THE 
 
 APPLICATIONS OP CHEMISTPY 
 
 THE ARTS 
 
 TAKEN FROM THE LECTURES OF PROFESSOR 
 RENWICK. 
 
 PRINTED AT THE COST AND FOR THE USE OF THE JUNIOR CLASS OF 
 COLUMBIA COLLEGE, NEW-YORK, 1851 AND 1852. 
 
 NE W-YORK: 
 
 PRINTED BY JOHN F. TROW, 49 ANN-STREET. 
 1851 . 
 
THE 
 
 
 APPLICATIONS OF CHEMISTRY 
 
 TO 
 
 THE ARTS. 
 
 TAKEN FROM THE LECTURES OF PROFESSOR 
 RENWICK. 
 
 PRINTED AT THE COST AND FOR THE USE OF THE JUNIOR CLASS OF 
 COLUMBIA COLLEGE, NEW- YORK, 1851 AND 1652. 
 
 NEW-YORK: 
 
 PRINTER BY JOHN F. TROW, 49 ANN-STREET. 
 1851. 
 
GQO 
 
 "R S,0a 
 
 Digitized by the Internet Archive 
 . in 2016- 
 
 https ’//archive. org/details/applicationsofchOOrenw 
 
I. 
 
 ACIDS OF COMMEECE. 
 
 1. SULPHURIC ACID, S + 30 + (H + 0). 
 
 Sulphuric acid was originally known as oil%of vitriol ; it was 
 prepared from metallic sulphates (vitriols) by a high heat. The 
 acid thus prepared, was impure ; after the chemical composition 
 of the acid was discovered, it was attempted to make it^ by the 
 direct union of the elements, and as this could not be effected by 
 simple combustion, it was proposed to burn the sulphur in con- 
 tact with a body abounding in oxygen, and easily decomposed. 
 The substance chosen for this purpose was nitre (Nitrate of Po- 
 tassa), instead of which however, the Nitrate of Soda is now used. 
 When this plan was carried into practice, it was not only found 
 successful, but a less quantity of nitre was required than appeared 
 to be necessary from its chemical constitution. The proportions 
 now used are, one part of nitre to eight of sulphur. The process 
 was originally performed in globular vessels of glass ; these were 
 expensive, and the quantity of gas obtained small. The process 
 is now performed in chambers lined with sheet lead. Upon this 
 metal, sulphuric acid and its vapor have but little action, and its 
 sulphate when formed is insoluble, and takes the shape of a crust 
 upon the metal. The form of the chamber is slightly inclined to- 
 wards one corner, and is covered with water to the depth of three 
 or four inches ; the mixture is placed in an iron vessel, which is 
 mounted on a carriage, and when the sulphur has been ignited^ 
 the carriage is shoved through a small door in the side of the 
 
 p31169 
 
4 
 
 ACIDS OF COMMEECE. 
 
 chamber. When the combustion is completed, the water is found 
 to contain sulphuric acid. To obtain this acid, the water is evap- 
 orated by heat. The evaporation is commenced in open vessels 
 of lead, but cannot be completed in consequence of the great at- 
 traction between sulphuric acid and water. The process is there- 
 fore completed in close vessels, or retorts of glass, set in an iron 
 vessel in a bed of sand. These retorts are liable to break, be- 
 cause the last portions of the vapor of water collect in large bub- 
 bles in sulphuric acid. The risk may be somewhat lessened by 
 placing strips of platinum in the retort ; but it is better to sub- 
 stitute retorts of platinum for glass. That the latter have not 
 come into general use, is owing to their high price, but after al- 
 lowing sufficient profit for the capital thus invested, sulphuric 
 acid can be afforded cheaper, when platinum is used. 
 
 Other improvements have been made in the process, the most 
 recent of which have been founded upon the chemical principles 
 involved, which are as follows : when a mixture of sulphur and 
 nitre is deflagrated in dry atmospheric air, sulphurous acid and 
 deutoxide of nitrogen are generated, the latter is immediately 
 converted into nitrous acid gas, and the two acids remain without 
 acting upon each other, unless moisture be present ; but if the 
 air be mixed with vapor, the two acids and water unite to form a 
 white crystalline solid, which falls into the water that covers the 
 floor of the chamber. As soon as this solid touches the water it 
 is decomposed ; the sulphurous acid takes two equivalents of oxy- 
 gen from the nitrous acids, is converted into sulphuric acid, and 
 the nitrous acid is converted into deutoxide of nitrogen ; this es- 
 capes in the form of gas, and if it meet with sulphurous acid, 
 vapor of water, and oxygen, the process will be repeated. Thus 
 it happens that no more of either nitrate is absolutely necessary, 
 than is just sufficient to cause the process to begin. 
 
 The first attempt at improvement consisted in rendering the 
 process perpetual ; for this purpose the iron vessel was placed at 
 the lower end of a cylinder of sheet lead, inserted in the floor of 
 the chamber. Beneath the vessel a furnace was built, in which a 
 sufficient heat was generated to cause the sulphur to take fire ; and 
 as the sulphur was consumed, a fresh supply of air was introduced. 
 
ACIDS OF COMMEECE. 
 
 5 
 
 In order to admit atmospheric air, valves were arranged for the 
 escape of the foul air and the admission of fresh. To supply the 
 necessary vapor of water, a small boiler was provided, whence steam 
 flowed continually into the chamber. The high price of nitre led 
 to the use of the nitrate of soda ; but at present, sulphuric acid is 
 manufactured, without the use of either nitrates. As a substitute, 
 a mixture of nitric acid and molasses is placed in a platinum dish, 
 which is supported by an iron tripod upon the iron vessel in 
 which the sulphur is burnt. By the action of these two. substan- 
 ces, oxalic acid is formed, and deutoxide of nitrogen is liberated. 
 The oxalic acid is as yet of more value than the materials from 
 which it is obtained, so that the whole cost of the nitrate is saved. 
 
 Besides the common sulphuric acid, another kind is manufac- 
 tured in Germany, which is a solution of the solid anhydrous 
 acids {S -j- 3 0) in the liquid acid. The process by which it is 
 manufactured is kept secret. It is chiefly employed in dissolving 
 indigo. This kind of sulphuric acid might be prepared in the 
 following manner : expose protosulphate of iron to a heat suffi- 
 cient to drive off its water of crystallization ; place the powder 
 in a retort, and expose it to a heat sufficient to decompose it ; 
 pass the vapor through vessels containing the common acid. 
 
 Sulphuric acid is perhaps the^most important of all substances 
 in the chemical arts. By means of it nearly all the other acids are 
 prepared, and by its action a great number of other substances are 
 obtained. The raw material, although obtained in large quanti- 
 ties from metallic sulphurets, is chiefly furnished from Naples 
 and Sicily ; the government of which countries possesses a con- 
 trol over the arts of others, and a change in the manner of dis- 
 posing of it was nearly the cause of war between France and 
 England. 
 
 2. NITBIC ACID. N + 5 0 + (0 + H). 
 
 Nitric acid has long been prepared from sulphur and nitre in 
 glass vessels. To obtain it in larger quantities, the nitre was decom- 
 posed by means of the alumina contained in clay, in large earthen 
 
6 
 
 ACIDS OF COMMEECE. 
 
 vessels. At present, nitric acid is prepared by the action of the 
 two first-named substances, in an apparatus of the following de- 
 scription. Open cylinders of iron are built into walls, by means 
 of which a furnace is formed ; each cylinder is provided with two 
 heads of cast-iron ; these heads have passages formed in them in 
 an inclined position ; one of the heads being set in its place, the 
 condensing apparatus is connected with the passage. The cylin- 
 der is then charged with nitre, and the other head is inserted. 
 To the passage in the latter head, a leaden funnel, whose tube is 
 bent into three branches, is adapted ; this funnel serves for the 
 introduction of the sulphuric acid. The condensing apparatus 
 is composed of a number of three-necked bottles ( Chemistry, p. 166). 
 Water is placed in only one of these vessels, because nitric acid 
 has the liquid form ; in order that the acid shall be free from 
 nitrous acid gas, an excess of nitre should be used. 
 
 The prepared nitric acid may contain some of the sulphuric 
 acid, and if the nitre be not pure, muriatic acid may also be pre- 
 sent. Sulphuric acid may be separated by nitrate of baryta ; mu- 
 riatic acid, by nitrate of silver ; pure nitric acid remains. 
 
