in a fit state for use. JAMES MARSH. PA PERS IN CHEMISTRY. No. I. NEUTRALIZING MAGNETISM. The Large Silver Medal was this session presented to Mr. J. H. Abraham, of Sheffield, F.L.S. for his method of Neutralizing the Magnetism which often occurs in the Balance, and other Steel Parts of the Works of Watches. The following communication has been received from Mr. Abraham on the subject. Holy Green House, Sheffield, Dear Sir, March, 29, 1826. Knowing that the Society for the encouragement of Arts, Manufactures, and Commerce, is always willing to coun- tenance any invention that may be of public utility, I feel pleasure in submitting a discovery in magnetism, which 1 have no doubt will be found to contribute to both indivi- dual and public advantage. c 2 20 OH K.MISTRY. The discovery to which I allude is a method of neutralizing concentrated magnetism in the most minute parts of the steel work of time-keepers, as chronometers, &e. without the aid of heat. [ have been frequently solicited to communicate the dis- cover} 7 for individual advantage only, at a fair price; but as my chief object in all my researches is public good, I prefer communicating the invention to the Society for pro- moting Arts, Manufactures, &.c. not doubting but that the testimony of their approbation will be in proportion to what they consider the value of the discovery to the public. I flatter myself that the respectable accompanying testi- monials will prove satisfactory as to the practibility and utility of the invention. I am, Sir, A. Aikin, Esq. Secretary, Sfc. SfC. &c. bee. &c. J. H. Abraham. Sheffield, March 31, 1826. It is, 1 believe, generally understood by those who have not made the science of magnetism a study, that the fluid is communicated to steel bars, and other articles capable of possessing permanent active magnetism, by induction, fric- tion with magnetic bars, & c. &c. In my opinion the very contrary is the fact. All ferrugi- nous bodies possess the magnetic fluid in a latent or inactive state, in proportion to their purity ; this fluid may be brought into action and concentrated bv various means, as position, friction, percussion, attraction, galvanism, electricity, ike. I believe that attraction is the most general cause of the steel works in time-pieces becoming actively magnetical. CHEMISTRY. •> j Valuable watches are frequently observed to keep very irregular time, from no visible cause, whilst the works re- main in connexion; nor after they are separated, unless the steel works are tested, by plunging them into fine steel filings. From the minuteness and delicacy of those parts of a time-piece which are manufactured from steel, it has been considered by those watch-makers with whom I have conversed on the subject to be almost an impossibility to deprive them of active magnetism by any other means than that of heat. When a balance or verge has been exposed to a sufficient heat to distribute the fluid, it becomes unfit for further use till hardened and polished, and even then it is frequently spoiled ; therefore watch-makers prefer either returning the watch in its magnetic state, or supplying new apparatus, which generally incurs an expense of six or seven shillings in a common watch, and a greater sum in proportion to the value of the works. In attempting to distribute (or, ac- cording to the general term, take out) the magnetism in anv part of the steel works of a watch, with a very fine magnet, by touching it in a contrary direction, or with a different polarity, it must be complete chance if the expe- riment succeed ; since the power applied, and the delicacy of the touch, must be in proportion to the activity of the magnetism, and the fineness of the part containing it ; for wherever the finest magnet last touches any part of a balance, it will leave a small concentration of magnetic power. With a series of fine and very delicate magnets I always failed in completely neutralizing the fluid by the touch. After spending much time without success, I was still deter- mined to surmount the difficulty if possible. Upon studying CHEMISTRY. 99 the hrst cause of all my trouble and disappointment, I was led to believe that I very probably might destroy the effect by means similar to those which produced it, and in this I was not disappointed, for the experiment succeeded equal to my expectations. Time-pieces generally become actively magnetical without being brought into contact with the agent that concentrates the fluid ; but, according to the laws of magnetism, a contrary polarity will always be found in the part rendered magnetical, to that of the magnet pre- sented to it. This proves that the fluid is put in motion and concen- trated by attraction ; present the contrary power in the agent (not in contact) to the same part of the machinery, and it will repel or re-distribute the fluid which was previ- ously attracted, and if it be kept in that position the least period of time beyond that which is necessary to neutralize the fluid, it will give contrary polarity to the part subjected to the experiment. For some time I found a little difficulty in performing the experiment satisfactorily, owing to the invisibility of the fluid; but I was relieved from this difficulty by dipping the apparatus to be experimented upon into fine steel filings, which rendered the situation of the active magnetism visible. Upon presenting a fine magnet to the part clothed with filings, at the distance of from one inch to a quarter of an inch, according to the power to be neutralized, it wall immediately be perceived whether the polarity of the magnet be of the same kind as that in the apparatus; if so, the filings will gradually fall from the part as the pow r cr becomes neutralized : when all the filings have fallen from the part submitted to experiment, dip it again into the filings, to prove w hether it has acquired opposite polarity, CHEMISTRY. 23 by remaining too long in the vicinity of the magnet; if that be the case, present the contrary end of the magnet at a distance in proportion to the power to be diffused. Very little practice will enable any person to deprive any part of the steel apparatus belonging to the time-piece of active magnetism in two or three minutes. I can generally per- form the experiment in one minute, however magnetical the balance or other part may be that is to be deprived of this concentrated power. CERTIFICATES. Dear Sir, Sheffield, March 28, 1826. Mr. J. H. Abraham called upon me this afternoon, and exhibited his new mode of neutralizing concentrated mag- netism in the fine steel works of watches and other time- pieces. The experiment was repeated many times with complete success, so far as i could judge by the test of steel filings presented on the occasion. If the Society, of which your are Secretary, find it, on examination, as per- fect for the purpose intended as it appears to me to be, I doubt not that they will deem the inventor worthy of a honourable testimonial of their respect for his ingenuity and talents, so well, and, I believe, usefully, applied. L am, Sir, &c. &c. &c. J. Montgomery. A. Aikin, Esq. Secretary, Sfc. fyc. •24 CHEMIST RY. 16, High-street, Sheffield, Sir, March 30, 1826. Upwards of four years ago, Mr. Kay, of this place, brought me his watch, complaining of its going badly, observing it had not kept time since he allowed a person to stop it by presenting a powerful magnet to it. On taking out the balance, I found it so strongly magnetical as to lift a common sewing needle. As the watch was a valuable one, 1 declined trying any means to rectify it, as the method I had taken with other watches, having the same fault, was attended with a deal of trouble, and a risk of breaking the balance, and not always successful. There- fore, the shortest way, I advised Mr. Ray to have a new balance put to his watch. Mr. Ray observed, he thought Mr. Abraham, perhaps, might rectify it. Mr. Abraham undertook it, and completely freed it from magnetic power, by a simple and expeditious method, and not attended with any risk or damage to the balance, which must be of great importance to watch-makers and others. A. Aik in, Esq. Samuel Snidall, Secretary, 8fc. fyc. Wcitcli-maker. Sir, Sheffield, March 31, 1826. About two years ago, Mr. E. Barber, merchant, of Shef- field, applied to me to regulate his watch, which, he re- marked, kept time very badly, although it had till lately gone very correctly. Upon examining the parts very mi- nutely, I perceived that the cause was owing to the ba- lance and verge having both become strongly magnetical. CHEMISTRY. 25 Not being able to deprive the parts of their magnetism without the application of heat, by which means they are very liable to be injured, I recommended Mr. Barber to apply to Mr. Abraham, who, I had been informed, had taken the magnetism out of a balance that was very strongly magnetical, without the aid of heat, or using any method that in the least injured the parts submitted to the experiment. Mr. Abraham returned the verge and ba- lance to me so completely free from magnetism, that they would not attract the least particle of fine steel filings, al- though, previous to the experiment, they lifted a strong needle. I consider that the discovery of a method of depriving the steel works of time-keepers of magnetism, without ap- plying heat, will be of great value to the trade, as from some cause new watches are often found to be magnetical before they have been worn. I am, Sir, ike. &c. ike. A. Aikin, Esq. Joseph Brown, Secretary, fyc. 8>c. Watch-maker. Sir, Sheffield, March 31, 1826. I feel pleasure in adding my testimony of the correct- ness of Mr. Brown’s statement respecting the magnetical state of my watch. It has gone as regularly since that period (upwards of two years since) as it had done previous to its becoming magnetical. I am, Sir. ike. ike. ike. Enoch Barber. A. Aikin, Esq. Secretary, Sfc. Sfc. MINERS’ SAFE LAMP. The Silver Vulcan Medal and Ten Guineas were this session presented to Mr. J. Roberts, of St. Helens, Lancashire, for his improved Safe Lamp for Miners; which has been placed in the Society's repo- sitory. The only real objection to the use of Sir H. Davy’s safe lamp for coal, miners, is the inferior degree of light that it gives when compared with that given bv a naked candle. This arises from two causes, namely, the necessary obstruc- tion offered by the black wire of which the cage or gauze is composed, within which the lamp is placed, and the casual obstruction occasioned by the adhesion of smoke to the inside of the cage when the lamp is not carefully trimmed, and of smut and dust to the outside of the cage. To diminish the obscuration occasioned by the first cause, Mr. Roberts proposes that the wire shall be kept bright and polished, by cleaning the cage every night with a soft brush and the black powder or smut which occurs in all coal mines, especially in the neighbourhood of faults: this smut is pulverulent non-bituminous coal, sufficiently hard to re- move the rust from the surface of the wire without mate- rially wearing the wire itself. CHEMISTRY. 27 As the lamp is at present constructed, the oil will run out of the cup or receptacle in which it is placed, if the lamp is laid in a horizontal position, an accident which frequently occurs on account of the lamp being rather top heavy. When this happens the gauze becomes smeared over with viscid oil, which causes the coal-dust floating in the air of the mine to adhere to it, and in a short time to fill up more or less the meshes of the gauze. By merely shaking or tapping the lamp the dust will not be dislodged; and if the miner attempts to clear his lamp by blowing through the wire gauze, he runs the risk of putting out the light, and after all very imperfectly clears the meshes; there is also perhaps some risk of forcing the flame through the meshes on the opposite side, and of producing an explosion, if the surrounding air is imflammable. In Mr. Roberts’s lamp the overflow of the oil is impos- sible, on account of the dome-shaped cover which surrounds the wick; the dust, therefore, that settles on the gauze, may be dislodged by a mere tap with the finger, or, what would perhaps be better, by the application of a small brush similar to that which soldiers carry to clear the pan of their muskets, and which might be attached by a bit of small chain to the handle of the lamp. Reference to the Engraving. Plate II. fig. 6 a section of the lamp pp , and wire gauze qq\ r r a screwed cap, with a hollow dome s ; it screws into the neck 1 1 of the lamp : the dome rises a little above the wick-holder m, having an opening at top to let the wick ClIKMISTRV. i>y and trimming wire v rise through. This dome serves to catch and retain any oil that may spill by shaking the lamp or knocking it over, thereby protecting the wire gauze q from being smeared ; ic and x two locks, the former to secure the cap g, and the latter to secure the wire gauze q from being removed. Fig. 7 a section of the cap and dome r r s, separate from the lamp : the wire gauze fits into the cavity y y, around the dome s; z z two of the four wires which serve to hold the wire gauze. C H E M I S T R Y. COLOURLESS LAC VARNISH. I. — The Sum of Twenty Pounds tv as this Session given to Mr. George Field, of Sy on-hill Park, for his Colourless Lac Varnish ; a sample of which has been placed in the Society’s Repository . II. — The Sum of Twenty Pounds was this Session given to Mr. Henry Tuning, of Apothecaries’ Hall, for his Colourless Lac Varnish; a sample of which has been placed in the Society’s Repository . The varnish prepared by dissolving sliell-lac in alcohol is, in hardness and brilliancy, superior to all others, except, perhaps, copal varnish, but can rarely be employed by the painter, on account of its dingy muddy yellowish brown colour. The Society have for some years endea- voured to draw the attention of artists to this subject, by offering a premium for lac varnish sufficiently colourless for the use of painters. The premium was claimed during the present Session by Mr. Field and by Mr. Liming ; and on examination the processes of each of these gentlemen appearing to answer the intended purpose, the Society have thought fit to reward both of them, Mr. Field’s process is as follows : — Six ounces of shell-lac, coarsely pounded, are to be dissolved by gentle heat in a pint of spirits of wine. To this is to be added a bleaching liquor, made by dissolving CHEMISTRY : (JO purified carbonate of potash in water, and then impreg- nating it with chlorine gas, till the silica precipitates, and the solution becomes slightly coloured. Of the above bleaching liquor add one or two ounces to the spiritous solution of lac, and stir the whole well together; effervescence takes place, and when this ceases, add more of the bleaching liquor, and thus proceed till the colour of the mixture has become pale. A second bleaching liquid is now to he added, made by diluting muriatic acid with thrice its bulk of water, and dropping into it pulverized red lead, till the last added portions do not become white. Of this acid bleaching liquor, small quantities at a time arc to be added to the half-bleached lac solution, allowing the effervescence which takes place on each addition to cease before a fresh portion is poured in. This is to be continued till the lac, now white, sepa- rates from the liquor. The supernatant fluid is now to be poured away, and the lac is to be well washed in repeated waters, and finally wrung as dry as possible in a cloth. The lac obtained in the foregoing process, is to be dissolved in a pint of alcohol, more or less, according to the required strength of the varnish ; and, after standing for some time in a gentle heat, the clear liquor, which is the varnish, is to be poured off from the sediment. “ White lac varnish,” says Mr. Field, “ as above pre- pared, and used in a temperature of not less than GO”, dries in a few minutes, and is not afterwards liable to chill, or bloom ; it is therefore applicable to drawings and prints which have been sized ; and may be safely and advantageously used upon oil-paintings, which have been painted a sufficient time, as it bears out colour with the purest effect. This quality prevents its obscuring gild- ing, and renders it a valuable leather-varnish to the book- binder, to whose use it has already been applied with I. II.— VARNISH. 61 happy effect, as il does not yield to the warmth of the hand, and resists damps which subject bindings to mildew. lackers, colourless lac may afford silver and steel lackers, with little or no obscuration of their lustre. Its varnish polishes better than any other, and is applicable to some uses of the jeweller, to which purpose it has also been applied, as it has also successfully to the varnishing of light-coloured woods, and cabinet work, to which it is applicable in the manner of French polish ; and there can be no doubt it would afford coloured lackers and varnishes of superior quality. In fine, the white lac varnish is generally applicable to the various purposes of other white hard spirit varnishes, and is to be used under the same conditions, and with the same management ,' ” 1 am desirous of certifying to the Society of Arts, &c. that, having been in the continual habit of using lac and amber varnishes fifty years, I have tried and proved the 1 consider a most valuable discovery for the Arts. 1 beg to assure the Society also, that i was authorized by an eminent artist and manufacturer, who had also used and approved it, to offer Mr. Field 100/. for the purchase of his process. “ As lac is the basis, even in name, of all the metallic CERTIFICATES. Sir j No. 3, Norris Street, Ilaymarket, April 28, 1827. A, Aik hi , JSsq. Secretary, fyc, fyc* I am, Sir, &c. &c. &c. George Veale. 62 CHEMISTRY: Sir j Ilarlcy Street, May 2, 1827- 1 am requested by Mr. Field to give my opinion of the white spirit varnish, made with gum lac, and spirits of wine, by him, and submitted to the Society of Arts for their premium. I am happy to have it in my power to give my testi- mony in its favour, as I cannot conceive it possible to make a spirit varnish from so hard and highly-coloured gum, so perfectly colourless and manageable in its appli- cation, more pure and excellent in any respect. I am, Sir, A. Atkin, Esq, &c, &c. &c. Secretary , fyc. fyc. W. Beechey. Sir ; As I have been informed that the Society will meet this evening, and that the merits of Mr. Field’s varnish will come under its consideration, 1 conceive it a duty on my part toward him to express the very high opinion I have formed of it for hardness, transparency, rapidity in dry- ing without tackiness, and the total absence of that worst of vices in the mastic and others, the vice of blooming . 1 have through life been in the habit of talking with artists on subjects always considered as desiderata amongst us 3 and the one most frequently mentioned was a varnish possessing the above qualities. On such occa- sions I have frequently heard the wish that lac could be deprived of its colour, as thence we might hope for that which is now proved possible, a perfect varnish. For myself, i can only be grateful for the individual advantage my own profession, that of painting, has re- ceived ; but it appears from various conversations I have had with persons in the habit of using varnishes over I. II.— VARNISH. 63 woods and metals, that its hardness without brittleness, and its colourless beauty, will give it a general value. I am, Sir, A, Atkin, Esq. &c. &c. &c. Secretary , fyc. fyc. G. F. Joseph, Sir ; 10£, Titchfield Street, April 30, 1827. I have tried Mr. Field’s varnish, and find it excellent, both in hardness and goodness of colour, which is whiter than any I have been in the habit of using, and which varnish above mentioned does not get yellow, I am, Sir, A. Atkin , Esq. &c. &e. &c. Secretary , §c. fyc* J. Varley, Dear Sir; 191, Regent Street, May 2, 1827. 1 have tried your white lac varnish upon coloured en- gravings, and highly approve of its colour and hardness. It certainly works very free, and dries well. I therefore hope it will receive the favour of the Society of Arts. I am, Sir, &c. &c, &c. Mr. Field. R. Ackermann, Jun, 6, Cirencester Place, Fitzroy Square, Dear Sir; May 2, 1827. Hearing that your lac varnish is before the Society of Arts, I beg to add my testimony to its excellence. I have tried it, and find in it every property that can be wished for in a spirit varnish. I have made many experiments in varnish-making myself, and use chiefly what is of my 64 C 11 OI I ST 11 Y own manufacture, because 1 cannot depend upon what is to be had at the shops 3 but 1 shall confidently use your’s for every purpose when 1 want a spirit varnish. I am, Sir, &c. &c. Sec. Mr . Field. J. Linnell. In examination of Mr. Field’s varnish by the Commit- tee, it was found slightly to change the colour of test paper, indicating the presence of a little acid ; on which it became a question whether the more tender of the colours used by painters were likely to be affected by it. This discussion produced the following letter from Mr. Field Sin; Syon-liill Park, April 28, 182/. i beg respectfully to suggest to the Committee, that if my white lac varnish contained chlorine, it would bleach test-paper, instead of which it only reddens it, in common with other spirit varnishes. Colours, which could be in- jured, however, by so weak an agency would be of no value 3 indeed, many pigments are heightened and im- proved by acids. I find also, that the brown lac varnish, mastic varnish, poppy oil, and even spirit of wine redden test-paper. Artists are in the constant use of vehicles even less neutral than these, such as vinegar, oils bleached by acids, and mucilage used in water-painting, which is seldom free from acidity ; while acetate of lead, and the sulphate of zinc, are constantly employed as dryers, with- out apparent injury to colours, some of which are salts, as verdigris, Sc c. and few of them arc perfectly neutral 3 add to which I do not find that bright iron, steel, Sc c. lackered with my varnish become in the slightest degree tarnished. I. II.— VARNISH. 65 I have accompanied this with a specimen of my varnish which does not change test-paper, and 1 am confident it may be completely edulcorated in the preparation, so as not at all to affect it. As a farther proof of its not having any property in- jurious to colours in its present state, I have varnished a coloured diagram, the colours of which are of my own preparing, for inspection of the Committee, without the previous usual defence of an intermediate sizeing ; and as the ultra-marine therein (which, though otherwise the most durable of colours, is instantly destroyed by an acid) and also the madder colours (which, resisting entirely the action of light and oxygen, are yet readily destroyed by chlorine) are both unaffected by this varnish, as are also the other colours of the diagram, I think my long ex- perience in such things justifies me in pronouncing it perfectly innocent with regard to colours. I am, Sir, A. Aikin , Esq. &c. &c. See. Secretary , fyc. fyc. George Field. Mr. Luning’s process is as follows Dissolve five ounces of shell lac in a quart of rectified spirit of wine ; boil for a few r minutes with ten ounces of well burnt and recently-heated animal charcoal, when a small quantity of the solution should be drawn off, and filtered ; if not colourless, a little more charcoal must be added. When all colour is removed, press the liquor through silk, as linen absorbs more varnish, and afterwards filter it through fine blotting-paper. In cases where the w T ax contained in gum lac would be objectionable, filter cold ; if the wax be not injurious, filler while hot. On comparing Mr. Luning’s varnish with Mr. Field’s, in the state in which each was sent to the Society* the VOL. XLV, F 66 CHEMISTRY: former was of a much thinner consistence, and was ren- dered turbid, by scales of wax and a few particles of charcoal floating in it. On passing it through common white filtering-paper, the impurities were separated, and tiip liquid came through in a more completely colourless state than Mr. Field’s. This seeming advantage was, how- ever, owing to the much greater state of dilution of Mr. Luning’s varnish ; for, when brought by evaporation to the consistence of Mr. Field’s, they each appeared as nearly as possible of the same very pale yellowish tint ; so that for the use of the painter and varnisher, they may each be called equally colourless. Mr. C. Varley having made some interesting compara- tive experiments on the two varnishes, his letter to the Secretary detailing the same is here added. 52, Upper Thornhaugh Street, Sir ; March 31, 1827. I have varnished some of my sketches with Mr. Field’s lac varnish, and some with Mr. Luning’s ditto. Mr. Field’s varnish appears to me to answer all that can be expected from a varnish. It may be laid on as freely as any other varnish, and dries quick, brilliant, and transparent. It is superior to all other varnishes in its approach to a glassy surface, and in freedom from tacki- ness. It is about a right strength or body, though 1 pre- fer a sample I had before from Mr. Field, which is as thick as can be laid on ; for it is desirable for a varnish to be as thick as will allow time for it to be spread on, be- cause it then thickens so soon, that its solvent has no time to act on the oil or colours of the picture. Mr. Luning’s varnish is a great deal too thin, and there- fore requires two or three coats before it will bear out ; and then, owing to its thinness, the activity of the spirit softens the first coat of varnish, and renders it uneven. f. II.—VA FINISH. 67 It is not so brilliant as Mr. Field’s, owing to the mixture (not solution) of wax, and is rather dirty, from the wax retaining some of the charcoal. Therefore I most de- cidedly give the preference to Mr. Field’s varnish. I have succeeded in throwing down both the wax and charcoal by adding spirit (essential oil) of turpentine, which dissolves the wax, and the solution then becomes sufficiently heavy to separate from the varnish ; it requires at least one of spirit of turpentine to three of the varnish before the former is heavy enough to separate, and then it is scarcely a liquid, and separates very slowly ; but if more spirit of turpentine is added, it goes down quicker. The varnish dissolves a small portion of the spirit of tur- pentine, which I feared might be an evil, when drying : but I cannot perceive that it makes any difference, Mr. Luning’s varnish, when so freed, appears more colourless than Mr. Field’s ; but, if brought to the same strength, there would be very little difference ; but probably a union of the two processes may produce the varnish like water, though the colour of each is at present equal or superior to most of the varnishes now in use, and will therefore stand at the head as the chief varnish. I am, Sir, A. Aikin , Rs<[. See. Se c. &c. Secretary , fyc. fyc. Cornelius Varley. In the Philosophical Transactions, Vol. LXXX1V. is a chemical examination of lac by Mr. Hatchett, from which it appears, that one hundred parts of shell lac consist of IX)*0 resin, 4 wax, 2*8 gluten, and 05 extract. Cold alco- hol will take up eighty-one parts of the resin, and leave the wax and gluten untouched ; it would, therefore, pro- bably, be an improvement on either of the above pro- cesses, to make the first solution of the shell lac in cold instead of in warn) or boiling alcohol. f 2 68 CHEMISTRY t III. — SODA LEY FOR DYERS. The Sum of Five Guineas was this Session given to Mr. C. Cameron, of Glasgow, for his mode of pre- paring Soda Ley for the use of Dyers of Turkey Red. The following Communication was received from him on the subject. No. 18, Saltinarket Street, Glasgow, Sir; April 7 , 1827- I beg leave to request of you to lay before the Committee the following communication : I hope it is not yet too late. You, Sir, as a man of science, will immediately appreciate its merit. I am. Sir, A. Aikhi , Esq. Sec. See. Sec. Secretary, fyc. lyc. Charles Cameron, Chemist. Method of making a cheap Soda Liquor , without Crys- tallizing, for the use of the Turkey-red Dyers. As the Turkey-red dyers are the great consumers of the common soda of commerce, it occurred to me, about four months ago, that they might make their own alkali, by the cheap and simple process of decomposing muriate of soda by pearl-ash, and thus procure a liquor equally pure, without the tedious and expensive operation of bringing the soda to the state of crystal. I pointed out the following plan to a Turkey-red dyer here, who imme- diately put it in practice, and it is now gradually adopt- ing by the trade. Into a cast-iron boiler capable of holding 450 gallons of water, I put ten hundred weight of pearl-ash (first sort), seven hundred weight muriate of soda, and four JII. — SODA LEY. 69 times the weight of the muriate of soda of water, apply- ing heat, and stirring until both are dissolved. After boiling for some time, the muriate of potash begins to crystallize on the surface. As the boiling is still continued, the muriate of potash is rapidly forming, and is lifted out of the vessel by means of a ladle pierced with small holes, and is thrown into a vessel placed in an inclined position, with its end or side a little within the edge of the boiler, which allows any of the liquor that may have been carried over, to drain back again into the pot. The boiling is continued until nearly the whole of the muriate of potash is deposited and taken out. The liquid is then removed into another vessel, either of cast iron or W'ood lined with lead, and allowed to remain until it has cooled to the temperature of sixty degrees, during which time it parts with the rest of its muriate ; it is then run off into another vessel, and diluted with water to twenty degrees specific gravity, more or less at pleasure, which prevents the soda from crystallizing, and gives an uniform strength of liquor, equally pure with the best crystallized soda, and at about half the price. The above weight of pearl-ash and muriate of soda, produces a mineral alkali equivalent in quantity to what is contained in one ton of soda of commerce, the best of which does not exceed 22 per cent. Present price of soda, 22/. per ton. oP. s. cl. Price of pearl-ash, first sort, per ton 28 0 0 14cwt.ofmuriateofsoda,30s.perton 12 0 29 2 0 These produce 1 £ tons of muriate of potash, price 5/. 10s. . . 6 17 6 Cost of alkali, equivalent to 2 tons of soda . . . . . 22 4 6 70 CHEMISTRY: The process is so simple, that one workman can de- compose one or more tons per day, dependent on the size of his vessels. As the Turkey-red work consumes from forty to two hundred and fifty tons annually, according to the extent of its establishment, it is of great importance to that valuable manufacture. I can claim no merit in merely decomposing muriate of soda by potash, that is a fact long known ; what properly belongs to me is, being the first to point out to the trade a simple and un- expensive method of making their own alkali, without being at the expense of erecting additional premises, and extensive apparatus, required for the purpose of crys- tallizing ; a common boiler and two or three other vessels being all that is requisite. Charles Cameron, IV. — MEDICINAL EXTRACTS. The Thanks of the Society were voted to J. Houlton, Esq. Grove Place, Lisson Grove, for his method of preparing Vegetable Extracts for Medicinal Use. 11, Grove Place, Lisson Grove, SiR; March 25, 1826. I beg to solicit the attention of the Society of Arts to specimens of Extracts ol Medicinal Plants, which have been prepared without the aid of artificial heat, and in a more easy and economical method than that ordinarily employed, and which, at the same time, produces an article in no respect inferior to the extracts made in the usual way, but In many points very superior ; and it IV.— MEDICINAL EXTRACTS. 71 ensures the preservation of the smell, flavour, and full medicinal power of the plant from which it is prepared ; and, with care, the colour may be preserved in a very superior manner. The process is not so liable to failure as the common way; in fact, failure to make a superior article is almost impossible. No. 1. A dry extract of taraxacum. No. 2. Extract of conium. No. 3. Extract of conium in a dry state, to show the resinous fracture. No. 4. Specimen of vegetable extract (conium), in which attention has been paid to colour. Should the Society deem the manufacture worthy their notice, I shall be happy to lay before them a fuller account of the process I adopt. I am, Sir, A. Aihin, Esq. & c. &c. &c. Secretary , fyc. fyc. Joseph Houlton, F.L.S. Member of the Royal College of Surgeons. It is well known to professional men, that the juices of almost all plants are more or less injured in their medicinal qualities, by being boiled down and evaporated in the usual way, to the consistence of extract. At Apothecaries’ Hall the evaporation is entirely effected by means of steam, so that the heat employed is under complete control ; and in Mr. Barry’s patent pro- cess, the evaporation is performed in vacuo. Mr. Houlton’s process is the following : the plant being bruised, is to be submitted to the action of a press, in order to squeeze out the juice, which is then to be strained through fine linen. The depurated juice is now 72 C II E M I S T R Y : to be poured to the depth of about one-eighth of an inch into an earthenware plate, or a glass dish, and is to he exposed to a constant current of air, by placing it on the inner sill of a window, and raising the sash about an inch. The constant current of air thus produced, occasions the rapid evaporation of the watery parts, and there remains a soft extract, retaining the colour, odour, and medical properties of the recent plant, with less alteration than by any other method. If the sun shines, a blind should he hung before the window, as vegetable juices arc speedily changed by the action of solar light. The consistence given to the extract is entirely optional, but those that are rather hard will keep better than those that are soft. The method is not adapted to a manufactory on a large scale \ but any individual practitioner may, without much trouble or expense, prepare in this way, for his own use, extracts far superior, in active properties, to those that are usually met with. V.— PREPARING LIME-JUICE. The Thanks of the Society were presented to Captain Ragnold, for the folloiving Letter , and the samples of Lime-juice by which it was accompanied. Sin; Falmouth, July 12, 1825. From some conversation I had with one or two of the members of the Transport Board, I find they are by no means satisfied with their knowledge of the effect pro- duced on the antiscorbutic qualities of lime-juice, by the 25 per cent of rum, now added for its preservation. This V.-LIME-JUICE. 73 induces me to hope, that the inode I have adopted to cure it for sea voyages may be of more consequence than I at first suspected. Last Christmas I caused some to be pre- pared in Jamaica, and one dozen has been sent home, samples of which will accompany this letter. I have simplified the process, and I trust where the directions are carefully followed, the juice will be permanently preserved in an unaltered state. The bottle which accom- panies this, is one of a dozen, prepared by a process far less troublesome, and equally efficacious, with that of Mr. Appert, for the application of which I had the honour of the Society’s thanks last year ; and by the alteration pro- posed, a great deal of the loss hitherto occasioned by the bursting of bottles in the boiler will be prevented. Should the Society be of opinion that I have made an improvement in the process, they will deal with it according to its merits. The expressed juice being well strained, to separate every particle of pulp and rind, is to be boiled in an earthen vessel smartly for half an hour ; a part of the water is driven off, and the vegetable albumen will sepa- rate, and subside on cooling ; decant the juice clean, and re-boil it for a few minutes ; fill it into bottles previously dried and heated, so as to leave just room enough for the cork ; cork tight, cement over the cork, and lay the bottles away on their sides. By this process the whole dozen were prepared, and if not opened till Christmas, will have been twelve months under cork. I shall direct another bottle to be sent, for the purpose of being deposited in the model room, to try the effect of time upon : have the goodness to cause its date to be noted. In fine, this process, instead of boiling the bottles with their corks tied in, and breaking many, perhaps twenty per cent, by the heat, is simply to put the boiling fluid into the bottle, 74 CHEMISTRY. instead of the bottle into the boiling fluid. It appears to be equally efficacious in preserving the juice without the alcohol, and leaves it in possession of all its flavour. The sample was bottled in Jamaica, at Christmas, 1824, and at the time of being examined, had been two years in bottle. Its acidity did not seem to be impaired, but the flavour had a slight smack of empyreuma. Notwith- standing this, it would probably be more grateful to invalids on board ship, and certainly would be more effi- cacious, than the juice preserved by means of rum, I am, Sir, A. A i/cm, Esq. Secretary, fyc, Sfc. &c. &c. Sec. Wm, Bagnold, PAPERS IN CHEMISTRY. No. I. APPARATUS FOR INSTANTANEOUS LIGHT. The Silver Isis Medal ivas presented to Mr. George Jackson, 30, Church Street, Spitalfields, for his Apparatus for Instantaneous Light, which has been placed in the Society’s Repository. 30, Church Street , Spitalfields, Sir, April 25, ] 827. I beg leave to inform you that I have contrived what I conceive to be an improvement on the apparatus usually employed for obtaining light by means of hydrogen gas and spongy platinum, and I shall feel particularly obliged by your laying the same before the Society of Arts. The objects which I had in view in constructing this apparatus were simplicity and cheapness. In these I have so far succeeded, that the uncovering of the cap of pla- tinum is rendered unnecessary, and a taper is fixed in a situation to be lighted by simply turning the cock ; and the instrument can be sold at about half the price of those in common use. My attention was turned to this subject by frequently ,12 CHEMISTRY. having occasion for a light when called to the practice of my profession by night. I tried in succession the phos- phorus bottle and the oxygenated matches, and was fit- ting up an instrument on Volta’s plan, when Dobereiner’s discovery of the action of hydrogen on spongy platinum was made public. I then substituted a cup with pla- tinum for the electrophorus, and in that state used the apparatus for a long time before I thought of making any improvement on it. The instrument which I have the honour of laying before the Society, consists of an inverted syphon, made of stout glass tube, about half an inch outside diameter, having a ball, about two inches and a quarter diameter, blown on each leg. The bend of the syphon is cemented into a wooden foot, loaded with lead, and the ball on the longer leg stands about six inches (measuring from centre to centre) above that on the shorter one. The tube ex- tends about an inch above each ball. That from the upper one is simply covered with a loose brass cap, more for ornament than use. On that which rises from the lower ball a brass cap is cemented, into the top of which a brass plug is ground, with a hole drilled across it, met by another drilled up the centre, so as to form a stopcock. A jet with a fine orifice is screwed into the side of the cap, so as to communicate with the lower ball through holes in the plug when the latter is turned ; and just below the jet an arm projects, which carries a short piece of brass tube, lying horizontally, that serves to support the platinum, and protect it from accidental displacement. The end of a thin platinum wire is formed into a small helix of two or three turns, by bending it round a wire or glass rod, and is covered with moist ammonio-muriate of platinum. It is then heated to redness in the flame of a CHEMISTRY. 13 spirit-lamp, again coated with the ammonio-muriate, and again heated, so as to form a platinum sponge, from the size of a pepper-corn to that of a pea. The wire is then attached to a ring, made of brass tube, of a size to admit of being pushed tightly into that which is supported by the arm ; so that the platinum sponge hangs in the centre of the tube directly before the jet. In the arm above mentioned, between the jet and the platinum, and a little to the side, is a hole just large enough to contain a piece of wax taper, the wick of which is thus placed so as not to obstruct the jet of gas, but yet near enough to be lighted when the gas is inflamed. In the part of the tube between the bend of the syphon and the lower ball, a cork, grooved at the sides, is inserted, to prevent the zinc from falling into the bend. To charge the instrument for use, the brass plug is taken out, and a number of narrow slips of zinc, about two inches long (cut from a piece of the thin malleable metal), are introduced into the lower ball, which is then nearly filled with diluted sulphuric acid, poured through the upper orifice. As soon as a brisk action commences, the plug is replaced, and the gas, accumulating in the lower ball, drives the acid into the upper one, when the produc- tion of gas ceases. The lower ball being thus filled with hydrogen, on turning the plug a portion of it escapes through the jet, becomes ignited by its action on the platinum sponge, and lights the taper, a portion of acid at the same time descending from the upper ball, acting on the zinc, and causing a fresh production of gas. It is not very material how much the acid is diluted : that which I have used is made by mixing one measure of oil of vitriol with about ten measures of water, and it answers very well. 14 CHEMISTRY. In the instrument in the Society’s possession, the upper ball is about six inches (from centre to centre) above the lower one. I have since made one wherein the distance is only four inches, and I think it lights with rather less expenditure of gas. To prepare the ammonio-muriate of platinum, a solu- tion of the metal in nitro-muriatic acid is dropped into a solution of muriate of ammonia in distilled water, and the yellow precipitate is collected on a filter. Should it be- come dry, it must be moistened with distilled water. I am, Sir, &c. &c. &c. A. Aikin, Esq. George Jackson. Secretary, §-c. fyc. Reference to Mr. Jackson's Platina Light. Figure 13. Plate I. a. The stopper through which the zinc is introduced into the bulb h ; it is prevented falling lower than c by a notched cork placed within. Diluted sulphuric acid is poured in through the bulb d till it fills the bulb h ; the stopper a is then put in, and as the hydrogen gas is generated, the liquid is forced down through the bottom c into the tube e and the bulb d, so that none remains in contact with the zinc. The stopper a also forms the cock, it being hollow, as shewn in section, fig. 14; and on turning its lateral aperture opposite the jet f the gas is pressed out by the weight of the fluid in d and e, and blows against a piece of spongy platina suspended by platina wire in the short tube g; the platina becoming CHEMISTRY. 15 hot, kindles the gas which heated it, and this flame lights the wax taper li, which is stuck in a hole in the arm i ; this hole is so much on one side of the jet as to let the wick only just touch the flame; the arm i, which holds the taper, is soldered to the brass neck j and to the tube g. Fig. 15 is a full-sized section of the tube g; within it slips a shorter ring of tube k, round the upper part of which the wire is twisted that holds the spongy platina ; thus the platina, though hanging loose, is pro- tected from accident, and is always opposite the jet. No. II. PURIFICATION OF LINSEED OIL. The Silver Isis Medal and Ten Pounds were presented to Mr. Thomas Cogan, for his Method of Purifying Linseed Oil. Of the seed-oils, those which are in the greatest demand are from rapeseed and from linseed. In France and in most other parts of continental Europe, rapeseed oil is that which is generally used for lamps; but it will not give a clear light till it has been freed from the mucilage and other matters which, when heated, become charred, and thus load the wick, and, by obstructing the capillary attraction, impair the free supply of oil. Acids, pro- perly applied, will precipitate the mucilage; but long subsidence or tedious filtration are necessary for this purpose; and, after all, the oil is found still to retain 16 CHEMISTRY. some acid, or at least its properties have undergone some change, which diminishes its inflammability. Linseed oil is not made use of in lamps ; but there is an immense consumption of it as the basis of oil paints, both of those that are used in house-painting within doors, and of those that are employed by the artist. Linseed contains so much mucilage, that it is necessary to roast the seed more or less, in order to enable it to give out its oil to the action of the press ; and on this account, the oil, which naturally has only a pale yellow colour, is generally reddish brown, from the previous toasting of the seeds, and still contains also a considerable proportion of mucilage. By separating from the oil this scorched mucilage, it is much improved as a vehicle for white and pale colours, and is also better able to resist the action of air and the weather. ■» M. Thenard was, it appears, the first who published a method of freeing the seed-oils from their mucilage, by the action of sulphuric acid ; but the subsequent separa- tion of the charred matter, by long standing, or by slow filtration, was a great objection to the process ; and the attempt to w r ash out the remains of the acid, by me- chanical agitation of the oil with- water, either cold or warm, was far from being fully successful. Mr. Cogan’s process, though resembling M. Thenard ’s in the first part of it, is completed by the judicious intro- duction of steam; by means of which the oil appears to be almost entirely freed from acid, and the black feculent dregs subside in the course of twelve hours, leaving the supernatant oil quite clear, and greatly improved in colour, and in those qualities for which it is valued by the painter. The quantity of oil that he operates upon at once CHEMISTRY. 