 3. MURIATIC ACID. Ch + H. 
 
 Muriatic acid was also prepared on a small scale in glass ves- 
 sels. It is at present prepared in an apparatus composed of iron 
 cylinders, and three-necked bottles, similar in general character to 
 that used in the manufacture of nitric acid. 
 
 The solid material is common salt, the liquid material sul- 
 phuric acid. The three-necked bottles contain water. 
 
 The purest acid is found in the middle bottles of the series. 
 Those nearest to the distilling apparatus contain some sulphuric 
 acid ; and those most distant contain a weak acid, which is used 
 in a subsequent process for filling a part of the bottles. The 
 residuum of the manufacture of these two acids is sulphate of 
 soda. This is now employed in the manufacture of carbonate of 
 soda ; and the quantity of the latter subtance, which is required 
 in the arts, is so great that the process last described is often 
 
ACIDS OF COMMEECE. 
 
 7 
 
 carried on for no other purpose than to obtain the sulphate of 
 soda. In this case the muriatic acid is not collected, but is con- 
 densed in a subterranean passage through which a stream of 
 water flows. 
 
 4. PYEOLIGNOUS ACID. 
 
 Pyrolignous acid is prepared by the distillation of wood in 
 iron cylinders. Charcoal is left in them ; and this process is 
 often connected with the manufacture of gunpowder, for which 
 this charcoal is peculiarly adapted. The decomposition of wood, 
 besides condensible matter, furnishes the gaseous compounds of 
 carbon and hydrogen ; and these are conveyed from the condens- 
 ing apparatus to the furnace, where they burn and thus serve as 
 fuel. The condensing apparatus is on the principle of Woolf’s ; 
 but is composed of wooden vessels, connected by wooden, pipes. 
 In these the acid is collected, being a combination of water, 
 acetic acid, and several liquid carburets of hydrogen, which are 
 rendered capable of mixing with the water by that acid. Pyro- 
 lignous acid is used in its original state in preserving meat ; it 
 is also employed as a source of acetic acid, which in its turn, is 
 converted into a substitute for vinegar. For the process in which 
 acetic acid is prepared, see Chemistry, p. 318. 
 
 To make vinegar, the concentrated acetic acid is mixed with 
 sixteen parts of water and one of alcohol. 
 
II. 
 
 HYDEOGEN. 
 
 1. AEROSTATION. 
 
 Balloons were originally filled with heated air, a supply of 
 which was kept up by a fire of straw. They are now filled with 
 hydrogen gas. 
 
 The joint weight of the balloon and the hydrogen gas it con- 
 tains, may be so much less than that of an equal bulk of atmos- 
 pheric air that the vessel will not only rise, but carry a consider- 
 able weight with it. Gold-beaters’ leaf may be used to make 
 balloons of a small size. 
 
 Balloons of larger size are made of silk, rendered impervious 
 to air by a varnish (India-rubber varnish). 
 
 The silk is cut into gores, which are sewed together ; the 
 balloon, when distended, has the shape of a sphere or spheroid. 
 One point of each gore being cut off, a circular opening is left 
 in the upper part. At the other end, the gores are produced in the 
 form of ribbon-shaped strips ; and these, when sewed together, 
 form a tube. To the circular opening is adapted a valve, made 
 by stretching silk over a hoop of rattan or whalebone. Atmos- 
 pheric air is removed from the balloon by compressing it ; the 
 balloon is filled from a gasometer, which is usually constructed 
 by inverting one wooden tube within another. The hydrogen is 
 usually prepared by the action of a dilute sulphuric acid on iron 
 filings. The latter substance is placed in barrels, which are then 
 closed by heads. In each head are inserted two pipes. One of 
 these has a funnel at the top, and reaches nearly to the bottom 
 of the barrel ; the other barely enters the barrel, and is long 
 
HYDEOGEN. 
 
 9 
 
 enough to re^ch the gasometer. The first pipe serves for the in- 
 troduction of the dilute acid ; through the second, the gas flows 
 to the gasometer. The barrels are usually arranged in the form 
 of a circle. 
 
 The gas is made to pass from the gasometer to the balloon, 
 through the flexible tube ; and while the gas is flowing into the 
 tube, the upper valve must be fastened down. The upper part 
 of the balloon is covered by a network of cords susceptible of 
 taking the shape of a hemisphere or hemispheroid, and from 
 what may be styled the equator, a number of ropes proceed; 
 to which a basket called the car is tied. The upper valve 
 is loosened after the balloon is filled, and is afterwards man- 
 aged by means of two ropes which reach to the car. If the 
 balloon is full of gas, it is necessary to leave the flexible tube open 
 while the balloon is rising, in order to prevent the balloon from 
 being burst by the expansion of the gas. When the balloon 
 reaches its utmost height, this tube is closed by twisting it into 
 a knot. In order to descend, the upper valve is opened and a 
 part of the hydrogen permitted to escape. In order to rise again^ 
 the balloon is furnished with ballast in the form of sand tied in 
 bags, and a part of this ballast is thrown out. The aeronaut, 
 ^erefore, has the power of ascending and descending within the 
 lipits of the quantity of gas and supply of ballast. No efficient 
 mipans have yet been contrived by which a balloon can be moved 
 in; a horizontal direction. 
 
 USES AND PUEIFICATION OF WATEE. 
 
 'ater is never found pure in nature. It may either contain 
 insoijible impurities, which produce a visible muddiness, or solu- 
 ble Impurities. The latter may be either solid, or gaseous. 
 GraseAus impurities are not always objectionable ; and when they 
 are restricted to oxygen and carbonic acid, their presence is abso- 
 lutely , necessary to render the water potable, and its quality 
 wholes(|me. The gases which arise from putrescent water, are 
 unwholesome. These may be removed by boiling. As this how- 
 
10 
 
 HYDKOGEN. 
 
 ever renders water disagreeable to the palate, in a country where 
 the necessity for thus purifying it exists, they added, many ages 
 since, the leaf of an indigenous plant, which rendered the water 
 palatable after it was boiled. And, in this necessity, we have 
 the origin of tea. Boiling also destroys the life of the animal- 
 culae which abound in stagnant water. 
 
 Insoluble impurities will settle when water is permitted to 
 remain at rest. The deposit may be accelerated b}^ placing a 
 lump of alum in the bottom of a vessel. The alum dissolves so 
 slowly and its solution is so dense, that the upper part of the 
 water will not acquire any taste. The best form of vessel for 
 this purpose is that of a sugar-loaf. 
 
 Water may be more rapidly clarified by filters: and when 
 the water is offensive, the filters should be in part composed of 
 charcoal. 
 
 Some waters containing soluble salts and gases, are entitled 
 mineral ; but these are never purified. 
 
 Common spring water may contain smaller quantities of solu- 
 ble matter, and this is chiefly of two kinds — common salt, and 
 calcareous salts. The presence of the first renders water brack' 
 ish ; the second makes it hard. There is no artificial method 
 used for purifying brackish water. In nature, however, the sak 
 appears to separate, when the water filters through a considei- 
 able thickness of sand. This indeed is the only means of ac- 
 counting for the existence of springs in sand-banks. 
 
 Hard water becomes soft and free from other soluble impuri- 
 ties, when it has been running for a long time with a gentle and 
 steady current. When the carbonate of lime is present, ii is 
 precipitated, because the excess of acid escapes, and the sulplate 
 of lime is converted into the carbonate. Soluble organic bodies 
 cease to be soluble, and gases escape. All the impurities, there- 
 fore, finally become mechanical, and are precipitated by rest, or 
 separated by filtering. It is to this action that the proverbial 
 excellence of the waters of the Nile, the Ganges, and the Missis- 
 sippi, is owing. If the water is stagnant, although it may become 
 soft, it retains its organic impurities, and in a more offensive 
 form than in running water. 
 
HYDEOGEN. 
 
 11 
 
 In rocky countries, the water is almost always hard, and 
 therefore unfit for many processes in the arts — particularly in 
 the woollen manufacture, in bleaching, and in dyeing. 
 
 Water has been rendered soft for the first of these purposes, 
 by the salts of ammonia contained in a putrescent animal liquid; 
 the use of this is disgusting ; and it has been a desideratum to ' 
 obtain soft water by a convenient and cleanly operation. The 
 following process has been successfully used for this purpose. 
 
 To render hard water soft, take for one hundred gallons six 
 ounces of common soda ; dissolve in one gallon of soft water by 
 boiling, and add to the boiling solution two ounces of white soap. 
 The ley will combine with the acids of the soap (organic acids, 
 see Chemistry, p. 321), forming a compound lighter than water, 
 which may be skimmed otf. Thus purified, the water is fit for 
 every process in the arts, and is not unpleasant to the taste. 
 
 3. AMMONIA. 
 
 The form in which ammonia was first known, was a salt found 
 in the stables of the Temple of Ammon. It was probably the 
 double phosphate of soda and ammonia. It is certain, however, 
 that common salt was also known by the same name. The salt 
 of ammonia was obtained in the interior of Africa, and was 
 shipped for Europe from the port of Alexandria. 
 
 When another article was brought into Europe from the 
 same port, and applied to the same uses, it went by the same 
 name. This latter article was the muriate of ammonia, which is 
 still prepared in large quantities in Egypt. It is obtained from 
 the soot of chimneys, in which animal matter is used as fuel. 
 The soot is mixed with common salt, and the mixture is placed in 
 globular glass vessels, of which it occupies about one half. The 
 globe is placed over a fire, and the muriate sublimes. The vapor 
 is condensed on the upper surface of the globe in crystals, which 
 unite to form a tenacious mass. 
 
 The first preparation of ammonia in Europe was known as 
 spirits of hartshorn, and was obtained from the shavings of horn 
 
12 
 
 HYDEOGEN. 
 
 by destructive distillation. The gas in the vapor was condensed 
 in water, which became a solution of ammonia and its carbonate. 
 
 A second source was found in woollen rags : these are sub- 
 jected to destructive distillation. The volatile product is con- 
 densed ; and is composed of water containing ammonia and its 
 carbonate, with an animal oil. The solution is converted into 
 muriate of ammonia by mixing it with the bittern of salt-works. 
 A great quantity of ammonia is obtained at Montfaucon, near 
 Paris, at an establishment where horses are slaughtered. 
 
 The most important source of ammonia, at the present day, is 
 in the liquor which is condensed when coal is distilled for making 
 gas. This is obtained in great abundance, and it has been pro- 
 posed to convert it into a sulphate by condensing the mixed va- 
 por and gas in sulphuric acid. 
 
 The sulphate has also been prepared by causing this liquor 
 to filter through sulphate of lime. The sulphate obtained in 
 either mode is now employed in agriculture, and is the most im- 
 portant material in artificial guano. It has not yet been intro- 
 duced in the arts in the place of the muriate, although there is no 
 good reason to prevent its being done. 
 
# 
 
 III. 
 
 CARBON. 
 
 • 1. CHARCOAL. 
 
 Charcoal is prepared for the manufacture of gunpowder in 
 iron cylinders and retorts, in the manner described under the 
 head of Pyrolignous Acid. It is usually prepared in coal-pits. 
 The wood is cut into billets four feet in length. A stake being 
 set up in the ground, with a rude cross nailed to its top, the 
 billets are placed leaning against it at the slightest possible in- 
 clination. Other billets are arranged around these until the 
 diameter of the base becomes twice the height of the pile. When 
 a large quantity of wood is provided, the heap may be built in 
 two, three, or even four layers, with the same proportion between 
 the height and the diameter of the base. The heap is then co- 
 vered with earth, preserving openings for the admission of air 
 and the escape of gas. One of these is at the vertex of the heap, 
 others around the base at equal distances ; and when the heap is 
 composed of more than a single layer, holes are left at the junc- 
 tion of the layers. The central stake is then withdrawn, and 
 fire is set to the heap by dropping burning brands through the 
 space which is thus left. The combustion extends towards the 
 surface, and is regulated by opening and closing the holes. The 
 hole at the top is closed as soon as flame makes its appearance 
 there, and all are closed as soon as the combustion has reached 
 the outward logs. This is known by the earthen cover becoming 
 red-hot. The heap is then enveloped in a second covering of 
 
14 
 
 CARBON. 
 
 earth ; and as this cracks it is removed, and replaced by a fresh 
 cover. This remains till the charcoal has cooled. In this way, 
 112 lbs. of wood yield no more than 17 lbs. of charcoal. In the 
 manufacture of charcoal for gunpowder, 1 00 parts of wood de- 
 composed by the combustion of 12 parts of the same wood, yield 
 28 of charcoal. Various plans have been proposed to prevent so 
 great a loss ; but none has yet been discovered, which is applica- 
 ble in the forest. 
 
 Where circumstances will admit of a stationary apparatus, 
 two methods have been employed. The first is applicable to 
 resinous woods, in which the tar and turpentine are products of 
 value. The apparatus consists in a vaulted chamber of masonry- 
 on one side of which is a furnace, and on the opposite side a chim. 
 ney. The flame from the furnace, is directed through the cham-. 
 ber to the chimney. The resin is collected in a gutter formed of 
 brick, in the floor of the chamber. In this way the product is 
 nearly as large as in iron cylinders. 
 
 The hard woods have been charred in kilns, formed in the ground. 
 The shape of these kilns is that of an inverted truncated cone, and 
 they are lined with brick. On the outside of the lining several iron 
 pipes proceed downwards and enter into the lower part of the kilns. 
 These serve for the admission of air, and are provided with stoppers 
 to regulate the draught. The cover of the kiln is made of sheet iron, 
 having as many short pipes placed around its circumference as 
 there are long pipes on the outside of the lining. There is a sim- 
 ilar pipe in the middle of the cover. The wood is laid horizon- 
 tally in the kiln, and the cover being set in its place, is loaded 
 with 12 or 15 inches of earth. The fire is lighted by dropping 
 fuel through the central pipe, and extinguished by closing all the 
 pipes. Pyrolignous acid may be collected by adapting a Woolfs 
 apparatus to one of the pipes, passing through the cover. The 
 first part of this apparatus is an iron pipe. All the rest is com- 
 posed of wood, barrels being substituted for three-necked bottles. 
 In this way, about 20 per cent, of charcoal is obtained from the 
 wood. The profitable use of this apparatus will depend upon the 
 relation between the expense of transporting the wood to the 
 place where the kiln is built and the increased profit derived 
 from the augmented quantity of charcoal. 
 
CARBON. 
 
 15 
 
 2. COKE. 
 
 Coke is more easily prepared than charcoal. 
 
 For this purpose it is sufficient to pile bituminous coal in a 
 heap, covering it with fine coal, and then with coke dust. It was 
 once considered necessary to coat the heaps with straw, and to 
 cover the straw with earth. The heaps can be of no other dimen- 
 sions than about 15 feet in diameter, and 3 feet in height. They 
 are ignited by placing burning coals in a cavity, at the vortex of 
 the heap. The process requires no attention whatever. 
 
 To obtain large quantities of coke, prismatic heaps are built, 
 15 feet wide, 3 feet in height, and of indefinite length. Fire is 
 applied at points distant 15 feet from each other, along the ridge 
 of the heap. 
 
 Coke cannot be transported without great loss. Hence, when 
 a place is distant from coal mines, it is important to make coke 
 with the smallest portion of coal. Kilns for this purpose are con- 
 structed by forming a circular chamber of brick, whose wall is 
 
 3 or 4 feet high. This chamber is surmounted by a dome, in the 
 middle of which is an opening, surrounded by a chimney 3 feet 
 high. An opening is also left in the circular wall to which an 
 iron door is adapted. The coal is introduced through this door 
 and the chimney, and is spread out to an uniform depth of 3 or 
 
 4 inches. Burning fuel is dropped through the chimney, and the 
 door is left open until the combustion is fairly established. The 
 door is then closed, and the combustion is finally checked by lay- 
 ing a fiat stone on the top of the chimney. 
 
 When the coal is of such a nature as to burn at once to ashes, 
 it may be coked by piling it around a permanent chimney, which 
 is circular, and in building which, alternate bricks are left out in 
 the two lower courses. The coal must be so arranged that the 
 largest pieces shall be nearest the middle of the base of the heap. 
 
 Coal-dust may be converted into coke by making it into a 
 paste with water, piling it into a pyramidal or prismatic form 
 around tapering sticks, so disposed, that when they are withdrawn 
 they will afibrd access for air, and an escape for gas. 
 
16 
 
 CAEBON. 
 