17 is about 100 gallons. For this, three quarts, that is about ten pounds, of sulphuric acid (oil of vitriol), is required. The acid is to be diluted with an equal bulk of water. The oil being put into a copper pan, of the shape of a boiler, two quarts of the dilute acid are to be added : the whole is then stirred up very carefully for an hour or more with a wooden scoop, till the acid has become completely incorporated with the oil, and the colour of this last has become much deeper than at first. A second similar quantity of acid is then to be added and mixed with the oil in the same way as the first was ; and after this, the remaining third part of acid is to be added. The stirring of the oil is to continue incessantly for about six hours in the whole, at the end of which time the colour of the mixture will be almost that of tar. It is then to be allowed to stand quiet for a night, and in the morning is to be transferred to the boiler ; — this is of copper, and has a steam-pipe entering it at the bottom, and then dividing into three or four branches, each of which terminates in a perforated plate. The steam, thus thrown in, passes in a very divided state into the oil, penetrates into every part of it, and heats it to the temperature of boiling water. The steaming process is to be continued for about six or seven hours, at the end of which time it is to be transferred to a cooler, of the form of an inverted cone, terminating in a short pipe, commanded by a stopcock, and also having a stopcock inserted in its side, a few inches from the bottom. After remaining a night in the cooler, the oil is fit to be withdrawn ; for this purpose the cock at bottom is opened, and the black watery acid liquor flows out. As soon as the oil begins to come, the cock is closed, and that in the side of the cooler is opened. From this the oil runs quite clear and limpid ; 18 CHEMISTRY. the whole of that which is still turbid remaining below the upper cock. The purified oil being drawn off, that which is turbid is let out into a reservoir, where it either remains to clarify by subsidence, or is mixed with the next portion of raw oil. PAPER IN CHEMISTRY. SAFE TUBE FOR THE OXY-HYDROGEN BLOWPIPE. The Large Silver Medal was presented to Mr. J. Hemming , 5, Brecknock Crescent , Camden Town, for his Safe Tube for the Qxy-hydrogen Blowpipe. The following communication has been received from the Inventor, and, one of his Tubes has been placed in the Society's Repository. 5, Brecknock Crescent , Camden Town, Sik, April 1 1, 1832. I send for the inspection of the Society of Arts, &c. a safety tube I have invented, for preventing accidents in the combustion of the mixed gases oxygen and hydrogen, when employed for the purposes of the blowpipe. It is a brass cylinder, fig. 1, about % inch internal diameter, and four inches long, filled with equal lengths of brass wire T Uo inch diameter. The number of wires in the tube is 4200, and they are wedged closely together by a pointed rod l inch diameter, forcibly inserted through the centre of them, as shewn in the section, fig. 2, and the end view, fig. 3. One extremity of the tube is provided with a 42 CHEMISTRY. screw for attachment to a bladder or other reservoir of the gases, and the other with a blowpipe jet of the usual kind. The interstices between the fine wires, which are extremely small, become in effect a congeries of metallic tubes of the smallest possible bore, as shewn fig. 4, the cooling and conducting power of which are far greater than could be effected by filling a tube of equal length with discs of wire gauze, (the contrivance adopted in the usual safety chamber), the apertures being so much smaller than those in the finest wire gauze, and possessing the decided advantage of uninterrupted continuity. In a great number of experiments with this safety- tube, I have never been able to produce a recession of the flame of the mixed gases oxygen and hydrogen, although I have frequently ignited them at the extremity, after removing the jet piece, which is nearly j inch diameter, and have relieved all pressure repeatedly. I am so fully convinced of the perfect safety of this instrument, that I have dispensed altogether with the well, &c. &c. of the usual blowpipes, and operate constantly with the gases contained in a bladder held under my arm, even when CHEMISTRY. 43 the jet piece is removed. I shall be happy to perform this experiment before the Society. It may be worthy of remark, that in the course of some experiments with Gurney’s blowpipe, provided with Wilkinson’s safety chamber, 8tc., I found that I could produce explosion of the gases in the well many times in succession, if even a very minute portion of water passed with the gases into the safety chamber. By filling the well nearly full of water (without a stratum of oil on the surface), I could always produce an explosion ; but when my own safety tube was attached, instead of the usual chamber, I found it impossible in any instance, and under any circumstances, to explode the gases in the well. It may be necessary to observe, it is indispensable that the wires in the tube be as fine as those I have employed. If thicker wire is used, the interstices are larger, and, consequently, there is a chance of the flame receding through them. The wires should also be as closely wedged together as they are in the accompanying instru- ment, in order to ensure minuteness of aperture. I am, Sir, &c. &c. A. Aikin, Esq. Jno. Hemming. Secretary, fyc. <§'C. The experiments alluded to in the preceding letter were performed in presence of the Committee, to their entire satisfaction. CHEMISTRY. No. 1. MAGNETS. The Silver Isis Medal was presented to Mr. Richard Knight , Jim., of Foster Lane , for his Experiments on the Texture of Steel, as affecting Magnets made of it. The two conditions, according to Mr. Knight, that enable a bar of steel to receive and retain a high degree of mag- netism, are, for the first, that the grain of the metal should be open, and, for the second, that it should be highly car- bonised : it also conduces to the same end if the bar is hardened at the poles, to that degree that a file will just touch it. In illustration of the importance of the above con- ditions, the following experiments were made : 1. A magnet was made of a bar of blistered steel, hammered smooth, but not so as to close the grain, the steel remaining fully carbonised. The quality of the magnet proved to be very good. 2. A bar of the same blistered steel as No. 1 was closed by hammering, till it became nearly as fine as the best shear steel : beincr then treated as No. 1, it produced a magnet of very inferior quality. CHEMISTRY. 39 3. A bar of the same blistered steel was treated as No. 2, and afterwards was opened by exposure to a white heat. It was found to have an open grain, but, having lost in this last process nearly the whole of its carbon, it produced a magnet inferior to No. 2. 4. A bar of the same blistered steel was treated as No. 3, and was afterwards exposed to red heat, in contact with powdered charcoal, till it was recon- verted into perfect steel. The magnet made of it proved very good, but not equal to No. 1. Hence Mr. R. Knight concludes that open-grained blistered steel is well fitted for powerful magnets ; that closing the grain by heating and hammering it, though it should still remain carbonised, greatly injures it, and that the subsequent action of heat, in opening it, though it much improves the quality, does not restore it to the same openness of grain that it had at first. The keeper, or bar, which connects the two ends of a horse-shoe magnet, is better of soft iron than of steel, being able in the former case to support a greater weight before it gives way, than in the latter case. The process according to which Mr. Knight makes his magnets, is as follows : Having procured a bar of blistered steel of the required size, heat it sufficiently, so as to allow of closing the blis- ters, and thus making the surface smooth, which must be done by as little hammering as possible. The middle of the bar is then to be heated, so as to allow of its beiiur o bent, and brought to the required shape : the ends of the horse-shoe bar are now to be filed smooth and flat, in order that they may touch the keeper by the whole of their areas. 40 CHEMISTRY. The bar is now ready for tempering, which is done by heating the two ends red-hot for about one-third of their respective distances from the bend, and then plunging it in cold water, by which the ends acquire such a degree of hardness as renders them just capable of yielding to a file. The last process is magnetising the bar ; which is done by laying it on a flat table, having its two ends connected by a soft iron keeper. The end which is to become the north pole being previously marked by a cut across it, another horse-slioe magnet, without its keeper, is to be held in the hand in a vertical position, the north pole out- wards : it is then to be slid over the surface of the bar as it lies on the table, beginning at the north pole of this latter, and so continuing in an uninterrupted circuit all round the bar and its keeper, for ten or twelve times, and finally leaving off at the south pole. The bar will then be found to be fully saturated with magnetism. If the newly formed magnet be now suspended, and weights be hung on the keeper till it separates from the magnet, and if the keeper be a second time applied to the magnet, and again separated as before, it will be found that the force required to cause the first separation is to that required to cause the second nearly in the proportion of ten to seven ; but the power of the magnet does not appear to be weakened by any number of subsequent separations. CHEMISTRY. 41 No. II. OXY-HYDROGEN BLOWPIPE. The Silver Isis Medal was presented to Mr. W. Maugham , for his oxy-hydrogen blowpipe , a Model of which has been placed in the Society's Repository. The following communication has been received from Mr. Maugham. Adelaide Street Gallery, Sir, May 12 th, 1835. Having had occasion to make a great number of experi- ments during the last two years with oxygen and hydro- gen gases, and having found all the blowpipes for burn- ing these gases in a mixed state, on an extensive scale, very inefficient for my purpose, I have been under the necessity of contriving an apparatus, easily manageable, and entirely free from danger. It would be useless to enter into even a slight history of the several contrivances that have already been laid before the public, from time to time, for burning these gases with safety in a mixed state, as I am aware that the Society are fully conversant with all that might be adduced on the subject. I may, however, be allowed to state, that such contrivances, although highly ingenious, can, in reality, only be con- sidered as toys in the hands of bold operators ; for they are by no means calculated to answer any purpose by which the public can be benefited ; for they cannot be trusted in the hands of ordinary manipulators. By means of the blowpipe which 1 herewith transmit, and which I 42 CHEMISTRY. trust you will submit to a full investigation and trial, these gases may be burnt for any length of time without any chance of explosion, as they are merely mixed in a very small quantity at once, the mixture taking place only as fast as the gases are consumed. The heat produced by this safe mode of burning the gases may undoubtedly be turned to an advantageous account by different mechanics, in fusing platinum and other refractory metals, by which means the expense now attendant upon the working of such metals would be considerably reduced. This mode of burning the gases will likewise be found eligible for producing a continuous and intense light through the medium of lime. Professor Daniell’s blowpipe is one that may be used with perfect safety, but, in my estimation, it labours under two great disadvantages, one of which is, that a sufficient degree of heat for many purposes cannot be ob- tained by it ; the other is, that the great consumption, or rather waste, of gas, occasioned by its wide apertures, unfits it for use on an extensive scale. In this blowpipe, the gases are brought along separate tubes, one of these tubes traversing the interior of the larger one, so as to allow the gases to come in contact only just where they respectively escape into the atmosphere. As this is already in the hands of most chemists who have any thing to do with oxy-hydrogen blowpipes, instead of beginning with a mode of conveying the gases ab origine into the chamber which I am about to propose to the Societv’s consideration, 1 will describe a method of rendering it complete, and fully efficient for all the purposes to which the safe combustion of the gases can be applied. I\ly motive for building upon Professor DanieH’s blowpipe is merely to serve the economical purpose just alluded to; CHEMISTRY. 43 ’ gggggggg for it will presently be perceived, that it would have been quite as easy to have constructed one altogether different as to have undertaken to finish what that philosopher has begun. The above diagram is a section of my blowpipe (part of the plain tube between the two arrows being omitted), with one of the nozzles, hereafter described, screwed on the end of it. At this part it will be seen that I have made a little addition to Professor Daniell’s arrange- ment ; for, at the end of the tube along which the hydro- gen passes, there is soldered on a piece of metal, per- forated with eight holes x (see the next diagram but one), and also with a larger central one, which receives the end of the pipe through which the oxygen passes : these smaller holes are not, as might at first be expected, to answer the purpose of wire-gauze, and to prevent 44 CHEMISTRY. explosion ; but are merely to divide the stream of hydrogen, so as to render its mixture with the oxygen in the chamber into which the pipe opens more uniform. On the outside of the chamber is a support for a cylinder of lime, hereafter described. The nozzle can be unscrewed, and the right-angled one, for fusing platinum, &c. put in its place. On the outside of the nozzle is placed the sup- port for the cylinder of lime. The apparatus here shewn is to be used as follows : It is to be screwed on at c to a gasometer, or to a tube lead- ing from a gasometer, containing oxygen, and is to be con- nected, by means of a flexible tube screwed on at d , to another gasometer containing hydrogen, — a connecting joint will be necessary in making the union complete. The cock e regulates the quantity of oxygen, and is part of Professor Daniell’s arrangement. The cock for regu- lating the quantity of hydrogen is to be attached to a flexi- ble tube screwed in at d , which is not seen in the diagram. By having an elbow-joint, a section of which is seen at n in the annexed figure, and screwed in its place at b b , CHEMISTRY. 45 a vertical position of the shaft of the blowpipe may be obtained, which will be found convenient for placing the lime-light in a parabolic reflector. The opposite diagram shews the support for the lime without the noz- zle ; a the rod on which a ball or cylinder of lime, &c. is to be placed, — the lime, &c. having, of course, a hole drilled through it, and turned perfectly cylindrical ; b the ring which slips on the nozzle of the blowpipe ; c a screw for fixing the ring tight ; d a small plate of metal on which the lime rests ; e a screw for raising or lowering the lime, so as to expose a fresh surface of the earth as often as may be necessary. This does away with the necessity of employing a watch or clock-work motion, in ordinary experiments, with the light in question. The annexed figure is a section of one of the nozzles of the blowpipe I beg to propose, shewing a chamber a in which the gases mix previously to being burnt ; b is a female screw for fitting it on the end of a Daniell’s blow- pipe. The jet c is of platinum. This nozzle is bent at right angles, and, when fixed on the blowpipe, the jet for delivering the mixed gases points perpendicularly down- 40 CHEMISTRY. wards, and is intended for fusing platinum, and other metals difficult, of fusion, the metal being supported on a proper rest. The oblique nozzle shewn in the first figure is for experimenting with light by means of lime. It is bent at an angle of about 45°. So long as the pressure at each gasometer is kept uni- form, a proper mixture of the gases in the chamber will always be kept up after it has once been established by the regulating cocks, and an explosion cannot possibly take place. The gases are thus burnt certainly in a mixed state ; but they are only mixed in a very trifling quantity, and only just before they escape from the blowpipe. It may here be necessary to observe, that in the several kinds of apparatus for burning the gases in a mixed state by the usual mode of mixing them, the mixture can never scarcely be what it precisely ought to be ; for they are mixed in the proportions of two volumes of hydrogen and one volume of oxygen, no regard being had to the impurities which are always present in these gases as ordinarily ob- tained ; which impurities are continually varying, not only in quantity, but in quality, as I have found by experience. By means of the apparatus just described, this incon- venience respecting mixture is entirely done away with ; for the regulating cocks allow us at any instant, if the flame vary from what it ought to be, to bring it to its proper state. It is true, the mixture is made by guess ; but a little experience will soon enable the operator to obtain at once the due proportions. If the hydrogen be in excess, a large bushy flame will be produced ; if the oxygen be in excess, the flame will be extinguished : the flame produced by the proper mixture is so characteristic, that when once seen it is easily remembered. When the gases are thrown upon lime and the other earths, we shall CHEMISTRY. 47 have a flickering light, if the mixture of the gases lie not properly adjusted ; and this flickering we always have, when the gases are mixed in the manner to which I object. Another addition to Mr. Daniell’s apparatus is a con- necting piece at h h in the first diagram, which being slightly unscrewed will enable the jet to be placed in any direction in the plane of a circle whose diameter shall cut the blowpipe transversely at right angles. With respect to the gasometers to be used with this apparatus, I have to observe, that on a small scale, those who are in possession of two gasometers, constructed on Mr. Pepys’s principle, may obtain an ecpial pressure by employing one funnel, terminating in a branched tube attached to each gasometer, as shewn in the annexed figure. Un- der ordinary circumstances, an assistant may pour water in the funnel «, and a little variation in the height of the column which will occur by this means, does not much affect the flame, and may be always counteracted by means of the regulating cocks. When there is conve- nience, the supply of water to the funnel may be regu- lated by a ball-cock attached to a pipe passing from a cistern, the ball being placed in the water in the funnel. This mode of proceeding, however, only relates to the use of the gases on a small scale, as in the lecture-room, &c. When the gases are to be used more extensively, and applied to the purposes which I have already proposed, a better mode of obtaining equal pressure will very readily suggest itself. It is to he remembered that, in describing 48 CHEMISTRY. a blowpipe, I cannot be expected to say much respecting gasometers : all I wish is, that the pressure may be always uniform, and ecpial to that of a column of water of at least twenty-four inches in height. I trust you will at once be convinced that the mode above proposed is entirely free from danger. I may say with truth that I have burnt thousands of gallons of oxygen and hydrogen gases in this way, and have never yet met with the slightest accident. In conclusion, I beg to observe, that I by no means wish to impress upon the Society that I have been the first to burn oxygen and hydrogen from separate vessels ; but that this mode which I have proposed has been the result of my own experiments. 1 believe there is no blowpipe at present before the public for burning the gases on this principle. The mode of producing the light upon lime for the oxy-hydrogen microscopes by Cary, Cooper, and others, I was not acquainted with until long after I had obtained the light myself for the proprietors of the Ade- laide Street Gallery ; I always employed balls of lime, and through Messrs. Cooper and Cary I learnt that cylinders of the same earth are decidedly better. The apparatus which I employed for a microscope commenced by Mi-. Tully, is still at the Gallery, and is open to the inspection of any person who wishes to see it. I am, Sir, &c. &c. A. Aik in, Esq. W. Maugham, Secretary, Sfc. fyc. Lecturer on Chemistry, Adelaide Street Gallery, and Charing Cross Hospital. P. S. If platinum be fused upon charcoal it will be brittle, and unfit for the purposes to which it is usually CHEMISTRY. 4f) applied. I have no doubt it is converted into a carburet. I have tried several substances as a support for it, of which I find Stourbridge clay the best. Mr. Johnson, of Hatton Garden, has been kind enough to witness some experiments with the blowpipe, and he suggested the use of the above material as a support. He brought with him some bone- ash cupels, but they were readily fused. All substances, indeed, seem to fuse under the intense heat produced by the combustion of the gases in question. I find the best mode of fusing platinum is to keep adding gradually to the fused mass small pieces of the metal. When an ounce or more has thus been acted upon, the metal will be in fusion at the surface, but will become solid at the bottom. We may thus go on welding or agglutinating the platinum to any extent. Before rolling or using the metal in any other way, lie careful to cut off* that end which was next the support, as this becomes incorporated with a portion of silica, which renders it unfit for working. By adhering to the principle laid down, by having gasometers sufficiently large (and their size may be increased to any extent with perfect safety), and by having the orifice whence the gases issue augmented to a considerable extent, I am convinced platinum may be fused in almost any quantity. I have succeeded in agglutinating more than half a pound of this metal by the process just described. E 50 CHEMISTRY. NOS. III. AND IV. CAPILLARY TUBES IN METAL. The Sum of Five Pounds was presented to Mr. J. Fo- il erts, 64 Queen Street , Cheap side, for his Method of subdividing a. Pipe into Capillary Tubes; a Specimen of which has been placed in the Society's Repository. The Thanhs of the Society were voted to Hen. Wilkin- son, Esg. Pall Mall, for his Method of producing a Ring of Capillary l\ibes. For gas-burners, for the safe combustion of mixtures of oxygen and hydrogen, and for other purposes, it is often desirable to divide the end of the discharge-pipe into line capillary tubes, of the depth of half an inch or more. It is difficult and expensive to bore such apertures in a piece of solid metal, and it is hardly possible to be executed at all if the apertures are required to be of very small diameter. Mr. Roberts very ingeniously and expeditiously sub- divides the end of a metal pipe into small tubes of any required depth, by means of pinion-wire. Pinion-wire is made by taking a cylindrical wire of soft steel, and passing it through a draw-plate of such a figure as to form on its surface deep grooves in the direction of radii to the axis of the wire : the ribs which separate these grooves from one another may be considered as leaves or teeth, and of such wire, when cut into proper lengths, are made the pinions CHEMISTRY. used by watchmakers. Hence arises the name by which this wire is commonly known. If now a piece of this wire be driven into the end of a brass pipe of such a size as to make a close fit with it, it is evident that that part of the pipe has thus been subdivided into as many smaller tubes as there are grooves in the wire. By using a draw-plate fitted to make smaller and shallower and more numerous grooves than are required in common pinion-wire, it is manifest that wires or cores may be produced, which, when driven into metal pipes, as already described, will subdivide them into capillary tubes of almost any degree of tenuity. Mr. H. Wilkinson’s method is described in the follow- ing letter : Sir, Pall Mall, May 25th, 1835 . In the course of some experiments on artificial light, which I was engaged in about twelve months since, I was desirous of obtaining a great number of extremely minute apertures for a gas-burner ; and, finding it impossible, in the ordinary way, to obtain them, a new method occurred to me, which immediately produced the desired effect. I shewed it at the time to several eminent scientific men, who were unable to conceive how these apertures were formed; and, as I made no secret of the method, they were equally pleased at the simplicity of the operation ; and the specimen herewith sent has been exhibiting at the Gallery of Practical Science for several months. I did not attach much importance to it myself; but, as I do not find that it is at all known, and now think it might be useful in a variety of ways, I have sent it for you to lay before the Society; and should they be of the same opinion, I shall 52 CHEMISTRY. feel much pleasure in communicating the mode of opera- tion, by which any number of apertures, hardly visible to the naked eye, and of any length {even afoot , if required ), may be made in any metal in ten minutes ! I am, Sir, &c. &c. A. Aik in , Esq. Henry Wilkinson. Secretary, fyc. fyc. The process consists merely in turning one cylinder to fit another very accurately, and then, by milling the out- side of the inner cylinder with a straight milling tool of the required degree of fineness, and afterwards sliding the milled cylinder within the other, apertures are produced perfectly distinct, and of course of the same length as the milled cylinder. A similar effect may be produced on flat surfaces, if required. H. W. No. V. COPAL VARNISH. Letter from Mr. C. Varley, on Copal Varnish. 7 Charles Street, Clarendon Square, Sir, November, 1835. The letter of mine, in the first part of this volume, on the essential oil of spruce, was written in February 1827, when the first small quantity only had been received by the Society. My letter was accompanied with specimens CHEMISTRY. 53 of copal in the different solvents therein mentioned, in order to exhibit the real facts to the Committee. That letter at this late date appears defective, in not being accompanied with any statement of what was than shewn to take place when different liquids are applied to copal. I will now give that account, premising that pure solutions of copal form the most perfect varnishes that have yet been used in the arts, from the fact that lumps of copal, or pure varnish when dried, may be exposed even to the atmosphere of London for years, or till they are obscured by dirt, and yet when washed will be found perfectly clean and as pure as ever ; whereas mastic and mastic varnish (so much used by artists, to the certain injury of their pictures), when so exposed, become brown through- out their whole substance. Copal, with this most excellent quality, is the whitest of all the resins, and a sufficient quantity for artists may always be picked absolutely pure, and free from colour. Hence it becomes very desirable to effect its solution by menstrua not only in themselves colourless, but which will not add that injurious quality of becoming coloured throughout by exposure to our London atmosphere : for the copal varnish that has been so long in the market is made with oil which does add that injurious quality of acquiring a dirty colour quite through. Va- rious methods of causing copal to dissolve in spirits, i. e. essential oil of turpentine, have been proposed, but they did not answer sufficiently well to bring it into the market. In 1813 I succeeded well enough to commence painting with solution of copal in spirit of turpentine, to the total exclusion of oil or any greasy matter. Copal is not only difficult to dissolve, but, when well dis- solved, it is liable to be precipitated in the form of a tough leathery substance, when a portion even of the original CHEMISTRY. 54 solvent is applied lo dilute it. Many artists who have tried to use it gave it up when this difficulty crossed them ; yet this may be avoided by a knowledge of the effect which different solvents have on copal. Very pure alcohol gives a strong and limpid solution of copal, in which long needles of crystals will appear, if left cpiiet for a length of time. This solution, when made as thick as can be used, may be applied as a varnish; but the alcohol evaporates very quickly, and also acts as a solvent on the surface of the picture to which it is applied : such varnish, therefore, can only be used with particular care. Oil of spike lavender (at present very expensive) quickly softens and then dissolves the small lumps of copal, so that it may be used as a varnish or as a vehicle for colours ; and yet if the solution, before it has been much disturbed, be carefully examined, the original form of the lumps may be detected as a nearly invisible jelly ; and, therefore, though it may be sufficiently dissolved for use, it is not a perfect solution : this effect is nearly ob- literated when the copal is previously ground to a very fine powder, for that diminishes the size of the jelly-like masses. But, as oil of lavender acts powerfully, also, on the surface of the picture, the varnish should be as thick as can be used, in order that it may soon become too stiff by drying to act much on the surface. Essential oil of spruce dissolves copal much like the oil of lavender, but is longer about it. Spirits of turpentine alone, if digested at the ordinary temperature on copal, will, in the course of a year, have softened the whole of it, and will have dissolved a portion into a pure solution, which forms a perfect and colourless varnish. This is what l first used for painting with : it perfectly preserves the colours, and retains its original transparency. A still CHEMISTRY. larger portion of copal is dissolved, if about one ounce of camphor is first dissolved in each pint of turpentine; and, when used as a varnish or to paint with, the camphor evaporates away with the turpentine, leaving no defect. These solutions are all made cold. Water, or moisture of some kind, is nearly always present in the copal and in the solvents ; and the more it can be expelled, the more readily will the copal be dissolved : and, to prove that water is injurious, I took one portion of the same powdered copal that 1 subjected to the other solvents, and just wetted it with water, but not enough to be able to pour any from it : this I left a few hours, hoping it might soften some parts, and thereby liberate the rest. Another portion I just wetted with alcohol, and a third portion was left dry : to these three I added spirits of turpentine, and corked them close, and occasionally shook them up. That which had been first moistened with alcohol soon became soft, and in a week or two was dissolved, giving a varnish, a portion of which was ropy. The dry copal in turpentine was softened, and a portion dissolved : this required nearly a year to be soft enough to give up all that the turpentine could dissolve ; whilst the portion that had been moistened with water never would dissolve in the turpentine. By shaking the vial, portions had ad- hered to the sides ; but these were only softened enough to become smooth as though they were melted to the sides, but not to run down ; and this sample, year after year, exhibited the same appearance : the re-adhesion was just enough to obliterate the pulverised character, and no more. Thus, water is shewn to be a formidable opponent to the solution of copal, and alcohol a very great assistant to its solution in turpentine. The solubility of copal, in either oil of spruce or oil of 5 (> CHEMISTRY. lavender, is likewise much improved by first wetting the powder with alcohol, and the varnishes so prepared dry quickly and completely. It is known to many, that oil of turpentine, by long exposure to air, becomes so thick as to appear like a strong varnish ; and glass and china-painters have availed themselves of this property, it being stiff enough to hold their colours on, and yet, with the heat of burning them in, will all dry away, leaving no coally sub- stance to burn and damage their colours, either by soiling or decomposing them. If powdered copal, in sufficient quantity, is added to the oil of turpentine while so ex- posed to air, the whole will be softened to a consistence like treacle. This increased solvent power is not owing to what the oil has lost by evaporation, for heat precipi- tates the copal, or most of it, and restores to the turpentine its original thinness ; or if fresh oil of turpentine be added, it will also precipitate the copal, and leave the fluid thin about it. A small quantity of oil of turpentine will soften copal all through, leaving it transparent, but stiff and ropy ; a large quantity poured on a small quantity of copal (and more quickly, if it is boiled on it) will dis- solve one portion, and leave the rest in a white crusty powder, or much like dry crumbs of bread, very fragile, as though it was quite an insoluble substance. Oil of turpentine, thickened by what it has dissolved of one por- tion of copal, will become a better solvent of a further portion. The older these solutions are, the more strongly do they indicate a smell of ether when the bottles are opened. Hence, copal appears to consist of two parts: one soluble in the essential oils, and its presence appears requisite to enable the fluid to dissolve the other part ; but, by carefully avoiding; moisture, and well softening; the copal with alcohol, I am now enabled to dissolve the CHEMISTRY. 57 whole in oil of turpentine, so as to use it all as a varnish ; though I would much rather have, for this purpose, oil of spruce. I have shewn above that water resists solution, and, I think, the tendency to precipitate by mere dilution is par- tially occasioned by the presence of moisture in the ad- ditional solvent. Alcohol alone being a good solvent, may, on that account, be supposed to aid the other sol- vents ; but I believe it also acts by taking possession of any moisture that may be present. The oil-varnish makers subject their oils and their resins to heat continued sufficiently long to expel all moisture, and then the two will more readily combine, and form a varnish of any recpiired strength ; but all these are more or less coloured by the heat. In the cold, I. can obtain varnish quite free from colour, but with heat I never could avoid some colour ; therefore, my endeavours were chiefly directed to obtain solutions without heat, yet the varnish that Mr. Neil prepared for the Society with oil of spruce and copal, the moisture of which he expelled by heat, was good, and had so little colour, that few painters would object to it. I have said above, that I use these essential -oil varnishes as the only vehicle to mix up my colours for painting; but they dry so quickly, that I should either lose much paint or much time if I had not found a ready re-solvent ; and here moisture, if present, shews its mis- chief. When the paint becomes too stiff, common oil of turpentine will occasionally thin it, but it frequently precipitates it. I next tried ordinary spirits of wine, and found that it would quickly dilute the paint once or twice, or re-dissolve it if quite hard ; but when oftener applied, it precipitated the paint and copal, like leather, 58 CHEMISTRY. leaving a clear fluid above. Knowing that this process conveyed a little water each time it was added, I took good alcohol, and found it would dilute or re-dissolve the dry paint very often (enough to answer my purpose) ; but even with this, the paint and copal would sometimes go down ; suspecting this might be owing to moisture, 1 dried the paint with a heat a little above boiling water, and then the alcohol acted as well as ever in re-softening: the paint. I therefore conclude, that in this case water is the chief cause of the precipitation. The presence of water is likewise very injurious in the solution of lac in spirits of wine, commonly called lacquer, and chiefly used for varnishing polished brass. If the spirit contain so much water as to be only just able to dissolve the lac, it can scarcely be used ; for it will require the brass to be made so hot, to drive off the water with the spirit, that it will render the varnish rough; and if the usual heat be employed, which is such as can just be handled, the water will remain after the alcohol is driven off and will prevent the lac from adhering to the brass; whilst the purer the alcohol, the lower is the heat that will serve to drive it off, and leave the lac bright, and uniformly spread over the brass so clear as to be invisible, and as firmly united as if it was melted on it, which, in fact, it is, by the agency of the alcohol. Another evil in lacquer is its being too thick, that is, in not having alcohol enough to allow time for spreading on and remov- ing the brush before the varnish has become so thick as to stick some of the hairs fast. PAPERS IN CHEMISTRY. No. I. APPARATUS FOR CLEARING BEER. The Large Silver Medal ivas this session given to Mr. R. W. DICKINSON, of the Albany Brewery, Kent- road, on an Apparatus for clearing Beer ivhile in a state of fermentation. A model of the apparatus is placed in the Society's repository. The brightness of malt-liquor depends much on the ac- curacy with which the yeast produced by fermentation is separated ; and the usual method of effecting this is the following. The wort, after being duly boiled with the proper quan- tity of hops, is transferred into coolers, and, when its temperature has thereby been sufficiently lowered, it is removed to a large vessel called the gyle-tun, either open 24 CHEMISTRY. or fitted with a moveable cover. Here, after being mixed with yeast, it undergoes the first fermentation. The half- fermented liquor is then put into barrels lying on their sides, with the bung-hole uppermost, out of which the yeast is continually discharging itself, till the fermentation has ceased, or nearly so. During this time the barrels are examined once, twice, or oftener, in the day, and are filled up with fresh liquor in proportion as the yeast works off, so that the barrels shall be always full, in order that the yeast, as soon as it rises to the surface of the liquor, shall flow off entirely. The object of Mr. Dickinson has been to conduct the whole of the fermentation in the barrel in which the beer is stored, and at the same time to provide for the escape of the yeast without the constant attention and expense of filling up as commonly practised. For this purpose he places the barrels upright, and, having filled them with the wort previously boiled and cooled and mixed with the proper quantity of yeast, adapts to each barrel the following apparatus. It consists of a tub c c, fig. 1, plate I., about the size of a peck measure, with a wooden cover e e, and having a vertical open pipe of pewter b, passing through the bot- tom : this pipe rises nearly to the top of the tub, and almost as soon as it has passed through the bottom expands into a broad flat margin, in order that it may be placed securely over the bung-hole of the barrel a a, with paper pack- ing if required. Into the tub is put liquor of the same kind as that with which the barrel is filled, except that it is not previously mixed with yeast : the quantity of the liquor (about one-twelfth) is such as will be rather more than suf- flate 1 4 CHEMISTRY. 25 ficient to supply the loss in the barrel in consequence of the fermentation. As soon as this process begins, the yeast, rising to the surface of the liquor in the barrel, passes through the bung-hole into the pewter pipe, and flows out of the upper end of it into the tub, the lighter particles, in the state of froth, floating on the surface of the liquor, and the heavier ones subsiding to the bottom. The va- cuity occasioned by the separation of the yeast is con- tinually supplied from the clear liquor in the tub, which flows in through the lateral hole d, in the vertical pipe. It is the opinion of Mr. Dickinson, that by the adoption of the above described apparatus he saves about one and a half per cent, in quantity, and that the quality of the li- quor is also considerably improved, besides avoiding the use of the gyle-tun, and the expense and loss of transfer- ring the liquor therefrom to the barrels, and the loss of liquor in filling up according to the usual mode. CHEMISTRY. 2 (> No. II. [MPROVED SAFETY-CHAMBER TO THE OXY-HYDROGEN BLOW PIPE. The Large Silver Medal was this session presented to Mr. Henry WILKINSON, of Ludgate-hill, for his im- proved Safety-chamber to the oxy-hydrogen Blow-PIPE. The following communication has been received from Mr. Wilkinson on the subject, and a mo- del of the apparatus has been placed in the Society s repository . Sir, Ludgate-hill, February 11, 1824. In consequence of an explosion which took place last November, while volatilizing- platinum with Mr. Gurney’s oxy-hydrogen blow-pipe, I was induced to try some expe- riments, in order to render that instrument, if possible, more secure. (It is but justice here to observe that at the time of the explosion I was using a much larger and longer jet than any of those sold with the blow-pipe, and differ- ently situated.) If the Society should consider the result I have obtained worth notice I shall be happy to prove the correctness of it by experiment and testimony. The construction of Mr. Gurney’s safety-tube is known to the Society ; the chambers in which not being able, un- der certain circumstances, to arrest the retrograde motion of the flame, I thought it probable that the interposition of any bad conductor of caloric might effectually prevent its return : how far 1 have succeeded may be judged by the CHEMISTRY. 27 following experiments made with the same jet, all other circumstances of position and dimensions being correctly alike. Having first chosen such a jet and arrangement of parts as would always explode with Mr. Gurney’s safety-tube on diminishing the pressure, and would frequently so at the moment of ignition, I removed that and substituted another safety-tube entirely filled with wire-gauze ; I still, however, found the flame return, driving out the cork every time, as in the preceding experiment. I then tried a third tube, into which I had introduced, between the layers of wire-gauze and in the centre, some asbestus, previously beaten with a mallet and pulled out, so as to resemble floss silk. With this I could never suc- ceed in causing an explosion to take place, although the flame of a wax taper was kept close to the orifice, and the pressure was diminished as gradually as possible ; nor did it explode even when the orifice of the jet was enlarged. These experiments have been repeated by myself, and by a friend, a great number of times, with the same result. I am not aware that asbestus has ever been proposed or em- ployed before for this purpose. The advantage of using this substance is evident, as the fibres cross each other in every possible direction, thus forming a filter for the gases to pass through much finer than any wire-gauze, and by its bad conducting quality it prevents those layers of wire- gauze which are behind it from being heated when an ex- plosion takes place in the cavity of the jet. The cylinder f f, fig. 2, plate I., is of brass, about three quarters of an inch long and the same diameter internally, (the figure represents it of the real size), and is filled in 28 CHEMISTRY. the following order, beginning at the end into which the jetj, screws. The wire-gauze being cut to fit the cylinder correctly, each disc is introduced separately, having a small quantity of glazier’s putty round the edge, and is pressed in with a piece of wood turned to fit the cylinder. After the first ten layers of wire-gauze g, have been introduced, a layer of asbestus h, is inserted one-eighth of an inch thick, equally laid and not pressed in too hard, then come ten more layers of wire-gauze g, another layer of asbestus h, and, lastly, twenty discs of wire gauze g, the two ends of the cylinders being concave, in order to afford as large an area as possible for the passage of the gas from the entrance pipe i, to the jet. As the object of this arrangement is to keep the last series of wire-gauze cool by the interposi- tion of bad conductors of caloric, it appears probable that the safety would be rendered theoretically more perfect if the cylinder itself were a bad conductor, such as earth- enware having brass caps cemented on the ends ; or plati- num, if metal were made use of, on account of its low con- ducting power. A brass cylinder, however, appears to be perfectly safe for every purpose, as I have never been able to cause an explosion to take place, although I have allowed the flame to retrograde, by gradually diminishing the pres- sure from GO to 100 times successively, while using very long jets of one-eighth of an inch diameter at the aperture and much larger within. The wire-gauze should not be finer than from 3600 to 4900 apertures to the square inch, as it is liable to be fused by the return of the flame. I found that when I used wire-gauze with 8100 apertures it was destroyed in a very short time. CHEMISTRY. 29 The model which accompanies this letter is made of glass, in order to show the internal arrangement. I am, Sir, A. Aik hi, Esq. & c * ^ c * Secretary, Sfc. SfC. HENRY WILKINSON. No. III. STOP COCK FOR TRANSFERRING COR- ROSIVE GASES. The Silver Vulcan Medal was this Session presented to Mr. T. GRIFFITHS, Church-street, Kensington, for an improved Stop-cock for Chemical purposes, &c. A model of his invention has been placed in the Society s repository. The common brass stop-cocks, if they have been employed for confining acid or other gases, especially when under pressure, are soon corroded throughout their whole interior extent, so that the plug or key becomes immoveable, and the bore filled up with a salt of copper, the consequent re- sult of chemical action upon the metal of the instrument. A stop-cock made entirely of glass has also many disad- vantages : its size and clumsiness of form, together with the difficulty of uniting it securely to other apparatus, are inconveniences often felt by the experimentalist. To obviate them, and to offer a method in which stop- cocks of the common form are united with security against CHEMISTRY. 