 3. LAMPBLACK. 
 
 Lampblack was originally collected from the soot of oil 
 lamps. When collected on ivory plates, it was called ivory- 
 black. It is at present prepared by burning refuse turpentine 
 in iron kettles, and directing the smoke through a cylindric 
 chamber. The chamber is lined with blankets or sheepskins, 
 and has within it a conical frame of sheet iron, having openings 
 for the escape of the heated air. This conical frame is suspended 
 by chains, and during the combustion is supported near the up- 
 per part of the chamber. When the combustion is completed, 
 the lampblack is removed from the woollen by raising and lower- 
 ing the frame of sheet iron. 
 
 Instead of ivory-black, animal charcoal is now usually em- 
 ployed. 
 
 Blue-black is prepared from peach-pits. The article called 
 black chalk is the charcoal of the holly. 
 
 4. ANIMAL CHAECOAL. 
 
 Animal charcoal is chiefly prepared from bones, calcined for 
 this purpose in iron cylinders. When the cylinders are opened, 
 the charcoal must be instantly inclosed in tight iron vessels. It 
 is used in great quantities in several useful arts for removing the 
 substances which give taste, smell, and color, to vegetable pro- 
 ducts. Thus it is used in the rectification of spirits, and in the 
 manufacture of sugar. 
 
 In sugar-making it is possible, by the use of animal charcoal, 
 to obtain white sugar at the first process from cane-juice, and 
 molasses may be rendered as colorless and transparent as the 
 finest syrup. Common charcoal may be prepared for the same 
 purpose, by heating it with an alkali until the fusion of the lat- 
 ter. The alkali is then removed by washing. The stone which 
 is found in contact with coal, and is known as bituminous shale, 
 may by charring be rendered capable of producing the same ef- 
 
CARBON. 
 
 17 
 
 feet as animal charcoal, and makes a more convenient filter. 
 When animal charcoal ceases to he effective, it makes a valuable 
 manure. 
 
 5. MINERALOaY OF CAKBON. 
 
 Species 1. — ^Diamond. 
 
 The diamond is composed of carbon almost pure. It usually 
 occurs in alluvial or diluvial soils. It is always crystalline, and 
 generally retains the external crystalline form, only slightly 
 abraded. The primitive form is a regular octoedron. It is the 
 hardest of all known substances, is usually transparent, has the 
 highest vitreous lustre, and a power of refracting light that gives 
 it a beauty beyond that of any other transparent body. Its 
 density is about 3 5. In consequence of their hardness, diamonds 
 can only be polished by their own powder, and cannot properly 
 be said to be cut. The cutting of diamonds consists in opening 
 out their crystalline surfaces, and the figure that can be given to 
 them depends upon their own crystalline form, of which, however, 
 a greater or less advantage may be taken by the skill of the 
 workman. 
 
 The forms into which diamonds can be cut are three in 
 number, the brilliant, the rose, and the table. The brilliant may 
 be described by conceiving a regular octoedron to be deeply 
 truncated at one of its pyramidal terminations, truncated to a 
 less depth at the opposite point, bevelled until the truncations 
 become octagons, and bevelled and truncated around the square 
 base of the two pyramids, until the number of faces becomes 58. 
 The rose diamond has the same general form as the brilliant, but 
 is so deeply truncated at one of its pyramidal terminations as to 
 leave but little of the pyramid. It is set with this surface lower- 
 most. The table has two deep and equal truncations. Dia- 
 monds are sold by weight, the unit of which is called a carat. 
 A fine brilliant weighing one carat is worth about $40, and the 
 value increases with the square of the weight, so that a brilliant 
 of two carats is worth $160. 
 
 2 
 
18 
 
 CARBON. 
 
 Species 2. — G-raphite, 
 
 Graphite is better known as plumbago or blacklead. It is 
 too familiar to require description. The finest quality is found 
 only at one locality in England. This is prepared for making 
 pencils by sawing it into strips, which are set in sticks of cedar. 
 In France pencils are made by mixing plumbago in fine powder 
 with tempered porcelain clay, and after giving the mixture the 
 proper form, baking it in a potter’s kiln. Pencils of inferior 
 quality are made in G-ermany by mixing powdered plumbago 
 with melted sulphur, and pouring the liquid mass into reeds. 
 The best graphite gives on analysis about 4 per cent, of iron, but this 
 metal does not appear to be an essential component, and it may 
 be considered as a form of pure carbon. The substance called 
 kish, which forms on the surface of pig-iron, has all the characters 
 of plumbago and contains no iron. 
 
 Species 3. — Anthracite Coal. 
 
 Species 4.— Semi-Bituminous Coal. 
 
 Species 5 . — Bituminous Coal. 
 
 Variety I. — Coking Coal. 
 
 Variety II.- — Coal that hums without forming coke. 
 
 Species 6. — Cannel Coal. 
 
 Species 7 . — Bitumen. 
 
 Variety I. — Asphaltum. 
 
 Variety II. — Mineral Tar. 
 
 Variety III. — Tetroleum. 
 
 Variety IV. — Naphtha. 
 
 6. GAS LiaHTS. 
 
 Gas has been obtained for illumination from bituminous and 
 cannel coal, from oil, and from common rosin. 
 
CAEBON. 
 
 19 
 
 Coal may be decomposed for the purpose in cylinders or re- 
 torts of iron. A number of these are built into the same furnace, 
 and the volatile pr.oducts of the whole are conveyed by a bent 
 pipe, proceeding from the top of each of them, to a close horizon- 
 tal channel or pipe, where the pipes dip into water to a small 
 depth. The water in the close channel serves as a valve, accom- 
 modating itself to an unequal flow of gas from the several retorts, 
 and permitting any one of the retorts to be opened for the pur- 
 pose of charging it, without interfering with the flow of gas from 
 the other retorts. The gas is finally collected in a gasometer 
 (Chemistry, p. 108), where it is stored for use, but requires to be 
 previously purified on the following principles. The volatile mat- 
 ter obtained from coal may be either condensible or gaseous. 
 The condensible products are: 1, coal-tar ; 2, water. The coal- 
 tar is of a very complex constitution {see Chemistry, p. 344). 
 The gaseous products are : 1, ammonia, in much larger quanti- 
 ties than can be accounted for by the nitrogen of the atmospheric 
 air enclosed in the retort ; 2, carbonic oxide, and carbonic acid ; 
 3, sulphurous acid, sulphuretted hydrogen ; 4, light carburetted 
 hydrogen, and olefiant gas (Chemistry, pp, 168 & 169). Of these, 
 ammonia, carbonic and sulphurous acids, are destructive of com- 
 bustion ; carbonic oxide yields but little light, sulphuretted hydro- 
 gen, although burning with a brilliant flame, is offensive. Means 
 of separating all except carbonic oxide have been discovered. 
 To condense the coal-tar and water, the volatile matter is con- 
 veyed from the close channel through a series of bent pipes, im- 
 mersed in a vessel of cold water. From each of the lower bends 
 of the pipe, an open pipe proceeds downwards nearly to the bot- 
 tom of a tub in which a small quantity of water is placed. The 
 coal-tar and condensed water drop from the open pipe into the 
 tubs, where the former occupies the lower place. The attraction 
 of ammonia for water is so great, that the greater part of that 
 gas is condensed with the water. To separate the carbonic acid, 
 the gas was originally made to pass in bubbles through milk of 
 lime ; to separate the sulphurous gases, it was washed by making 
 it pass in fine streams through a cistern of water. The first pro- 
 cess has been improved by making the mixed gas pass through a 
 
20 
 
 CARBON. 
 
 close vessel filled with straw, dipped in the milk of lime. Under 
 these circumstances, the hydrate of lime is found capable of 
 condensing the sulphurous gases, and the washing can be dis- 
 pensed with. This is advantageous, because olefiant gas is solu- 
 ble in water, and a part of this, the most valuable of all the pro- 
 ducts, was thus lost. 
 
 To prepare gas from oil, that liquid is permitted to fall in 
 drops upon coke, or pieces of brick, heated in a retort. Rosin is 
 dissolved in hot spirits of turpentine, and treated in the same 
 way. 
 
 From the liability of olefiant gas to decomposition at high 
 temperatures, it is of the greatest importance that the heat of the 
 retorts should be well regulated. At too high a temperature, 
 not only is that gas decomposed, but its volume is doubled, thus 
 causing far more than a double consumption of gas for a given 
 quantity of light. 
 
 The decomposition of oil and rosin, is more easily regulated 
 than that of coal. Hence, oil-gas in particular, was more esteemed 
 than coal-gas. At present, gas is manufactured at some estab- 
 lishments from cannel coal, which is little inferior to the best 
 oil-gas. 
 
 Gas is distributed to the consumers, in iron pipes, through 
 which it is forced by applying a pressure to the gasometers. It 
 has also been condensed into l-15th, or even l-30th of its bulk, 
 and delivered to the consumers in strong close vessels. The lat- 
 ter method has been found more costly than the distribution in 
 pipes. 
 
IV. 
 
 CHLORINE. 
 
 1. PEEPAEATION OP THE CHLOEIDES. 
 
 To prepare the chloride of lime, a large retort of lead is 
 used. This retort is in two pieces ; the upper of which is hemi- 
 spherical, the lower nearly cylindrical and of no great height. 
 To unite them, the lower part has a groove around its edge that 
 receives the upper part. This groove is filled with water. The 
 upper part of the retort has three openings, to one of which a 
 leaden three-branched funnel is adapted. The second opening 
 is provided with a stopper, and through it the retort may be 
 charged either with peroxide of manganese, or with a mixture of 
 that substance and common salt. In the first instance, muriatic 
 acid is poured through the funnel ; and in the second water, followed 
 by sulphuric acid. When muriatic is used, artificial heat is 
 necessary from the beginning of the process. But in the latter 
 case, heat is generated by the mixture of the water and acid, 
 which is sufficient to drive off nearly the whole of. the chlorine. 
 Through the third opening an iron rod is passed, at the lower 
 end of which is an iron frame which serves to mix and stir up 
 the materials daring the process. The condensing apparatus is 
 composed of several vaulted chambers. In these chambers a num- 
 ber of shallow trays are arranged, and at the beginning of the 
 process only each alternate tray is charged with a thin layer of 
 hydrate of lime. After the process has continued for a day iti 
 
22 
 
 CHLOEINE. 
 
 suspended, and the chambers are ventilated. The other trays 
 are then also charged with hydrate of lime. 
 
 At the end of forty-eight hours, the trays first charged are 
 replaced by others, and the process then proceeds regularly. 
 
 Various attempts have been made to charge milk of lime with 
 chlorine. This would be advantageous, because lime in this state 
 absorbs a much larger quantity of chlorine than when dry • but 
 it has not been successfully applied to large quantities. 
 
 Chloride of soda is usually prepared by passing chlorine, which 
 may be obtained from the chloride of lime, through a solution of 
 carbonate of soda. The chlorine may be caused to pass without 
 escaping until the whole of the carbonate is decomposed, giving 
 the strongest solution of chloride. But the liquor thus prepared 
 is speedily converted into a solution of common salt, and the 
 chloride of soda when properly prepared contains only half this 
 quantity of chlorine. The completion of the process is known by 
 the commencement of an efi’ervescence arising from the escape of 
 carbonic acid, which appears as soon as the chlorine begins to be 
 in excess. When the chlorine first enters into the solution of soda 
 it decomposes a part of it, and the carbonic acid instead of escap- 
 ing combines with another part to form the bi-carbonate. When 
 half the soda has been thus combined, any further action of the 
 chlorine will decompose the bi-carbonate also, and the acid takes, 
 as has been stated, the form of gas. The chloride of soda thus 
 prepared, goes by the name of the Liquor of Labarraque. 
 
 2. BLEACHINa. 
 
 Bleaching is the art of removing the native coloring matters 
 which exist in the materials employed in spinning and weaving. 
 These materials may be of animal origin, as silk and wool, or vege- 
 table products, as flax or cotton. 
 
 The bleaching of linen was originally performed by repeated 
 washings in an alkaline solution, neutralizing the alkali by an 
 acid, and long exposure to light and air. 
 
 The acid was obtained from sour milk. In the exposure to 
 light and air, the article was spread upon meadows, where it re- 
 
CHLOEINE. 
 
 23 
 
 mained for weeks or even months, being kept moist by soft 
 water. This process, therefore, could only be performed in 
 countries containing a great extent of meadow land and well 
 supplied with soft water. For this reason, the people of Holland 
 monopolized the bleaching of all northern Europe. The process 
 was so slow that the capital could not be turned more than once 
 a year. 
 
 The first improvement consisted- in the substitution of diluted 
 sulphuric acid for the acid of sour milk. Subsequent improve- 
 ments were founded upon an examination of the chemical consti- 
 tution of the coloring matter of the vegetable substances. The 
 coloring matter is made up of two parts, an oil and a resin. The 
 oil combines with alkalies to form a soap soluble in water. The 
 resin, by exposure, enters into the putrefactive fermentation, by 
 which it is finally destroyed ; but before it is completely de- 
 stroyed, the fibres of the material will be impaired. Chlorine 
 decomposes the resin as soon as it comes in contact with it, and 
 therefore, when skilfully used, does not weaken the vegetable 
 fibre. 
 
 Chlorine was first employed in the gaseous form, and next in 
 its aqueous solution. The first mode is objectionable from the 
 great space that is required ; the second because muriatic acid 
 was generated in the solution. Both are inconvenient, because 
 they require the presence and attention of a chemical manipulator 
 during the process. The dry chloride of lime is therefore uni- 
 versally employed at present. This article can be kept without 
 loss of the gas for many months ; and the greater part of that 
 used in this country is manufactured in Europe. 
 
 To bleach cotton yarn the following baths are employed. 
 
 l5^. Alkaline Bath. 
 
 This is prepared by boiling a solution of good pearlash with 
 quick lime and filtering. The yarn, done up into hanks, is boiled 
 some hours in this bath, and then rinsed in running water. 
 
 2d. Bath of Chlorine. 
 
 This is prepared by adding chloride of lime to water in the 
 proportion of two ounces to each gallon. There is no need of 
 
24 
 
 CHLOKINE. 
 
 filtering the liquid, and it must not be heated, as heat would 
 drive off the chlorine. 
 
 ^d. Acid Bath. 
 
 This is prepared by mixing one part of sulphuric acid with 
 sixty parts of water, and is also cold. The article must not re- 
 main in it more than an hour. 
 
 Uh. Soa.p Bath. 
 
 This is composed of white soap and boiling water. After 
 immersion in this bath, as well as after the two preceding, the 
 article is well rinsed in running water ; finally, the color is height- 
 ened by steeping the article in water through which a small 
 quantity of cobalt blue is diffused. To bleach cotton cloths, or 
 well twisted threads, the several baths are repeated. The colors 
 of dyed or printed cottons may be discharged by the bath of 
 chlorine. 
 
 Flax must be prepared for bleaching by steeping it in water 
 for several hours, but the process is of a like character. Hemp 
 may also be bleached in the same manner. 
 
 3. DISINFECTINH. 
 
 Many of the substances which arise from putrefying vegetable 
 and animal substances, are compounds of hydrogen. They are 
 always disagreeable to the sense of smell, often unwholesome, and 
 are sometimes the vehicles of contagious matter. Even the ex- 
 halations of a healthy body are unwholesome, and that of an un- 
 healthy person much more so. The disease is sometimes propa- 
 gated by these exhalations, and there are cases in which liquids 
 are formed in the body which may communicate disease by mere 
 contact, as in the small-pox, and vaccine pustules. These exhala- 
 tions and liquids all contain hydrogen, and may, as well as the 
 products of putrefaction, be decomposed by chlorine. 
 
 Chlorine of course cannot be employed to disinfect wide dis- 
 tricts, or even open and airy parts of cities, but may be success- 
 fully used in houses, and closely built streets. 
 
CHLORINE. 
 
 25 
 
 To disinfect a building, the ventilation is to be checked and 
 chlorine freely liberated within it. This is most easily done by 
 chloride of lime, which gives out the gas slowly by mere e:^posure ; 
 more rapidly by adding small quantities of water ; and still more 
 freely by pouring on an acid. Vinegar is the most convenient 
 acid for domestic use. 
 
 When a disease is contagious, it may be prevented from being 
 communicated by washing in dilute chloride of soda, and this has 
 been found to be efficacious after several hours had intervened. 
 In the case of the plague, a person has worn with safety the 
 clothes of those who have died of that disease, after they had been 
 merely steeped in chloride of soda and dried, without any wash- 
 ing or other purification. 
 
V. 
 
 SILICON. 
 
 1. MINERALOGY OF SILICA. 
 
 Species 1. — Quartz. 
 