30 the attacks of active chemical agents, is the object of the present communication. In accurate experiments on the absorption of gases by solid or other bodies, the advantage of having an appa- ratus not liable to be acted upon by the substances under examination will be readily acknowledged. Platina is the material best adapted for this purpose, if its high price did not in most cases prohibit its use ; most, or, perhaps, all its advantages may however be obtained in the method about to be described, and at a comparatively moderate expense. The invention consists in making a stop-cock of the usual form, but of rather smaller dimensions, and selecting a piece of platina wire of sufficient thickness to allow a hole being drilled through its axis ; this operation forms a thin tube of platina, which is afterwards accurately fitted into the bore of the brass stop-cock, leaving about one- sixteenth of an inch projecting at each end, which is to be opened and extended so as to cover each extremity with a plate of platina. The brass plug or key has a platina tube secured as above described, with the addition of two small discs of platina, placed at right angles to the gas- way or bore ; these, together with the platina tube and brass parts of the instrument, are ground down perfectly air tight. It will be obvious from this explanation, and upon re- ference to the engraving, that whether the stop-cock be open or closed, platina is opposed to the action of the gas or other agent. In the one case it protects the gas-way and ends of the instrument, in the other the small disc of platina prevents corrosion of the plug. If it were desired to confer security to a moderate ex- tent upon a stop-cock as usually employed, this. may be F/aU 3. I/ / A’ ,/ . c(wr&/tr/'r Z Zn/r/s . /■) White lead Grind for use. Red Brown. Take brown sulphate of iron calcined dark 1 > Flux, No. 1, .... 3 J Grind for use. Vandyke 58 CHEMISTRY. Vandyke Brown. Melted together in a crucible, and drawn out with curl- ing tongs with so much metal it will not pour out freely. Grind for use. Black for painting and mixing zvith other colours. yellow heat in a crucible, till quite black, then washed in * la this and in other cases where a muffle is not in readiness, an earthen crucible washed with flint powder inside, or with dry flint pow- der rubbed inside of an inch thick, may be used, and the materials when partially melted, so as to stick together, are completely taken out without loss. Take of the above ... 5 Black oxide of cobalt 1 Grind for use. Another Brown. Take manganese ... r ‘' Red lead m • . i Flint pow'der calcined to stick together. Of this mixture take Of flux, No. 4, and iron filin 0 ^ melted as above Flux, No. 4, Take of umber, broken into small bits and calcined to a boiling water and dried 10 Black oxide of cobalt... 10 Blue flint glass Raw borax .... Red lead Calcine CHEMISTRY. 69 Calcine these well together and take of it... 2 I Flux, No. 4, l/ Grind in water for use. Blacks are compounded in other proportions of these in- gredients, and manganese is sometimes substituted in the place of umber. Another Black. Take umber calcined black 1 Black oxide of cobalt Black oxide of copper \ Flux, No. 4, 3 Grind these in water, and when dried place them on a piece of Dutch tile (washed over with flint-powder ground in water) in a muffle in a charcoal fire, and calcine them so as to stick together, then add to it one half of Flux, No. 4. Both these blacks if too soft, are hardened by adding a little black oxide of cobalt. Black for shading and drawing under the greens. Take manganase ...5"\ Royal smalt I J Ground fine in water, and calcined to a high degree of heat in a muffle. A beautiful Black, for solid grounds or inlaying, but does not mix generally. Take black oxide of copper 1 ) Flux, No. 4, 2 f Grind in water for use. } A Frit 60 CHEMISTRY. A Frit for transparent Greens. Take flint powder 3 'i Flux, No. 2, 3 Green pot-metal glass If Red lead 7f Raw borax 2f Green oxide of copper 1| - Melt them in a crucible, pour out the mass, and pound it in an earthenware mortar. Green. Take of the green frit 3 Of yellow enamel colour made up as before directed If If too soft add Naples yellow. Grind in water for use. Another Green. Take of green frit 5 -v Flux, No. 2, f > Flux, No. 6, 2f J Grind in water for use. Greens in painting on enamel, are formed of various shades by mixing blue and yellow, or blue and orange, &c. in different proportions. Blue. Take of black oxide of cobalt. ..4 Flint powder 9 Nitre 13 Mix them well in an earthenware mortar, and heat them in the crucible, in a strong fire of coke and charcoal, till perfectly CHEMISTRY. 61 perfectly melted ;* then pound the mass, wash it in cold water, and dry it. Of this take Flux, No. 5, Grind in water for use. f Another Blue. Take black oxide of cobalt Raw borax Melt them together. Of this mixture take 2 Blue pot-metal glass 10 Red lead Melt them in a very strong fire. If either blue is too soft, add a little royal smalt ; if too hard, a little flux made of blue glass 2, borax 1. Purple. Take fine grain gold from the refiners, and dissolve it to saturation in an aqua regia made of strongest Nitric acid 1^ Muriatic acid 3 >by measure. Distilled water 3 ' Make the solution in a clean Florence oil flask, placed on sand near the fire. Pour melted tin into cold water, and take of the clean parts of this tin... 1 Aqua regia, diluted with water in the same pro- > 4 portion as above / * If these preparations are not sufficiently fluid in the melted slate to pour out of the crucible, the colour will slick to a piece of steel bar when it is warm, and may be drawn out ; and sometimes the blues are made in crucibles lined with flint powder as before mentioned. Place 62 CHEMISTRY. Place the acid and the tin in a large bason covered \vith a plate, in a temperate heat; when the tin is all dissolved, add, Tin... 1 1 Strong; red fuming- nitrous acid ...]i / and instantly cover the bason with the plate, to prevent the fumes from escaping. After standing 24 hours, a little distilled water should be poured into the bason. The solu- tion of tin may then be put into a clean phial for use, adding to it a few grains of tin; examine it after four or five days, when the solution, if carefully made, will be of a fine and clear dark colour, and fit to make the purple with. Then of the solution of gold take sufficient to colour distilled water of a faint straw yellow, and drop gradually into it the solution of tin, and a most beautiful purple pre- cipitate will immediately be formed, which must be thrown as it is made into a large vessel, and two or three pieces of the melted tin should be put at the bottom. Mix the solution of tin with that of the gold in this man- ner till the last added drops occasion no turbidness in the liquor; the precipitate is then to be washed in several ho.t waters, filtered on the blotting paper and canvas, and while in a moist and soft state, mixed with flux, No. 4, finely powdered. The proportion of flux to the purple precipitate is always various, and is judged of by the mass being of a good rich and dark colour, as the ingredients are ground together on the plate glass. Care must be taken to grind this colour before it gets dry. Twenty-four grains of gold made into a precipitate in this manner will take two ounces of flux, and this may be a rule to the inexperienced practitioner. Rose CHEMISTRY. 03 Rose Colour. To a saturated solution of gold in aqua regia (containing twenty four grains of gold), diluted with 100 times its bulk of warm distilled water, having 20 grains of alum* dis- solved in it, add caustic ammonia drop by drop as long as any precipitate is thrown down, which wash in several hot waters. To 24 grains of gold, precipitated in this manner put Flux, No. 4 2 oz \ Flux, No. 3 2 oz J Mix them together wet, and grind them on a plate glass, adding, by a leaf at a time, 16 leaves of leaf silver ; when the whole is ground fine, let it be dried on the glass, scraped off, and put in a bottle for use. This rose colour grinds of a gray or slate colour, but after being ground, if placed in a muffle and exposed to a gentle heat, it will turn to a red ; but it is fit for use in either state. If too yellow, add a little purple; and if too purple, add more leaf silver. Another Rose Colour. Take purple made as before directed... 1 oz. Flux, No. 3, 4 Muriate of silver 10 gr. The latter ingredient is prepared by dissolving silver in aqua fortis, and precipitating it with common salt. Grind in water for use ; if too purple, add more muriate of silver. * The rose colour is sometimes made without any alum. Opake 64 CHEMISTRY. Opake White. Hartshorn shavings burnt in a crucible, in a charcoal fire, till perfectly white 11 Flux, No. 1, 1 ) Grind in water for use. Venetian white cake enamel 1 Flux, No. 8 | Grind in water, then calcine them together in a muffle. Flux, No. 2, pounded and washed, then dried and cal- cined in a muffle. It would not be difficult to exhibit a multitude of speci- mens of different tints, and fill a volume with descriptions of them, by combining these original enamel colours in various proportions : this, however, may safely be left to the taste and experience of the artist. My object has been to avoid every thing superfluous, and at the same time to explain the processes adapted to immediate practice in terms not liable to be mistaken. SIR, w hen I had the honour of explaining my Treatise on Enamel Colours to the gentlemen forming the committee of Chemistry, I was requested by them to produce the method of staining glass , with a view of adding it as a second part to the Treatise on Enamel Colours. I have inserted the most valuable information which I pos- sess on this subject in the paper that accompanies this letter, and CHEMISTRY. 65 and request that you will present it in my name to the So- ciety of Arts. I am, Sir, Your most obedient humble Servant, ROBERT WYNN. No. 3, Taylor's- Buildings, May 6th, 1817. To A. Aikin Esq. Sec. The Art of Staining Glass. In coloured glass, the whole body of the material is tinged throughout by means of some colouring ingredient uni- formly diffused through, or dissolved in, the substance of the glass. In enamelling, the colours, being ground up with an easily verifiable flux, are laid on the surface of metal, or porcelain, or glass, and are then exposed to such a degree of heat as shall just melt the enamel, and then fix it on the surface of the substance on which it has been applied. In staining glass, the colouring ingredients are mixed with water, or some other fluid vehicle, by means of which they are spread over the surface of a plate of glass, and when dry, are exposed to such a degree of heat, as by ex- perience has been found to be sufficient. The colour is then rubbed off from the surface of the glass, to which it does not adhere, and those parts of the plate which have been thus covered are found to have acquired a permanent and transparent tinge or stain, doubtless from some parti- cles of the colour having been absorbed, and fixed in the pores of the glass. In all the compositions for staining glass, silver, in some form or other, enters as an essential ingredient ; I shall therefore F 66 CHEMISTRY. therefore begin by describing the different preparations of silver that I make use of. Take two or thrfe ounces of pure nitric acid, dilute it with three times its bulk of distilled water, put it into a Florence flask, or any other convenient glass vessel, and add to it refined silver, by small pieces at a time, till the acid, though kept at a warm temperature, refuses to dis- solve any more. After standing quiet for some hours, pour off the clear liquor into a clean ground stoppered phial, and label it nitrate of silver. Preparations of Silver. No. 1. Dissolve common salt in water, and add nitrate of silver, drop by drop, till it ceases to occasion any preci- pitate ; there will thus be obtained a heavy white curd- like substance, which must be well washed in hot water and dried ; by exposure to light, it becomes of a dull purple colour. It is known by the name of muriate of silver, or Inna cornea. \ No. 2. Dissolve subcarbonate of soda, in water, and add nitrate of silver, as above described. The white preci- pitate thus obtained, when washed and dried, is ready for use. It is called carbonate of silver. No. 3. Dissolve subcarbonate of potash in water, and pro- ceed precisely as directed for No. 2. The white powder thus obtained is also carbonate of silver. No. 4. Dissolve phosphate of soda, in water, and proceed as already mentioned. The precipitate thus obtained is of a yellow colour, and is called phosphate of silver. No. 5. Take any quantity of pure silver rolled out into thin plates, and put it into a crucible, together with some sulphur. CHEMISTRY. 67 sulphur. When the'cruciblehas been a short time on the fire, (he sulphur will first melt, and then will gradually burn away with a blue flame. When the flame has ceased, add some more sulphur, and proceed as before; then take the silver out, and heat it red in a muffle ; it will now be white, and very brittle, and, after having been reduced to powder in a mortar, is fit for use. No. 6. Take any quantity of a dilute solution of nitrate of silver, and put into it a stick of metallic tin, warm it a little, and the silver will be precipitated in the form of metallic leaves, on the surface of the tin. Scrape it off, wash it in warm water, dry it, and grind it in a mortar. No. 7. Take any quantity of nitrate of silver, and put into it a piece of copper-plate ; then proceed precisely as in No. 6. The foregoing preparations of silver mixed with other ingredients, in the proportions about to be described, com- pose all the varieties of pigment which are requisite for staining glass. Yellow. Take silver, No. 2, 1 \ p Yellow lake 1 / Mix the ingredients, and grind them well with oil of tur- pentine mixed with the thick oil of turpentine; lay it on thin. Take silver, No. 1, .....1 White clay, precipitated from a so- lution of alum by subcarbonate of soda 3 Oxalate of iron, prepared by precipi- tating a clear solution of sulphate of iron by oxalate of potash 3 Oxide of zinc 2y ) Parts. Let 68 CHEMISTRY. Let the silver be ground first in water with the oxide of zinc and then with the other ingredients. This is in- tended for floating on thick. Take silver, No. 3. ...1 ) Yellow lake...d PartS ' Grind them in spirit of turpentine and oil, and lay the mixture on very thin. Take silver , No. 4, 1 ^ Yellow lake, 1> Parts. White clay \ ) Grind them in spirit of turpentine and oil, and lay the mixture on thin. t Orange. Take silver, No. 6, 1 Venetian red and yellow ochre, equal parts, washed in water, and calcined red 2 Grind the ingredients in spirit of turpentine, with thick of ditto, and lay the mixture on thin. Take silver, No. 7, 1) t Venetian red and vellow ochre ...1 $ %r Grind in turpentine and oil, &c., as the foregoing. If entire panes of glass are to be tinged orange, the propor- tion of ochre may be greatly increased. The depth of the tinge depends in some measure on the heat of the furnace, and on the time that the glass is exposed to it, which, though easily learned by experience, cannot be made the object of precise rules. ^ Parts. Red CHEMISTRY. 69 Red, Take silver, No. 5, I s Brown oxide of iron prepared by heating scales of iron, then quench- p ar ts ing them in water, reducing them to a fine powder, and lastly calcin- ing it in a muffle 1^ Grind the ingredients with turpentine and oil, and lay the mixture on thick. Parts. Take of antimonial silver, prepared by melting together one part of silver, and two ditto of crude antimony, and pulverizing the mass 1 Colcothar 1 Grind the ingredients in turpentine and oil, and lay the mixture on thick. Take antimonial silver, prepared as above, 1 1 Venetian red, and yellow ochre, of K Parts. each 1 J Grind, &c. as before mentioned. When whole panes of glass are to be tinged, the propor- tions of ochre or of colcothar may be much increased, and the ingredients should be ground in water. Of laying on the Colour. The method practised by most Stainers of glass is, to draw the outline in Indian ink, or in a brown colour, ground with turpentine and oil, and then to float on the colour thick, having previously ground it with water. But in 70 CHEMISTRY. in this way of proceeding it is very subject either to flow over, or to come short of the outline, and thus render the skill of the draftsman of little effect. My method is to draw the pattern in Indian ink, and having ground the colour as fine as possible in spirits of turpentine, brought to a proper consistence with thick oil of turpentine, to add a little oil of spike lavender, and to cover the outline entirely with this composition. When it has become dry, I work out the colour with the point of a stick and a knife from those parts that are not intended to be stained, and am thus enabled to execute the most delicate ornaments, and most intricate designs, with exactness and precision. If the colour is required to be laid on so thick that the outline would not be visible through it, let the colour be first laid on as smoothly as possible, and when it has be- come dry draw the outline upon it with vermillion water- colour, and work out the design as before. Besides the precision acquired by the above method, it enables the artist to apply different shades in the same de- sign ; whereas the old method of floating only communi- cates an uniform tint to the whole pattern. The artist should contrive to charge his furnace with pieces, the colour of which is ground in the same vehicle, and not to mix in the same burning some colours ground in turpentine and others ground in water. The pieces must also be very carefully dried, and must be placed in the furnace when this latter is moderately warm. To &ild Glass. O of pure mercury Parts. Warm CHEMISTRY. 71 Warm the mercury and then add the gold, previously making it red hot. When the gold is perfectly dissolved pour the mixture into cold water and wash it well. Then press out the superfluous mercury through linen or soft leather, and the mercury which runs through (as it retains some gold) should be reserved for the next opportunity. The amalgam which remains in the leather is to be di- gested in warm aqua fortis, which will take up the mer- cury, but will leave the gold in the form of an extremely fine powder. This powder, when washed and dried, must be rubbed up with one-third of its weight of mercury ; then mix one grain of this amalgam with three grains of gold flux (see the former part of this paper, p. 63), which is to be applied in the usual manner. Fifteen Guineas were this Session voted to Mr. James Callender, of King's Head Court , Holborn , for a Method of Seasoning Mahogany . The following Communications were received from him on the subject , and Specimens of the Maho- gany seasoned after his Plan are preserved in the Society’s Repository. SIR, I take the liberty of submitting to the consideration of the Society of Arts a method of seasoning mahogany plank in a few hours, which hitherto has not been done in less than a year. The importance of this method is considerable : in the first place a considerable part of the capital which is in- vested in wood lying to season, during many months, may be saved. In 72 CHEMISTRY. In the second place, as none of the small stuff, from two to six inches thick, is ever seasoned, according to the usual course of trade, all articles made of such wood, such as chairs, ballustrades, &c. must necessarily be excessively subject to warp, which is prevented by adopting my expe- ditious mode of seasoning. The following is the method I make use of. Having provided a steam-tight wooden box, capable of holding conveniently such pieces of maho- gany as are fit for chairs, &c. I adapt to it a pipe from a boiler, by means of which I fill the box (after the maho- gany has been put into it) with steam, the temperature of which is about equal to that of boiling water. The time required for inch and a-half wood is about two hours, and pieces of this thickness will become suffi- ciently dry to work after being placed in a warm room or workshop for 24 hours. The wood by this treatment is somewhat improved in its general colour, and those blemishes which are technically called green veins are entirely removed. It is also obvious, that the eggs or larvae of any insects which may be contained in the wood, will be destroyed by the heat. I have myself made use of the method described for a year and a-half, and Mr. Dalziel, 26, Great James-street, Bedford-row, and Messrs. Gee and Hole, King-street, Holborn, have by my advice, used the same practice with good success. I am, Sir, Your very humble Servant, JAMES C ALLEN HER. 16 , King’s- head-court, Holhorn-hill. To A. Atkin, Esq, Sec. Mr. CHEMISTRY. 73 Mr. Dalziel and Mr. Gee attended the Committee ac- cording to summons, and stated that they had adopted the practice of steaming mahogany as communicated to them by Mr. Callender, and which was in their opinion an ori- ginal invention of the candidate. They farther said, that they had found by experience, that the method of steaming was an effectual way of seasoning small-sized mahogany for chairs and other similar articles, and that mahogany so seasoned did not crack or warp by exposure to heat, a de- fect that wood, even after being seasoned in the ordinary way, is very liable to. A piece of mahogany abounding in green veins had been sawn in two, one half had been exposed to steam, the other remained in its original state ; the latter of these was de- dared by the above-mentioned cabinet-makers to befit only for frame-work, while the former was in their opinion ap- plicable to outside work. The following certificates also were delivered in to the Committee. Certificates. Sir, You have known me in the wood trade sixteen years. I was twelve years prior to that time in the same trade ; but I never heard (either among cabinet-makers, chair- makers, or any other branch in the wood line), of steam being applied either to hard or soft wood, to take out the sap or to season them. I am, Sir, Your humble Servant, Thomas Sadgrove. Mulberry-court , Wilson-sheet } Moorfields. May 1 it, 1817. N. JB. 74 CHEMISTRY. \ N. B. I think if any thing of the kind had been prac- tised I must have heard of it. To Mr. C. Callender, 8cc. Sir, I have been upwards of twenty years in the mahogany trade, but never heard of steam being applied for the pur- pose of drying mahogany. I am, Sir, Your most obedient Servant, M. Gillcock. No. 35 , Maid-lane , Banksidc, Southwark. To Mr. Callender, 8cc. Sir, I have been above fifty-five years in the cabinet-making business, having served my apprenticeship to Mr. Seddon, of Aldersgate-street, where there were above 200 men em- ployed in his manufactory ; but I never heard of steam be- ing applied for the purpose of drying wood, and should your method answer the purpose, it will be a most valuable acquisition to the trade. I am, Sir, Wishing you success, Your obedient Servant, George Biggs. No. 9 , Clerkcnwell Green. To Mr. Callender, &c. Sir, Having seen mahogany dried by steam in your shop, 1 must CHEMISTRY. 75 must confess that it far excels any way of drying mahogany I ever saw : as regards the originality of the process, I can only say, although I have been in the cabinet business between twenty and thirty years, I never heard of steam- ing mahogany to dry it, till you informed me of your invention. I am, Sir, Your obedient Servant, Henry Brown, Cabinet-maker. No. 96, Curtain Road, Shoreditch. May 1st , 1817. To Mr. Callender, &c. The Gold Medal was this Session voted to W. R. Clanny, M. D. of Bishopswearmouth , Dur- ham, for a Steam Safety-Lamp. The following Communications were received from him , , and one of the Lamps is preserved in the Society’s Reposi- tory. SIR, I have the honour of transmitting you one of my steam safety-lamps, and a copy of my pamphlet on safety-lamps, for the inspection of the Society of Arts. From the multiplicity of experiments which I formerly made with fire-damp, upon a large scale, at the neighbour- ing collieries, I am happy to report to the Society of Arts, that steam is an admirable preventive of explosion ; and in this I am corroborated by other experimenters who have lately 76 CHEMISTRY. lately made similar trials with carbonated hydrogen and steam.* My steam safety-lamps may be constructed of any size, from eight inches in height, to more than three feet ; and, when much light is required, the lamps should of course be made large, such as those in use at the Painsher engine- pit, of which some account will be found in the inclosed Certificate of Mr. Wood, the viewer. In these lamps the steam is constantly extricated, and in considerable quantity, which not only keeps the whole ap- paratus cool, but is likewise an excellent medium for causing the fire-damp to burn silently, and without explosion at the wick of the oil-lamp, as Mr. Wood has stated in his Certi- ficate : such is the strength of light afforded by these lamps, that it may be thrown to a considerable distance by a mir- ror or mirrors in those parts of the mine where there may be such a scarcity of oxigenthat no light could be supported, and where the pitmen have hitherto carried on their work in darkness, as is often the case in coal-mines. These lamps have given a clear light for sixteen hours, without trimming or a second supply of oil, as the workmen of the Rainton colliery, near the city of Durham, have informed me. I might say much more upon this subject, but shall leave the rest to the investigation of that illustrious body into whose hands I commit the result of much exertion, anxiety, and trouble. Mr. Easton, viewer at Birtley in this county, has authorised me not only to mention his name, but to re- fer any gentleman to him who may be desirous of ascertain- * Vide Philosophical Magazine for Dec. 1816 ; Annals of Philosophy, Vol. 9, p. 152, &c. ing CHEMISTRY. 77 ing his opinion of the value of these lamps, which he has had in use under his eye for some time. I am, Sir, Your most obedient, very humble servant, W. REID CLANNY. Sunderland , April 2, 1817. To A. Aikin, Esq. Sec. Extract of a Letter addressed toG. D. Midgley, Esq., one of the Chairmen of the Committee of Chemistry. 1 beg to remark, that the water should be put into the cylinder of the steam safety-lamp at the boiling point, and that the lamp is so constructed, that the flame keeps the water always at the boiling point, and thereby extricates an abundance of steam under all circumstances, as has been clearly proved by the constant use of these lamps at the Painsher engine-pit for several months, and in several other collieries where there are considerable quan- tities of fire-damp. I acknowledge that I did not antici- pate any objection to these lamps on the score of safety, after so many months severe trials in different highly-ex- plosive collieries. Three months ago, I accompanied Mr. Easton, an emi- nent viewer in this county, and a few workmen, into a large cavern of fire-damp, in the Gateshead-park colliery, and observed, that the flame of the lamp was silently extin- guished by reason of the great quantity of fire damp, and consequently inferior proportion of atmospheric air which we found in this cavern. After all, should any doubts still remain, I beg to say, that I will myself take my steam safety-lamp 78 CHEMISTRY. safety-lamp into any colliery in the united kingdom, let the fire-damp be ever so pure or so great in quantity, at any time and in any manner which may be desired ; for such is the value of steam, that in no case and under no circum- stances can any accident ever happen from fire-damp, when it is so used as a preventive of explosion. W. REID CLANNY, M. D. Sunderland , May 14, 1817. Certificates. I certify that fire-damp is frequently discharged at the engine-pit at Painsher colliery, and that no light has been taken into this pit for upwards of two years, till the engine- wrighttook Dr. Clanny’s original water-lamp into it about eight months ago, which permitted him to examine that pit in every part, and to make his report accordingly. The shaft of this pit now requires to be repaired, and Dr. Clan- ny’s original safety water-lamp was taken into it, when it burnt very bright for four hours, but the workmen having occasion to come to bank, when they went down with the same lamp again, after using it for about half an hour, the fire-damp exploded within this lamp, and with the greatest safety. The engine-wright took down sir H. Davy’s ware gauze-lamp, which he had carefully trimmed with the best oil, and to render the matter as certain as he could, being very desirous of having a light in this pit, he placed the wire gauze-lamp in an old lanthorn (which had the glass taken out) in order to screen it from the wet, and descended the said pit; but the lamp went out, although he took the greatest care possible from his wish to have a light in this pit when at work : the trial was afterwards made in the same CHEMISTRY. 79 same way, but it turned out equally unsuccessful, so that sir II. Davy’s lamp could not be made to burn in this pit, although the greatest care was taken to make it do so. Dr. Clanny’s steam safety-lamp, in its present improved state, was then tried, which gave the workmen a clear and very brilliant light in all parts of the engine-pit, and for any length of time that they wished ; for it has never gone or been put out since they put it to use, and, from the increased size of the flame at the wick of the lamp, which frequently occurs, there is no doubt but it burns the fire-damp, which is of the greatest importance, and, from the steady and permanent light which it affords, the workmen, are enabled to get rapidly forward with their work. John Wood. Puinsher Colliery, September 10, 1816. Newbottle Colliery Office , June 3, 1817. Dear Sir, I am glad to inform you that we have had your steam safety-lamps in use at the above colliery for some time past, and that the head wastemen and others who travel the old working with him are well satisfied with the utility and safety of the same ; and also they state to me that they are not afraid to pass through the most inflammable part, should they meet with it in their travels. Likewise they say, the brilliant light which shines from it far exceeds the naked flame of our small candles which we use for working the coals, which makes the said lamp very use- ful indeed. Also they say, after the wick is lighted it will burn 80 CHEMISTRY. bum for eighteen or twenty hours without snuffing, or any supply of oil or water to it. I am, Dear Sir, Your most obedient Servant, Andrew Watson. To Dr. Clanny. Dear Sir, Your steam safety-lamp (for the use of coal mines) that I experimented upon answered fully to my expectation ; gave a very good light, was in a variety of mixtures of air, which did not at all affect it, until it was immersed in pure carburetted hydrogen, when the light w 7 as extinguished. From the time you made some slight alterations in the lamp, and returned it as a present to the colliery, it has not been tried, the colliery not being in a situation to require the use of any safety-lamp. I remain, Dear Sir, Your’s, sincerely, Thomas Easton. Birtley , June 6 , 1817 . To Dr. R. Clanny. Reference to the Engraving of Dr. Clanny' s Steam Safety- Lamp, Plate 1. t a, figs. 1. 2. 6. The cylinder which holds the oil and the wick. The piece through which the wick passes (fig. 7) is received into the socket of the cylinder, fig. 8, which is purposely f an9?/^J (y Sl?n Atl/r yy CHEMISTRY. 81 purposely made deep, in order that as little as possible of the wick may be consumed, and thus the necessity for fre- quent snuffing may be avoided. b, figs. 2, 4, 5, The boiler, filled with hot water, and kept in a state of ebullition by the heat from the flame of the wick placed directly below it. c, figs. 1, 2, 8, A row of holes surrounding the base of the lamp, through which the air enters. d, figs. 2, 4, 5, 6, A cylindrical tube, which conducts the air that has entered through c into the cover of the boiler. It supports the boiler, and is composed of two pieces fitting closely on each other, but capable of being separated for the purpose of detaching the boiler with its appendages (fig. 5), in order to fill or empty it. e, The cover of the boiler (fig. 2), shown by itself (fig. 3), within which the mixture of the air and steam takes place. f ft 2, 4, 5, 6, Two tubes passing though the boilers, and perforated at their lower extremities, in order to convey the air mixed with steam into the body of the lamp. g g, fig. 2, A space between the lamp and its case, through which the air that has been burnt passes into the chimney h. i, figs. 1, 2, 6, The window made of clear glass half an inch thick. k, fig. 2, The handle. Fig. 1, is a front view of the lamp, the whole outer case of which is made of strong tinned iron, except the window. Fig. 2, is a vertical section of the same, at right angles to fig. 1. Fig. 4, a view of the top of the boiler and its append- ages, the cover being removed. G Fi £T. 6 82 CHEMISTRY. Fig. 6, a horizontal section of the lamp through the middle of the window. Fig. 8, the cylinder to hold the oil and wick, showing the depth of the socket which receives the piece (fig. 7) ; behind it is the air tube, d, in section. The Silver Medal and Ten Guineas were this Session voted to Mr. Thomas Stiles, of Norwich , for his method of preparing an Ex- tract of Sprats. The following Communica- tion has been received from him on the subject. DEAR SIR, ' The attention shown by you in the case of my method of curing herrings in 1813, induces me to hope that you will give me an opportunity of presenting before a Com- mittee of the Society an invention which, after much labour, has been crowned with success. I have submitted it to the inspection of competent judges, one of whom is industriously communicating the utility of it to the circle of his acquaintance. My friend, William Spratt, Esq., of the city of Norwich, will have the honour of presenting to you a sample of Essence, liquid and solid, prepared from my cured fish. These articles can be produced in any quanti- ties, should the public receive them with the same avidity as the individuals within the circle of my acquaintance. It is equally suitable for foreign and home consumption, being so highly charged with preservatives as to warrant its keep- ing in any climate. I need not enlarge on the utility of this invention CHEMISTRY. 83 invention as you have the article before you, which will plead my cause. The Essence herewith sent is prepared from fish of my curing in November, 1813, which are now as bright as they were on the day of pickling, of which 1 have several cwt. now by me. I am, Dear Sir, With every mark of respect, yours, THOMAS STILES. Norwich, September 1 6 th, 1816 . To Dr. Taylor, Sec. The process by which Mr. Stiles makes his liquid and solid Essence of Sprats is as follows : He commences by salting and curing any quantity of sprats, according to the method described in the 31st Vol. of the Transactions of the Society. He then pours the sprats with their liquor into a copper, and brings them to a boiling heat ; after which they are put into hair bags and strongly pressed. The liquor thus obtained is put into a vat or any other convenient vessel for a few days, till the oil has risen to the surface ; the oil is to be removed very carefully, and the remaining liquor (called by Mr. Stiles Essence ) will be found to be wholly free from the coarse peculiar flavour of the sprat, and to be scarcely distinguish- able from the essence of anchovy. In order to prepare the solid essence, he takes a quantity of wheaten flour and carefully dries it in a water bath for the space of 60 hours, the lumps being then broken to pieces he mixes it well, by hand, with the liquid essence till the mass is about the consistence of cream, adding at g 2 the 84 CHEMISTRY. the same time a little bole armenic to give it a red colour. He then reduces the mass by farther evaporation in a water bath, stirring it constantly with a wooden spatula till it has acquired the consistence of butter; the preparation is then complete, and is packed in barrels for sale. PAPERS P A P E II S IN CHEMIST R Y. N° I. DISCOVERY OF CHROMATE OF IRON IN SHETLAND. The smaller , or Isis Gold Medal of the So- ciety was this Session voted to Samuel Hib- bert, M. D., of Edinburgh , for the discovery of Chromate of Iron in Shetland. The following communication has been received from him on the subject . 5, Ilill Place, Edinburgh, SIR; February 7, 1820. I HAVE the honour to make a communication to the Society of Arts, &c. &c., respecting the discovery which I originally made two years and a half ago, of the Chro- mate of Tron in the Shetland Islands, which substance is at present obtained for the manufacturers of colours at a considerable expense from the United States of America. Since a notice first appeared in the journals relating to the discovery, considerable inquiries have been made concerning it ; but, that I might not create expectations 24 CHEMISTRY. which could not be realised, I was unwilling to make further communications on the subject until I had made a second visit to Shetland, when I ascertained that it exists there in great abundance. Conceiving, therefore, that the patriotic Institution of London for the promotion of the Arts and Commerce of Great Britain, was the most suitable medium through which the knowledge of the place and circumstances under which the chromate of iron is found might be first communicated to those who are commercially interested in the discovery, I have taken the liberty of transmitting to you a set of specimens,* which, in reference to the annexed description, will illus- trate the varied character of the mineral. If my discovery shall be considered as a contribution to the commercial resources of the British Islands, it will afford me some recompense for the considerable time and labour which 1 have expended in the prosecution of the search after this important ore. I am, Sir, A. Aikin, Esq., &c. &c. Sec. Secretary, fyc. $c. Samuel Hibbert, M.D. Circumstances under which the Chromate of Iron is found in Shetland. The Chromate of Iron occurs in the Serpentine rocks in the neighbourhood of Balta Sound, in the Island of Unst. I was first led to a search after this ore by ob- serving innumerable fragments of it strewed about the hill in which it is found, and even contributing to strengthen the fences of the country. It is observed in the form of imbedded and insulated masses, at Buness, close to the house of the proprietor, Thomas Edmon- * Which arc now in the repository of the Society. CHEMISTRY. 25 stone, esq. The extent of the greatest mass is not, how- ever, ascertained, as it is on one side concealed by the sea, and on the other by the deep soil of a meadow. It was traced 3 feet in breadth and fifteen feet in length. At Hagdale, near Haroldwick, the chromate of iron occurs in the form of numerous thin ramifying veins, but these are only from 2 to 3 inches in breadth, sometimes increasing to the breadth of 5 or 6 inches. Many masses are elsewhere observable, extending a few feet and then losing themselves in a general dissemination throughout the serpentine rock in which they occur. This dissemination consists in the diffusion of granular particles of the colour and size of gunpowder. It is evident from this description that the most pro- mising appearance of the ore is adjoining the house of Mr. Edmonstone, and from this gentleman, whom I have made acquainted with all the circumstances of the mi- neral, any commercial inquiry will meet with the most satisfactory answer. Letters may be directed, “ Thomas Edmonstone, Esq., of Buness, Island of Unst, Shetland.” Upon the encouragement, however, from London will depend the renewed searches after the chromate of iron, not only on Mr. Edmonstone’s grounds, but in the ad- joining hills, which are the joint property of several landed proprietors in Unst. From the quantity, therefore, of the ore which has been found in detached portions on the hills, and from the promising appearance on Mr. Edmonstone’s grounds, I would submit to the manu- facturing chemists in London the propriety of rendering to the Shetland gentlemen every scientific assistance which they may require from their advice, or even if wanted, from other exertions in prosecuting the search after this ore, provided its quality suits their purpose. It appears to me that some serious obstacles cannot fail to 26 CHEMISTRY. result from the inexperience of the Shetland gentlemen in whatever concerns the operations of mining. Vessels trading from Leith to Shetland visit Balta Sound almost every month in the course of the Spring and Summer. In furnishing the foregoing particulars relating to the chromate of iron, I have only to add that I shall be happy to answer any personal inquiries on the subject, concerning whatever I may have left unexplained. Samuel Hibbert, M. D. Portions of the specimens of chromate of iron trans- mitted by Dr. Hibbert were put into the hands of several members of the Society for examination, with respect both to the quality and richness of the ore as compared with that imported from the United States. Samples of chro- mate of lead prepared from the American and Shetland varieties of chromate of iron were laid before the Com- mittee by Mr. Midgley, one of the chairmen of the com- mittee of chemistry, who has had large experience in this branch of chemical manufacture. The result of this gentleman’s investigation (confirmed by the experiments made by other members of the Society) is, that the ore from Shetland in quality is quite equal to that imported from America, and in richness, as far as can be judged from a few specimens, is superior. C H E M I S T R Y. 27 N° II. GLASS HYDROMETER FOR SPIRITS. The smaller, or Isis Silver Medal was this Session voted to Mr. Henry Stokes, of Hatton Garden , for his Hydrometer for Spirits. The following communication has been received from the Candidate on the subject, and one of his Hydrometers has been jilaced in the repository of the Society. 110, Ilatton Garden, SIR; March 7, 1820. I request, through you, to lay before the Society for the Encouragement of Arts, &c. 8cc., a Glass Hydrometer for ascertaining the specific gravity of spirits. This in- strument will be found to possess quite sufficient accuracy for all practical purposes, is cheap, and of very easy ap- plication, as it requires the assistance neither of a book of tables, of a sliding rule, nor of weights. By means of it the value of a given spirit may be ascertained to one- fourth of a degree above or below proof ; and hence I conceive it is likely to be of great service to those dealers in spirituous liquors who either object to the cost of the instruments employed by the excise and by the distillers, or who feel embarrassed in making the calculations re- quired for the correct employment of them. The very fragility also of the material of which it is made (which by 28 C H E M I S T R Y. many may at first sight be considered as an objection to the use of it) is in fact, if duly considered, a real advan- tage. Accidents will occasionally occur in the use of the hydrometer as of every other instrument, either by letting it fall on the ground, or by its coming too rudely in con- tact with other hard substances. When this happens to a hydrometer made of metal, the ball of it being thin, will be more or less indented, and therefore, in a degree pro- portioned to the injury, will be rendered ever after incor- rect. Many persons in the habitual use of the hydro- meter are entirely ignorant of the principles on which it acts, and therefore of the injury which the slightest in- dentation will inflict on its accuracy, and consequently on its utility ; and even those w ho are w r ell aw 7 are of this will feel no small reluctance to discard an expensive instru- ment, unless the injury which it has received should be considerable. By the employment of the glass hydro- meter, on the contrary, all sources of error arising from casual injury are effectually prevented : a slight blow, such as would, in a small degree, derange the metallic hydrometer by indenting it, will not affect the glass hy- drometer on account of the elasticity of the material ; and a harder blow, by breaking the instrument, puts the pos- sessor indeed to the expense of a new one, but at the same time secures him from the errors arising; from the use of a defective instrument. The only real objection to the use of glass hydrometers is, that, as made hitherto, they have not been sufficiently comparable one with another ; this is, however, entirely obviated in the instruments of my construction ; three of which, differing in the length of their respective stems, accompany this communication, and which I beg leave respectfully to recommend to be put by the Committee to the test of experiment. The graduation of the instruments is made to cones- CHEMISTRY. 29 pond exactly with that projected by Sikes, and at pre- sent employed by the excise. Their construction may be explained in a few words, and their use by means of an example. Reference to the Plate of Mr. Stokes’s Hydrometer . A, fig. 4, plate I, is a spherical ball, with a short tube at the bottom, connecting with a smaller bulb B, in which is contained the quicksilver requisite to bring the instru- ment to its real weight so as to correspond with the scale. The stem C C is about seven inches long, and contains a double scale, one D, coloured, the other E, white or plain. These scales are drawn on paper, which is introduced into the hollow of the stem, and being fixed by means of cement at the lower end, is afterwards prevented from derangement or injury by hermetically sealing the mouth of the stem. Fig. 3 represents the scale taken out of the stem, and laid on a plain surface, the shaded part repre- senting the coloured scale. This latter is that by which the proper correction for temperature is obtained, as indicated by the small thermometer, fig. 2. The plain scale of the hydrometer shows the per-centage of the spirit above or below proof, and can be extended, if required (upward) to 70 per cent over proof, or (downward) to water. The thermometer is divided into 15 degrees more or less, and each division subdivided into halves and quarters, com- puted from zero or 0 upward, and from the same point downward, to the extent of the tube. The words * add/ below zero, and 1 subtract’ above the same, show the number of degrees to be added to, or subtracted from the line of indication on the coloured scale of the hydrometer ; such number being the variation of the temperature from the point zero, above or below, is thus used to ascertain the real from the apparent indication. 30 CHEMISTRY. Directions for the use of the Instrument. Fill a glass cylinder nearly with the spirit which is to be tried, and immerse the hydrometer therein to the depth of the ball ; suffer it then to sink until if find its resting point. When the instrument at length becomes quite stationary, observe what number of degrees marked on the coloured part of the scale within the stem corres- ponds with the surface of the spirit— suppose it be 27f ; place this number on a slip of paper : this done, the hy- drometer is to be taken out, and the thermometer dipped into the spirit, in order to ascertain the temperature of the latter. Observe now the point or degree at which the quicksilver settles — suppose it be 2y belozo zero or 0 ; place this number down also on the slip of paper under 2 7 \ the 27*, and add them together thus : _2j, making a sum 30 \ of 30jf. Look, in the next place, for 30| on the coloured scale, in a line with which, on the white or plain scale, will be found 18.2. This last number is the per-centage above proof of the spirit, and corresponds exactly with what would be determined by Sikes’s hydrometer. But suppose, secondly, the resting point of the hydro- meter and corresponding surface of the spirit be 22.0 on the coloured scale j and on the hydrometer being again drawn and the thermometer immersed, that the quick- silver in the latter should stand at 2^ above 0, place these two numbers down as before, and subtract the lower from 22.0 the upper, thus : 2 i , the number remaining indicates 19 | the strength of the spirit ; which at I9f, as in this example, is exactly of prooj strength , as shown by Sikes’s hydrometer. Thirdly, suppose the indication or surface number of CHEMISTRY. 31 degrees on the coloured scale, when the hydrometer is at its subsiding point, to be 14^, and the quicksilver in the thermometer (on its subsequent immersion) to settle at 0 ; it being obvious here that there is no number either to add or to subtract, a reference to the white or plain scale alone will be sufficient. The per-centage or strength of the spirit will, in this case, be indicated by that number of degrees on the plain scale which stands level with the surface of the spirit ; and the strength of the latter will, in this example, be found to be 10 per cent under proof. s. d. f Glass Hydrometer 14 0Y Price in detail ) Iv °‘' y Thermometerl ° 0 ( . 10s - \ Glass Cylinder . . 2 6£ price complete. vBox 36J Any part of the apparatus may be replaced at the above prices. Henry Stokes. 32 CHEMISTRY. N° III. MARINE THERMOMETER CASE. The large Silver Medal of the Society teas this Session voted to Mr. Robert Jamieson, Mathematical Instrument Maker , Glasgow, for a Marine Thermometer Case. The fol- lowing communications have been received from him on the subject , and the instrument itself is jdaced in the Repository of the Society. Glasgow, SIR ; March 10, 1820. I beg leave, through you, to present for the inspection of the Society, a Marine Thermometer Case which I have constructed for captain Livingston. The directions given to me by that gentleman, were, to make a case capable of preserving a thermometer from being broken when lowered into the sea, and drawn up again from the side of a ship ; also, that it should admit water at any given depth, and retain it during the drawing up of the instru- ment, so as to enable a thermometer of the usual con- struction to indicate the temperature at different depths, undisturbed by the greater or inferior heat of the surface water. The accompanying statement, drawn up by captain Livingston and confirmed by his own experience, of the utility of thermometrical observations to the navigator, renders wholly unnecessary any remarks of mine on the />/. CHEMISTRY. 33 same subject. 1 shall therefore coniine myself to the mecha- nical construction of the instrument as exhibited in the draw- ing and model herewith transmitted. In order to answer its purpose, it was necessary to combine in the construction, strength, simplicity and portability ; but although these objects have been attained so as to produce a practically advantageous result, I am far from claiming for it abso- lute perfection. Longer experience and greater skill will probably be able to improve upon the present first at- tempt ; and it is with this view, and also in order to call the public attention to a subject which promises to be highly beneficial to this maritime nation, that I have taken the liberty of offering the instrument to the notice and encouragement of your patriotic Society. I am, Sir, Sec. 8tc. Sec. Robert Jamieson. Reference to the engraving of Mr. Jamieson’s Marine Thermometer Case , Plate XV. Fig. 5 is an exterior view of the instrument, and fig. 3 is a section of the same, with the inclosed thermometer. The general form of the case is that of a cylinder or tube of copper, one-eighth of an inch in thickness, and seventeen inches in length ; each end is open, and is bevelled off at the mouth for the more free admission of water. v is the handle for the purpose of fixing it to the end of a cord . This handle is moveable on two pivots, by means of which it can readily be thrown on one side when it is necessary to take out or put in the thermometer. At 2$ inches from the top, is the circular joint o o, by means of which the lid forms a water-tight joint with the VOL. XXXVIII. D 34 CHEMISTRY. body of the case ; the lid is also furnished with a hinge, on which it may be thrown back. The valves are placed at each extremity of the tube, the upper one opening outwards, and the lower one inwards : they are composed of the following parts : p q, a short cylinder or box, bevelled at each extremity. s s, a bridge or cross bar, bulging at the middle, and there perforated, for the purpose of receiving an upright pin, to the upper end of which is fixed the circular plate of the valve, and to the lower end a screw ed stud t , the round head of which prevents the pin of the valve from being drawn, by the pressure of the water, through the perforation in the cross bar. r r, a circular projection, on which the bottom of the thermometer rests. From this description, it is obvious that when the case containing the thermometer, and having its lid carefully closed, is dropped into the sea with a line attached to the handle, it sinks rapidly in nearly a vertical direction, and at. the same time the pressure of the w^ater throws up both the valves. In consequence of this, a current of water is constantly passing through the case while the instrument continues to sink. As soon, however, as by the check of the cord the instrument becomes stationary, the valves fall into their places, and intercept the escape of the water; the quicker the cord is drawn up, the more completely are the valves secured, and the influx of the upper water the more perfectly prevented. As soon as the case comes to hand, the lid is to be thrown back and the thermometer withdrawn just sufficiently to enable the observer to read off the degree at which the mercury stands. CHEMISTRY. 35 44, Adelphi-street, Hutcheson Town, Glasgow, DEAR SIR; February 25th, 1820. As I understand you have advised Mr. Jamieson, mathematical instrument maker of this city, to sub- mit the model of the Marin eThermometer Case constructed by him, for my use, to the notice of the Society for the Encouragement of Arts, &c., &c., and that you have ex- pressed a wish to have a written statement of the causes which led to my application to Mr. Jamieson, in conse- quence of which, he was led to undertake the construction of that instrument, and also of my opinion of its utility for nautical purposes, I shall endeavour to comply with your wishes as concisely as in my power ; though 1 am much afraid the detail into which I must necessarily enter, will not admit of all the brevity which might be desirable. My attention was first directed to the thermometer, as a valuable nautical instrument, by the excellent memoir compiled by Mr. John Purdy, hydrographer, London, to accompany the admirable Chart of the North Atlantic Ocean, constructed by him, and published by Messrs. Whittle and Laurie, of 53, Fleet-street, in the year 1812. The late celebrated Dr. Benjamin Franklin, was, I believe, the first person who suggested the utility of the thermometer as an indicator of the proximity of, or an approach to, the American coast, having remarked the great difference of temperature between the water of the Gulf stream as it sweeps along the coasts of the United States, and the water upon the soundings between the inner edge of the stream and the shore. This interesting subject was afterwards taken up by colonel Jonathan Williams, who endeavoured, with some success, to attract the attention of nautical men to the vast importance of the thermometer, in an ingenious work n 2 36 CHEMISTRY. intituled “ Thermometrical Navigation/’ published at Phil- adelphia, in 1799. To avoid unnecessarily extending the length of this letter, by quoting evidence already before the public, I beg to refer to the third edition of the Memoir by Mr. Purdy, already mentioned, the perusal of which must satisfy the most sceptical, that the thermometer is not only a certain indicator of the proximity of the American coast, but also an infallible monitor of an approach to islands of ice, so perilous to navigators, and the dangers of which are tenfold increased by the circumstance of their being generally surrounded by dense fogs. Mr. P.’s Memoir, from the 73rd to the 78th page, is occupied with these important subjects. Colonel Williams recommends that the thermometer should be slung, u so as to tow in the dead water of the ship’s wake.” I tried this mode, and had three of my thermometers broken in consequence ; this led me first to think of having a case to prevent my instruments from being fractured by any accidental contact with the ship. Some gentlemen, whose opinions I respected, suggested that while towed by the ship, her way through the water would naturally cause the thermometer to rise to the surface, and that thus only the temperature of the surface water could be obtained, and that they conceived this temperature liable to be influenced by the effects of tbe solar rays. To obviate this objection, I saw the ne- cessity of a case to inclose the thermometer, which would admit the water freely as long as it was permitted to descend, but would shut as soon as it was begun to be hauled up. After I was satisfied how useful a thermometer case, adapted properly for these purposes, must prove, I applied to various mechanics in different places to construct one CHEMISTRY. 37 for me, but they either did not sufficiently understand the matter, or considered the safety of human lives and mer- chants ships and cargoes of too trivial importance to in- duce them to exercise their abilities ; be this as it may, I was always disappointed of my object, until I became ac- cidentally acquainted with Mr. Jamieson, who readily entered into my views, and made a case for my thermo- meter, which completely answers my ideas, of which the model intended to be sent to the Honourable the Society of Arts, &c. is, as you know, a correct copy, i. e. allow- ing for the difference of sizes, the original case being l T v inch in diameter within, which I consider large enough to contain a column of water that will retain its original temperature a sufficient space of time (after the case is hauled up), to allow of the degrees indicated by the scale being read off by the observer, which is all that is neces- sary ; while, if the magnitude of the apparatus had been in- creased, it must have become almost useless from its weight, when a vessel had fresh way through the water, and by the time she came to run eight or nine knots, must have been totally unserviceable. The same objection applies to any addition of weight. The objection to Jamieson’s Marine Thermometer Case, which has I understand been made, that the valves do not permit a sufficient column of water to pass com- pletely to fill the interior of the case in a constant stream as it descends, appears tome of little importance, as enough must pass through to regulate the altitude of the mercury in the thermometer tube, and before there can possibly be time to haul up any part of the attached line, the mere pressure of the water must infallibly fill the thermometer case. Purdy’s Memoir shows incontestibly that no vessel on board of which there is a thermometer, can possibly run ashore on the coasts of the United States of America to the northward of the Strait of Florida, without her com- 38 CHEMISTRY. mander (unless he is guilty of the most culpable negli- gence) having at least warning in sufficient time to avoid the danger (i. e. if his vessel is not so much crippled as to render it impossible for him to use any means to get off shore) ; and various circumstances induce me to hope that the thermometer will ultimately be found not only an in- dicator of an approach to the coasts of the United States, but also, that it will point out the proximity of land or soundings in all places to the northward of the Tropics, and probably also to the southward of them, though my own experience does not warrant me in the hope that it will within them. Besides these advantages, the use of the thermometer has already been ascertained as illustrative of several of the oceanic currents. The venerable and indefatigable geographer, major Rennell, in a letter to myself dated 6th of November last, observes, “ The current from the Indian Ocean round the Cape of Good Hope differs 10 ° from the Ocean water , i. e. is warmer ; the equatorial current colder by b or 6 deg. than the Guinea current , which brushes it in passing , fyc” Thus far already established. We may surely venture to hope that as ther- mometrical observations are multiplied, their utility will become more obvious, and be more generally acknowledged. In my own experience I have found a difference of 12 deg. in the temperature of the water in a few hours. Running out of the Delaware, in 9 fathoms water, the mercury stood at 60 deg. (in October 1817) ; as the water deepened, it rose to 64 deg. ; and as we entered into the Gulf stream, it suddenly increased to 72 deg. In September 1818, when bound from New Orleans to Gibraltar, in the ship Asia, of Scarborough, then under my command, a fever broke out on board the ship, and for a considerable number of^days after we cleared the Strait of Florida, we had only four men and a boy fit for duty, CHEMISTRY. 39 and three out of that number merely convalescents. I was myself confined to bed, and my mate in the same situation ; we were the only two navigators on board, and both unable to make up any reckoning, and some days unable even to crawl on deck to take an observation at noon. In this dilemma I trusted entirely to my thermo- meters, having given orders that the instant the mercury fell two or three degrees, the ship’s head should be wore round off shore. In this way I kept the ship from danger, and also availed myself of the Gulf stream current to carry us to the northward, and I really believe that under Divine Providence, the safety of the ship, cargo, and crew, was attributable to my thermometers. On the same voyage, on approaching very near the Azores Islands, the mercury sank 2 deg., and when we made the coast of Portugal, it rapidly fell from 69 deg. to 61 deg., at which it stood when we rounded Cape St. Vincent, at the distance of about a league. After we passed that promontory, the mercury again rose to 69 deg., at which it continued until the ship entered the Strait of Gibraltar. In the Strait the wind was adverse ; and in beating through it, the mercury stood at 68 deg. in the middle of the Strait, 64 deg on the Spanish shore, and 61 deg. on the African coast : this difference between the temperature on the Spanish and African shores is appa- rently easily accounted for, as we stood much closer to the latter, avoiding the former on account of the rocks and shoals to the westward of Tariffa ; yet as we found the mercury at our anchorage in Gibraltar Bay stood at 64 deg., perhaps there really was a difference of tempera- ture in the water on the opposite shores : this was in October, 1818. Major Rennell, to whom science is under so many obligations, has communicated to me, that cap- tain Beaufort, of the Royal Navy, found a difference of 10 deg. between the water in the middle of the Strait and 40 CHEMISTRY. that in Gibraltar Bay, but I am not aware at what season Captain Beaufort’s experiments were made. Since Mr. Jamieson completed the thermometer case for me 1 carried it down to Greenock, and exhibited it to Mr. Colin Lamont, Mr. Quintin Leitch, and Mr. William Heron. Mr. Leitch procured a boat, and we went off, and made a number of experiments, which proved completely satisfactory. My opinion of Jamieson’s Marine Thermometer Case is, that the simplicity of its construction, and its strength, render it as complete a thing as could be desired for the purpose for which it is intended. I fully concur in the opinion expressed in the certificate by Messrs. Lamont, Leitch, and Heron ; and I am decidedly of opinion that either to increase the size, or to add lead to it to increase the weight, will never be proposed by any practical seaman. The mode in which I propose to use the apparatus is, by making about 20 fathoms of strong line fast to it,-— to cause the officer of the watch to stand aft with the end of the line made secure to one of the staunchions, or some other thing, lest it should accidentally slip through his hands, and the whole be lost ; he must then cause the apparatus to be passed forward, as in heaving the deep sea lead : when the vessel has much way through the water, it may be passed to the bowsprit end, and dropped (not hove) from it; but for general use the fore-chains may be far enough : when all is ready, let the officer call out to let go, and when that is done he must immediately haul in the line, and when he gets hold of the case, open it, and draw out the thermometer a sufficient length to read off the altitude of the mercury indicated by the scale, which he ought immediately to mark on the log slate, in a column which should be traced upon the slate for the purpose. CHEMISTRY. 41 In my own practice I have always caused two columns to be marked, the one T. A. for temperature of the air, the other T. W. for temperature of the water. In these columns I ordered the officer of the watch to insert the temperature both of the air and water twice (sometimes oftener) each watch. The temperature of the air is, how- ever, of little importance farther than as a comparative observation, it being only the variations of temperature in the water which are of importance to the navigator. In reading off, the observer should take care to keep as much of the thermometer as possible immersed in the water, which this marine case allows of being done with I have said enough to convince you of the immense importance of the thermometer as a nautical instrument, and that Mr. Jamieson’s Marine Case renders the use of it both more easy and certain. I am, Sir, William Warren , Esq. Andrew Livingston, Shipmaster. P. S. You are at perfect liberty to use this letter in any mode you think may be advantageous to Mr. Jamieson, whom I consider entitled to much credit for this simple and useful invention. A. L. 2nd P. S. Since writing the above, Mr. Jamieson has informed me that he is anxious to send the instrument with which the experiments were actually made at Greenock, and begged me to let him have it, promising to replace it to me ; although with some reluctance I have complied, thus the Society of Arts will actually have the real marine thermometer case in place of a model ; and I doubt not but the scientific members of that honourable body, will neither wish its size or weight increased, what- ever individuals (here) ignorant of seamanship may say. A. L. 42 CM EMISTRY. N° IV. IMPROVED GLAZE FOR PORCELAIN. The smaller or Isis Gold Medal was this Session voted to Mr. John Rose, of Coalport, Shrop- I M P R O V E D G L A Z E FOR PoRCELAI N. The following communication on the subject has been received from the candidate , and specimens of the Felspar , the principal ingredient of the Glaze , of the entire glaze ready mixed for use , and of the Porcelain in a finished slate, have been placed in the Society's Repository. Coalport, SIR ; March 24th, 1820. Having for some time made use of a glaze for porcelain, which gives me great satisfaction, and into the composi- tion of which, neither lead nor arsenic are admitted, I beg leave to submit the same to the consideration of the Society of Arts, &c. The common glaze for porcelain and the finer kinds of earthenware contains a considerable proportion of glass of lead ; this ingredient however, on account of its being mixed with a certain proportion of siliceous earth and other vitrefiable materials, unites with them into a glass, which although easily fusible, is not in the least corroded or acted on by any articles of food. It is not, therefore, from the apprehension of any injury to the health of those who use vessels of porcelain, that the use of lead in the CHEMISTRY. 43 glaze is objectionable, but because it is extremely liable to combine with, and degrade the more delicate colours, especially those given by preparations of chrome and of gold. This is particularly the case in the more expensive and elaborate products which, on account of the multipli- city of their colours, require to be repeatedly heated, or fired. I trust, therefore, that the Society will consider the communication of a receipt for glazing, in which the above mentioned defects are avoided, as worthy of their favourable notice. The principal ingredient of my glaze is felspar, of a somewhat compact texture, and a pale flesh red colour, which forms veins in a slaty rock adjoining to the town of Welsh Pool, in Montgomeryshire. This material being freed from all adhering pieces of slate and of quartz, is ground to a fine powder, and being thus prepared, I mix with 27 parts of felspar, 18 of borax, 4 of Lynn sand, 3 of nitre, 3 of soda, and 3 of Cornwall China clay. This mixture is to be melted to a frit, and is then to be ground to a fine powder, 3 parts of calcined borax being added previously to the grinding. The specimens accompanying this letter, are, 1. The felspar in its rough state. 2. Do. ground to a fine powder. 3. Some of the glaze ready prepared for dipping. 4. Specimens of porcelain glazed. 5. Do. both glazed and afterwards painted, in order to show the solidity and brilliancy of the colours when used on this glaze. I am, Sir, A. Aik hi, Esq. &c. &c. &c. Secretary , fyc. fyc. John Rose. Some of the specimens furnished by Mr. Rose were placed by the committee in the hands of Mr. Muss, and of 44 CHEMISTRY. other artists, in order to be submitted to experiment both with regard to the perfection of the glaze itself at high temperatures, and its re-action on the several colouring materials. Mr. Muss’s trial pieces were proved first in a common kiln, and afterwards were subjected to the action of a much higher degree of heat than it is possible that they can ever be exposed to in the fair course of enamelling. In this extreme heat the ground of the ware is not in the least degree softened or affected ; the glaze remains firm and perfectly uniform without any specks or spits having been produced on its surface ; the colours, even the pinks and chrome greens, come out remarkably well upon it. Mr. Rose’s glaze not being so hard as that used by the French manufacturers, incorporates more completely with the colours, and renders them perfectly firm, whereas, every artist knows that colours laid on French porcelain are extremely apt to chip 'off, crackle, and flake, if it is necessary to make them pass the fire a second time. On the whole, therefore, Mr. Muss considers the samples placed in his hands by the committee, as the best both in body and glaze that have ever come under his observation. Similar reports of the excellency of the glaze, in the particulars above mentioned, were made by the other artists who had made trial of it. P A P E Ft S IN CHEMISTR Y. N° I. PORTABLE ELECTRO-MAGNETIC APPARATUS. The Large Silver Medal and Thirty Guineas were this Session presented to Mr. James Marsh, of Rush -grove-place, Woolwich , for a Portable Electro-Magnetic Appa- ratus, which has been placed in the Society's Repository. Exceedingl V interesting and important experiments on the intimate connexion between electricity and magnetism, mark the principal track of philosophical investigation during the last four years. Professor Oersted, of Copenhagen, led the way and was followed with zealous emulation by M. M. Ampere, Biot, and Arago, in France; by sir II. Davy, 48 CHEMISTR Y. Dr. Wollaston, Professor Cummings, Mr. Faraday, and Mr. Barlow, in England. The large and costly apparatus em- ployed by most of these philosophers, necessarily restricted to a few persons placed in singularly favourable circumstances, the prosecution of these discoveries, and almost prevented the possibility of repeating the experiments on distant parts of the Earth’s surface where the variation of terrestrial magnetism, as compared with that which takes place in our latitudes, may be expected to produce corresponding differences in the results. The mathematical laws of electro-magnetism as laid down by Mr. Barlow, however probable and consistent among them- selves, would in particular derive great advantage from such investigations, as his theory of terrestrial magnetism already has, from experiments made by scientific officers on board his majesty’s ships in different parts of the world. Mr. Marsh, occupying a very subordinate department in the royal laboratory at Woolwich, was employed by Mr. Barlow as an assistant in his magnetic and electro-magnetic experiments. Thus favourably circumstanced, he was in- duced to turn his attention to the construction of an apparatus capable of exhibiting all the known facts of electro-magnetism, and of enabling the possessor to prosecute farther researches in this interesting and important branch of natural philosophy ; while, at the same time, the portability of the apparatus and its moderate price, should place it within the purchase of most experimenters, and should peculiarly adapt it to the use^f the traveller by land or sea. Having succeeded in his object, Mr. Marsh submitted his apparatus to the inspection and judg- ment of the Society, and before two numerous Committees, exhibited by means of it, with perfect success, all the facts of electro-magnetism which at that time had been discovered. The Society in recompence of the talents and ingenuity of the PLATE 1. C H E M I S T R Y. 49 inventor, voted to him the reward specified above, and directed the insertion, in the next volume of their Transactions, of a description of the apparatus, conceiving it likely to be useful to private individuals, and to be peculiarly well adapted for service on board ship, in some of those naval expeditions for the promotion of science and general knowledge which so honourably characterize the present Board of Admiralty. The whole apparatus is included in a box 14£ inches high? 15 inches broad, and 10| inches wide, which when folded out forms a convenient table for the operator. Plate I, fig. 1, is a perspective view of the box ready for use, the flap a being raised up and supported by the leg b, which screws into it The voltaic battery, with its appendages, occupies about half the box, and consists of a plate of copper, with a plate of zinc on each side. Figs. 3 and 4 are a front and transverse view of the battery ; the two exterior or zinc plates are united at each corner by metal fastenings, and the intermediate or copper plate is cut aw T ay at the corners just sufficiently to prevent it from contact with the fastenings of the zinc plates, and is secured in its position by pieces of wood ; i i are two copper feet upon which the battery rests when in action. T wo brass pipes C and Z are soldered, the former to the copper plate, the latter to one of the zinc plates ; they are intended to hold a little mercury for the purpose of forming a perfect connexion between the conductors C and Z, fig. 1, and the battery; in order still farther to secure the connexion, the ends of the con- ductors that are inserted into the pipes are first tinned and afterwards amalgamated, as well as the other ends on which the spiral wires, fig. 18, forming the poles of the battery, are fixed. The battery when not in use is lodged in the cell e, figs. 1, 2, which is lined with wood and varnished ; the tw o Jointed handles, by means of which it is raised, being laid VOL. XT, i. E 50 CHEMISTRY. down into notches cut in the partition between the two cells. The cell d is somewhat wider than the other, and is lined with sheet copper: into this the exciting fluid (dilute muriatic acid) is poured when the battery is intended to be put into activity, and the united copper and zinc plates being raised, by means of the two handles, out ol cell c, are to bt gently let down into the fluid, resting on the bottom of cell d, by means of the two copper feet i i , already mentioned. By this arrangement the battery forms a series of three copper and two zinc plates, the lining of the cell forming the two exterior copper plates, and consists ol about eight square feet of metallic surface. Two pieces of varnished wood g h, fig. 2, are fixed to the sides of the cell to prevent the zinc plates from coming in contact with its copper lining. A small tray fig. 2, is placed on the flap a, in order to retain any fluid which may be accidentally spilled during the experiment. Fif. 5, shows the general arrangement of that part of the box, covered by flap a, fig- 1, in which the different articles of apparatus are deposited. The lowest compartment, represented more at large fig' 6, contains a pair ol horse-shoe magnets, a cylindrical magnet, a pocket compass, some spare copper wire, and two tin boxes, in one of which are contained iron filings, in the other spiral wires of iron, tinned and amalgamated. Over this is placed the lower shelf, figs. 7 and 8; the under projections of which secure in their places the articles already mentioned. The three upper shelves, figs. 10? 11? 12, are cut out in the forms represented, in order to admit in the most secure and compact manner, the various pieces ol apparatus described and figured in Mr. Barlows lreatise on Electro-magnetism, to which the reader is referred. Ihree, however, of these pieces of apparatus being the original inven- tion of Mr. Marsh, are here represented. CHEMISTR Y. 51 Figs. 13 and 14 are the view and section of a central cylindrical magnet, having an agate socket inserted in each pole ; on this socket rests a pivot having two branches of wire, by means of which, a hollow cylindrical cup of copper is suspended. In the copper cup is placed a cylinder of zinc also suspended by two wire branches, and balanced on the pivot k, which has free motion in a socket fixed on the wire by which the copper cup is suspended. Some dilute acid being placed in the copper cup, voltaic action is excited, and the copper cup will revolve slowly in one direction, while the zinc cylinder moves round in the opposite direction. By supporting this apparatus on the other pole of the central magnet, the motions of the copper and zinc will be reversed. Fig. 15 exhibits a glass tube closed at its lower end, and passed through a circular piece of cork for the purpose of floating it, a voltaic combination is contained in the tube with which the spiral wire l l communicates ; dilute acid being put into the tube, and the whole apparatus being floated in water, the spiral wire will place itself North and South in the same manner as a common magnetic needle will. Fig. 16 is a stand with a long narrow reservoir for mercury, out of Avhich rises a metallic pillar which supports a fine wire attached by a loop to the eye m : the lower end of the wire dips in the mercury, and, as well as the upper end, is amal- gamated in order to render the contact more compleat. A horse- shoe magnet is then laid with a pole on each side of the trough, and as soon as the voltaic circuit is compleated, by means of the cups n and o filled with mercury, the moveable wire continues to leap out of the mercury, and to fall into it again in the direction indicated by one of the dotted lines. On f. 2 53 C H E M I S T R Y. reversing the poles of the magnet, the former motions will cease, and others similar to them will take place in the direc- tion of the other dotted line. N° II. MELTING POTS. The Large Silver Medal was this Session pre- sented to Mr. Henry Marshall, of Newcastle on Tyne, for his improved Melting Pots for Brass Founders and other workers in Metal. Samples of the Pots are placed in the Society’s Repository. Large earthenware crucibles (technically called melting pots) are used in great quantities by brass founders, steel melters, and other workers in metal. They are made in London, Birmingham, Sheffield, and other places ; and their ingredients are tenacious refractory clay, together with frag- ments of earthenware made of the same or similar clay, re- duced to powder more or less coarse according to the experience of the manufacturer. It is not necessary that they should be possessed of the highest degree of refractoriness, since the heat to which they are exposed is not so great, nor are the fluxes employed by the founders so active, as are necessarv for the reduction of metallic ones to their remdine state. But it is O especially expedient that they should be capable of enduring. CHEMISTR Y. 53 considerable changes of temperature without cracking or becoming unsound, as otherwise, each pot would not be capable of standing more than a single fusion. The common melting pots being made entirely of earthy ingredients, a;e very apt to crack, either if allowed to cool gradually after the first fusion, or if a second charge of cold or nearly cold material is thrown in while the pot remains in a heated state. The German black lead pots (or blue pots as they are called) contain a considerable quantity of plumbago in their composi- tion, and hence will stand a greater number of fusions; but the cost of these is considerably greater than the common melting pots, and in time of war they are not alw ays to be had. Mr. Marshall’s pots are made of a mixture of Stourbridge clay, potsherds, and pulverized coke, well incorporated together by beating; and instead of being thrown on the potter’s wheel, the pot is made by pressing the above composi- tion into a brass mould of the proper size and figure, by means of a core worked by a powerful screw press. Thus the vessel acquires a great and equal degree of solidity throughout, while the intermixture of coke with the clay, by giving a certain porosity of texture, renders it much less liable to crack, on transition from heat to cold, than those melting pots com- posed entirely of earthy ingredients. The following certificates from founders of great respect- ability attest the goodness of the pots made by Mr. Marshall, and that the price of them is not greater than of those from other makers. 54 CHEMISTR Y. CERTIFICATES. Gateshead, near Newcastle, SIR; March 9, 1822. I have for some time past used the improved earthenware crucibles made by Mr. Henry Marshall, of this place, and find them much superior to those I have formerly had from Birmingham and other places ; I have them frequently in use a second day, which I never before could accomplish, and con- sider them in many respects equal to the black-lead pots ; and come equally as low as the pots I have used generally. I am, Sir, To A. Aik in, Esq. & c. &c. &c. Secretary, <§*c. §c. John Abbot. No. 69, Red Lion Street, Clerkenwell, SIR; March 21, 1822. Observing the offer of a premium for improved earthen- ware crucibles, I beg to acquaint the Society that those made by Air. Henry Marshall, of Newcastle-upon-Tyne, are much superior to any I ever saw, or used, for bearing great heats and standing changes of temperature without cracking ; I use them frequently a second day, which I could not accom- plish by any other make ; in short, I conceive them superior to black-lead pots. I am, Sir, &c. &c. &c. Robert Bower, Brass Founder. To A. Aikin, Esq . Secretary, Sc. Sc. C H E M I S T R Y. 55 February 15, 1822. I certify that the large crucibles, with H. Marshall, Newcastle, pressed upon the edge, are the best clay crucibles I ever made use of. H. Vernon, Master of the Metal Mills t Portsmouth Yard. SIR; Brownlow Street. I beg to acquaint you, for the information of the Society of Arts, that I am in daily use of Mr. Henry Marshall’s crucibles, and find them of a very improved quality : I use them frequently tw T o or three days, and, from having made use of the black-lead pots in my business, I now find that Mr. Marshall’s are equal, if not superior, to them, and not higher in price than the earthenware crucibles before in common use. I am, Sir, To A. Aikin , Esq. &c. &c. &c. Secretary , #c. fyc. A. Harcouiit, Brass Founder. 46, 47, 48, & 49 Shoe-lane, March 23, 1822. This is to certify that we, the undersigned, can and do assert, from experience, that the melting pots manufactured by Mr. H. Marshall, of Newcastle, are superior to any we ever used, and that we have tried various other manufacturers pots, but give a decided preference to those manufactured by the above-named Henry Marshall. Wm. Pontifex, Sons, & Wood. 56 C II E M I S T 11 Y. N° III. IMPROVED APPARATUS FOR THE ANALYSIS OF ORGANIC PRODUCTS. The Large Silver Medal am this Session pre- sented to Mr. J. T. Cooper, of Paradise-street, Lambeth, for an improved Apparatus for the Analysis of Organic Products. The following Communication has been received from him on the subject, and the Apparatus has been placed in the Societies Repository. An easy and accurate method of determining the ultimate elements of bodies composed of carbon, hydrogen, oxygen, and azote, has been of late years a great desideratum among » chemists, as such a variety of contrivances have been suggested by scientific individuals, all of which have their peculiar merits and defects. It is presumed the instrument and method of operating now presented to the Society and the public, if not entirely, may be considered as nearly free from those objections which in my opinion may be fairly urged against those heretofore in use. It might, however, be con- sidered ungenerous, was I to take upon me the task of point- ing out those defects, I shall therefore content myself by briefly stating in this communication, the class of substances % to which it is applicable with a view to determining the pro- Ifrawri by C. Varley. Engraved by W.Eelrctdl. C H E M I S T 11 Y. 57 portions of their elements, and a description of the method of operating upon each of them. As this apparatus seems more particularly calculated than any other for operating on volatile matter, such as the essential oils, camphor, benzoic acid, and a variety of similar substances, I shall in the first place describe the method I have adopted in the analysis of this class of bodies ; and when it is consi- dered that I write not for those who are accustomed to the more minute and delicate operations of chemical analysis, but for those who are or may be considered as unacquainted for the most part with this subject, I hope I may not be consi- dered as tedious should I venture to give those directions which to the more matured in science may seem to be un- necessary. The oxid of copper used in the experiments is best pro- cured from the residuum of verdigris (binacetate of copper), which is or was used to be distilled in glass retorts for the preparation of strong acetic acid. The reason I prefer the oxid of copper prepared by this process over any other is, that it is more likely to be free from impurity than that which is prepared by precipitation from acid solutions. Every one who is in the habit of preparing precipitates, knows the diffi- culty there generally is in freeing considerable quantities of precipitated matter from adhering neutral salts ; and as the smallest impurity would in some measure contaminate the result of the analysis, it is a very necessary precaution that the oxid, which is by far the greatest in quantity of any substance that is employed in the operation, should be perfectly pure. Should it however happen that at any time such an oxid is not readily to be procured, the oxid that is obtained by heat- ing copper plate and quenching it in water may be substituted ; although I give the decided preference to the former on ac- CHE M I S T R Y. count of its mechanical texture being much more porous, and consequently exposing a larger surface to the action of sub- stances in vapour passing through it, neither is it so likely to choak up the tube and endanger its bursting, and of course a failure in the experiment. Supposing the residuum above mentioned to be employed, it is requisite to expose it to a red heat for twenty minutes or half an hour to destroy the carbo- naceous matter that invariably accompanies it ; it should then be pulverised and sifted through a fine wire sieve ; that por- tion which has passed the sieve being again sifted through a fine Cyprus or lawn sieve, the finer dust is got rid of, and each of these portions may be separately kept, and is applic- able to different purposes. A tube of hard glass, either of crown or green bottle glass, being selected about fourteen or fifteen inches long, and from one to two tenths of an inch internal diameter, clean the in- side from dust by passing through it a piece of cotton, then make it as hot from end to end as the fingers can conveniently bear, and draw air through it into the mouth (but not blow through it) while it is still hot, to ensure its perfect freedom from adhering moisture on its inside, and while still warm seal up one end with the blowpipe ; the tube may be now balanced, but it is necessary in this, as in all other operations of analysis where very small quantities are concerned, that the beam should be affected by - 3-^7 or s-hr of a grain, even when loaded with 4 or 5 hundred grains at each end.