 Silica is found nearly pure in quartz and flint. Quartz is 
 always crystalline. The primitive form is a rhomb, the most 
 usual external figure a six-sided prism — terminated by six-sided 
 pyramids. The prism often disappears, and only one of the ter- 
 minations is visible in most other cases. Quartz is hard enough 
 to scratch glass ; it is infusible by the mouth blowpipe, with the 
 exception of one of its varieties ; it may be transparent and color- 
 less, in which case it is called rock-crystal ; when white and opaque 
 it is called milk quartz. It is frequently colored by metallic ox- 
 ides without losing its transparency. When the colors are yel- 
 low, brown, or smoky, it is called cairngorm, and is used by the 
 lapidary. When of a violet color it has been called, but im- 
 properly, amethyst ; when the opaque variety is tinged with 
 crimson it is called rose quartz. In one variety the quantity of 
 oxide of iron, which is present, renders it fusible — from its color 
 this is called ferruginous color ; and when in handsome crystals, 
 of high lustre, it is used as a gem under the name of hyacinth of 
 compostella. The lustre of quartz is vitreous, and its fracture 
 conchoidal. 
 
 Species 2. — Flint. 
 
 Flint is opaque, and has a conchoidal fracture. 
 
SILICON. 
 
 27 
 
 Species 3. — Opal. 
 
 Silica, combined with water, forms a species of minerals which 
 is distinguished by a resinous lustre. When these are transpa- 
 rent, or translucent, they go by the name of opal. The precious 
 opal, emits from its interior a play of the prismatic colors, a pro- 
 perty called opalescence. The fire-opal reflects flashes of orange- 
 - colored light. The common opal has no internal reflection, but 
 is translucent ; while menilite is opaque, and of a dark-gray 
 color. 
 
 » 
 
 Species 4 and 5. — Chalcedony and Jasper. 
 
 Silica, combined with a small quantity of alumina, forms chal- 
 cedony and jasper. The first of these is translucent, the second 
 opaque. Both may derive various colors from metallic oxides, 
 and jasper is most frequently colored brownish-red by oxide of 
 iron. When jasper and white chalcedony occur in parallel layers, 
 the compound is called onyx, and was much used by the ancients 
 in making the gems called cameos. Modern cameos are usually 
 made of a shell found in the Bed Sea, the inner layers of which 
 are red and the outer layers white. Chalcedony of various colors, 
 arranged with other silicious minerals in bands or concentric 
 layers, goes by the name of agate. Some of these are used by 
 the lapidary, and others are of sufficient beauty to be employed 
 as gems. One description of agate exhibits arborescent crystals, 
 and is known as moss-agate or mocha stone. The same mineral, 
 when of a pale-red color, is called cornelian. The sard, which 
 is of a fine red color, may also be considered as a variety of chal- 
 cedony, and forms with a white variety the sardonyx. 
 
 Among other silicious minerals is horn-stone, which has a 
 strong resemblance to flint, with the exception that it is translu- 
 cent and has a splintery fracture, like that of horn. 
 
 Species 6. — Felspar. 
 
 The silicates are exceedingly numerous. Among them are the 
 felspars, which are all silicates of alumina and an alkali, fre- 
 
28 
 
 SILICON. 
 
 quently containing also an alkaline earth. Common felspar is a 
 silicate of alumina, potassa, and lime. It is generally crystal- 
 lized, having for its primitive form an oblique rectangular prism. 
 The secondary forms are very numerous, and most of them are 
 oblique prisms differing in the number of sides. The lustre of 
 felspar is usually vitreous ; but there is one variety so much so 
 that it has a direct resemblance to common glass. 
 
 Another variety of felspar has a pearly lustre, and is called 
 adularia. 
 
 Albite is a silicate of potassa, soda, and lime. Its primitive 
 form is a doubly oblique prism, its color white. It has less 
 lustre than common felspar, with which, however, it was long 
 confounded. 
 
 The Labrador felspar is opalescent. It was originally found 
 as pebbles, on the shores of that country. It has more recently 
 been discovered in place, and in large quantities in the Adirondac 
 Mountains. Some forms of felspar decompose spontaneously, 
 and after being transported by water, become porcelain clay — the 
 kaolin oi the Chinese, 
 
 Species 7. — Mica. 
 
 Mica is also a silicate of alumina and potassa, in which the 
 proportion of silica is less. It is infusible, and occurs in masses 
 made up of thin plates, into which it can be drawn almost with- 
 out limit. These plates are the cleavages of crystals whose primi- 
 tive form is a rhomb, and most usual external figure a regular 
 six-sided prism. The plates are fiexible and elastic, usually 
 transparent and sometimes colorless. When colorless it is used, 
 in some parts of Russia, instead of glass ; and we employ it in 
 the front of stoves. When opaque, it may be white, yellow, or 
 bronze-colored, and has a metallic lustre, so that it is frequently 
 mistaken for metallic ores. 
 
 Species 8. — Talc. 
 
 Tale is a silicate of magnesia and potassa, and has the same 
 structure as mica. It is however unctuous, and the plates al- 
 
SILICON. 
 
 29 
 
 though flexible are not elastic. When compact, it is used by the 
 Chinese in statuary. When granular and of a dark color, it is 
 used in some parts of France for cooking vessels. When com- 
 pact and sufficiently friable to make a mark, it is called French 
 chalk. The same substance, mixed with grains of silica, is our 
 soap-stone. 
 
 Sulphate of lime occurs in transparent sheets, like mica and 
 talc ; but it is neither flexible nor elastic, and becomes opaque 
 by heat. 
 
 Species 9. — Hornblende. 
 
 Hornblende is a silicate of alumina, lime, and oxide of iron. It 
 is of a dark green, approaching to black. It is always crystalline^ 
 the primitive form being a rhomb. Several other minerals have 
 the same primitive form and general composition, with the ex- 
 ception of the proportion of iron, which is less in all of them and 
 wanting in one. Hornblende is a constituent of several rocks, 
 which, on exposure to the air, decompose into a green earth. 
 These rocks are hence called green stones. 
 
 Species 10. — Pyroxene. 
 
 Pyroxene is a silicate of lime, magnesia, and metallic oxides. 
 Its primitive form is a four-sided prism, of very small obliquity. 
 Its most usual form is a six or eight-sided prism, of which four of 
 the sides are larger than the others, with diedral summits. When 
 of a black, or dark green color, it is called augite. There are 
 several other sub-species, one of which is white and contains no 
 metallic oxides. 
 
 2. MANUFACTUKE OF GLASS. 
 
 Glass may be distinguished by the following names : 
 
 1. Soluble glass ^ a subsilicate of potassa. 
 
 2. Crown glass ^ a silicate of potassa. 
 
 3. French glass^ a silicate of soda. 
 
 4. Flint glass^ a silicate of potassa and lead. 
 
30 
 
 SILICON. 
 
 , 5. Paste^ a silicate and borate of potassa and lead. 
 
 6. Enamel^ a silicate and stannate of potassa and lead. 
 
 7. Bottle glass^ of any bases whatever. 
 
 Grlass which contains potassa is liable to deliquesce, and that 
 which contains soda to effervesce. By the addition of a small 
 quantity of lime, both of these faults may be overcome. Lime is 
 therefore an essential constituent of the first six kinds. 
 
 The oxide of arsenic also tends to render glass white, and a 
 small quantity of it is added to flint glass. 
 
 The alkaline substance, except in the case of paste, is always 
 employed in the form of a carbonate. The silicious matter, with 
 the same exception, is sand, and as this sand is often of quartz 
 colored by metallic oxides, the same color would appear in the 
 glass. It has been found, however, that the peroxide of manga- 
 nese, when added to melted glass, will sink through it and carry 
 with it the other metallic oxides. By the use of this substance, 
 it has therefore become possible to substitute common sand for 
 pulverized flints in making the best kinds of glass. 
 
 When the carbonate of an alkali is mixed with sand and 
 heated, the carbonate fuses ; as soon as it becomes liquid the 
 silica begins to act upon it, causing the carbonic acid to escape. 
 This gas being evolved in the midst of a viscid liquid, causes it 
 to swell to many times its original bulk ; the continued applica- 
 tion of heat, however, will finally expel all the gas, and the mix- 
 ture will subside to even less than its original bulk. We thus 
 obtain a silicate of the alkali, which, however,-is not yet vitreous. 
 To convert it into glass it is necessary to fuse this compound. 
 Grlass-making is therefore divided into two processes, in the first 
 of which the carbonic acid is liberated, and in the second, the 
 compound is melted. The first is called fritting, the second 
 melting. 
 