* The substance intended for analysis is now to be introduced into the tube, if it be solid, as for instance camphor or a like substance, it may be broken * The balance I have been in the habit of using was made for me by Mr. Robinson, and is sensibly affected by (> f 9 grain when loaded with 1000 grains at each end. C HEMIST R Y. 59 into small fragments and shaken down to the bottom ; if it be a fluid, as a volatile or fixed oil, it may be introduced by means of a smail funnel, as is shown in fig. 7, which funnel is prepared, on the instant, from a piece of flint glass tube of con- venient size and substance, by heating it near one of its extremities, and suddenly drawing it out, it is evident the semifluid glass will be thus elongated, and a funnel with nearly a capillary tube and of any required length, may be thus obtained ; a very little practice will render this part of the business very easy to be accomplished ; the funnel is to be put into the tube, reaching very near its bottom or sealed end, and the fluid matter introduced without soiling the upper part of it ; care must also be taken on withdrawing the funnel, that no portion of the fluid is attached to its lower extremity, or other- wise this will happen. The volatile substance, or that which is capable of being rendered so by a red heat, being now intro- duced into the tube, its weight is to be very carefully taken, which when done the oxid of copper previously freed from its fine dust by the lawn or Cyprus sieve* and recently heated red hot, is to be poured into the tube while warm, to the length of 8 or 10 inches, having previously put into the tube as much only of perfectly cold oxid as will absorb the fluid portion of matter, and about a quarter of an inch above it, or to stand about the same height above the solid substance. Why I recommend the present proceeding is, that a small quantity of the cold oxid only is used to prevent the hot oxid from coming in contact with the volatile matter which might other- wise endanger the escape of a small portion from the tube, and of course would give erroneous results ; and that portion of * The finer portion is taken from the oxid to allow more freedom of passage for the vapour through it, in some cases the rush of gas is so sudden, was it not for this precaution, it would be likely to burst the tube. 60 C H E M I S T II Y. cold oxid, even if it be fully saturated with moisture, can con- tain such a very minute quantity of w r ater as not to sensibly aftect the accuracy of the analysis. Having proceeded thus far, a quantity of recently-ignited asbestos, or spun glass (the former is best), is put into the tube, so as to occupy an inch or two, depending on the quantity of water that is ex- pected to be formed ; this must not be crammed but put rather lightly into the tube. The tube is now to be bent as represented in fig. I , and its weight may be again taken, but this is not absolutely requisite, it is however well to do it. The tube is then to be covered with thin sheet copper, and placed between the forceps as represented in the same figure, with its open extremity inserted under a jar in the ordinary mercurial pneumatic trough, or it may be connected with a gasometer of Mr. Pepys’s construction, which when ten or tw r enty grains of a substance are employed, and the quantity of either carbon or azote it contains is considerable, is convenient. Small mercurial graduated jars may be used, even if very large quantities of gas are obtained, as the process of decom- position may at any time be stopped almost instantaneously,* and the quantity contained in them being registered, they may be alternately filled with mercury and displaced by the gaseous products, as long as any comes over, reserving only the last portions for examination, of which a few cubic inches alone arc requisite. The lamps being trimmed with very short wicks are now to be lighted, lighting those first that are nearest the gasometer, and when the tube is red hot the remaining ones may be set fire to in succession, until the whole length of tube that is filled with the oxid is red hot. One set of lamps for a tube of the size I have mentioned above is generally sufficient, but I consider this as one of the advantages of this apparatus. C H E M ISTRY. C>1 should tubes be used of larger size, such as half an inch in diameter, both sets will then be required. In, coating the tube with sheet copper care must be taken not to cover that part of it which contains the asbestos, otherwise the heat will be conducted by it to that portion of tube and prevent the condensation of the vapour of water, which is very essential ; and in placing the tube between the forceps, it will be convenient to allow that part of it which contains the volatile matter to project beyond the forceps, the heat that is conducted by the copper coating is generally enough to volatilize most substances. In the analysis of substances con- taining much hydrogen, and especially when ten or twelve grains of them are taken, it will be found convenient to attach to the tube a small bulb to contain the water that is generated ; this is represented by fig. 6. I believe I have stated the whole that is necessary as respects the management and use of this apparatus as far as regards the decomposition of volatile sub- stances ; in the next place, I shall speak of its application to the decomposition of fixed substances, which after what has been said will require but very few words. If the substance be a vegetable salt it must be freed from all extraneous moisture, this is best effected by suffering it to remain over an hygrometric substance in vacuo for some time. Those who have not the convenience of an air-pump, may content themselves, by operating in this way, which although not quite so elegant, answers the purpose extremely well. A wide-mouthed phial provided with an accurately-ground stopper being procured, select another and much smaller phial that will easily go into it, and allow the stopper of the larger one to close accurately ; it is as well to apply a little tallow to the stopper to ensure its more perfect fitting ; strew on the bottom of the larger phial a quantity of chloride of calcium (dry mu- CHE M 1 S T R Y. riate of Hme), put into the smaller phial the substance in fine powder intended to be dried, and place this in the larger phial standing on the chloride ; moisten a small piece of bibulous paper with alcohol, and put it into the larger phial, but not inside of the smaller one ; when thus arranged set fire to the moistened paper, and when it has burned a second or two put the stopper in its place ; a very good vacuum is by this means formed, and the process of dessication goes on rapidly. I have repeatedly used this method and found it succeed very well ; I think equally so with that usually adopted by means of the air-pump ; although by some it may be ridiculed in these days of elegance and refinement. The substance in this state is to be mixed with a portion of the oxid recently ignited, but in this case suffered to cool then as quickly as possible introduced into the tube. As much of the oxid may be used as would occupy an extent of tube equal in proportion to that shown in fig. 5 ; a quantity of oxid is then to be put upon the mixture, and over this it is sometimes well to put a small quantity of copper-filings or scrapings ; upon these the asbestos is to be used as above, and the operation of ignition is to be conducted in a somewhat different manner to that last-mentioned. The lamps in this case are to be lighted at the extremity next the gasometer, and as soon as the gas ceases to be libe- rated, the next in succession may be employed, and so on to the end ; but instead of suffering the whole of them to continue in flame, it is as well to extinguish a portion, and to suffer only about three or four to remain in operation at once, but taking care to ignite the whole extent of tube at the close of the process. The gaseous products being collected, and their bulk noticed, their analysis is to be conducted in the usual manner, taking care, however, in all instances to observe the C H E M ISTR Y. 63 precise temperature of the gases, that their bulk, as also the quantity of aqueous vapour they contain, may be estimated,* and either to equalize the internal and external surfaces of the mercury, or to calculate the volume of gas by the difference of mercurial levels. Reference to the Drawing of Mr. J. T. Cooper’s Apparatus for Analysis. — Plate II. Fig. 1, a a and b b, two long spirit lamps each having ten burners and wicks, the burners of each lamp sloping towards those of the other, as seen in the end view, fig 2 ; they are placed in a tin tray, c c , mounted on four feet ; this tray is perforated in the middle the whole length of the lamps, and as wide as e e, fig. 2 ; the object in making the burners sloping is that they may clear the lamps and approach each other as near as requisite, and yet leave a clear current of air to the flames, and the tray is perforated and mounted on feet to admit this current. d d, are springing wires placed at each end of the tray to receive the tube f f which contains the substance to be ana- lysed, and to hold it over or between the two rows of flames; by pressing the finger and thumb on the two shoulders, g g, fig. 2, the wires open to receive the tube, and close on letting go ; and should the tube be shorter than the lamps, an additional support on a leaden foot, fig. 3, is placed through the opening e e of the tray to rise between the flames, and hold the end of the tube ; the tubes are hermetically sealed at one end, and the materials then put in while the tube is straight ; it is then bent at the other end to suit the mercurial trough. * For which very convenient formula; will be found in the ninth edition of Dr. Henry’s Elements of Chemistry. 64 C H E M I S T R Y. The tubes are coated with copper foil, wrapped spirally round them ; if each succeeding fold lie on half the other there will be a double coat of copper all the way ; if it lie on two-thirds, there will be three layers of copper, and so on ; by which the glass tube is supported from bending when hot, and becomes very uniformly heated. The spirals are continued beyond the end of the tube, to reach the support, and leave the end within the flames. The dotted lines at Zr, fig. 4, shew the end of the tube, short of the support; the foil is secured at the last coil by binding wire, as at i. Fig. 5 shows the foil in act of being wrapped on, also the proportion of the space occupied by the materials ; first, the mixture of oxide of copper with the material to be analysed, next pure oxide of copper, or copper filings, and, lastly, asbestos. When the quantity of water formed is considerable, the tube is either blown into a bulb, as at k, fig. 6, or melted on to one ready prepared as at /. Fig. 7 is a long funnel, made by drawing out the end of a tube of a suitable thickness at till it is long and small enough through n n to reach to the bottom of the tube, and then cutting it off at m, by which liquids may be introduced to the bottom of the tube without wetting the sides. As the wicks nearest the trough are to be lit first and the re- mainder in succession, as the former finish their action, there are upright supports of tin, o o, fixed on the lamps, one for each space between the burners, against which to rest a slip of tin p p, to prevent the lighted wicks from kindling those next, and it also enables the experimenter to blow out those that have done their duty. In fig. 2, the tin slip, p p , is shown by dotted lines, reaching from lamp to lamp : little flat caps are put on each burner when done with, to prevent the waste of spirit. Fig. ///6535 1,83 ,5464 ,94 1,0638 1,24 ,8064 1,54 ,6493 1,84 ,5434 ,95 1,0526 1,25 ,8000 1,55 ,6452 1,85 ,5405 ,96 1,0416 1,26 ,7936 1 ,56 ,6410 1,86 ,5376 ,97 1 ,0309 1,27 ,7874 1,57 ,6305 1,87 ,5342 ,98 1,0204 1,28 ,7812 1,58 ,6329 1,88 ,5319 ,99 1,0101 1,29 ,7751 1,59 ,6289 1,89 ,5291 To apply this scale— suppose it has been ascertained that from the point to which the instrument sinks in distilled water of a given temperature, to the point to which it sinks in a fluid whose specific gravity is 1,3, and of the same tem- perature, measures five inches, or any other quantity ; take C II EM IS T 11 Y. GO this quantity in a pair of compasses, and having set one leg on the point marked 1, plate III, place the other on the vertical line drawn from the point marked 1, 3; then, by drawing a line between these two points, all the intermediate divisions will be found at the points where the verticals inter- sect this line. Next, take a heavier weight, and such as will sink the hydrometer in a fluid whose specific gravity is 1,3, nearly to the top of the scale; then transfer it into a solution whose specific gravity is 1,6 ; take off by the compasses the distance between those two points, and transfer it to the scale, as before. Lastly, take a heavier weight, that will sink the instrument, as before, in the fluid whose specific gravity is 1 ,6, to somewhere near the top of the scale ; then plunge it into sulphuric acid whose specific gravity is 1,845, and mark, this distance, and apply it to the scale, as before ; thus all the in- termediate divisions between water and oil of vitriol will have been obtained with accuracy to the second place of decimals, and these may now be transferred to the proper scale, as re- presented in plate II, fig. 9, ready for insertion into the tube of the hydrometer, which when done and fixed in its proper place the extremity of the tube may be sealed her- metically with the blow-pipe ; but care must be taken to seal it by the impulse of the flame only, and not by allowing any- thing to touch it, otherwise the weight of the instrument might be changed, and its accuracy, consequently, be affected throughout its whole range. I find it convenient to introduce into the tube while I am determining the distance between the points, a temporary scale, divided into minute arbitrary divisions, made of the same size and of the same paper as the one I intend for the real scale, by which 1 avoid any risk of error in measuring the divisions, and of ultimately effecting a change in the whole weight of the hydrometer. 70 CHEMISTRY. It is almost needless to mention, that the same plan of con- struction may be extended to a hydrometer for fluids lighter than water ; such an instrument may be advantageously em- ployed for determining the specific gravity of ammoniacal solutions, of sulphuric tether, &c. and will be found to give results sufficiently near for commercial purposes, if tempera- ture be correctly taken into the account ; but for alcohol I cannot do better than recommend the use of Stokes's Hydro- meter, as improved by Mr. Ainger. The above method, as has been premised, depends upon the stem of the instrument being truly cylindrical ; but should the stem be otherwise, a greater number of points must of consequence be taken, and, of course, a greater number of fluids will be required ; not less than seventeen ought to be used under these circumstances ; the interpolations may then be made as above. N° V. OXY-HYDROGEN BLOW-PIPE. The Gold Isis Medal of the Society teas this Session presented to Goldsworthy Gurney, Esq. Surgeon , for his Oxy-Hydrogen Blow- pipe, which has been placed in the Society's Repository. The investigations and discoveries of sir II. Davy, on the nature of flame, and the successful application of them in ty JB.ravltrr. % C H E M ISTR Y. 71 the construction of the miner’s safe-lamp, demonstrated that the flame produced from the detonation of explosive mixtures of carburetted hydrogen and oxygen is not capable of passing through the small interstices of iron wire gauze. It was hence concluded that a similar barrier interposed between two por- tions of a mixture of oxygen and hydrogen in the proportions necessary to produce water, would prevent the inflammation of one portion from being communicated to the other, and thus would render safe the use of that most powerful instrument, cf combustion, the oxy-hydrogen blow-pipe. Accidents, how- ever, occasionally occurred, notwithstanding the interposition of the wire gauze, and this circumstance induced Mr. Gurney to institute experiments, with the view of ascertaining the cause of these accidents, and, if possible, of preventing them. Accordingly, he first provided a jet, consisting of a cylinder of copper, three inches long, one inch in diameter, and per- forated by a hole one-eightieth of an inch in diameter, in which the difference between the areas of the section of the solid metal and of the aperture, gave to the experiment nearly all the chance of success which it could derive from such means. Through this tube, however, the flame repeatedly passed, each time exploding the reservoir. He next reduced the size and increased the number of the apertures, by casting plaster of Paris round twenty lengths of the finest steel harp- sichord wire, which were afterwards drawn out, and a brass cap fitted on, uniting all the gas passing through the apertures into one common jet. This succeeded no better, nor was any security obtained by increasing the length of the tube from three to six inches and casting lead round the wires instead of plaster. After trying, without success, tubes of all descriptions, and many modifications of wire gauze, Mr. Gurney observed, that 7 a C H EMIS T R Y. when the mixed gas was issuing from the reservoir in a state of great compression, it would not burn at the jet, and he further noticed that the explosions in the former experiments had all taken place when the pressure in the reservoir had become considerably lessened. It appeared, therefore, that though the gas under diminished pressure will pass in a state of ignition through very small tubes, yet that under stronger pressure it will not ignite w r hen actually passing through the flame of a taper, and, of consequence, that its combustion is in a greater degree affected by the mechanical force with wdiich it is impelled, than by the size of the current, or of the tube through which it passes. It immediately oc- curred that this principle might be applied in giving safety to the instrument : a new series of experiments w'as accord- ingly instituted, with an apparatus in which the amount of pressure on the gas could be accurately ascertained and regu- lated. By various modifications of the impelling power, it was proved that the gas, under moderate pressure, will return, in a state of ignition, through the smallest possible tubes, of whatever material, through the pores of cane, and even through those of Honduras mahogany ; while, by increasing the pressure, the gas may be burned with safety at the end of a tube, one -eighth of an inch in diameter, and by still greater pressure is extinguished altogether. The principle being thus established, it seemed necessary, merely to give due rapidity to the current of gas, to ensure safety to the reservoir; but that every slight diminution of its force, to which from various circumstances it might be exposed, would occasion a retrograde movement of the flame, and consequently cause the reservoir, or gasometer, to explode. After many fruitless attempts, the idea suggested itself to Mr. Gurney that he might make use of this retrograde movement of the C H E M I S T R Y. 73 flame to effect its own extinction, by allowing a partial ex- plosion in a small chamber constructed for that purpose, and interposing between the chamber and the gasometer such a combination of tubes, or wire gauze, as would, agreeably to the principles already deduced, prevent the passage of inflamed gas into the reservoir, by taking advantage of the increased rapidity which it would acquire from the explosion in the chamber. On trial this contrivance appeared perfectly to accomplish its object ; for the instant that the pressure was reduced, the flame passed back through the jet, exploded in the chamber, and was there extinguished : continuing the experiments, however, it was discovered, that when the jets exceeded a certain size they allowed the free escape outwards of the expanded gas and aqueous vapour, and thus greatly diminished the rapidity with which the remainder of the gas contained in the chamber was propelled through the interposed wire gauze ; the consequence w T as, that the flame was commu- nicated to the gasometer. To obviate this, however, merely required an increase of the mechanical force of the explosion, by enlarging the size of the chamber ; and it was ascertained that, to ensure safety, the capacity of the chamber must be proportioned to the size of the jet and of the meshes of wire gauze. With these provisions, the apparatus has, by innu- merable trials, been r proved to be effectual ; and even when acted on precisely under the same circumstances as those which allowed the explosion to pass even through the pores of dense wood, the flame has never receded beyond the safety chamber. Thus assured of having obtained his object, Mr. Gurney would have remained satisfied; but considering how difficult it is to remove the general impression of hazard attending the use of the oxy-hydrogen blow-pipe, he has introduced into 74 CHEMISTRY. the construction of the instrument the additional precaution of a cistern of water between the jet and the bladder contain- ing the gas. The following references to the engravings, plates IV and V, will supply a complete description of the form and con- struction of the instrument. a is the reservoir or gasometer, consisting of a small bladder, supported on a table b , and surmounted by a thin board c, which is strengthened by the ribs d d, and attached by slight threads to the four wires e e e e which pass freely through holes in the table b and are fastened at their lower extremi- ties to the board f called the pressure board. This board is perforated in the centre, and the aperture is occupied by the upright rodgg, which guides it in its motion up and down. To this board the hand of the operator is applied for the pur- pose of compressing the gasometer and of causing the gas to escape at the jet A, the nature of the communication of which with the gasometer is explained in the section fig. 1 , plate V, in which a is the lower part of the gasometer, attached to a brass neck in the cap over the cylindrical chamber A:, of which a horizontal section is shown on a larger scale at fig. 2. This chamber, together with the tubes on each side of it, as far as the letters z z, is concealed in the table b , which has a slight concavity formed in its centre, to offer a more convenient resisting surface to the pressure of the bladder. The gas is driven in the direction marked by the arrows, till it passes into the curved pipe /, immersed in the cylindrical water- vessel m, through which it rises in bubbles. The water- vessel is closed by a cork m, so fitted, that in the event of an explo- sion taking place there, the cork would be thrown out and no farther consequences ensue. There is another curved pipe o o, running up into the cork n, which, for the present, it may CHEMISTRY. 75 be supposed does not exist, and that the gas finds its way im- mediately from the surface of the water to the chamber p ; it then passes through about sixty layers of wire gauze q (having eighty meshes to the inch), next into the chamber r, thence through about twenty other layers of similar gauze s, into the chamber t f and lastly escapes at the jet h, where it is inflamed. Having described the progress of the gas from the gasometer to the jet, it will best explain the nature of the contrivance for preventing any mischief arising from explosion, to trace the effect of an explosion backwards to the gasometer. As soon as the pressure on this last is sufficiently reduced, the flame at the jet recedes and inflames the gas in the chamber t, the mechanical force of which explosion is supposed adequate to prevent the passage of the flame through the wire gauze s , according to the principles before alluded to. Should it fail to do this, a second explosion takes place in the chamber r, the force of which acts on the second series of wire gauze layers ed ^ very extensive : I traced its presence to a distance of half a mile m the square. It is fine gra- nular, and may be employed for the finest works of com- mon sculpture; and 1 have no doubt but that there may also be raised fine blocks fit for statuary. As to its quality, its texture and whiteness approach nearer to that of the Parian than to the Carrara marble. It is very well known that perfect blocks of the Carrara marble are procured with great difficulty; and I firmly believe that the marble of Dunloughy is free from mica quartz grains, and other substances interfering with the chisel, which so frequently disappoint the artist who works upon the marble from Carrara.” In a subsequent letter, Mr. Dombrain says, that a small block of the marble has been put into the hands of Mi. Hogan, a statuary lately arrived from Italy. CHEMISTRY. 225 Having roughed out a head from it, he reports that the grain is coarse, but that it would answer extremely well for colossal statues ; and that it has the rare quality of being entirely free from metallic substances. On breaking off a small piece from the outside of the block its colour appears white; it is coarse-grained, and the granulations consist of slightly iridescent curvilinear laminae. A member of the Committee (a sculptor) observed, that all British marble hitherto known is harder than the Italian ; and as, at present, the price of this latter in block is not more than from one and a half to three guineas per foot cube, the use of Devonshire and other native marbles has been entirely discontinued. Of the sample actually before the Society no fair judgment can be formed till it has been cut up. The block was accordingly divided into three slabs, two of which were cut in the direction of the bed, and one at right angles to it. The colour of the former is more or less greyish blue ; but there is reason to believe that this tint will disappear on exposure to light and weather, because the stone from the outside to the depth of an inch or more has been thus bleached. The latter slab has none of the grey colour, but is generally of a very pale buff, which here and there is of a deeper stain. One sculptor who examined these slabs finds the marble to be decidedly inferior to that of Carrara, in being composed of larger crystalline grains, with inter- stices between, in which the putty and other polishing powders imbed themselves, producing black specks. If, however, large blocks, equal in quality to the sample, could be procured, they would be applicable to colossal works in sculpture, sepulchral monuments, &c. Q VOL. XLV I II. 226 CHEMISTRY. Another sculptor states, that this Irish marble differs from, and is inferior to Parian, in being porous and less compact; but this defect is apparent chiefly in the slabs cut in the direction of the bed. It nearly resembles a specimen of North American marble that he has seen. It might be advantageously applied to common purposes, such as slabs for paving halls, and common chimney- pieces, if it could be brought to market at a price not exceeding half a guinea per cube foot, this being about half the price at present of Italian veined marble. The price of Devonshire marble at the quarry is about eight shillings per cube foot. It was likewise stated, that, ten or twelve years since, an Italian artist, of the name of Prosperi, cut a recumbent figure, about two feet long, from a block of Irish marble, extremely similar to Mr. Dombrain’s, and probably from this very quarry, while it was worked, or attempted to be worked, by Mr. Walker. Magnitude, and tolerable uniformity of colour, are essential requisites in marble for the higher uses of art : and the specimen sent by Mr. Dombrain is not large enough to enable the Society to form a fair opinion of it in these respects. PAPERS IN CHEMISTR Y. No. I. MELTING-POTS. The Sum of Twenty Pounds was this Session presented to Mr. Charles Sidney Smith, for his Method of manufacturing Melting-pots for Iron and Steel. It appeared in evidence before the Committee, that Mr. Smith’s pots were made while he was in the service of a manufacturer of metallic axle-trees, who therefore had occasion for a considerable quantity of metal castings. The fusions were performed in earthen pots, each of which was required to stand an entire day’s work without cracking, or becoming leaky by the formation of small holes called pin-holes. The failure of a pot is a serious inconvenience, both on account of the loss of time and of metal, as well as of the interruption which it creates. Great variations are observable in the duration of pots from different makers, and even in those by the same maker ; arising not so much from difference in the materials employed, as from CHEMIST 11 Y . r r oo a difference of skill or care in mixing the ingredients, and in the other parts of the manipulation. Whenever a bubble of air is left in the clay after being tempered, a pin-hole in the pot made of such clay will be the common result, for the pressure of the melted metal will probably force a way through this weak part. In order to submit the pots made by Mr. Smith to a very severe trial, one was kept constantly in work for two days and the intervening night ; during which time it received twenty-three charges, of 70 lbs. each, of cast- iron. Another pot was worked for three successive days, being raked at night in order to prevent it from cooling : under this management it received eighteen charges of cast-iron, of the same weight as the former. Neither of the pots had cracked or leaked in the least, but were now become unserviceable from the lip having- been worn down into the side, in consequence of the necessity of knocking away the scoriae after each fusion, which could not be done without breaking down a little of the lip. The pots made by Mr. Smith are composed of the three following ingredients : — Stourbridge clay, coke, and plumbago, or black lead, as it is usually called. Stourbridge clay comes to market either ground or in lump ; the price charged for each is the same, and there- fore the latter is to be preferred, as less mixed with impurities. A convenient quantity of this clay is to be put on a sieve 1 -4th of an inch in the mesh, and is to be carefully hand-picked, all pebbles and other impurities being thrown aside ; it is then sifted on a board and put into a bin. Those pieces which will not pass through are transferred to a mortar with a spring pestle, in which they are pounded till they are fine enough to pass through the < 5(5 CHEMISTRY. fine sieve, the meshes of which are 1 -8th of an inch wide. This fine clay is put in a barrel by itself. The coke is thus prepared : — The masses, in the state they come out of the oven (for gas coke is of inferior quality), have their tops and bottoms knocked off; the middle part only, which is of a uniform firm texture, being reserved for use. The coke is now to be pounded, taking care so to manage, by moderating the blow of the pestle, that as little dust as possible may be made. When duly pounded, it is to be thrown on the fine sieve, and all that passes through is to be rejected; it is then to be transferred to the coarse sieve, and what comes through is now of a proper size. The plumbago is Mexican, and is to be reduced to a very fine powder. Ihe board called the walking board, on which the mixing and tempering the ingredients is performed, is six feet square, having cross pieces on the underside to raise it about an inch from the ground. The process commences by mixing on the coarse sieve eight quarts of clay and five quarts of coke, and sifting them together on the walking board ; here they are to be still farther mixed by hand, till the mass appearing uniform, it is to be collected in a heap : clean water is then to be added and stirred in, so as to make the mixture ol the consistence of mortar. One treader, or, for expedition sake, two, is then to get on the board, and is to tread the mass well with his naked feet, working it chiefly with the heels: when trodden, it is to be turned over or thrown with a spade, and is again to be trodden, alternating these two processes for about twenty minutes. Then mix on the fine sieve four quarts of finely- pounded clay and 2 lbs. of the pounded plumbago, and CHEMISTRY. 57 sift a little of it over the mixture on the board ; tread and throw it as already described, then sift on more of the fine clay and plumbago ; and proceed in this manner till the ingredients are thoroughly incorporated, and the air has been all trodden out. The mixture should remain a night in lump, and the manufacture of melting-pots from it may begin the next morning. The apparatus is, on the whole, very similar to that used by Mr. Anstey, and figured and described in the 43d vol. of the Society’s Transactions, p. 32, consisting of a four-legged board, called a horse, for the workman to sit on, having near its fore end two uprights supporting a cross board, through which a round hole is made, capable of receiving the stem of the plug or core. Per- pendicular to this hole is a socket for the reception of a pin that terminates the stem of the core, and tends to keep it upright and steady ; the core, fixed on the top of the stem, and therefore an inch or two above the cross board, is a cone as large as the cavity of the melting-pot, with a border below to regulate the thickness of the pot. The best dimensions for the horse are 3 feet 6 inches in length, 9 inches in width, and 3| inches in thickness: it should be raised sufficiently high to allow the workman to sit on it with his feet resting on the ground, and the part where the thighs press should be rounded off and curved in a little. The cross board, which receives the stem of the core, should be raised 6 inches above the horse; and upon it is erected the square or gage, 18 inches high, and 10 inches in the blade. The cap of the core should be of basil or thin sheepskin. Every thing being ready, the core is first to be rubbed well with plumbago, to prevent the cap from sticking to it ; the cap is then to be put on the core, and a piece of 58 CHEMIST RY. the mixed materials, or walk, as it is technically called, large enough for the melting-pot, is to be cut off from the mass. A pot capable of holding 70 lbs. of cast-iron requires 16^ lbs. ; one for 35 lbs. of brass requires 10 lbs. The piece is to be worked and beaten up well on the walk-board, and is to be carefully made into a lump, which, a hole being then made in it, is to be fixed on the top of the core. The workman then takes a flat piece of board 4 inches square with a handle, called a flatter-, and strikes it, beginning at the top and bringing down the clay gradually till it has got as low as the rim at the bottom of the core. During this, the stem of the core being grasped by one hand and turned gently round, the core itself, with the clay on it, is brought successively under the action of the flatter. Great care is to be taken during this operation that no air gets into it, or, if any bubble should appear in the clay, it is to be cut out with a knife. The bottom of the pot is now to be beaten quite flat, making it of the proper thickness by the gage, and observing that the core is not made to rise from its socket by any clay getting under the bottom of the core; for the consequence of this would be, that the bottom of the pot, though regu- lated by the gage, would be too thin by all the rising of the core. The workman now dips one hand in water, and presses the pot, rubbing it from top to bottom, while the other hand is turning round the core. The effect of this is, that the pot becomes of a uniform thickness, not varying in any part so much as T V of an inch. Finally, the pot is to be smoothed all round as well as at the bottom, and the process is completed. The first pot of each day’s work should be cut up with a knife, to ascer- tain that there are no air-holes, and that the tempering has been properly performed. CHEMISTRY. 59 A soft, new-made pot might get out of shape by being handled ; the core, with the pot on it, is, therefore, taken off the horse and carried to a quiet sheltered place, and the pot being then set on its bottom, the core is raised out, leaving the cap within, which itself parts from the pot with a little management. The lip is then made by pressing the handle of the trowel from within against the edge of the pot, having placed the fore-finger and thumb, one on each side of the edge, to limit the action of the pressure. It is by no means an unnecessary precaution to put the new-made pot in a quiet place, for if subject to any considerable jarring before it gets dry and hard, the pot will sink and not carry its rated charge of metal. From twenty to thirty-six melting pots, of excellent quality, may thus be made in a day. No. II. PREVENTION OF DRY ROT. The large Silver Medal was voted to Mr. Edward Carey, It. N., for his method of Preventing Dry Rot in Ships’ Timbers ; a Model, illustrative <>J his method, has been placed in the Society’s Repository . Every one knows that deciduous trees are full of sap during the period which begins in early spring, and terminates with the complete expansion of the leaves. 60 CHEMl STRY. If at this time a branch be cut off, or if a hole be bored into the trunk, an exsudation of the sap, in greater or less abundance, will follow. The bark at this time may be stripped off from the wood with ease, and in large flakes ; and every part of the tree is, so to speak, bathed in moisture. A chemical analysis of sap shews it to be a watery liquor containing some sugar, mucilage, and extractive matter. In several trees, as the birch and sycamore, the sap is sufficiently copious and saccharine to furnish a fermentable liquor, from which a weak, though perfect, wine may be made ; and the sugar-maple of North America produces a sap, from which sugar is annually made in considerable quantity, by boiling it down to a proper consistence. At the fall of the leaf the wood of a living tree is considerably dryer than it was in spring, and contains a less quantity of sugar and of other easily decomposable vegetable principles. The old method of preparing oak timber for naval use appears to have been, to cut down the tree in the winter, and, after lopping the ends of the branches, to let it remain where it fell till the next summer, without stripping the bark from it. During the spring the buds in the bark, and in those sprays which had not been removed, began to vegetate and grow ; and in so doing- absorbed, consumed, and removed a part, probably nearly the whole, of the sap which was contained in the trunk at the time of its being felled. The imperfect condition of the roads rendered it impossible to convey heavy timber along them, except in the height of summer, so that a tree grown in the weald of Sussex, or even in the remote parts of the New Forest, often did not reach Portsmouth yard till the second year after it had been felled. Here it was stripped of its bark, and stacked either in the open OH EM ISTRY. 61 air or under cover, till, by continued exposure to a free draught of air, it was seasoned, that is, dried. During this method of management fungous rot ap- pears to have scarcely existed in our shipping, whether naval or mercantile. Of late, within the last fifty years, a great increase has taken place in the navy, without a corresponding supply of oak timber of home growth ; and, at the same time, the price of oak bark, for the use of the tanner, has been continually augmenting. These circumstances have led to the practice of felling timber in spring, when, from the abundance of sap, the bark is easiest stripped. But, with the removal of the bark, that vegetation which used to take place during the summer after felling, and which probably was so advantageous in seasoning the wood, is prevented. The naked wood, full of moisture, is exposed to the drying winds of spring and the heat of summer; in consequence of which it becomes shaken and injured by numerous wide clefts, occasioned by partial drying, which admit the rain, and probably also the microscopic seeds of fungi to the heart of the tree. The immense demand of our dock-yards during the last half century of almost incessant war, necessarily occasioned a diminution of the time requisite for seasoning. Hence the timber employed in the construction of shipping has probably of late years been defective, not only from insufficient drying, but also from containing sugar, mucilage, 8tc. the elements of sap, which, when not acted on by the living power of vege- tation, are susceptible of vinous and acetous fermentation, and, finally, are resolvable into a matter in which the seeds of fungi will grow with great vigour. To the duration of timber so circumstanced, its situ- ation in the hull of a ship is singularly unfavourable. 62 CH EMISTRY. The external surface, both without and within the ship, is covered with pitch, turpentine, or paint, by which the further escape of moisture (or the process of seasoning) is entirely prevented. The other surfaces of the timber are exposed, in darkness, to the action of a warm, moist, stagnant air ; that is, are in a situation the most fa- vourable for spontaneous decomposition, the rapidity of which is probably hastened tenfold by the grow T th of fungi, the slender roots of which penetrating into the pores of the wood occasion the destruction of its sub- stance to proceed even more rapidly than that of its surface. It is well known that a saturated solution of common salt is destructive of vegetable life even in those plants which flourish only in sea water, and a still weaker solution is fatal to all except the maritime plants. Hence it might be argued that ship timber would be secured from rot (as far as this is occasioned by the growth of fungi) by injecting its sap vessels with a solution of salt; and this treatment has been found efficacious in practice. Merchant vessels that convey salt in bulk are not liable to fungi. A frigate, infested with fungous rot, was acci- dentally sunk in the Mediterranean, and when weighed again, after remaining under water for some months, was found to be free from fungi, and so continued. In the United States of America, many vessels are built of timber quite green ; and in these it is by no means uncommon to fill up the spaces between the timbers with salt; and vessels so salted, it is understood, bear a higher price in the market, on account of their greater durability. Again, it might be argued, that oil would be effica- cious, by penetrating into the sap vessels of timber, and CHEMISTRY. 63 thus preventing the access of moisture : in confirmation of which, it may be observed that Greenland ships and other whalers are not liable to fungi. Agreeable to this theory is the practice which prevailed at Boston more than forty-five years ago, to hollow the heads of the timbers and to fill them with oil during the building of the ship. The efficacy of oil combined with salt, may be argued from the known fact, that vessels engaged in the New- foundland fishery, in which the salted fish are stowed in bulk, are not at all liable to fungous rot, and that the bottom of the hull of such vessels will last as long as two or three successive tops. From these and similar facts, Mr. Carey was con- vinced that a mixture of oil and salt, applied to the timbers of ships, would be very efficacious in preventing rot. He also thought that it would be found useful to add to this composition a quantity of powdered charcoal, in order to increase its bulk at small expense, without introducing any noxious ingredient; and which should have the farther advantage of being so light as in the least possible degree to affect the buoyancy of the vessel. In the year 1785 he built two schooners of eighty tons each, in the island of Cape Breton, for a Mr. Simmonds, and filled up all the spaces between the timbers and elsewhere with a composition made of the before-men- tioned ingredients. The next year he removed to the Gut of Canso, and there built, of green wood, fresh from the forest, a brig of 200 tons for a Mr. Williams, an American refugee. In this vessel, before he put on the plank sheers, he bored a hole in the centre of each timber-head, fore and aft, on each side, as deep as he could without injuring the til EM 1ST R Y, 64 treenails, keeping clear of the bolts and nails. These holes he filled up with a mixture of cod or seal oil, salt, and fine charcoal, brought to as thick a consistence as would run. The spaces between the timbers and else- where he filled with a similar composition, but of the consistence of mortar. The way in which it was applied was this: — The space being filled with the composition, a block of wood smaller than the space was then laid on the surface and driven in : the compression forced the mixture into the smallest adjacent crevices, and the block was allowed to remain. Stops of wood were also inserted where required, in order to keep the whole in its place and prevent it from slipping down. The brig, filled in as described, was launched, and was employed in the trade between the United States and the West Indies. In the year 1816, Mr. Carey, on his return from the West Indies, by way of the United States, proceeded to New York, where he accidentally met with Mr. Williams, the owner of the brig. This gentleman informed Mr. Carey that the vessel which he had built for him thirty years before was then at New York, that he had had occasion to open her a short time before, and found her as sound as on the day she was launched. He invited Mr. Carey to come on board, and allowed him to bore with a half-inch auger into any parts where he suspected decomposition might have taken place. Mr. C. ac- cordingly did so, and found every core brought out by the auger to be perfectly sound. As Mr. Carey had no intention at that time of making public the result of his experiment, he did not request of Mr. Williams any certificate of the facts above stated : but when, in 1827, he communicated these particulars to CH EM1STKY. 65 the Society, it was conceived by the Committee, to whom the investigation of the subject was committed, that, although they had no reason whatever to question the correctness of Mr. Carey’s statement, the public would be better satisfied to have the particulars of this very interesting and important experiment substantiated by the attestation of Mr. Williams. But Mr. W. was not a resident at New York; and although Mr. Carey inserted an advertisement in the New York newspapers, as also did J. A. Yates, Esq. of Liverpool, on the part of the Society, in the newspapers both of New York and Boston, nothing could be heard of Mr. Williams till Mr. Carey learnt, some time after, that Mr. W. had died in the West Indies three years before.* No. III. BONE GLUE. Mr. Walter Macqueen, 8 , Marine Street, Brighton, communicated to the Society a sample of Bone Glue, prepared by him in the following manner. The bone, previously deprived of its fat by boiling, is to be macerated in muriatic acid, diluted with twice its bulk of cold water. When the phosphate and carbonate of * It is understood that the Navy Board at present have the spaces between the timbers in men-of-war filled with a mixture of chalk, oil, and Stockholm tar, injected into the bottom of the frame by means of a forcing pump. VOI,. XLV1I. F 66 CHEMIST R V. lime have been thus removed, a mass of gelatinous fibre remains, which is to be repeatedly washed in warm water till the whole of the acid is got rid of. It is then to be put into a covered digester, with a proper quantity of water, and is to be kept at a heat not exceeding 200° F. without stirring till the solution is completed. The thick liquor is then to be poured into a box and allowed to grow cold, when it will be found to have acquired the consistence of a stiff jelly, and is to be cut into cakes and dried in the usual manner. Five pounds of bone and five pounds of muriatic acid yield one pound of glue, of an orange - yellow colour, dry, hard, brittle, and of less specific gravity than glue from skin. Part of the specimen sent by Mr. Macqueen was put into the hands of the carpenter usually employed by the Society, who reported that he took equal weights of bone glue and of the best London-made glue, and soaked them for a night in water; they were then put into separate pots, were just covered with water, and were boiled. The bone glue was quite thin and did not require more water ; the other boiled thick, and it was necessary to add more water, in order to bring it to a state fit for use. The solution of bone glue was found to chill, i. e. to become gelatinous, much sooner than the other ; and is, therefore, not applicable to cementing long joints, but answers very well for small work. It is also well adapted for laying veneers, being stronger than common glue, making a closer joint, and not being liable to be affected by damp. The Committee directed the Secretary to make some comparative experiments, which was accordingly done, with the following: result : — Two varieties of London glue were taken. No. 1. Common glue, of a yellowish - brown colour. CM KM IS TRY. 67 somewhat flexible, and with an odour like that of stale liquid glue. No. 2. Best London glue, of a darker colour than the preceding, hard, brittle, inodorous. No. 3. Mr. Macqueen’s bone glue. Two hundred grains of each were put into separate equal coffee cups, with two liquid ounces of river water. On the second day : — No. 1. Has swelled the least, and has a putrid odour. No. 2. Has swelled the most, and is inodorous. No. 3. Has swelled nearly as much as No. 2, and is also inodorous. On the third day : — No. 1. Is less swelled than the others, much of the water remaining unabsorbed, and its odour is very putrid. No. 2. Has absorbed nearly the whole of the water, and is inodorous. No. 3. Is in the same state as No. 2. Each cup was put over the fire in a vessel of cold water, and by the time that the water began to boil, each of the glues was perfectly dissolved. No. 2 made the thickest solution. No. 1 was thinner. No. 3 was almost as thin as water. The water lost by evaporation since the beginning of the experiment was, in No. 1, 125 grs. ; in No. 2, 124 grs.; in No. 3, 78 grs. The real proportions, therefore, of glue and of water, in the respective solutions, were — No. Glue. Water. 1 1 : 8-35 2 1 : 8-36 3 1 : 8*82 On cooling, all the three solutions became gelatinous 68 CHEMISTRY. nearly at the same time. No. 1 was an imperfect tre- mulous jelly. No. 2 was less tremulous. No. 3 con- siderably sti tier than No. 2. The glues thus prepared were put into the hands of the same carpenter as made the former trials. At a subsequent meeting of the Committee, three pieces of mahogany were produced (each composed of two pieces), cemented by the three samples of glue. The carpenter reported, that all the solutions were thinner than glue as usually prepared ; that No. 3 was by far the thinnest, and, if used quickly, before it had time to chill, a smaller quantity of it than of the others was required ; and that it made rather a firmer joint. He also stated that in laying veneers, and in certain kinds of cabinet-work, the bone glue may be used with great advantage, because, from the extraordinary fluidity of its solution, a glue might be prepared containing twice the proportion of solid jelly that is contained in other liquid glues, and yet remain quite fluid enough for use. Such a glue would, in many cases, be of great advantage, where extraordinary strength is required. Of the three specimens of mahogany : — No. 1 broke altogether in the joint, and is, therefore, decidedly the weakest. Nos. 2 and 3 broke partly in the joint, but chiefly in the wood ; and there does not appear to be much difference between them. «'l) F. MIST R Y. 09 No. IV. OBSERVATIONS ON WRITING-INK. j By J. Bostock, M.D., F.R.S. fyc., Chairman of the Committee of Chemistry. When the sulphate of iron and the infusion of galls are added together, for the purpose of forming ink, we may presume that the metallic salt or oxide enters into com- bination with at least four proximate vegetable principles, — gallic acid, tan, mucilage, and extractive matter; all of which appear to enter into the composition of the soluble part of the gall-nut. It has been generally supposed, that two of these, the gallic acid and the tan, are more especially necessary to the constitution of ink ; and hence it is considered, by our best systematic writers, to be essentially a tanno-gallate of iron. It has been also sup- posed, that the peroxide of iron alone possesses the property of forming the black compound which consti- tutes ink, and that the substance of ink is rather mecha- nically suspended in the fluid than dissolved in it. Ink, as it is usually prepared, is disposed to undergo certain changes, which considerably impair its value; of these the three following are the most important : its tendency to moulding; the liability of the black matter to separate from the fluid, the ink then becoming what is termed ropy ; and its loss of colour, the black first changing to brown, and at length almost entirely dis- appearing. 70 C II EM I ST R Y. Besides these, there are objects of minor importance to be attended to in the formation of ink. Its consistence should be such as to enable it to flow easily from the pen, without, on the one hand, its being so liquid as to blur the paper, or, on the other, so adhesive as to clog the pen, and to be long in drying. The shade of colour is not to be disregarded ; a black, approaching to blue, is more agreeable to the eye than a browner ink ; and a degree of lustre or glossiness, if compatible with the due consistence of the fluid, tends to render the characters more legible and beautiful. With respect to the chemical constitution of ink, I may remark, that although, as usually prepared, it is a combination of the metallic salt or oxide with all the four vegetable principles mentioned above, yet I am induced to believe, that the last three of them, so far from being essential, are the principal cause of the difficulty which we meet with in the formation of a perfect and durable ink. I endeavoured to prove this point by a series of experiments, of which the following is a brief abstract. Having prepared a cold infusion of galls, I allowed a portion of it to remain exposed to the atmosphere, in a shallow capsule, until it was covered with a thick stratum of mould ; the mould was removed by filtration, and the proper proportion of sulphate of iron being added to the clear fluid, a compound was formed of a deep black colour, which shewed no farther tendency to mould, and which remained for a long time without experiencing any further alteration. Another portion of the same infusion of galls had solution of isinglass added to it, until it no longer pro- duced a precipitate; by employing the sulphate of iron, a black compound was produced, which, although paler (’ll EM 1ST RY. / than that formed from the entire fluid, appeared to be a perfect and durable ink. Lastly, a portion of the infusion of galls was kept for some time at the boiling temperature, by which means a part of its contents became insoluble; this was removed by filtration, when, by the addition of the sulphate of iron, a very perfect and durable ink was produced. In the above three processes, I conceive that a considerable part of the mucilage, the tan, and the extract, were respectively removed from the infusion, while the greatest part of the gallic acid would be left in solution. The three causes of deterioration in ink, the moulding, the precipitation of the black matter, and the loss of colour, as they are distinct operations, so we may presume that they depend on the operation of different proximate principles. It is probable that the moulding more parti- cularly depends on the mucilage, and the precipitation on the extract, from the property which extractive matter possesses of forming insoluble compounds with metallic oxides. As to the operation of the tan, from its affinity for metallic salts, we may conjecture, that, in the first instance, it forms a triple compound with the gallic acid and the iron, and that, in consequence of the decom- position of the tan, this compound is afterwards destroyed. Owing to the difficulty, if not impossibility, of entirely depriving the infusion of galls of any one of its ingre- dients, without, in some degree, affecting the others, I was not able to obtain any results which can be regarded as decisive ; but the general result of my experiments favours the above opinion, and leads me to conclude, that, in pro- portion as ink consists merely of the gallate of iron, it is less liable to decomposition, or to experience any kind of change. 72 CM EM 1ST RY. The experiments to which 1 have alluded above, con- sisted in forming a standard infusion, by macerating the powder of galls in five times its weight of water, and comparing this with other infusions which had either been suffered to mould, from which the tan had been abstracted by jelly, or which had been kept for some time at the boiling temperature, and by adding to each of these respectively both the recent solution of the sulphate of iron, and a solution which had been exposed for some time to the atmosphere. The nature of the black com- pound produced was examined by putting portions of it into cylindrical jars, and observing the changes which they experienced, with respect either to the formation of mould, the deposition of their contents, or any change of colour. The fluids were also compared by dropping portions of them upon white tissue-paper, in which way both their colour and their consistence might be minutely ascertained. A third method was, to add together the respective infusions and the solutions of the sulphate of iron in a very diluted state, by which I was enabled to form a more correct comparison of the quantity and of the shade of the colouring matter, and of the degree of its solubility. The practical conclusions that I think myself war- ranted in drawing from these experiments are as follow : — In order to procure an ink which may be little disposed either to mould or to deposit its contents, and which, at the same time, may possess a deep black colour not liable to fade, the galls should be macerated for some hours in hot water, and the fluid filtered ; it should be then exposed for about fourteen days to a warm atmosphere, when any mould which may have been produced must be removed. A solution of sulphate of iron is to be employed which <11 EM1STRY. 73 has been exposed for some time to the atmosphere, and which consequently contains a certain quantity of the red oxide of iron diffused through it. I should recommend tlie infusion of galls to be made of considerably greater strength than is generally directed, and I believe that an ink formed in this manner will not necessarily require the addition of any mucilaginous substance to render it of a proper consistence. I have only to add further, that one of the best sub- stances for diluting ink, if it be, in the first instance, too thick for use, or afterwards become so by evaporation, is a strong decoction of coffee, which appears in no respect to promote the decomposition of the ink, while it improves its colour, and gives it an additional lustre. No. V. RAISIN WINE. Descrwtion of a method of making Raisin Wine, by A. Aikin, Secretary , F.L.S. F.G.S. fyc. I have for some years been in the habit of making, for use in my own family, a light, dry raisin wine ; I have also noted down, with more or less minuteness, the pro- gress and result of several of these experiments ; and I beg leave now to offer them to the Society, in the hope that thereby some additional light may be thrown on a very important branch of domestic economy. It appeared to me, from some previous comparative 74 CH EM 1ST U Y. trials with black currants, and with others of our native fruits, that none of them are so well adapted to make light d ry wines as the better kinds of raisins : a farther advantage attends the use of this latter fruit, that the wine may be made at the season when the temperature is most favourable to the due progress of the fermentation. The raisin which I have been most in the habit of using, and which I prefer, is the Muscatel. It is im- ported in boxes, containing about twenty pounds; and, when new, is in common use as a table fruit. In this state it would, doubtless, make a wine of excellent qua- lity ; but its price prohibits its employment for this purpose. In those which remain unsold for about a year, the rich pulp of the recent raisin becomes mixed with sugary concretions which render it less acceptable at the dessert; and the price of such fruit, being from tenpence to a shilling a pound, brings it within the reach of the domestic wine-maker. That matter, whatever it be, which, through the pro- cess of fermentation, converts a solution of sugar into vinous liquor, exists in raisins in sufficient abundance to change into wine a greater quantity of sugar than the fruit itself contains ; and I have found it advantageous, both as regards the price and the quality of the product, to add to any given quantity of raisins from one-tenth to one-third of their weight of sugar. In order, however, to avoid tainting the wine with the peculiar flavour of cane- sugar, I use good loaf, at the average price of 10 d. or 1 1 c/. a pound. In my early experiments I poured hot water on the raisins, and allowed them to remain therein twelve hours, more or less : by this time the raisins were plumped up, and I pressed them between fluted wooden rollers, in < H EMISTRY. order to break the skins and press out the juice. This process, however, by no means succeeded to my wish ; the rollers were clogged and strained by the fruit which adhered to them, and many of the berries, in consequence of the toughness of their skin, passed through the rollers entire. I therefore adopted the plan of having the raisins chopped (without previous maceration) on the same kind of tray, and with the same kind of chopper, as is used in making minced meat ; and I have had no reason to vary from this method, except that of late I have directed the raisins to be chopped finer than they were at first. Previous to the raisins being chopped, the stalks are separated for a use that will be mentioned hereafter. I have tried several proportions of ingredients, but those from which I have obtained the best results are, three pounds of raisins and one pound of sugar to an ale gallon of water. I prepare the must sometimes by mashing, sometimes by maceration. The mashing is performed in the following manner : — The chopped raisins being put into an open tub or earthenware pan, I pour on them hot water, in the pro- portion of about a quart to four pounds of fruit. My object, in this first mash, is to extract the greater part of the saccharine mucilage as little altered as possible ; I therefore heat the water no higher than about 120° Fahr. : the water and fruit are mixed, and, after standing for about a quarter of an hour, the whole is stirred together as accurately as possible by hand, taking care to break down all the lumps, and, in a few minutes after- wards, is placed on a sieve over a tub, where it drains for CHEMISTRY. 76 a short time: the husks are then lightly pressed by hand, and are returned to the mash-tub. d he second mash is made exactly in the same manner as the hi st , and the husks, after pressing, are returned again to the mash-tub. Ihey will now be found to have lost the whole of their clamminess, though they are still sweet; I therefore con- clude that the saccharine mucilage is now for the most part extracted, and my principal object in the subsequent mashes is to dissolve out the tartar. For this purpose the water of the third mash is put on at the heat of 150° 01 160, and is conducted in the same manner as the former. The liquor thus obtained is considerably acidulous, having the flavour of the raisins and but little sva eetness. Three-fourths of the mash being now made, it is tasted in order to ascertain whether it is sufficiently astnngent, and according to the intended astnngency of the wine, I either altogether reject the stalks or use the whole or a part of them. If a somewhat astringent wine is intended, the last mash is thus prepared : I pour boiling water on the stalks, in a separate tub, and after they have been macerated for about a quarter of an hour, I pour the liquor on the husks and mix them well with it: in a quarter of an hour more the liquor is put on the sieve and the husks are well squeezed by hand. W hile the last mash is preparing, I transfer the liquor of the fiist three mashes to the fermenting* tun, and dissolve the sugar in it : I then add as much of the last mash as is requisite to bring the must to the due pro- portions, viz. one ale-gallon of must to three pounds of fruit and one pound of sugar. The time occupied by the above processes is four or five hours, and the temperature CHEMISTRY. 77 of the must, when put in the fermenting tun, is usually about 70°. If the weather is warm and apparently more likely to become hotter than colder, I pour the must into the fermenting tun with as little agitation as possible ; but if the weather is cool and not likely to get warmer, I dash each pailful against the sides of the tun, pouring it in from as great a height as I can conveniently reach : by this means it is more mixed with atmospheric air; and liquor thus treated will often begin to ferment in less than twelve hours. If the must is at the temperature of 70°, fermentation begins in from twelve to thirty-six hours, according as it is treated ; and the scum which rises is sometimes taken off every day, and sometimes allowed to remain till the liquor is about to be removed from the fermenting tun. If the fermentation is languid, I keep on the cover of the tun and stir the scum daily into the liquor : if too rapid, I take off the cover and remove the scum as it rises. The lowest temperature at which I have observed fermentation to take place is 48°. On this occasion the must was at 48° when it was put into the tun, the tem- perature of the cellar being 46°. On the next morning it was at 47°, and on the second morning at 46°; the temperature of the cellar remaining the same: on the third morning both the liquor and cellar were at 45°, no signs of fermentation having yet appeared. The liquor was then placed before a fire for some hours, and fermentation began ; it was then removed to the cellar, and on the fourth day the fermentation was going on steadily but slowly at 48°. I have never made wine when the heat of the air was above 70°, and, on the whole, 1 prefer a temperature of from 55° to 60°. That 78 CHEMISTRY. of the liquor, after the second day, continues about 2° above that of the cellar till the eighth or ninth day, when the fermentation has usually become languid, and the heat of the liquor and of the cellar at that time rarely differ more than one degree. The liquor is now vinous but sweet; and after care- fully skimming it, I transfer it to glass carboys, con- taining about six or seven gallons, or to stoneware barrels of the same size.* I insert in the bungs glass tubes of safety, and, on the second day, pour into them about an inch of quicksilver to exclude the air. The cement that I use for covering the bungs is a mixture of wax and resin. Carbonic acid continues to bubble through the quick- silver in the safety tube for some weeks ; after which it ceases ; but the column of quicksilver in the exterior leg of the syphon is always higher than that in the interior leg. I have never seen a single instance of the outer air passing into the carboy. The loss during the fermentation in the tun is about 6 per cent; subject, however, to variations from the tem- perature of the liquor, from the scum being removed once or oftener, and from the cover of the tun being left on or off. I think the wine ought to remain an entire summer in the cask or carboy, in order that the fermentation may proceed so far as almost entirely to decompose the sugar ; and as my usual times of wine-making are April and * As barrels of stoneware are always more or less porous, they should be warmed thoroughly before a fire and rubbed over with a mixture of bees’-wax and turpentine (about one part of turpentine to three of bees’- wax) : when this thin coating is grown cold, it should be well rubbed in with a hard brush. CHEMISTRY. 79 October, that made in the former month is bottled in the March following, and that made in October is bottled about the end of September, or a week or two later, according to circumstances. I never fine the wine, being of opinion that the light dry wine which it is my aim to produce would be mate- rially injured by being deprived of its tannin through the action of isinglass or any similar substance. At the time of bottling I have seldom observed the wine to have any very sensible flavour, — meaning by flavour that compound sensation of smell and taste which characterises the finer kind of wines ; but after remaining for a year in bottle, a flavour resembling elder flowers is strongly developed, mingled generally, in a slight degree, with that of prussic acid. As soon as the wine begins to run turbid from the carboy, I pass the whole of what remains through a flannel filter ; but though I am careful that the wine, when bottled, should be clear though not bright, there is always more or less of flocculent matter deposited, which requires the bottles to be set upright in the bin, and to be decanted with care. The wine, when first decanted, is often of a very pale yellow colour, especially if high flavoured ; but in an hour or two it deepens more or less, and at length acquires a tint like that of Bucellas, the prussic acid flavour at the same time disappearing. Instead of mashing as above described, I have some- times pursued a still more simple way, — that of macera- tion; by mixing in the fermenting tun the usual propor- tions of chopped raisins and sugar with cold water, and leaving the raisins in the liquor during the whole of the first fermentation. By this method I obtain a higher-coloured 80 CHEMIST RY. wine ; but, the fermentation being generally slower and consequently longer, it is destitute of that Frontignac or elder-flower flavour which it generally acquires when treated according to the first process, and is apt to get a less agreeable flavour from the husks of the raisins. Sometimes, however, the method succeeds very well ; and the elder-flower flavour not being pleasant to many per- sons, such wine is more generally acceptable than the former. In May 1827 I made some wine in the way last described. The materials were put together on the 3d day of the month, the temperature of the liquor and of the cellar being 56°. On the 5th, at night, fermentation had just begun, the temperature of the liquor and cellar being 57°. On the 7th the liquor was 58°. From that time to the 19th fermentation went on, though languidly, the temperature of the liquor varying from 57° to 58i°, and that of the cellar from 55° to 57°. From the 19th to the 24th the weather became warm, the temperature of the cellar rose to 59°, and that of the liquor to 61°. It had now been twenty-one days under fermentation, and therefore, though it was still rather too sweet, I put it into carboys, and bottled it about half a year afterwards. This wine is now (December 1828) strong, dark-coloured for white wine, but still rather sweet, and tastes too much of the husks. CHEMISTRY. No. I. PURIFICATION OF GOLD. The Sum of Twenty Guineas icas presented to Mr. Lewis Thompson, for the following communication on his Method of Purifying Gold. Gentlemen, In the common mode of assaying gold, the alloy to be assayed is subjected to two operations, cupellation and parting, each of which requires great care and skill ; so much so indeed that success seems rather to be the effect of a particular tact on the part of the assayer than the result of a well-defined chemical process. The plan which I now propose for assaying and purifying gold is no less simple in execution than certain in effect, and is founded upon a circumstance long known to chemists, viz.: — that not only has gold no affinity for chlorine at a red heat, but that it actually parts with it at that tem- perature, although previously combined ; that is to say, the chloride of gold is reduced to the metallic state by heat alone, it cannot, therefore, possess any affinity for chlorine when red hot : this, however, is not the case with those metals with which gold is usually alloyed, it CHEMISTRY. 17 offers, therefore, at once an easy and certain means of separation. The application of these facts is all, there- fore, to which I can lay claim, as the facts themselves have been known for many years, and the reason why they have not been so applied is, that hitherto chemists have not directed their attention to this art, but have left it entirely in the hands of the assayers, who are, for the most part, ignorant of chemistry. The process here pro- posed has been abundantly tested by myself and others, and employed by those wholly unacquainted with che- mistry, as well as by men of eminence in that science, with equal success. There is, indeed, but one source of failure, and this arises from the intense action of chlorine upon the baser metals when melted, by which portions of the alloy are spirted up or projected from the cupel, as happens in the common mode of assaying silver when the heat is too great. This inconvenience is to be avoided in two ways. Firstly, by allowing the chlorine to be evolved slowly at the commencement of the operation, by which the intensity of the action at first is diminished, until the relative proportion of gold in the alloy is increased ; or, secondly, by passing the chlorine over the alloy in powder, or laminated into a thin plate at a dull red heat for a few minutes, and then raising the temperature so as to melt it when the fumes of the metallic chlorides have visibly diminished. In conclusion, I can only add, that a very little practice will enable any one in possession of a good balance to make assays of gold with the greatest accuracy. In a course of experiments, conducted at Guy’s Hospital, in the presence of Mr. A. Aikin and other scientific gentlemen, a piece of gold was twice alloyed, and then purified by chlorine, without any sensible loss when VOL. LIU. c 18 CHEMISTRY. weighed in a balance which readily turned with the -j-i^th of a grain. The furnace which I employ for the process is made out of one of those pots employed for melting steel, and which cost about Is. 6d. each. They are from 14 to 16 inches in height, and consist principally of Stour- bridge clay and coke. Their form is rather peculiar, as the upper part is contracted so as to form a kind of dome, as in the figure. They are so soft as to be easily cut with a knife : and I have been thus far particular in describing them because the practical chemist will find them of great use in the laboratory for small furnace operations. One of these pots, then, is pierced near the bottom with four holes, at equal distances from each other and from the bottom ; parallel to and between them, but about two inches higher up, another row of similar holes is placed, the whole of which holes should be from a half to three- fourths of an inch in diameter; about three inches above these the sides of the pot are perforated with two larger holes of at least one inch in diameter. These must be diametrically opposed to each other, and upon the same level, i. e. at equal distances from the bottom. The furnace is now finished. To assay gold, place an earthenware tube in the two upper holes, and light the furnace (a mixture of coke and charcoal answers best, though coke alone will do) ; when the tube is seen to be white hot, place in it the alloy contained in a little cupel made of bone-ash, and push it along to the centre of the furnace by means of a wire, then connect one end of the tube with a bottle in which chlorine is forming from a mixture of peroxide of manganese and muriatic acid ; the chlorine will, conse- CHEMISTRY. 19 quently, pass along the heated tube and over the melted alloy, with the silver, copper, &c. of which it will com- bine and leave the gold pure and untouched. During the process dense fumes may be observed to fill the tube, and when these are no longer produced the process is finished ; the cupel may now be withdrawn, and the gold removed and weighed. I am, Gentlemen, &c. &c. To the President , $-c. Lewis Thompson. of the Society of Arts, fyc. Description. A A, steel pot. BBB, holes for the admission of air. CC, holes for the admission of the tube. D D, the tube placed horizontally in the furnace, containing E, the cupel and gold. F, the bottle in which chlorine is generated. 20 CHEMISTRY. Report of Arthur Aikin, Esq. F.L.S. Sfc. The experiments above alluded to as having been made in my laboratory, were conducted by Mr. Thompson him- self under my inspection. The gold was obtained from an assayer, and was stated to be perfectly pure ; but in many instances, on being subjected at a melting heat to the action of chlorine gas, a very small diminution of weight was observed, occasioned, no doubt, by the vola- tilisation of a little alloy, for the button of gold under- went no further diminution whatever on a repetition of the process. The gold thus purified was mixed with silver and copper, or with silver and brass ; and, being- put into a small porcelain tray, with a little chalk or common salt, was slidden cautiously to the hottest part of the tube. When the alloy was judged to be melted, chlorine gas was passed in at one end of the tube, the other either being left quite open or communicating with a small glass retort to collect the volatile products. A dense yellowish vapour almost immediately filled the tube, part of which concreted in filamentous crystals in the end of the tube ; the remainder passed into the retort, lining it with a brownish yellow crust, or, if a little water had been put into the retort, producing a greenish liquor which, by the usual tests, was shewn to contain chlorids of copper, zinc, and iron. The latter was, no doubt, derived from the ferruginous clay of which the tube was made, for the inside of it, after the process, was found to be nearly white. On examining the contents of the tray, after the pro- duction of vapour had ceased, the button of gold was found imbedded in a melted mass of clilorid of sodium (or chlorid of calcium, if chalk had been put into the tray) CHEMISTRY. 2] mixed with clilorid of silver, the presence of alkaline chlorid seeming to have the property of preventing the volatilisation of chlorid of silver. In all the first trials, the button of gold was found to weigh considerably less than before the process, and the accidental breaking of one of the tubes shewed that in the part directly over the tray several globules of gold adhered, having probably been thrown up thither by the ebullition of the alloy when the chlorine was first passed over it. Having thus discovered the cause of the failure, the process was twice more repeated, taking care to give only a low red heat in the beginning, and to pass the chlorine slowly. With these precautions, the button of gold, remaining at the end of the process, w 7 as found to be exactly ecpial to its original weight as shewn by a balance that indicated well to the -g^tli part of a grain. 7 Bloomsbury Square. A. Aiicin. No. II. GALVANIC BATTERY. The Gold Isis Medal was presented to Mr. Alfred Smee, Surgeon , Bank of England , for the following Communication on a Galvanic Battery of a new Con- struction ; a Model of which has been placed in the Society's Repository. The most valuable instrument which chemists employ for their analytical experiments is, no doubt, the galvanic 22 CHEMISTRY. battery ; but so much trouble attends its use, that, except in the laboratory of the professed chemist, it is not em- ployed to any considerable extent. Experiencing this inconvenience in the experiments which I conducted on the red ferrocyanate of potash, it became a matter of the greatest importance to ascertain how far a battery could be constructed, that at once should possess a capability of being used at a moment’s notice, and have besides con- siderable power united with cheapness of action, and, at the same time, without the necessity of much laborious cleaning after its employment. After experimenting with the batteries before known to the public, 1 became convinced that it was of the high- est importance to supersede the necessity of diaphragms, attended as they are with continual trouble and expense ; and as the power of the battery seems to depend upon the facility offered to the evolution of the hydrogen and pre- venting its adhesion to the negative metal, whereby it is coated as with a varnish, and the action almost entirely destroyed, all my experiments were directed to this ob- ject. I first perceived that the gas was not evolved equally from every part of the surface of a smooth piece of platinum, but chiefly from the corners, edges, and points. Following this hint, I roughened the metal with sand-paper and found the evolution of the gas to be increased ; and when the surface of other metals, as silver or iron, was roughened by some acid, I found the gas also to be much increased. Moreover, zinc shavings, which present the singular anomaly of having one surface ex- tremely bright and the other of a delicate frosted appear- ance, shew this property well, gas being freely given off from the rough, but adhering firmly to the bright surface. The same differences are also observed when rough and CHEMISTRY. 23 polished steel are employed. These experiments induced the idea that spongy platinum, which may he considered as a mass of metallic points, would he very efficient in forming a galvanic circuit ; and on trying the experi- ment, the quantity of hydrogen evolved from a minute portion of this substance, when touched with a piece of zinc, was truly astonishing. The mass in this state was so fragile, that the hydrogen disintegrated it almost instan- taneously, shewing that in this form it could not he used for a voltaic battery. My next experiments were to coat other metals with this finely divided platinum; and I found that platinum, palladium, or silver, answered admirably for the recep- tion of it, and similar help was afforded to the evolution of the hydrogen as the contrast between the gas given off from the smooth metal and rough metal forms a most striking experiment. Other metals received the platinum with advantage ; as plated copper or iron, and even charcoal, was benefited to a similar extent.* The metals thus roughened by platinum have, in addition to their power, some properties which are very interesting ; thus, when a piece of the prepared metal is placed in dilute sulphuric acid and touched with a small rod of zinc, gas is not given off' from its whole extent, but only from the space of a small circle ; and when contact is completed with a smooth piece of platinum, the gas will not be given off from the latter, but will travel principally to the rough portion, there to be evolved. This curious experiment affords a marked difference from those cases where the hydrogen is absorbed, as when a piece of silver is touched with a rod of zinc in dilute sulphate of copper, * Charcoal and plumbago might he considered to afford points enough for the escape of the hydrogen, but to these there is great adhesion of the gas. 24 CHEMISTRY. for in this case an immense circle of copper will be thrown down. A difficulty now arose in this stage of the proceeding, for the finely divided platinum was so easily rubbed off that it could not be practically used with advantage. However, when the silver or other metal was first roughened by the removal of the surface by an acid, then the adhesion was so great that a piece of platinum thus prepared was sent accidentally to the instrument-maker, where the workman mistook the finely divided platinum for dirt, and could only remove it with sand-paper. It now became desirable to ascertain the pow r er of the metal thus prepared relatively with the other batteries, and also with metals uncovered with the finely divided platinum ; and to make this comparison, 1 perceived that considerable difficulty occurred, for as this preparation of the metals increases the quantity, hut does not interfere with the intensity, a fair comparison can not be made where there is any impediment or difficulty to be over- come, unless that difficulty be superseded by increasing the number of cells of the battery ; and therefore, had 1 at first taken the decomposition of water as the test for my numerous experiments, they would have been attended with an immense expense ; had I taken the heating of wire as my test, that would also have been uncertain, according as the heating of large or small wires was esti- mated, but I considered that a close relative estimate of power could be ascertained by the magnetical effect. ; for, by using large wires round the temporary magnet, but little impediment was offered to the current, and thus the quantity, independent of the intensity, could be accurately ascertained ; and in repeating my experiments, at different times, on the same magnet and with the same surface of CHEMISTRY. 25 like metals, I found that they coincided with remarkable accuracy, and only one cell was required for the experi- ment. Though the weight, which was supported even by a small magnet with large wires , was inconveniently great, I determined to ascertain the distance at which a small but lesser weight was attracted. The following are the results of like surface of metal with the same metal : Layers of paper. Smooth silver, supported keeper through. . 2 Smooth copper 1 Silver heated, quenched in acid 9 — surface removed by nitric acid .... 9 Iron rough 8 Daniell’s battery 6 Platinised silver 20 iron, two or three varieties .... 20 platinum 18 Grove’s battery 26 — platinised platinum 30 Plain platinum heated, quenched in acid. . 12 By these experiments we see the great advantage of the rough metals and those covered with platinum over the smooth metals and Daniell’s arrangement. The only metal which may take the place of finely divided platinum is palladium, but probably rhodium, iridium, and osmium, would have the same property as they are precipitated in a fine black powder by zinc. The cause of this black colour is not at all evident ; and the form of the black deposit has eluded not only my own but the observation of others, although aided by the microscope. Probably, however, the colour is owing to 26 CHEMISTRY. the particles being too small to reflect the light, as is said to be the case with a specimen of quartz in the cabinet of the Duchess of Gordon, but this is merely hypothetical. We have now seen that platinum, palladium, silver, plated copper, or iron, are suitable for the finely divided metal, and these are to be first roughened, the two former with sand-paper and the three latter with a little nitric acid, which is to be again cleaned off by washing. The metals are then to be placed in any convenient vessel with a little dilute sulphuric acid, to which a small quantity of nitro-muriate of platinum has been added ; a porous tube or paper bag, containing a piece of zinc, with more dilute sulphuric acid, is also to be placed in the vessel, when, as soon as the circuit is completed, the platinum is precipi- tated on the metal placed for its reception. The cost of this process will be best understood by mentioning that the assayers sell one ounce of the prepared silver for one shilling above the price which is charged for the silver alone. The zinc which is used for the battery should be the best thick rolled zinc, as this is far preferable to the cast zinc, and it is to be amalgamated with mercury aided by dilute sulphuric acid ; for, the application of this process to the zinc of my battery will be found, unlike other batteries, not to require repeating. The form which is most suitable for the battery appears to me a matter of fancy rather than of importance, -one circumstance alone being requisite ; that is, if we are desirous of obtaining the greatest power with the utmost economy of silver, it is requisite that every portion of silver should be opposed to a piece of zinc, but the size of the latter, within moderate limits, is but of little conse- CHEMISTRY. 27 quence.* Thus, if we use the many-celled porcelain trough, it is better to surround the silver by zinc in the same way as the copper surrounds the zinc in the old Woollaston battery. If the circular form be adopted, a piece of zinc should be placed in the interior as well as the exterior of the cylinder, as by that means both surfaces of the silver are brought into action ; if the Cruikshanks be adopted, one surface is necessarily lost, but in this case plated copper answers sufficiently well, as the edges are sunk into the cement which, if exposed as in the other forms, are apt to have a portion of the copper dissolved, which is again deposited on the silver, and is liable to become oxydised and be detrimental to the power of the battery. The closer the zinc can conveniently be brought to the other metal, the more favourable will it be. Whichsoever form is adopted, the power will depend on the series and size of the plates. For decomposition of water and most other purposes, it is better to have twelve pairs of plates and then to increase their size. The bat- tery having twelve five-inch plates, which was exhibited to the Committee of the Society of Arts, gave off fifteen cubic inches of mixed gas in the first minute, and shewed great calorific power by immediately burning stout steel music wire. The duration of the action of the battery will depend, like a fire, upon the quantity of fuel supplied to it in the first instance, for, as there is no local action, it follows that the solution of the zinc will be exactly proportionate to the power produced ; and for this reason, when the battery is required to continue in operation for a long * It is of great disadvantage to employ the zinc too small, as a simple rod to a large cylinder of silver. A certain quantity of zinc seems absolutely necessary to elicit the full power of this arrangement. 28 CHEMISTRY. period, as in the method which I detailed elsewhere for the production of electrotypes, a larger receptacle for acid should be employed, or a contrivance can easily be adopted to carry off gradually, by means of syphon tubes, the saturated solution of sulphate of zinc, whilst at the same time dilute acid is supplied from another tube. A galvanic battery thus constructed owes its increase of power to the mechanical evolution of the gas, and as the experiments of Faraday have shewn that the source of power in any voltaic pile is chemical action, I have ven- tured to call my form of apparatus the “ Chemico-Me- chanical Battery.” To those versed in electrical science it may be needless to mention, that, this form of battery simply increasing the quantity of electricity, it is most important that large communications and large wires should be used in its construction, or else the whole of the additional power might be lost. # The advantages of the Chemico-Mechanical Battery are, the cheapness in its employment, and its requiring not only less manipulation than any other battery, but also less cleaning. It can be put into action at a moment’s notice, and, after having been used, can be as readily laid by. When in the fluid it will be quiet till communica- tions are made, and will then possess considerable power. It neither gives off poisonous fumes nor requires the aid of strong acids, and but one fluid is employed ; and, lastly, the amalgamation of the zinc does not require to be renewed. Such are the principal advantages of this battery, and they appear to be sufficient to entitle it to * This I have actually known to be the case : the power of the battery being almost destroyed by the use of small wires and small connexions. CHEMISTRY. 29 the very extensive application which it has met with ; but, in conclusion, I wish to be clearly understood that it does not possess the absolute constancy of Daniell’s, or the intensity of Grove’s battery. Bank of England, June I, 1840. Alfred Smee. CHEMISTRY. No. I. IMPROVED METHOD OF BLEACHING PALM-OIL. The Sum of Seven Pounds was 'presented to Mr . Charles Cameron, Ao. 50 Gascoyne Street, Liver- pool, for his Method of Pleaching Palm-Oil. 50 Gascoyjie Street, Liverpool, SlR ’ April 19, 1841. Please to favour me by laying the following communi- cation before the Society, for their consideration. I am, Sir, &c. &c. W. A. Graham, Esq. Charles Cameron, Chemist. About six years ago a process for discharging the colouring matter of palm-oil was introduced into the soap-manufactories here, which was as follows : Into a strong cast-iron pan (built in the usual way, with a fur- nace below it) the manufacturers put two, three, or more tons of oil, according to its capacity; they then, by means of the fire below, increased the temperature of the oil to 450 ; the lesult was, that the colouring matter was completely destroyed. But after working on it in the most careful manner, they were at last obliged to abandon it, for the following reasons : — CHEMISTRY. 15 1st. By the time that the whole body of the oil was raised to 450°, the bottom of the boiler was heated to above 600°, and, consequently, the portion of oil in con- tact was decomposed, and, being converted into gas, frequently caused explosions to take place. 2d. The effluvium from the decomposed portion was insufferable. 3d. If not immediately run off, on the colour being discharged, they frequently procured a black colour from the charred oil being mixed with the other. The process was cheap, but from these reasons, and the danger attending it, they were obliged to relinquish it. I have stated the above that you may the better under- stand the improvement I have effected in the process. About four months ago I was induced to make some experiments to ascertain at what point of temperature the colouring matter began to give way, when I satisfactorily found that it began to change at 230°, and on continuing the process to within 2° or 3°, more or less, of that tem- perature, with continued agitation, it gradually lost its colour, and at last became as white as home-made tallow, and of a hardness superior to any imported. I then fully established the fact, that a low temperature (230° instead of 450°), length of time, and agitation (agitation was not employed in the old process), removed all the difficulties that prevented its former success. The process which I recommend, and which is now acted upon here, may be thus described : A cast-iron pot is provided, containing from three to four tons of oil, with the ordinary furnace below it, and a horizontal revolving fan of sheet-iron placed within it, for agitation, power being obtained from a steam-engine with a speed of six revolutions per minute. In the absence of an engine, a 16 CHEMISTRY. wooden rake may be employed. The oil is then, by means of the fire, raised to a temperature of 230°; the fire is then withdrawn from below, and high-pressure steam is introduced from a boiler (15 lbs. pressure on the squaie inch of the valve), by means of leaden pipes, two oi more (according to the size of the boiler), of two inches diameter. By this means an equable temperature of 230° is obtained, without any danger of decomposing the oil, and the pi ocess is continued until the colour is completely gone. A vessel containing four tons will require ten hours to complete the process, at an expense of only 2 or 3cw r t. of slack to each ton of oil. It appears to me that the colouring matter is discharged by the absorption of oxygen from the atmosphere, as oil at a high temperature is known to have a strong affinity for oxygen at a high temperature, and hence agitation is essential, so as continually to present a new surface. I inadvertently made it known, and although it is of great importance to the trade, I shall derive no benefit from it. 50 Gascoyne Street, Liverpool. ^ TR * May 1 3th, 1841 . I received yours of the 10th inst., in which you observe that the principal cause of the postponement was the absence of evidence of the efficacy of the process,” and requesting the names and address of persons having adopted it on a large scale, that you might write to them, &c. With regard to scale, it has been applied to from tv'o to four tons at a time, according to the extent of establishment. But the Committee must be little ac- quainted with the soap-boilers if they suppose that they CHEMISTRY. 17 will get evidence from them.. On receipt of your letter yesterday, I called on one house, G. and J. Blake, the first to whom I had communicated it, and merely men- tioned that I proposed to communicate it to the Society, and stated that, as I might probably receive a premium, I should like to have a favourable report from them, to which they objected, and considered such request as unreasonable, having paid me 51. Whatever improve- ment they made on their manufacture they considered as capital, so long as they could retain it to themselves, and would rather pay me any premium the Society might award than be a party to a publication of it in the Journal of the Society, from which it could be copied into the newspapers and other journals, and laid open gratuitously to the whole trade of London, Bristol, &c., and consequently render it of little value to them. I could make no reply. The Committee must judge for themselves. The soap-boilers here have been discharging the colour from their palm-oil on a patent process from a Mr. Watt, by means of chromic acid, produced from hydro-chloric acid and chromate of iron, the expense of which is about 1/. 5s. per ton of oil, freed from colour. My improvement costs only a few cwt. of coal- slack. I therefore consider that the gentlemen were fully justified in their observations, especially if it will effect a saving of three or four hundred pounds a-year. I declined calling on any other persons, convinced that I should only receive the same, if not more, uncivil treat- ment. I am, Sir, &c. &c. Charles Cameron. W. A. Graham , Esq. Secretary, fyc. fyc. \ c 18 CHEMISTRY. 