 Fritting is performed in large ovens, and the frit, which has 
 the consistence of paste, is cut into blocks of the shape and size 
 of bricks. Melting is performed in vessels called glass-pots, 
 made of plastic clay mixed with clay heated until all the water is 
 removed, and then pulverized. The clay must be as refractory 
 as possible. However carefully the material may be prepared 
 
SILICON. 
 
 31 
 
 and mixed, the glass-pots are liable to crack by sudden changes 
 of temperature, and hence they are never permitted to cool. The 
 fires of glass-works continue day and night for indefinite periods. 
 When a glass-pot is to be replaced, it is heated red-hot by the 
 gradual application of fire in a separate furnace ; the old pot is 
 then removed by pulling down a part of the furnace. The new 
 pot is placed upon an iron carriage, and thus introduced into the 
 furnace, which is rebuilt with brick laid in tempered clay. When 
 wood is employed as the fuel, the fire, if well managed, is free 
 from smoke. But when bituminous coal is employed, it is ne- 
 cessary to place hoods upon the top of the glass-pot. 
 
 A ffreat proportion of the glass articles which are found in 
 commerce, are made by blowing. This is performed by the breath 
 applied to an iron tube. This tube when introduced into the 
 glass-pot causes a small portion of glass to adhere. If this tube 
 be withdrawn and permitted to cool a little, more glass will ad- 
 here, when it is again dipped. This is continued until the re- 
 quisite quantity of glass is collected on the tube. By blowing 
 through the tube, the glass will be distended into the form of a 
 hollow vessel, whose figure may be modified by its own weight, 
 and the motion of the tube ; a perfect sphere may be obtained by 
 holding the tube horizontally and spinning it around. A cylin- 
 der terminated by round ends may be obtained by holding the 
 tube vertically, and swinging it from side to side. A cylinder 
 may also be formed by holding the tube horizontally and causing 
 the glass to revolve on a plain surface. The first method is em- 
 ployed in making crown glass. When the sphere has been blown 
 into its full extant, another workman takes a small portion of 
 melted glass upon a rod and applies it to the sphere at a point 
 directly opposite to that where the tube is inserted ; the neck is 
 then cut off by means o'f a drop of water. The opening is then 
 applied to the point of a triangular plank, and being turned 
 around, takes the shape of a hollow cone. The hollow cone is 
 then spun around rapidly, and the glass arranges itself by the 
 centrifugal force in the form of a round plate, one of whose sur- 
 faces is plain, and the other has a knob in the middle to which 
 the rod is attached. This knob gives the name to glass made in 
 
32 
 
 SILICON. 
 
 this way, from its resemblance to the crowyi of a broad-brimmed 
 hat. These round plates are cut into rectangles for glazing. 
 
 Window glass may also be made by blowing it into the shape 
 of a phial. For this purpose the glass is turned upon a plain 
 surface, while in the act of blowing. The phial is made into a 
 cylinder, open at each end by cutting off the top and bottom. It 
 is then split up on one side, and the cylinder is brought into the 
 form of a flat plate by heating in an oven, until it drops by its 
 own weight. The oven employed is the annealing oven, in which 
 all glass is placed before it can be used. Annealing consists in 
 bringing it to a red heat, and causing it to cool very slowly. If 
 this were not done, the glass would be so brittle that it would not 
 bear the slightest blow. This same method was used for forming 
 the Venetian mirrors, and in the looking-glasses still manufactured 
 in Bohemia. Both of these are free from color, which depends 
 however upon the quality of the materials — the sand employed 
 in both cases being pure white, and the alkalies employed in Bo- 
 hemia being the best pearlash. 
 
 French window glass is made of sand, and barilla or kelp. 
 Plate glass is of the same chemical constitution as French window 
 glass, but the materials are, 1, a colorless sand; 2, crystallized 
 carbonate of soda ; 3, white marble. The plates are prepared by 
 casting ; for this purpose, a quantity of glass is poured into a 
 small glass-pot and kept melted for 24 hours. The glass-pot is 
 then raised from the furnace by machinery, so arranged that it 
 can be carried over the middle of a large table made of bronze ; 
 while it is thus carried, it is tilted so that the glass may pour 
 out. The stream of glass is followed by a roller of bronze, which 
 moves upon two of the rollers by which the surface of the table 
 is inclosed. The table is heated by a fire made beneath it. 
 
 The plate thus formed has not the polished surface of blown 
 glass, and therefore requires to be polished. In polishing, plate- 
 glass undergoes three separate operal^ions. In the first, it is 
 rubbed with coarse sand, one of the plates being employed as 
 the rubber of another. In the second, it is ground by means of 
 fine sand upon a wooden rubber : the sand is in both cases 
 wet. In the third operation, the oxide of tin (tutty) is employed. 
 
SILICON. 
 
 38 
 
 When the glass has received its final polish, it often exhibits 
 flaws and stria ; therefore it rarely happens that one of these 
 large plates can be used entire. The glass is then to be silvered ; 
 this is effected by applying an amalgam of tin and mercury to 
 one of the surfaces of the glass. The tin is in the form of foil, 
 and the sheet must be free from holes or flaws. The French 
 lay the tin upon the glass, and pour mercury over it. The Eng- 
 lish pour the mercury first upon the surface of the glass, and 
 apply the tin-foil to it. 
 
 The materials in flint-glass are the best sand, pearlash, and 
 red-lead. It is softer than the foregoing descriptions of glass, 
 and more liable to break by changes of temperature. It possesses 
 higher lustre, is usually more free from color, and is the only de- 
 scri^ion employed in cut glass. 
 
 Griass is cut by the successive action of four wheels revolving 
 with great velocity, and dipping in troughs containing water. 
 The first wheel is of iron, and the trough contains sand. The 
 second wheel is a common grindstone. The third is of wood, 
 and the trough contains pumice-stone. The fourth wheel is 
 covered with felt, and coated with fine emery or tutty. Flint- 
 glass is also cast in moulds of copper, which must be previously 
 heated. The surface is afterwards polished by a succession of 
 powders similar to those employed in cutting. Flint-glass is also 
 employed in optical instruments, and particularly as a part of the 
 object-glass of telescopes. The flint-glass thus employed ought 
 to contain a greater proportion of lead. It was long manufac- 
 tured only in England. The English flint-glass for optical instru- 
 ments was made by blowing, by which it is rendered more uniform 
 in structure, and more free from flaw than if it were left at rest 
 until it became solid. But it is difficult to procure in this way 
 pieces of large size ; and the largest disks, made in England, have 
 not exceeded six inches in diameter. In Switzerland and Ger- 
 many, the disks are made by casting; and after they have become 
 cold, they are set in a ring of copper and annealed under strong 
 pressure. In this way, disks sufficient to make telescopes four- 
 teen feet in length have been obtained. 
 
 The materials employed in paste are rock crystal, precipi- 
 3 
 
34 
 
 SILICON. 
 
 tated carbonate of lead, fused borax, and potassa purified by al- 
 cohol. The glass is melted in crucibles, in which it is permitted 
 to cool. The lump obtained by breaking the crucible is sawn 
 into pieces by means of soft iron and emery. This paste is co- 
 lorless, and has a high lustre. It is employed to imitate the 
 diamond ; and the imitation, by candle-light, is very good. 
 When colored, by being fused with metallic oxides, it may be 
 used to imitate other gems. The art is therefore restricted. 
 The most difficult of all the gems to imitate, is the ruby. The 
 coloring matters, used in making paste, are now employed in the 
 manufacture of flint-glass; some specimens of which are composed 
 of layers of different colors. By grinding away a part of either, 
 the other is exposed. 
 
 To prepare enamel, lead and tin are fused together, an4 ex- 
 posed to a current of air until both are oxidated. This combina- 
 tion is fused with good crown-glass. The mixture is nearly 
 opaque and white. It may be colored by fusing it with metallic 
 oxides. 
 
 Enamel is used in the two arts of painting — in enamel and 
 in mosaic. To paint in enamel, no other colors are necessary 
 than white, black, red, yellow, blue, and a neutral gray. 
 