50 Gascoyne Street , Liverpool, Sir, December 1, 1841. I duly received yours of yesterday, and regret to state that the same objections as to certificates from proper persons, which I mentioned in a former letter, still exist, except in the case of Mr. Richard Vaughan, soap-boiler, of Earle Street, who has promised me that if you should write to him he will give you his opinion. If any gentleman of the Committee will take the trouble, I would suggest the following process for his government in coming to a decision as to the correctness of the principle of my communication. Take a small cast- iron saucepan (say a quart), and put into it a pound or pound and a half of palm-oil, place it on a gentle fire, and when it has reached 212°, commence agitating it, either with a metal spoon or piece of wood. If it is kept at a range between 212° and 220° for some time (say an hour), there will be a considerable change of colour. Raise the oil to between 230° and 240°, the colour of the oil will disappear more rapidly. The pan will require occasionally to be taken off the fire to prevent too high a temperature, which would char it. What I claim as my improvement is agitation, and the low temperature, which prevents injuring the quality of the oil. The process is not so complete in a small as in a large quantity ; and high-pressure steam is far pre- ferable to actual fire for regulating the temperature. As Professor Grahame is a townsman of mine, probably at your request he might be induced to allow, under his superintendence, one of his pupils to perform the experi- ment, and report the result to the Committee. I am anxious to satisfy the Committee, but circumstances over CHEMISTRY. 19 which I have no control prevent me from giving any further proofs of its efficiency. I am, Sir, &c. &c. Charles Cameron. IF. A. Graham, Esq. Secretary , fyc. fyc. 50 Gascoyne Street, Liverpool. Sir, February 1th, 1842. Enclosed you will find two certificates of my improved process of discharging the colour of palm-oil. In a former letter I stated to you that 1 had applied to G. and J. Blake for a certificate, and, at the same time, stated their reasons for declining to do so. These reasons now no longer exist. About two months ago they had occasion to discharge their foreman, who proceeded to Newcastle and Hull, and fitted up apparatus exactly the same, inch for inch, as that which I fitted up for them. They now, in justice to me as the first inventor, have granted the enclosed. Both the firms whose certificates I enclose are the oldest and most extensive in town, and their saving of expense (compared with any other process) will amount to 700/. or 800/. per annum, independent of producing a superior colour. Had I secured it by patent I might have made 2000/. to 3000/. by it. My process discolours a ton of oil here at 2s. per ton. Watt’s process (formerly acted on) cost 20s. per ton. I have the authority of the two firms I have given you to say that, if you think proper to write to them, they will satisfy you in any inquiry you may make. You may form some idea of the description of charac- ters I have to deal with, when I tell you that four of the 20 CHEMISTRY. manufacturers here have adopted my plan without the slightest acknowledgment to me. It cannot be kept a secret ; I have no legal redress ; and therefore must submit to a robbery of my property. With this you will receive a specimen of the oil. I am, Sir, &c. &c. W. A. Graham , Esq. Charles Cameron. Secretary, <§*c. fyc. P.S. Please let me know the decision of the Committee as early as possible. — C. C. We have adopted Mr. Cameron’s method of discharging the colour from palm-oil, and are satisfied with the result. Geo. and j. Blake. 3 Earle Street, Liverpool, Gentlemen, Dec. 7, 1841. I find Mr. Charles Cameron’s method of discharging the colour of palm-oil perfectly efficient. It is simple, at- tended with little expense, and far preferable to dis- charging with acids, as the quality of the oil is not injuied, and where the oil is used for the purpose of soap-making there is no alkali destroyed thereby. I am, Gentlemen, &c. &c. To the Committee of Chemistry , Society of Arts. Richd. Vaughan. Liverpool, Feb. 5, 1842. I have seen Mr. Cameron’s method of discharging the colour of palm-oil, which I think a very good one. Wm. Lund. CHEMISTRY. 21 No. II. PRESERVING IRON FROM RUST. The Thanhs of the Society were voted to Mr. E. White- sides , of No. 14 Bateman s Buildings, Soho, for his Method of Preserving Iron from Rust. 14 Bateman' s Buildings, Soho, Sir, February 9, 1841. I have sent you a method of preserving* iron from rust, which I am desirous of laying before the Society. I am, Sir, &c. &c. To the Secretary of the E. Whitesides. Society of Arts. The method adopted by Mr. Whitesides of preserving iron from rust may be explained in a few words. The iron is heated to redness, just perceptible in the dark, and then quenched in tallow. In order to test the value of Mr. Whitesides’ method, Mr. Binyon undertook to make experiments with iron liinges, one of which had been prepared according to Mr. Whiteside’s plan, and fixed on a door of Mr. Binyon’s premises, within twenty inches of the tiling, and when examined two months after being fixed, appeared to be tolerably clean, whereas an unprepared hinge, fixed at thirty-six inches from the top of the door, after the same lapse of time was considerably rusted. A third hinge, which had been prepared by Mr. Whitesides’ process, was fixed at twenty inches from the ground, and was found, at the expiration of two months, to be less free 22 CHEMISTRY. from rust than that near the roof, but considerably cleaner than the unprepared hinge. It is to he observed, that little rain had fallen during the time of trial. No. III. TITANIUM FOUND IN THE BUTTERLEY IRON-WORKS. The Thanks of the Society were voted to Joseph Glynn, Esq. F.R.S. for his Communication on Titanium found in the Blast-furnaces at the Butterley Iron-works ; Specimens of which have been placed in the Society s Repository. Butterley Iron-Works, by A If reton, Derbyshire, March 2 , 1842 . I send you herewith some specimens of Titanium mixed with iron, which were found in the hearth or bottom of a blast-furnace belonging to the Butterley Company, which was lately blown out, that is to say, extinguished for repairing. The hearth or cavity at the bottom of the furnace is composed of large blocks of grit-stone, of nearly pure silex, of small grain, which are found par- tially vitrified and rent in pieces by the heat to which they have been exposed. The Butterley Company have six of these furnaces ; they are about forty feet in height, fifteen feet inside diameter at the largest part, and each furnace produces weekly from seventy to eighty tons of best melting iron, or “No. 1 Pig.” The quantity of iron-stone is nearly three tons for CHEMISTRY. 23 each ton of iron made ; so that it may be said the iron- stone smelted weekly in each furnace is, in round num- bers, 220 tons, and taking fifty weeks to a year, 11,000 tons of iron-stone will have been consumed by a single furnace. Each furnace may continue working* without intermission for five years or more, before it requires so much repairs as to cause it to be blown out. So that 55,000 tons of iron stone, nearly an equal weight of coal, and about 18,000 tons of limestone, will have been reduced during that period. The limestone is used as a flux. The ironstone is chiefly clay combined with the metal ; and although clay or lime separately are difficult of fusion, yet, when combined, they melt with comparative ease in the heat of a blast-furnace. The coal used is dry and carbonaceous, containing but little bitumen, and leaves, when burnt in the open air, a small quantity of white ashes. The quantity of titanium found in the furnace bottom or clefts of the hearth, will probably not exceed one hundred pounds weight ; and although the quantity of titanium is exceedingly small in proportion to the minerals from which it is thus accidentally produced, yet it is probable that so much of this metal may not be found under other circumstances ; and the chief object of my having brought this matter before the Society, is to make the members more generally acquainted with the fact that the metal in question may be obtained from the hearths of blast-furnaces in sufficient quantities for the purpose of experiment. Unfortunately, at the present moment there are too many extinct blast-furnaces. Al- most one-fourtli of them have been recently blown out throughout the United Kingdom. The titanium is of a brighter red colour than copper ; it is almost of a rose colour. It is also more brilliant, and it does not easily 24 CHEMISTRY. tarnish. Dr. Faraday has suggested a ready method of freeing it from the iron and other impurities, by pounding the mass and dissolving the iron with sulphuric acid, which does not touch titanium when so treated, and then washing it. The beds of iron-stone found at Butterley are numerous. I send three specimens — namely, a “module,” which is found in clay shale; a piece of the “ Black Rake,” with traces of freshwater shells in it ; and a piece of the “ Whatstone Rake,” which is the “ leanest,” or poorest kind of iron-stone used in the furnaces. The beds of iron-stone are termed “ rakes.” The stone is calcined in heaps by mixing it with small coal and setting fire to it. All the shells found in the iron stove-beds seem to be freshwater shells ; whilst in the limestone, which is the mountain lime of Crich Cliff, the shells are of marine origin. Crich is about four miles from Butterley, which is ten miles north of Derby. The coal, of which a specimen is also sent, is the “ long-coal,” much resembling charred wood. Unlike the Newcastle bituminous coal generally sent to the London market, which breaks in cakes, this coal can be raised from the pit in pieces ten feet long and more. 1 have been thus minute in detailing the quantity and kind of minerals put into the blast-furnace, that this scarce metal may be understood as existing only in minute proportions ; yet it has been noticed that where it does so exist the iron is of good quality. The cast-iron is fluid, and the wrought- iron made from it strong and ductile. I send you specimens of them. The wrought-iron was bent cold. And I also send a specimen of the slag or cinder formed by the earthy parts of the iron-stone and the limestone. I am, Sir, &c. Joseph Glynn. IF. A. Graham , Esq. Secretary , fyc. SfC. CHEMISTRY. 25 But ter ley by Alfreton, Derbyshire. Dear Sir, March 21 , 1842. On Saturday night I sent by railway a box, which I hope you will receive in due time, containing specimens of minerals and the iron, both cast and wrought, obtained from them. The wrought shavings sent were turned off a bar in the lathe, and shew the tenacity of the material. I sent also an additional specimen of the titanium, and I enclose a very hasty account of the quantities used in making iron at these works of the different minerals, which I hope you will be able to make out. It is in the box with the specimens. I am, Sir, &c. W. A. Graham , Esq. Joseph Glynn. Secretary , Sfc. fyc. No. IV. IMPROVEMENTS IN THE MANUFACTURE OF IRON. The Thanhs of the Society were voted to Thomas W. Booker , Esq. of Melin Griffith, near Cardiff, for his Communication respecting his Patent Process of mulling Iron — a Model shewing the Arrangement of the Fur- naces, as, also. Specimens of the Iron made by AIr. Bookers Process, have been placed in the Society's Repository. Sir, Velindra House, 3Iay 7, 1842. I have forwarded to you this day, by the Great Western Railway from Bristol, a box containing a model and 26 CHEMISTRY. drawing, and a paper on the manufacture of iron, which I shall feel much obliged by your laying before the Society of Arts, whose acceptance 1 beg of them. The model is perfect, and to scale in all its parts. The roof of the puddling reverberatory furnace is taken off by sliding back the brass bars which lie over it, and when taken off, the shape and dimensions of the inside of the furnace are seen. I shall feel much obliged by your informing me of the arrival of the box, and by any communication with which you may honour me on the subject. I am, Sir, &c. W. A. Graham , Esq. Tnos. W. Booker. Secretary , 8fc. fyc. There are at present in the United Kingdom five hundred and twenty-seven blast-furnaces, capable of producing at their ordinary rate of work 42,160 tons of pig-iron weekly, or 2,192,320 tons in one year. By far the largest portion of the pig-iron produced is wrought or converted into bar-iron in this country ; the cost of manu- facture of bar-iron depends on a variety of circum- stances and contingencies, such as the locality of the works, the application of water or steam power, the capital expended in their establishment and employed in their operations, the cost of ore and fuel, the rate of wages, the economy of management, the yield and con- sumption of raw materials, by means of and out of which the finished article of manufacture is produced, and the attention given to the quality of the finished production. When we consider the vast variety of purposes to which iron is now applied, how extensively it is used in the arts and manufactures, and in the instruments of CHEMISTRY. 27 comfort, safety, and convenience of life, it must be obvious that the quality of an article of such extensive use and consumption is of the first importance; and when we consider also the immense establishments which have grown up for its production, and the competition to which those who are engaged in its manufacture are liable, it must be alike obvious that any diminution that can be effected in the cost of its manufacture will be eagerly adopted ; and without, perhaps, in every instance due regard being paid to the beneficial or injurious effects arising therefrom, upon the quality of the metal being observed. Certain improvements, effected by the author of this paper, in the manufacture of this great staple article of national commerce, have been patented, and which he begs leave to lay before the Society of Arts. A copy of the specification of his patent is subjoined, together with a drawing and a model explanatory thereof ; and to bring the results of his improvements fairly before the Society, he will only add the following summary of his plan and its effects. The method usually, now and heretofore, adopted in the manufacture of bar-iron (where the dangerous, and, as the author thinks, reprehensible practice of puddling the crude or raw pig-iron, without the intervention of the refining process, is not adopted), is as follows: The pig- iron is thrown up on what is called the milling finery, or run into the finery in a fluid state, from the smelting or blast-furnace, and after undergoing the process of refining, it is run out into cakes or moulds, and suffered to get cold ; it is then broken up into lumps of a con- venient size, and thrown into the puddling reverberatory furnace, which is usually constructed with one door, and 28 CHEMISTRY. at which only one man can work at a time. The authors improved method is detailed in his specification, plan, and model, and its effect is this — a saving of full 50 per cent in fuel, and nearly 50 per cent in metal, an immense saving of labour, and a greatly increased product of work in the puddling furnace — the usual product of a puddling furnace being from fourteen to eighteen tons in a week while the author’s will as easily produce from forty to fifty tons in a week. The author thus combines the processes of refining with puddling, and to shew the importance of preserving, and the hazard of dispensing with the refining process, he subjoins the results of analysis by M. Berthier of three samples of cinder or scoria, in one of which the remarkable fact of the presence of phosphoric acid shews how important this operation is to the purification of the iron : — Sllica - Alumina. A Staffordshire sample 0-276 .. 0-612 .. 0 040 .. 0-072 A South Wales sample 0-368 . . 0-610 . . 0-015 . . none Ditto ditto 0-424 . . 0-520 . . 0-033 . . none Tuos. W. Booker. The object of Mr. Booker’s invention is to simplify and accelerate the conversion of cast-iron from its crude state into malleable or wrought iron, for which purpose the refinery or furnace is adapted to the various qualities or descriptions of cast or pig-iron which it may be neces- sary to use, by surrounding or enclosing the hearth with blocks of cast-iron, into and through which water is allowed to flow or not as may be expedient, and as is well understood in making refinery furnaces, the blast of air being introduced through one, two, or more aper- tures or turies, as usual. CHEMISTRY. 29 The refinery is connected with the reverberatory or puddling furnace, which is constructed of the requisite form and dimensions. The bottom of the body of the furnace, and the grate bars, and binding plates and bars, are formed of iron ; the other parts of the furnace are constructed with fire-bricks, sand-stone, or fire-clay, as is well understood. In the neck, or near the flue of the reverberatory furnace is an aperture through which the iron, when it has become decarburetted or refined in the refinery, is introduced or run in a fluid state direct from the refining hearth into the puddling or reverberatory furnace. On each side of which reverberatory furnace a door is constructed ; the door in the one side being im- mediately opposite to the door in the other, through which two doors the workmen perform the process of puddling in the ordinary way in which puddling is done, when working only with one door, which is the general practice. As respects the Refining. Having thrown up the fuel, and having, by the appli- cation of fire and blast, produced the necessary heat, a charge of 9 cwt. or thereabouts of pig or cast-iron, of the description generally used for forge purposes, is thrown on and melted down and decarburetted or refined in the ordinary way ; and when the refining process is completed, the whole charge of metal is run off in a fluid state direct into the reverberatory or puddling furnace previously prepared to receive it, by having been already heated to a proper degree of temperature, and by the bottom, sides, bridge, and opening to the flue being protected in the ordinary way, by the workmen having previously thrown in a sufficient quantity of limestone and iron-cinder. The metal having been introduced into the reverberatory or 30 CHEMISTRY. puddling furnace in a fluid state, the workmen raise, apply, and regulate, and vary the heat in the ordinary way, by feeding and moving the fire in the grate, and raising or lowering the damper on the top of the stack or flue, as circumstances require, and as is well understood; they at the same time stir and agitate the iron with bars and puddles, while the escape of the oxide of carbon in a gaseous shape takes place, and until the whole mass of iron agglutinates. The workmen then divide it into lumps or balls of a convenient size, and draw the charge from the furnace, passing the lumps to the squeezer, hammer, or rolling cylinders, or such other contrivance or machinery as are used for forging or compressing the iron. During the process of refining the iron, by the appli- cation of heat and blast, in the open refining hearth, a considerable quantity of scoria or cinder is produced, which is tapped and run off' as heretofore, as circum- stances require; but it is to be observed, that during the process which the iron undergoes in the reverberatory or puddling furnace, the author does not find that any cinder need be generated or produced, and cinders and lime- stones are thrown in, as already described, for the pro- tection of the various parts of the furnace exposed to the action or agitation of the fluid metal, but no cinder need be tapped or drawn off. Mr. Aik i n s Opinion. The principal novelty in Mr. Booker’s invention con- sists in placing the refining and the puddling furnace so near each other that the refined iron may be run in a liquid state into the puddling furnace, instead of allowing it (as is usual) to cool and become solid when let out of CHEMISTRY. 31 the refinery, previous to its being transferred to the pud- dling furnace. The heat lost by the iron is thus saved, as well as the time required to bring the solid refined iron to a state of fusion. Both the refining and puddling are to be performed, according to Mr. Booker, in the usual way ; it was there- fore incumbent on him to shew how it happens that while the common process of puddling produces slag, his does not. Mr. Booker’s statement that by his process a saving of full 50 per cent in fuel, and nearly 50 per cent in metal, is effected, appears to be an enormous exaggera- tion ; the saving in the former being only (as far as appears) the fuel required to melt the refined iron. In making iron of the best quality, 31*74 cwt. of pig-iron give 26*45 refined, which is reduced to 23 in the puddling process. 8*74, therefore, is the loss which 31*74 pig suffers in becoming puddled iron. Half this loss, namely, 4*37, will represent 50 per cent of saving, and this, added to 23, makes 27*37, which is 0*92 more than the entire quantity of refined iron. Berthier’s analysis of two samples of scoriae from South Wales, and one from Staffordshire, shewing the presence of phosphoric acid in the former and none in the latter, has no bearing on Mr. Booker’s statement, that in the process of refining, the phosphoric acid is separated from the iron. If the quality of the iron produced by Mr. Booker’s process is not worse than that of iron refined and puddled in the usual method, Mr. B.’s process deserves the appro- bation of the Society. But I would recommend that Sir J. Guest, or some other practical iron-master, should be consulted. 32 CHEMISTRY. Society of Arts, Adelphi, Sir, April 24, 1 843. I beg to inform you that the subject of your process in the manufacture of iron was laid before the Committee of Chemistry on the 13th instant, and I am desired to ask you, “ How it happens that while the common process of puddling produces slag, yours does not?” and to obtain from you an explanation as to the “ saving of full 50 per cent in fuel and nearly 50 per cent of metal.” I am, Sir, &c. &c. Thos. W. Booker , Esq. Francis Whishaw, Secretary. Velindra House , near Cardiff, Sir, April 27 , 1843. I account for “ the production of slag in the common pud- dling furnace, and its non-production in mine,” as follows : The common puddling furnace is so constructed that the iron operated upon in it is exposed to a very rapid draught or current of air, which rushes in at the grate at the back of the furnace, and passes off through the body and into the flue and stack at the head thereof. This draught is so great as to oxidize the iron, and transform a great portion of it into slag or scoria during the process of puddling, which process, moreover, is effected so slowly, that the charge of iron, consisting of from 3^ cwt. to 4| cwt. is exposed to the heat and draughts in the pud- dling furnace during the space of full an hour and a half. My puddling furnace is so constructed, that the draught or current of air admitted at the grate is broken, and its oxidizing effects upon the surface of the iron while fluid, and upon the fibrous particles as they cohere, CHEMISTRY. 33 after the oxide of carbon has been expelled, are entirely neutralised. That portion, therefore, of the charge which in the common puddling furnace is converted into slag or cinder, in mine is not wasted or oxidised, but remains, and is converted into pure malleable iron. In the common puddling furnace, too, the charge, either of refined metal from the refinery, or of raw pig- iron from the blast-furnace, as the case may be, is placed, in cold lumps, in the puddling furnace. In mine, the charge of iron, consisting of 9 cwt. is run off (after under- going the process of refining) direct, and in a fluid state, from the refinery into the puddling furnace, where it is acted upon by the heat, and operated upon by the work- men at once, and where the whole charge thus run off is converted from refined cast-iron into wrought or malle- able iron within the space of (at the very outside) three- quarters of an hour, and it is generally done within the half hour. “ The saving of fuel” is accounted for thus: In the common puddling furnace not more than 4| cwt. of metal is admitted at one time, and this in a solid cold state. In mine, double the quantity is admitted, and that in a melted and fluid state. It is obvious that the time, fuel, and labour necessary for melting the iron are saved, and that double the quantity of iron is converted from a cast into a malleable state within half the same space of time. I send you in a box by Great Western Railway (the carriage of which is paid) samples of iron (smelted from the ore, and manufactured at the works of my firm, Richard Blakemore, M.P. and Co.), refined and puddled by my process, and afterwards manufactured in the ordinary way with pit coal. The samples consist of a rough puddled or No. 1 bar, in the state in which it VOL. l l v . D 34 CHEMISTRY. comes from the machinery which compresses and rolls it immediately after it has been refined and puddled in my furnace; also of a finished No. 2 bar, in the ordinary state of merchant bar-iron ; and two specimens of No. 3 bolt-cable or rivet-iron. The whole have been bent and twisted, as you will see them, while perfectly cold ; and one of the bolts has been notched, in order to break it, so as to shew its fibrous texture. The whole are 'produced entirely from iron smelted with hot blast. I hope and trust the Society of Arts will take up the question, practically and scientifically, of the relative qualities and properties of iron smelted in the hot and cold blast, and of that also produced with the various kinds of vegetable and mineral fuel, and from the cal- careous and argillaceous ores. Considering the purposes to which iron is now so extensively applied, and how much the safety and convenience of the public and of individuals are hazarded by its various uses ; and con- sidering, also, the temptations which the existing competi- tions in the iron trade hold out to its cheap production and manufacture, without any reference or regard to the essential properties which iron ought to possess, there are few subjects, as it appears to me, of greater importance, and none on which the attention of the Society of Arts of Great Britain can he bestowed with greater public and national advantage. I shall at all times be happy to communicate to the Society any information in my power. I am, Sir, &c. Francis Whishaw, Esq. Tnos. W. Booker. Society of Arts. CHEMISTRY. 35 No. V. ANATOMICAL PREPARATIONS. Tl \e Gold Medal was presented to Mn. Henry G o AD by , No. 18 South Villa , Wandsworth Road , for his Method of putting -up Anatomical Preparations. 18 South Villa , Wandsworth Road. Sir, Nov. 17 th, 1841. I am desirous of making- a communication to the Society of Arts relative to a new mode of putting up anatomical, zoological, or other preparations, rendering them avail- able for microscopical purposes, &c. I am in attendance with several specimens, which I should like to lay before the Committee, especially as they may not remain long in my possession. I am, Sir, &c. The Secretary, fyc. Henry Goadby, F.L.S. The method adopted by Mr. Goadby of putting up and preserving anatomical preparations is deserving of notice ; first, on account of the form of, and second, the plan of making the vessels, which contain them, and, lastly, on account of the composition of the fluid in which they are prepared. The vessels are constructed of plate-glass, and are of rectangular form, the edges of each plate having pre- viously been ground square on pewter with emery powder. The plates are cemented together with a composition of gold-size and lamp-black, the latter ingredient being- mixed with the former in sufficient quantity to make the 36 CHEMISTRY. cement of a deep black colour. The use of the lamp- black is to prevent the gold-size from running. The advantages of this form of vessel are, that the objects may be viewed, either by the naked eye or the microscope, without any appearance of distortion or indistinctness occasioned by the aberration of light in its passage through the curved sides of glass bottles. The vessels for the larger specimens are made of such dimensions as to support them by contact with all the sides, and retain them permanently in the most favourable position for examination. Many preparations are of such a form as to collapse, when suspended, in an ordinary glass bottle, and conceal that part of the surface which it may be most interesting to examine. Some of the more delicate specimens are supported in the vessels at different points by threads, the ends of which pass between the edges of the glass and are embedded in the cement. The flat glasses enable the most minute specimens to be accurately examined by the microscope. The fluid in which Mr. Goadby’s preparations are preserved consists of a solution of salt, alum, and coi- rosive sublimate, in the following proportions, viz. bay- salt, 4 oz. ; alum, 2 oz. ; hydro-chlorate of mercury, 4 grains, dissolved in two quarts of boiling water. The fluid commonly used for preserving anatomical preparations is alcohol ; and the ingredients of the fluid used by Mr. Goadby have also been used by others, but singly as simple solutions. lhe candidates object in combining these substances is to obtain more peifect specimens, both as to their appearance and their actual preservation ; the astringent and antiseptic properties of the alum and salt tending to preserve the organic struc- CHEMISTRY. 37 ture in a firm and undecomposed state, and the poisonous action of the corrosive sublimate preventing a species of vegetation, which frequently appears in the preparations made in the ordinary way, in the form of flocculi, which render them indistinct in form and colour, and diminish the transparency of the fluid. The cost of the fluid is less than sixpence a gallon. In the Society’s Repository is a human eye preserved in a saturated solution of salt, which was deposited by W. Cooke, Esq. in 1819, whose communication on the subject of anatomical preparations generally will he found at page 43, Yol. XXXVII. of the Society’s Trans- actions. The specimen alluded to above appears at the present time, October 28, 1843, to be in a good state of preservation. PAPERS IN CHEMISTRY AND MINERALOGY. No. I. OIL FOR CHRONOMETERS. The Gold Isis Medal, being the Premium offered, was presented to Mr. Henry Wilkinson, of Pall Mall , for his Oil for Chronometers. The following Com - munication has been received from him on the subject ; and a Specimen of the Oil has been placed in the Societf s Repository. Sir, Pall Mall, Feb. 4, 1830. Perceiving that the Society annually renew their offer of a premium “ for a method of purifying oil for chro- nometers superior to any in use,” I conclude the desired object has not yet been obtained; and I am induced to lay before the Society the process I have employed for that purpose ten or twelve years, and which has never, to my knowledge, been made public. It has been used by Messrs. Barraud, of Cornhill, for several years ; and I herewith enclose their opinion. From the long trial I have made of it myself, I think it is not possible to render oil purer, or better qualified CHEMISTRY AN1) MINERALOGY. 43 for the required purposes, as no extraneous substance is introduced which can in the slightest degree injure its quality ; and the method is so economical that time is the only expense. The small sample of oil sent has been pre- pared two years ; and any further quantity that may be desired 1 shall be happy to supply, leaving the Society to judge, whether there is any novelty or merit in my process. I am, Sir, &c. &c. A. Aikin, Esq. Henry Wilkinson. Secretary , fyc. fyc. The best olive oil in its recent state possesses that peculiar bland flavour which fits it for the table, and which appears to arise principally from the quantity of mucilage and water, either held in solution, or mechani- cally mixed with it. By keeping one or two years in jars, a considerable portion of the mucilage and water subsides, which renders such oil not only cheaper, but better qualified for yielding a greater proportion of pure oil than that which is recently expressed from the fruit. Two or three gallons skimmed from the surface of a large jar that has remained at rest for twelve months or upwards, is preferable to any succeeding portion from the same jar, and may be considered the cream of the oil. Having procured good oil in the first instance, put about one gallon into a cast-iron vessel capable of holding two gal- lons ; place it over a slow clear fire, keeping a thermo- meter suspended in it; and when the temperature rises to 220°, check the heat, never allowing it to exceed 230°, nor descend below 212°, for one hour ; by which time the whole of the water and acetic acid will be evaporated : the oil is then exposed to a temperature of 30° to 36° for 44 CHEMISTRY AND MINERALOGY. two or three days (consequently winter is preferable for the preparation, as avoiding the trouble and expense of producing artificial cold); by this operation a considerable portion is congealed ; and, while in this state, pour the whole on a muslin filter, to allow the fluid portion to run through ; the solid, when re-dissolved, may be used for common purposes. Lastly, the fluid portion must be filtered once or more through newly-prepared animal charcoal, grossly powdered, or rather broken, and placed on bibulous paper in a wire frame, within a funnel ; by which operation, rancidity (if any be present) is entirely removed, and the oil is rendered perfectly bright and colourless. Henry Wilkinson. Sir, 41, Comhill , 13 th Feb. 1830. On referring to our books, we find it to be upwards of seven years since we first began to use the oil you were kind enough to supply ; and we have much pleasure in adding, that it has proved so superior to any other we could procure, that we have used none else during the last four or five years, and have applied it to all our chro- nometers, watches, and clocks, finding that it preserved a fluid state more perfectly than the oils we had previously used ; all of which had been liable to considerable varia- tion of appearance and condition, after having been some time in action ; whereas yours has been very uniform in preserving a favourable state. We cannot forego this opportunity of repeating our thanks for the advantage derived from its use by Dear Sir, yours faithfully, Barra ud and Sons. Henry Wilkinson, Esq. CHEMISTRY AND MINERALOGY. 45 No. II. GEOLOGICAL MODEL. The Gold Isis Medal was presented to Mr. Richard Cowling Taylor, F.G .S., for two Models, repre- senting Part of the Coalfield of South Wales. The two models represent the same country, namely, about eleven square miles north of Pontipool, in the most valuable part of the South Wales coal-field. One of the models is intended to exhibit in relief those parts which would form the subject of a map, namely, the surface, and the objects on the surface. The other model shews the geological structure of the country, distinguishing the beds of useful minerals, and the adits or galleries by which they are wrought, as well as the faults or disloca- tions of the strata, as far as they have been traced. The tract belongs chiefly to the British Iron Com- pany ; and the models have been constructed from sur- veys, both mineral and superficial, made professionally by Mr. Taylor, in the years 1825-6. The vertical and horizontal scales in these models approach more to an equality than they do in most others, and therefore there is far less of that distortion which must necessarily result from the use of two different scales. The lowest point shewn in the model is 350 feet above the sea; the highest elevation is about 1600 feet. The strata incline, at an average, about 2% inches in a yard, or 46 CHEMISTRY AND MINERALOGY. 350 feet in a mile. The lowest bed shewn is the old red sandstone, over which lie 400 feet in thickness of cal- careous beds, forming the mountain limestone, and these are covered by about 1600 feet of coal measures. There are about twenty beds of coal, the aggregate thickness of which is nearly sixty feet : of these, six beds are in working, and yield upwards of 30,000 tons per acre. Alternating with the coal beds are others of clay-iron- stone; the best alone of which are worked, producing about 15,000 tons per acre. Alternating with the beds of ironstone and coal are ten beds of clay, of good quality, for fire bricks. The middle part of the series consists of sandstone, in which are opened many quarries of excellent building stone. Towards the top of the series the sandstone be- comes schistose, and is extensively quarried for tile-stone, paving flags, and slabs for tombstones. The whole of the coal-formation lies above the level of the river, and therefore the contents of this valuable deposit are easily got at; while the slope itself, from the top of the hills to the river, presents a very interesting natural section, illustrated and verified by the numerous adits and other excavations. CHEMISTRY AND MINERALOGY. 47 No. III. MORDANT FOR CALICO PRINTERS. The Thanks of the Society were voted to Mr. Francis Davis, of Cold Bath Square, for the following Ex- periments on the Use of Oxide of Uranium, as a Mordant in Dying Cotton Prints. 29, Cold Bath Square, Sin, Nov. 15, 1829. Mr. Faraday has already noticed, in a periodical pub- lication, the property which solutions of the salts of uranium possess, even with a superabundance of acid, of producing a red stain on turmeric test-paper, similar to that which is produced on the same paper by solutions of the alkalies. By pursuing Mr. Faraday’s inquiries further than it appears that he himself carried them, I found that solutions of the salts of this metal give a reddish brown colour to paper made yellow by French berries, fustic, quercitron bark, and weld, as well as to paper impregnated with infusion of nut-galls. This suggested to me the possibility of adding to the mordants at present in use, one, which, when printed on calico, &c., would give, with the above-mentioned drugs, by means of the same copper of dye, an additional colour, and thus add a considerable variety to patterns of cotton-prints, without the trouble employed in dying them being at all increased. The mordants at present in use, and the only ones, I believe, ever used in cotton-printing, are alumina and the 48 CHEMISTRY AND MINERALOGY. buff or deutoxidc of iron. These are applied to the cloth, united with acetic acid, but are not fixed in it upon the same principle. Acetate of alumina is of such a nature that, when its solution receives a high temperature, say about 212° Fah., part of the alumina is deposited. Being laid on cold, the cloth is afterwards passed round heated tubes, and thus alumina is deposited in intimate union with the fibre of the cotton, &c. The case is somewhat different with respect to the iron mordant. The iron liquor, or solution of acetate of iron, contains this metal in the state of a protoxide, which is very soluble in acetic acid ; and if, in this state, it be exposed to the atmosphere, a larger portion of oxygen is acquired, and the deutoxide of iron which is then formed being less soluble, precipitates. After the iron mordant has been applied to the cloth, it is necessarily exposed to the atmosphere, and consequently the oxide of iron is precipitated and fixed in it. The oxide must be fixed in the cloth, that the latter may, before being put into the dye-bath, go through the cleansing processes to which the manufacturer is obliged to subject it after application of the mordant. The oxide of uranium, before it can be applied as a mordant, must also be intimately combined with the fibre of the cotton, as I have shewn to be the case with the others. I found that the acetate of uranium possessed neither the property of the acetate of alumina, nor of that of iron, and was in all respects unfit for the purpose re- quired. It therefore became necessary to search for some liquid combination of uranium, which should resemble, in its mode of action, one or other of those salts. As the three following solutions all possess the property of acetate CHEMISTRY AND MINERALOGY. 49 of alumina, they appear to me to be well adapted to obtain the end proposed. The yellow oxide of uranium (called by some the per- oxide) is soluble with heat, in a solution of The subcarbonate of ammonia ; The bi-carbonate of soda ; and The bi-carbonate of potass. To one or other of the above solutions, saturated with oxide of uranium, and become cold, add strong acetic acid in sufficient quantity to saturate the ammonia, soda, or potass, employed ; as, for example, to prepare the one in which the carbonate of soda is used, dissolve two parts by weight of this salt in sixteen parts by weight of water; this solution, boiled in one part by weight of oxide of uranium in powder, will dissolve it: when cold, add five parts, also by weight, of strong purified wood-vinegar of commerce ; agitate the mixture. The quantity of acetic acid added must of course depend upon its strength. When the acid is added to the solution of the oxide, in any one of the above-mentioned salts, the transparency of the solution is not disturbed, nor is any of the oxide of uranium deposited ; but if it be made to boil, it will ex- hibit the same property as a solution of the acetate of alumina, by becoming turbid ; and if the ebullition be continued for a short time, the whole of the oxide of uranium will be precipitated, leaving, when the oxide has had time to settle, a colourless, supernatant liquor. This liquor being entirely colourless, may be considered as a criterion of the acid having been added in proper pro- portion to the other ingredients; for the liquor will retain a yellow colour, if the acid be added in too great or in too small a quantity. Any one of these solutions, thus prepared, when mixed VOL. X L V III. E 50 CHEMISTRY AND MINERALOGY. up with gum, and laid by a pencil on cloth, and this after- wards passed through the same heating process as that used for it when prepared with acetate of alumina, will be found to deposit the oxide so firmly in the fibre of the cotton, &c., as to qualify it to bear any cleansing to which the calico printer may find it necessary to subject it. With respect to which of these solutions may be best adapted for this purpose, I think it likely that the one made with the subcarbonate of ammonia will be found preferable; but as in this communication I intend to confine myself to that of which my experiments qualify me to treat, so I feel diffident in pronouncing positively upon the relative merits of these solutions, because, when used by me, they were only pencilled upon the cloth, instead of being im- pressed by the block of the calico printer. An obvious way of precipitating the oxide in the cloth must suggest itself to any person acquainted with the nature of metallic salts ; namely, by printing the cloth with any of the soluble salts of this metal, and then dipping it into a solution of an alkali, or lime-water. There are many very serious objections to this mode of effecting the end proposed. I shall confine myself to stating two : first, it would be introducing an additional manipulation — an inconvenience which will be avoided by the use of the solution of the oxide in the alkaline car- bonates above proposed ; secondly, when a piece of cloth, treated by me in this way, was passed through a dye-stuff’, it was found to have received the colouring matter very unevenly, and exhibited a fainter colour than that im- parted by the same dye-stuff’ to places mordanted by the solutions of the oxide in the carbonates, although a greater quantity of oxide was, to all appearance, fixed in the cloth by treatment with the alkali than by the other way. In CHEMISTRY AND MINERALOGY. 51 this manner, indeed, a very permanent bright yellow colour — a circumstance which ought not to be lost sight of by the manufacturer — may be produced in cloth, with- out its undergoing any other preparation. With Nutgalls. In infusion of nutgalls solutions of the salts of uranium occasion a brown precipitate : it was therefore to be anticipated that the colour given by this dye to the uranium mordant would be the same. The colour re- ceived is, in fact, a dull brown. This appears to be as permanent as the black produced by iron, and stands washing as well. When used in conjunction with the iron mordant, colours having all the varieties that can be formed from these two may thus be produced in the same bath of dye. To ascertain whether the brown colour of the uranium mordant was produced by the same principle (generally considered as the gallic acid) which produces black with the iron, a piece of calico, previously dyed brown by uranium and galls, after being thoroughly washed, was boiled in a solution of muriate of iron, and, as might have been expected, was by these means changed to black. With Weld and Quercitron Bark. The colours obtained from these dying drugs re- semble one another in every respect. They are yellow, brown, or faded-leaf colour : they appear as permanent in the sun’s rays as the yellow that is given with alumina, and will stand washing. If uranium, alumina, and iron, be used together, a bright yellow, light brown, and dark olive green, as well as all the various com- binations of these three colours, may be obtained by 52 CHEMISTRY AND MINERALOGY. one bath of these dye-stuffs at the same time. This brown colour gave the same indications of the presence of gallic acid as the one from nutgalls, when treated with solution of muriate of iron. With Fustic and French Berries. But the most valuable property of the uranium mordant is, its producing, with the above articles, a very agreeable and permanent colour, varying from a light red to a chestnut colour. The colour from French berries approaches nearer to pink than that derived from fustic. It might be imagined that the gallic acid is concerned in producing these colours, as well as the ones obtained from weld and quercitron bark, as the infusion of both fustic and French berries will give a black precipitate with a solution of iron, in the same manner as the infusion of weld or of quercitron bark ; and they are also, as well as the two latter, capable of giving an olive- green colour with the iron mordant. But, notwithstanding these strong grounds for supposing that the colour pro- duced by fustic and French berries is a compound of gallic acid and uranium, when tried by the test before men- tioned, of boiling with a solution of iron, the colour was found to be very little, if at all, altered. The calico printer will find, by the use of the uranium mordant, that he will be enabled to print a very permanent, and, as I think, a very desirable colour, by the use of either of these two drugs, which have only hitherto furnished fugitive yellows with alumina, the one from French berries being particularly worthless. If this colour may be said to change by being much washed, it is by becoming more red than at first. CHEMISTRY AND MINERALOGY. 53 Turmeric. This dye is not capable of being fixed or rendered permanent in cloth either by this, or by any of the other mordants ; and although, if the cloth be first dyed by turmeric, and then impregnated with a solution of a salt of uranium, it is changed to red, yet it returns to its original yellow colour with very little washing, indeed by merely'holding it in a stream of running water. Turkey berries, sumach, and valonea, are so similar in their properties to some of the drugs already noticed, that I have not considered it necessary to make any trial with them. Annotta, when dissolved in an alkaline solution, the usual mode, I believe, of applying it, was not affected by uranium. It was also tried along with the red dying drugs madder and cochineal, as also with logwood ; but as no discovery, likely to be useful to the manufacturer, resulted from my experiments, I shall not trouble you with any remarks upon these dyes, further than by saying, that the colour imparted to it by madder resembled that given by this drug to alumina, only of a considerably darker shade; and that received from cochineal was of a slate gray colour. The oxide of uranium made use of by me was obtained from the pitch ore, or native sulphuret of that metal. I am, Sir, &c. &c. A. Aikin, Esq. Secretary, SfC. <§r. Francis Davis. CH EM I ST R Y AND MINERALOG Y. GLAZING FOR COMMON RED EARTHENWARE. Hie Large Gold Medal, being the •premium offered, was this Session given to J. Meigh Esq., of Shelton, Staffordshire, for a Glaze for Vessels of common Red Earthenware, not preju- dicial to the health of those who make use of them. Specimens of the Ware, so glazed, and of the glaze itself, as well as of the ingredients of which it is composed, are placed in the Repository of the Society. THE common coarse red earthenware is made of brick clay, hence it is very porous : it is also baked at as low a heat as possible, partly in order to save the expense ot fuel, and partly, because being made of common clay, which varies considerably in its fusibility, it will not always bear CHEMISTRY. 45 a high firing, without losing its shape, and becoming un- saleable. For the reasons above-mentioned it is necessary to em- ploy a glaze, fusible, cheap, and capable of filling up the pores of the ware, so as to enable it to hold fluids, in or- dinary use, either as articles of food, or of domestic em- ployment. Litharge, and the common potter’s lead ore, are the articles usually employed, the one for the transparent, the other for the black opake glaze. The objections, however, to a glaze wholly or in part composed of lead, are, first, that it cracks when raised rapidly to the temperature of boiling water, on account of the different ratio of ex- pansibility, between the glaze and the clay, and then ad- mits the liquor into the body of the ware ; secondly, the glass of lead by itself, or even when mixed in small propor- tion with earthy substances, is very soluble in vinegar, in the acid juices of the common fruits, and in animal fat when boiling. When such substances, therefore, are cooked in vessels of common red earthenware, a quantity of salt of lead, is formed, which, mixing with the food, produces violent cholics, and all the serious, and often fatal effects that attend the internal administration of the salts of lead. The discovery of a better and more wholesome glaze, suf- ficiently cheap to be applied to the common red ware, ap- peared to the Society to be an important desideratum, and in their opinion this is now effectually supplied by the dis- covery about to be detailed. The rock called red marl, is usually in the form of beds of a soft, coarsely slaty structure, and red colour, forming the chief part of the common soil, in many extensive dis- tricts in this island, to the N. and W. of a line running ob- liquely from Durham to Exeter. This marl is easily ground 46 CUE MI ST II Y AND in water to an impalpable powder, which remains sus- pended for a considerable time in the fluid. A mixture of this kind is prepared, and the ware, previously well dried, but not burnt, is immersed in it. The superficial pores of the clay are thus filled with fine particles of the marl, and a fit surface is prepared on which to lay the glazing. Being again carefully dried, the ware is ready for the glaze, which is thus composed, Take 1 part Cornish Granite, consisting chiefly of Felspar, 1 part Glass. 1 part Black Manganese, the whole well ground together, and diffused in water, to the consistence of cream. Dip the ware in this mix- ture, and, when thoroughly dry, place it in the kiln and fire it in the usual way. The result will be, a solid black glaze, very permanent, and not containing any ingredients noxious to health. If an opake white glaze]is required,* omit the manganese. Mr. Meigh has also employed common marl and the red marl as ingredients of the body of the w are, with ex- cellent effect without increasing its expense ; he uses for this purpose, 4 parts of common marl, 1 part of red marl, and 1 part of brick clay. Vessels made of the above mixture, are in possession of the Society. The colour of the body is a reddish cream brown, it is harder, more com- pact, and less porous than the common red ware ; and its general adoption, with the above mentioned glaze, would contribute in no inconsiderable degree to the health of the lower classes, by whom alone the common red ware is used for vessels of cooking. MINERALOGY. 47 N° II. TUSCAN MILL-STONES. Th e La rge Silver Medal was t h is Session given to Henry Willey Reveley, Esq. for his Com- munication, respecting the nature and preparation of the Stones used in Tuscany, for Grinding fine Flour. Specimens of the Stones have been placed in the Repository of the Society. King-street, West, Rryanstone-square, SIR; I>ec. 11th, 1821. I take tlie liberty of offering to the Society some specimens of mill-stones, from Tuscany, which I beg you to lay before them on the first convenient opportunity. Having detached them myself from stones of tried quality, I can answer for their being genuine; and such as are most esteemed, and most generally used. From the great difference which exists between these stones and the French burr-stones ; and the certainty of their being’ capable of producing flour equal both in quality and quan- tity to that afforded by the latter; I presume it might be worth the trouble of ascertaining, if similar stones are to be met with in this country. The specimens marked No. 1 and No. 2 are used for producing white flour only. No. 1 is from the upper or running mill-stone. It is diallage rock, consisting of 48 CHEMISTRY AND crystals of diallage, imbedded in apparently, compact felspar : both ingredients are so soft as to yield without much difficulty to the knife, but the various position of the crystals of diallage, and their very distinct lamellar structure, always preserve a certain degree of roughness, even after long-continued friction. This rock forms a hill at Prato, a few miles from Florence. The stones, while in the quarry, are first shaped out with a pick, care being taken to make the face of the stone perpendicular to the plane of the bed of the rock ; they are then detached bv driving in wedges of soft dry wood, between the stone and the adhering mass ; finally, water is thrown upon them, which, by increasing their bulk, detaches the stones. No. 2, is a compact, porcellanous limestone, of a pale flesh colour, and somewhat softer than the diallage rock. No. 3, is a granular talcose quartz, with imperfect imbedded garnets ; it is the material of which both stones are formed for producing brown flour. The only prepara- tion that the corn receives previously to grinding is wash- ing. For this purpose, a basket is sunk into a tub of water, and the corn is slowly poured into the basket : the light grains and dust are thus brought to the surface, and are removed ; and the corn having been dried in the air and sun, till it is only very slightly damp, is ready for the miller’s use. In this state, less flour is lost in the form of dust, and the grains being somewhat softened exter- nally, the bran is more easily disengaged in broad flakes without any flour adhering. I shall be happy to communicate to the Society, any more detailed information in my power to give them on this subject. I am, Sir, A. Atkin , Esq. &c. &c. &c. Sec. Sfc. fyc. Henry W. Revelry. JV. a. M I N E R A L O G Y. 49 Description of the Engraving . — Plate VIII. Fig. 1 represents the face of the under mill-stone pre- pared for work ; the teeth, to possess their utmost per- fection, should have the form of the hyperbolic spiral ; but, being cut by the hand of the workman without any great regard to mathematical precision, they will, in general, be found to be portions of circles, the locus of the centres of which would be the periphery of a circle of the radius of fourteen inches, described from the centre of the mill-stone. The tool employed to cut the teeth is a double • edged hammer, four inches wide, very sharp, and weighing about twelve pounds ; in general, the teeth are as close as possible to each other, but in approaching the eye, they become more rare, deeper and coarser. When the stones are new from the quarry, a few days only are necessary to complete this operation ; but when they have beenalready in use, any able miller’s man, wholly unassisted by others or by machinery of any kind, will complete it in the course of twenty minutes. That part of the face which is the real grinding surface (called by the Italians, “ il vero macinante") extends from six to eight inches from the circumference of the stone. Fig. 2 represents a section of the mill-stones when set to work; the dimension usually preferred, equally for the most powerful mills as for those of inferior strength, is a diameter of four feet, that of the eye being about seven inches. The face of the upper stone is hollowed to a conical surface, the alti- tude of the cone being about one inch and a half, while that of the lower stone receives a convex form, its surface VOL. XL. E 50 C II E M I S T R Y AND approaching to that of a sphere of which the radius is about thirty feet, leaving a distance of about one inch between the centres of the two faces. The deep socket let into the runner, as indicated by fig. 2, is made for the reception of the iron nut placed on the square of the spindle. The runner is balanced, and rendered parallel to the bed-stone, by inserting four small wedges of soft wood, two on each side, between the nut and the bottom of its socket. Figs. 3 and 4 represent the iron nuts and the spindle, with the wooden bush by means of which it is held in the centre of the under mill-stone. The dark part in fig. 1 represents the relative position of the teeth of the upper and under stones, the former turning on the latter in the direction indicated by the arrow, and thus continually comminuting the oraim and driving it at the same time from the centre to the circumference, where it escapes. Having concluded the description of the drawings, inter- spersed with some particulars immediately connected with them, I have now to observe, with regard to the specimens of stones which I presented to the Society ; that those from which the samples Nos. 1 and 2 were taken, are applied to the grinding of the finer kinds of wheat, from which white bread is made ; the combination of the hard runner with the soft bed-stone being peculiarly adapted to grind into fine white flour the central parts only of the gram, leaving the bran broad and clean. It is difficult even by coarse sifting to give a brown tinge to biead made from this flour. The samples No. 3 were taken from that kind of stone, in use for grinding the coarse and harder kinds of corn. Their excellence depends upon that quality which enables them to grind almost the whole of the sub- stance exposed to their action ; however carefully the flour produced by this style of grinding may be sifted, t he MINERALOGY. 51 bread which it produces, although very wholesome and agreeable, is always dark, and in some cases almost black. Provided that these stones possess the essential grinding qualities already specified, they are never deemed too hard; this mode of grinding is essentially economical, for since the quantity of bran which remains after sifting is ex- tremely small, nearly the whole of the grain is converted into flour. Henry W. Reveley. Though from the above particulars stated by Mr. Reveley, it is evident how greatly the system of the Tuscan millers differs from that of the English ones, it may not be im- proper to state briefly those points of practice which are most at variance in the two modes, and the practical con- clusions which may be deduced from them. In England, for fine flour, the hardest French buhrs are employed, and both mill-stones are of the same material ; the furrows, or teeth, are in right lines, and the grinding surfaces are flat and parallel to each other ; the consequence is, that the grinding is performed partly by grinding, and partly by cutting, so that the bran is more or less torn ; and it is found difficult to separate the flour from the bran, without the introduction of what the millers technically call “ greys,” which are small particles of the darker parts of the corn, ground as fine as the flour itself; and, therefore, not separable by dressing or bolting. The Tuscan method, by combining the hard and soft stones, overcomes this difficulty much more readily ; since white flour is produced by means of the same dressing, which, when applied to two hard stones, produces brown flour. The friction of grinding also excites considerable heat, so that the meal comes out sensibly warm to the touch ; and it is w r ell known, that flour which has been over heated in grinding, CHEMISTRY AND r.o D/v or technically speaking, has been killed, is incapable of making light bread. In Tuscany, the upper mill-stone is far from hard, and the lower one is still softer ; the teeth or furrows are very shallow, and their form is such as to impel the grain towards the circumference, the distance between the stones is also continually lessening in the same direction, so that the grain appears to be ground wholly by friction without any cutting of the bran, and to this the soft state of the corn, from the previous washing, materially contributes. The consequence of this is, that the bran is separated almost wholly by the first sieve, the flour is pure, and not liable to be overheated. In another point of view, Mr. Reveley’s communication is interesting, as showing, that other stones besides French buhr and others of similar quality, are at least equally fit for the use of the miller. The diallage rock has long been known to exist in Cornwall ; it is also to be met with at Girvan, in Scotland ; and the hyperstene rock recently discovered by Dr. McCulloch, in the Isle of Sky, judging from the specimens deposited by him at the Geological Society, appears equally fit for the purpose as the diallage rock. Mr. Reveley, during a late visit in Cornwall, dis- covered considerable masses of diallage rock of good quality, near the village of St. Kevern, not far from Hel- ford. He has also had the good fortune to discover a quarry of porcellanous lime-stone, equal to the Tuscan, at Coleford, in the forest of Dean, in Gloucestershire. From the information of D. Mushett, esq. the proprietor of the quarry, it appears that this bed is of considerable extent, and that quarries may be opened in it at a very easy dis- tance from water carriage. As the Tuscan method of dressing mill-stones, appears MINERALOGY. 53 to possess considerable advantages over the common mode practised in this country, even when applied to French buhrs, the following letter from Mr. Reveley is inserted as an appendix to the preceding communication. King-street, West, Bryanstone-square, SIR ; 11th November, 1822. I beg to acquaint you for the information of the Society, that, about four months since, the Tuscan method of dressing millstones has been applied by me to two pair of French buhrs, at the mills belonging to Messrs. Smith and Co. of the White Chapel distillery. Since that period, these stones have been constantly grinding according to the new plan; and, I am happy to state, much to the satisfaction of the proprietors. I am, Sir, &c. &c. &c. Henry W. Reveley. A. Aikin, Esq . Sec. t Sfc. fyc. CHEMIST EY. No. I. APPLICATION OF PLUMBAGO TO NON-CONDUCTING SUBSTANCES FOR THE PRODUCTION OF VOLTATYPES. The Silver Medal and Ten Pounds were presented to Mr. Robert Murray , 122 Regent Street, for his Method of obtaining Voltatype Impressions from Non- conducting Substances by Means of Plumbago ; speci- mens have been placed in the Society s Repository. 122 Regent Street , Sir, May 26, 1840. I shall feel obliged by your informing the Committee that I shall be happy to lay before them my process of copying, by the electrotype, works of art from wood, plaster, wax, &c. See., by rendering the surface a con- ductor by means of Plumbago. I remain, &c. &c., Robert Murray. W. A. Graham, Esq. CHEMISTRY. 11 As soon as the first excitement of admiration for the beautiful application of the voltatype process in copying from metallic surfaces had subsided, it became a desider- atum to be enabled to copy such non-conducting bodies as paper, wax, wood, plaster, <$cc. And it is to Mr. Edward Solly, jun. that we owe the first successful essay in copying a receipt stamp from paper, which was done in the most perfect manner. His process was to render the surface of the paper a conductor, by covering the paper with a solution of nitrate of silver, and then submitting it to the action of light : the surface became blackened by the reduction of the silver ; and upon this he deposited his copper. This beautiful process, as a first step, was perfectly successful. From a knowledge of Professor Daniell’s and Mr. Cooper’s experiments with carbon for galvanic purposes — the former, in effecting decompositions with electrodes of plumbago, and the latter, by making a battery with common coke, &c. — it occurred to me that a thin surface of plumbago* would suffice as a conducting medium for voltatype purposes, for such substances as wax, plaster, &c., to which the nitrate of silver was in- applicable. I accordingly tried it on a plaster cast with success. 1 next tried sealing-wax, and then a wood- block, with equal success ; in short, any non-conducting surface, covered with the thinnest possible coating, is sufficient for the purpose. f An objection was made as to the probability of its filling up the fine lines, which I * This substance is also known by the names of graphite and black lead, and was supposed to be a carburet of iron; but it has been found by Dr. Karsten of Berlin to consist of nearly all pure carbon, with a small quantity of iron in the state of mechanical mixture. f Up to this time it was supposed that a metallic surface was indispens- able ; and many persons still talk of metallising the surface when they use plumbago. 12 CHEMISTRY. liave been enabled to set at rest as fallacious ; for 1 have copied Barton’s Iris buttons (which have 2000 lines to the inch) from sealing-wax impressions. I have also suc- ceeded in copying some specimens from sealing-wax im- pressions furnished me by Mr. Barton, ruled by his beau- tiful machine, as many as 8000 to the inch. In using plumbago for the voltatype process, it is necessary that it be perfectly dry, and tolerably pure, — that usually sold under the denomination of the “Servant’s friend, or true Mexican jet lead,” being quite sufficient for every pur- pose. Care should be taken that every part of the object is covered ; and as a few instructions will be necessary for the preparation of the moulds, the covering them with the plumbago, &c., I shall briefly state them. Nothing appears so easy as to take a common sealing- wax impression : this, however, will be found a little more difficult than is at first imagined, and many precautions are necessary for complete success. A stout paper* should be selected, and must be well dried before the fire, or over the flame of a candle : the wax is then to be heated over the flame (care being taken that it does not take fire) until it is sufficiently softened to be deposited on the paper; the paper with the wax is then, for a short time, to be held some distance above the flame, until the wax is sufficiently fluid to be worked up with the stick of wax. When the whole of the air-bubbles are got rid of, and a clear surface obtained, the seal is to be warmed to a degree just bearable on the back of the hand, and then pressed firmly into the wax, and, when cold, to be re- moved with a sudden perpendicular pull. In the event • Card should never be used for this purpose, as the paste and air con- tained between the folds expand, and prevent the possibility of obtaining a perfect impression. CHEMISTRY. 13 of the impression not being satisfactory, it may again be used by bolding the paper over the flame until the wax is sufficiently soft to be worked up with the stick, as before described. A good impression having been ob- tained, the plumbago is to be applied to the surface, and quickly brushed with a circular motion with a stiff brush, such as is used by jew r ellers. Some persons, I find, have a difficulty in making the plumbago take to the per- pendicular sides of the impression : this part may be touched with the point of a stick dipped in spirit of wine, great care being taken that none of it gets on the surface of the impression, as it will injure the sharpness. The surface having been well covered with plumbago, a copper wire is to be made hot enough to melt the wax, and is to be pressed into some convenient part of the margin of the mould which will not interfere with the impression: and now, to ensure 'p er f e ^t contact between the Avire and the plumbago on the surface, a small quantity must be rubbed on to both with the finger. This I find the most effectual means of securing perfect continuity between the Avire and the blackened surface. (I need hardly say that whatever material is used for the mould, unless great care be taken to ensure a perfect contact between those tAvo surfaces, Ave shall be continually subjected to disappointments.) Having prepared it thus far, it is ready to be put into any of the usual forms of voltatype apparatus. But just before immersing it into the solution, the surface of the mould should be slightly moistened by breathing on it; and this holds good for any sort of voltatype mould, as it prevents the accumulation of air-bubbles, by ensuring a complete contact between the surface and the fluid in Avhich it is immersed. Having obtained a good deposit 14 CHEMISTRY. of copper, we next proceed to fill in the back with solder, and this is best effected by wetting the back surface of the copper with a camel’s hair pencil dipped in a mixture of the solution of the muriate of zinc and muriate of ammonia : common tinman’s solder is then to be placed on it, and melted by holding it over the spirit-lamp. White wax, such as is used for candles, is a very excellent material for larger moulds. The wax having been melted in any convenient vessel over the fire, the object to be copied, if of metal, should be made very warm, and the edge surrounded by a narrow strip of paper passed several times round ; the surface of the object must be oiled with a very small quantity of salad oil. The wax is now to be poured on, and left for a few hours before it is removed, that is, until it is perfectly cold ; should the wax adhere firmly to the medal (which will be the case, more or less, according to the depth of the sub- ject), the back of the medal should be slightly warmed before the fire, trying from time to time to remove the wax ; for, if made too hot, the surface of tlie impression will be spoiled. The same process as recommended for preparing the sealing-wax with plumbago, &c. is to be pursued, using now, instead of the jeweller's brush, a stiff camel’s hair pencil of tolerable size. Stearine may also be used (for copying from metal) with advantage, with this additional recommendation, that it is not so liable to adhere as the white wax. If a reverse from a plaster cast is required in white wax, it is only necessary to very slightly oil its surface, and afterwards dip the back of the plaster in water, so that it may imbibe enough to force the oil to the surface : the oil will be thus prevented from soaking into the body of the plaster. Paper is now CHEMISTRY. 15 to be fastened round the edge, the melted wax is to be poured on as before described, and, as soon as it is cold, it will immediately separate. Fruit, leaves, &c., are very readily covered with copper by merely brushing them over with the plumbago, and attaching the stalk to a piece of copper-wire, so as to make a good contact between it and the surface. To copy wood-blocks, it is only necessary to well varnish the back and edges of the block with shell lac dissolved in spirit of wine, so as to prevent any of the sulphate of copper entering the pores ; and, having covered the face with plumbago by well brushing it with a hard brush, fasten a riband of copper round the edge, proceed, as before directed, to ensure perfect contact, . sulphurous 1 di J l acid given on j Copper ditto slight action. Greatly disappointed at my numerous failures, I at last hit upon the mode which forms the subject of my present paper, and which I have convinced myself, by repeated experiments, is exceedingly accurate and certain in effect, and easy of execution. It possesses, moreover, this advantage, that it is similar to the plan which the bleacher or manufacturer uses in his ordinary processes. The assay is, therefore, practically correct ; for whatever the value of the ore found by this plan may be, such, and no more, must be its value to the manufacturer. The method which I employ is the following: — A fair sample of the ore to be assayed is reduced to powder; one hundred grains of this are then introduced into a flask, jirovided with a bent tube in which a bulb is blown, as shewn in the figure: this bulb is partly filled with marble in fragments ; one and a half or two ounces of strong muriatic acid are then poured upon the ore, and the tube being adapted, a gentle heat is applied, and the chlorine thus produced is driven along the glass tube, and through a red hot earthemvare tube containing a coil of thin sheet copper previously weighed ; the copper is acted on by the chlorine, and a portion of it is volatilised as perchloride of copper. When chlorine ceases to form in the flask, the mixture is to be boiled until a portion of muriatic acid distils over into the bulb, wdiere it decom- CHEMISTRY. 21 poses the marble, and the carbonic acid thus formed, traversing the red hot tube, drives before it the last por- tions of chlorine, which are thus made to act upon the red hot copper. The whole is now allowed to cool a little, and the copper removed, washed, dried, and weighed, the loss of which determines the percentage of peroxide in the ore, every sixty-four parts of copper indicating eighty-eight parts of peroxide of manganese. I am, Gentlemen, &c. &c. To the President, Sfc. ' Lewis Thompson. of the Society of Arts, 8fc. a. Flask containing manganese ore and muriatic acid. b. Bulb and glass tube containing marble. c. Earthenware tube passing through furnace. d. Coil of copper foil previously weighed. 22 CHEMI8THY. The following Paper is published as an Appendix to Mr. Thom pso n’s Communication. The Society having bestowed two rewards for chemical processes requiring the use of red hot tubes, it may be useful at this time to draw attention to the conditions requisite for obtaining the full effect with such tubes, and to describe the means that have been used successfully to avoid the dangers which haye been incurred by using such tubes for other purposes. Having had, early in life, frequent occasion to use red hot tubes for the production of gas, I was instructed to use them in a safe and efficient manner. It is evident that when a gas passes through any ma- terial to act on it, unless every interior particle can be- come an outside one in some part of the passage, those particles will pass on without being acted on; and during the process, the material being dissolved or lessened in bulk, will increase the size of the passages, and thereby allow more of the gas to pass unacted on. In order to secure the contact of every particle of gas with the material in the tube, there must be a sufficient length of passage kept red hot, and that divided into as many close and intricate ramifications as possible, those intricacies continually dividing the portions of gas, will ensure such contact in some part of the passage; and where a freer passage is wanted for a more abundant action, it is not so eligible to enlarge the diameter of the tubes, from the difficulty there would be in keeping the central por- tion quite hot: but the purpose may be answered by using coarser materials and making a much longer portion of the tube red hot. Again, when the process is to be con- CHEMISTRY. 23 tinuecl for a considerable time, we must provide, that as fast as any portion of the material disappears, other por- tions shall be ready to fall in and take its place, so as to securely fill every avenue. Now, I think it will be seen that the ordinary mode of laying a straight tube horizontally across the fire will not answer these conditions, for directly the material is acted on it becomes diminished in bulk, and that alone will open the passages ; but the material lying on the lower side will leave clear room above for the gas to pass over it without contact. If metal foil is used, its thinness will enable it to be rolled close at the centre, but it will soon give room above for the gas to pass without action ; if it is thick enough to hold out and fill the circumference, its central parts will be too open, so that it does not appear that complete action can be secured in a horizontal tube, and yet, for analysis, complete action is indispens- able. But if we place the tube vertically with a perforated plug just below the red hot part, and provide a number of metal slips, cut taper like nails, and nearly as long as the red hot part of the tube, and first fill the lower portion with as many as it will hold, the thick ends downwards, and then follow them with as many with their points downwards, they will wedge in between each other, and thus completely divide the spaces into very narrow passages, and will keep them so by falling in as fast as any room is made. Again, if the metal is cast into small shot, and the tube filled a little higher than the red hot portion, there will be plenty to fall in and keep the ave- nues so effectually divided that any analysis so performed may be depended on. 24 CHEMISTRY. Red hot tubes have long been used for the production of gas, and serious accidents have occurred with them. The celebrated chemist Lavoisier, whilst producing car- buretted hydrogen, had an explosion, by which several persons were killed and others wounded ; another chemist had a similar accident with less mischief; and a third case occurred with myself about the year 1799, at the Middle- sex Hospital. Whilst I was producing carburetted hydro- gen, the apparatus burst, and wounded five gentlemen among the audience, who were attending the lecture. My late uncle, Mr. S. Varley, for whom I w r as operating, perceived the cause, and ever after removed it, and used to explain the cause when lecturing on those gases. In all these cases, one chemist had followed the other in laying the tube sufficiently filled with materials horizon- tally across the fire; in our case, a gun-barrel, well filled with charcoal powder, was laid across the fire, and for the sake of rendering the process visible, the water was made to boil in a glass retort connected by a metal tube with the gun-barrel, and from the other end a tube pro- ceeded to the pneumatic trough. At first there was a plentiful decomposition of the steam, for the gas came freely over ; but after a while it slackened, and not know- ing the cause, I urged the fire, when suddenly the ap- paratus burst, and shattered the glass about the room, wounding five of the audience. The cause w 7 as thus explained during the operation ; the red hot charcoal decomposed the steam, and com- bining with it, went over in the form of gas ; the charcoal continued to diminish in bulk, by which it soon left room enough for some of the steam to pass over without decom- position, which condensed in the farther end of the barrel CHEMISTRY. 25 and choked the passage through the charcoal that was in that end to such an extent that the gas could not escape as fast as it was produced : this occasioned considerable pressure within, which caused a still quicker decompo- sition, till it burst the apparatus. The extra charcoal was put in to hold up the red hot portion. If no more had been put in than was made red hot, the first production of gas would have been liable to distribute it so as to leave room above for the passage of steam with but little decomposition, and then, with ap- parent safety, there w r ould have been a very unsatisfactory supply of gas. In all subsequent cases the finer parts of the charcoal were removed by sifting, in order to ensure a freer pass- age of the gas, and enable us to fill the barrel quite full to suit with a new arrangement, in which the barrel was placed upright in a high fireplace. For this purpose we had German stoves, made with much deeper cast-iron lining than usual ; a round hole was made in the top, or cover, for the top of the gun-barrel to rise through, and a hole was cast in the middle of the grating to let the lower end through, and an angular tube was fitted to it in the ash pit, through which the steam entered. The gun- barrel being thus placed upright, and brim full of granu- lar charcoal free from dust, was kept red hot at the lower half, the steam rising through the intricate ramifications of this long portion of red hot charcoal was completely de- composed into carburetted hydrogen and carbonic oxide, and as fast as it dissolved the charcoal into gas, the upper portion continued falling down into its place, and kept that red hot portion quite full. Thus a continuous and rapid supply of gas was secured as long as there was any spare charcoal to fall down, after which a diminishing 26 CHEMISTRY. supply warned us to leave off, or else to refill the tube with charcoal, and we never after had any explosion. Cornelius Varley. 1 Charles Street , Clarendon Square , October , 1841. No. III. PREPARED VEGETABLE JUICES. The Silver Medal was presented to Mr. Edward Jj ENT LEV, 41 Moor gate Street , for the following Communication on his Method of obtaining the more Powerful Vegetable Preparations for Medical Use. Samples of the Juices are deposited in the Society's Repository . At the present time a difference of opinion exists as to the best method of administering the more Powerful Ve- getable Preparations of the Materia Medica. Most practitioners, I believe, are willing to concede that the Extracts and Tinctures, as at present prepared, are not uniform in their action ; and that not unfrequently their skill is frustrated by the inadequacy of the prepa- ration they administer. I am aware that the dried powder of the leaves is by some persons considered to possess the whole properties of the plant ; and I do not doubt that when the powder is fresh it may do so : but it is essential to bear in mind that light acts as a decomposing agent, and that much precaution is necessary to prevent chemical action dis- sipating the principle upon which its efficacy depends. CHEMISTRY. 27 It will be my endeavour to shew, by a process equally simple as that at present employed for obtaining the extracts and tinctures, that we may procure a prepara- tion, uniform in strength, certain in its action, and not decomposed by light. It has been frequently urged, and with some degree of truth, that vegetables vary according to the season when they are gathered, and the nature of the soil from whence they are procured ; but I am not willing to attri- bute so much to this cause as to the careless, and at pre- sent, defective, method of manipulating. In the preparation of extracts the main point to be attended to is equality of temperature. My observation on this point has been extensive ; and I am fully persuaded that a temperature above 120° Farn. is sufficient to volatilise the principle upon which their efficacy depends. The manner in which the leaves are dried equally affects the strength of the tincture. The plan which I have adopted and am about to detail, has elicited such valuable opinions from those best acquainted with the subject, that I am induced to believe it worthy of the particular attention of the profession. It is by preserving the expressed juices of the plants in the following manner : The plant being carefully selected from its healthy character and full maturity, the leaves, stem, and when advisable the root, are well bruised in a marble mortar, and then placed in a powerful wooden press. The juice thus collected is allowed to stand, in order that a deposition of feculent matter may take place, which usually does in very lnrgc quantities in the course of twenty-four hours. Alcohol, 5 6° over proof, is then added, in the proportion of four fluid ounces to every sixteen 28 CH EMISTR V. fluid ounces of the juice, which is quite sufficient to render the preservation complete, and throw down any mucilage which may be mechanically suspended. After standing for twenty-fours, the juice filtered through bibulous paper (that made from wool is the best) will be found to retain the whole virtues of the plant for any length of time. It may be as well to state that the best time for ga- thering the plant is just as it is coming into flower. The juices which I have thus prepared, and which have been put to the test of experience, are those of Conium, Digitalis, Belladonna, Hyoscyamus, Taraxacum, and Artemisia Vulgaris. I have prepared a supply of each of these juices, ac- cording to the mode previously described, which may be obtained on application at my establishment ; and it is my intention, as speedily as possible, to preserve the expressed juices of other vegetables in a similar manner. Edward Bentley. Laboratory, 41 Moorgate Street. Sir, In answer to your inquiries concerning the effects of the expressed juices of digitalis, hyoscyamus, and belladonna, with which you favoured me, I have much pleasure in stating that the trials which have been made under my direction, at the London Hospital, have proved the supe- riority of your mode of preparing these important reme- dies. I am, &c. &c. VV. J. Little, M.D. Assistant- Physician to the London Hospital. Mr. Edward Best ley. CHEMISTRY. 29 Dear Sir, I think your method of preparing certain tinctures, as tincture of hemlock, by adding rectified spirit to the expressed juices of the plants, a great improvement on the ordinary method, and calculated to obtain uninjured the activity of the plants employed. The samples of the tinctures given by you to me are the best I have seen. The process of the Edinburgh Pharmacopoeia for 1839 for making tincture of hemlock, though an improvement on preceding methods, is inferior to yours in several re- spects. The percolation which is directed is unnecessary, and in your process is entirely dispensed with. The sub- stitution of simple spirit for tincture of cardamoms, has the advantage of yielding a tincture, the active properties of which may be judged of by the colour, taste, and smell, and by the action of potash on the resulting com- pound. Ever yours, &c. &c. Jonathan Pereira. Lecturer in the Medical School of the London Hospital, and at the Aldersgate School of Medicine. Mr. Edward Bentley. No. IV. GALVANIC TEST APPARATUS FOR ARSENIC. The Thanks of the Society were presented to Mr. W. J. T. Morton, Royal Veterinary Colleye, Camden Town , for the following Communication of his Method of . Testing the Presence of Arsenic. This apparatus has been invented with a view to obviate one of the objections raised against Marsh’s mode of 30 CHEMISTRY. detecting arsenious acid in organic and other fluids ; namely, that the zinc employed may contain arsenic. In it the suspected fluid, slightly acidified with sulphuric acid, so as to render it a better conductor of electricity, is decomposed by the aid of a galvanic battery of a few plates, when, if any arsenic be present, it will be evolved at the negative electrode in combination with the hydrogen, forming arseniuretted hydrogen gas, which, being allowed to escape by turning the cock, is to be inflamed as it issues from the jet ; and on bringing a watch-glass, or a piece of porcelain over the flame, a film of arsenicum will be deposited on it. That it is arsenicum may be proved by dissolving it in excess of nitric acid, evaporating to dryness, and adding to the salt a solution of the nitrate of silver, when, according to Orfila, a brick-red precipitate will be thrown down — the arseniate of silver. By this apparatus the existence of one grain of arse- nious acid, when dissolved in a gallon of water, or oi one part in above 76,000, has been demonstrated ; many metallic films having been obtained ; and there is little doubt but that the dilution might have been carried much further, and still the presence of the poison indicated. W. J. T. Morton, Lecturer on Veterinary Materia Medica, Royal Veterinary College. In the apparatus which Mr. Morton originally sent to the Society, the oxygen and hydrogen were collected in two tubes inserted in the wooden cover of the glass cylinder containing the liquid to be tested ; each tube was furnished with a brass jet and stop-cock similarly to CHEMISTRY. 31 the single bell-mouthed tube in the annexed drawing. The lower and open ends of the tubes were placed over the electrode points of the wires connected with the mer- cury cups in the sides of the wooden stand ; when the pole-wires of a galvanic battery are placed in the cups, a small quantity of sulphuric acid having been added to the liquid, the decomposition proceeds, and if any arsenic be present, it may be collected in the same manner as with Mr. Marsh’s apparatus. The following letters explain Mr. Morton’s motives for altering his apparatus to the form represented by the drawing. Royal Veterinary College, Sir, March 4th, 1841. I am obliged by your communication; and, if possible, I will attend on Saturday evening, as requested : but my object in sending the apparatus to the Society of Arts was 32 CHEMISTRY. merely to give publicity to that which I thought might prove of service, and which appears to merit your notice. The battery I have employed is either a Wollaston’s trough of ten plates, or a Smee’s. I am now about to make such an alteration in the apparatus as will, I hope, do away with the necessity of using any acid, and thus to obviate the other objection that has been raised to Marsh’s test ; but I cannot as yet speak positively. I hope to have the new apparatus home to-morrow, and before Saturday to try it. If I am unable to attend on Saturday evening, I will forward it to you, with a battery. I am, Sir, &c. &c. W. A. Graham, Esq. W. J. Morton. Secretary, $-c. ^c. Royal Veterinary College, Sir, April 17, 1841. I forward my original Galvano-Arsenical Apparatus, with another in which I think I have made some im- provements. You will perceive the alteration to consist, firstly, in haviim- but one tube instead of two, and which is much larger. The advantage resulting from which is that a oreater quantity of gas may be collected for examina- tion, while the froth that forms when organic fluids are being operated upon falls more readily, and hence is less likely to interfere with the analysis. Secondly, the elec- tricity enters by means of a number of pointed wires instead of pieces of platinum foil, by which the decom- position of the suspected fluid is more quickly effected. CHEMISTRY. 33 The only care required on the part of the analyst is, that the negative electrode be connected with the gas receiver, otherwise the arseniuretted hydrogen that may be evolved will be lost. The oxygen may be allowed to escape. It appears desirable that the aid of sulphuric acid as a conductor of electricity should be dispensed with, since much of that now met with in the market is contami- nated with arsenic, from iron pyrites being used in its formation. I have been, therefore, extremely anxious to find a substitute ; and although I have not discovered any agent that so readily causes the disengagement of minute quantities of arsenic as it, yet a small portion of pure potash, or its carbonate or nitrate, may be advan- tageously used instead. About two draclnns to a pint I have found sufficient. The advantage is, the arseniate of potash formed is much more soluble than arsenious acid. This being the case, the plan to be pursued in cases of suspected poisoning is rendered sufficiently simple. It is this; portions of the stomach that have been acted on, or the contents of that viscus, are to be boiled in distilled water for a short time, adding either some pure potash, or its carbonate. The solution is then to be tested by means of the galvano-arsenical apparatus, in the man- ner already shewn to the Committee. Thus I have removed the objections that have been raised to nascent hydrogen as a test for arsenious acid, by not employing either zinc or sulphuric acid. I am, Sir, &c. &c. W. A. Graham, Esq. W. J. T. Morton. Secretary , fyc. fyc. VOL. LI 1 1 . jj 34 CHEMISTRY. In presenting Mr. Morton’s method to the public, the Society recommend it as an ingenious and useful addition to the methods already in practice, and anti- cipate that it may frequently prove serviceable in cor- roborating the results of other experiments, if not in furnishing independent evidence. It is, however, necessary to call attention to the fact, that according to the experiments of Mr. Thompson, the sulphurets of arsenic are unacted on by this method, unless dissolved in alkaline menstruum, and even then a large portion of the arsenic remains attached to the electrode in the form of a black powder (hydroguret of arsenic). * A X sgt i o, S&k-i t V -j