 The colors are ground with gum, and applied like water-co- 
 lors. For staining glass, they may be ground with oil and diluted 
 with spirits of turpentine. The principle of painting is the 
 same as in oil. The colors are applied in the inverted order of 
 their fusibility ; and after each has been applied, it is placed in a 
 furnace where it is vitrified. 
 
 To paint in mosaic, as many shades of color must be pro- 
 vided as exist in the original picture. These colors are broken 
 into fragments, and are applied to a bed of plaster. After the 
 whole surface is covered, it is reduced to a uniform level and 
 polished. In the establishment at Borne, 17000 different shades 
 of colors have been accumulated. 
 
 The Florentine mosaic is made by setting pieces of colored 
 glass, or gems, in slabs of marble. 
 
 Under the head of glass is to be ranked the porcelain of 
 Beaumur. This is prepared by bedding glass in sand, and heat- 
 
SILICON. 
 
 85 
 
 ing it to redness. A part of the alkali is driven off and com- 
 bines with the sand. The glass thus loses its transparency and 
 much of its fusibility, while it becomes harder and less brittle. 
 When crown-glass is treated in this way, it makes excellent ves- 
 sels for chemical purposes ; and when flint-glass has the sand in 
 contact with only one of its surfaces it becomes opaque only on 
 that side, and retains its vitreous appearance on the other. 
 
YI. 
 
 ALUMINUM. 
 
 1. MINERALS OF ALUMINA. 
 
 Species 1. — Corundum. 
 
 Alumina is found nearly pure in minerals to which the generic 
 name of Corundum may he given. This mineral occurs in crys- 
 tals, whose primitive form is a rhomb, and whose most usual form 
 is a very acute triangular dodecahedron. Corundum is harder 
 than any other substance, except the diamond. It is sometimes 
 colorless and transparent, with high vitreous lustre. This variety 
 is used in jewelling clocks and watches. When it is transparent 
 and of a fine red color, it is the oriental ruby ; when blue, sap- 
 phire ; when green, the oriental emerald ; and when violet, it is the 
 true amethyst. It is sometimes opaque, or merely translucent, 
 when it is of no value except to be crushed into emery. 
 
 Species 2. — Emery. 
 
 Emery is a fine-grained corundum, which occurs in the island 
 of Naxos, &c. Emery is crushed and sorted, and used in grind- 
 ing and polishing, being capable of cutting every substance ex- 
 cept the diamond. 
 
 The Gribbsite is a hydrate of alumina found only at Rich- 
 mond, Mass. The Wavelite which was supposed to be a hydrate, 
 contains fiuoric acid. 
 
 Species 3. — Turquoise. 
 
 The turquoise is a hydrate of alumina, covered by oxide of 
 
ALUMINUM. 
 
 37 
 
 copper ; there is also a turquoise which is a fossil, and is colored 
 by carbonate of copper. 
 
 Species 4. — Spinelle. 
 
 Spinelle is a compound of alumina and magnesia. It is dis- 
 tinguished by its crystalline form, which is a regular octaedron ; 
 when transparent, and colored red by chrome acid, it is valued 
 as a gem and bears the name of oriental ruby. It is more fre- 
 quently opaque, and colored by metallic oxides. There is a com- 
 pound of alumina, magnesia, and oxide of zinc, which has the same 
 crystalline form, and is called Automalite. 
 
 Species 5. — Garnet. 
 
 Garnet is a silicate of alumina, and metallic oxides ; of these 
 the protoxide of iron is sometimes in such quantity that the min- 
 eral is magnetic. The structure is always crystalline ; the prim- 
 itive form being the rhombic dodecahedron. This is one of the 
 most usual forms, and another frequent form is a solid bounded 
 by 24 irregular faces. When transparent, and of a red color it 
 is employed as a gem. Large garnets were much valued by the 
 ancients under the name of Carbuncle. 
 
 Species 6. — Slate. 
 
 Slate is a silicate of alumina. In roof and writing slate the 
 alumina preponderates. 
 
 There is another description in which silica preponderates to 
 such a degree that it will strike fire with steel, and one of its 
 forms is used as a whetstone. Another called basanite or Lydian 
 stone, is employed to test the quality of gold. 
 
 Species 7. — Clays. 
 
 All the clays are compounds of silica and alumina. That 
 which is called china-clay, is formed by the decomposition of fel- 
 spar, and the loose matter being transported by water loses 
 the alkali. Blue clay is colored by protoxide of iron, and red 
 
88 
 
 ALUMINUM. 
 
 clay by the peroxide. Both of these have been generated by 
 the decomposition of hornblende. 
 
 2. POTTEKY. 
 
 Pottery may be divided into the following kinds : 
 
 1. — Brick and Tile. 
 
 2. — Red and Black Ware, 
 
 3. — Stone Ware. 
 
 4. — Delft Ware. 
 
 5. — Queens Ware. 
 
 6. — Porcelain Ware. 
 
 7.. — Wedgewood. 
 
 8. — Crucibles. 
 
 1. Brick and tile, inay be made of any description of clay. 
 In the United States that which burns of red color is preferred. 
 In making brick, when the clay contains too large a proportion 
 of alumina, it is tempered with common sand. The tempering 
 is now performed by means of machines ; the simplest and most 
 efficient of which is composed of a vertical shaft, around which a 
 number of iron blades are placed in the form of a screw. This 
 screw is usually turned by horses, and not only mixes the clay, 
 sand, and water, but forces the mixture from the bottom of a tub 
 in which the screw works. As the mixture issues, it is received 
 in moulds. These are open frames of wood, placed upon a plank. 
 The clay is pressed into these moulds, and the excess removed by 
 means of a roller or scraper. The brick is then laid upon a level 
 earthen floor, covered by a shed, where it dries until it becomes 
 sufficiently firm to be handled. It is then piled in the manner of a 
 wall, hollow and with the greatest practicable amount of empty 
 space. When it has dried in this position as much as it can by 
 exposure, it is removed to the kiln in which it is burnt. 
 
 The kiln may be either temporary or permanent. 
 
 The temporary kilns are formed by building walls and arches 
 of soft bricks, which serve as fire-places and flues. Upon these 
 arches the dried bricks are piled in courses, with the largest at- 
 
ALUMINUM. 
 
 39 
 
 tamable space between the several bricks. The outside of the 
 kiln has the shape of a truncated pyramid, and is inclosed by 
 walls built of dry brick, laid in tempered clay. Wood, bitu- 
 minous coal, and turf, may be used as fuel. 
 
 Two other descriptions of fuel may be used in the manufac- 
 ture of bricks. The first of these is composed of the cinders 
 of bituminous coal. These are carefully sifted, and the finer 
 portions are mixed with the clay, replacing about an equal quan- 
 tity of sand. The coarser parts are arranged in alternate strata, 
 with dried brick, each stratum of which is composed of seven hori- 
 zontal courses. The advantage of this method is not limited to 
 the cheap description of fuel, but insures a more perfect burning 
 of the brick, because the ashes contain a considerable quantity 
 of carbonaceous matter. The other fuel is the fine dust of an- 
 thracite coal. Although it cannot be applied as successfully as 
 the cinders of bituminous coal, yet by mixing it with the brick a 
 considerable quantity of fuel may be saved, and the brick will be 
 more thoroughly burnt. 
 
 Tile is made of the same clay as brick ; but the sand mixed 
 with the clay must be finer. When used in the interior of build- 
 ings, it need not be rendered impervious to water. When used 
 for roofing, it requires to be glazed at least on one side. 
 
 The glazing of pottery consists in covering it with a vitrifia- 
 ble substance, which in the burning is converted into a coat of 
 glass. It may be applied either before burning, or after the 
 ware has been once passed through the fire. In this intermediate 
 state the ware is called biscuit. 
 
 Tile is generally glazed while raw ; the glaze is a mixture of 
 clay, water, and the oxides of lead and manganese. This mix- 
 ture is applied to one of the surfaces with a brush. In placing 
 tile in the kiln, great care must be taken to prevent the surfaces 
 from touching each other, and to let the diff'erent layers touch at 
 as few surfaces as possible. 
 
 2. Common red and black ware is made of brick clay ; the 
 glaze is also applied to it while raw. The red ware is glazed 
 with a mixture of red lead and white clay ; the black with clay, 
 red lead, and oxide of manganese. 
 
40 
 
 ALUMINUM. 
 
 3. Stone ware is made in Europe of a white clay called pipe- 
 clay, and powdered flints. In this neighborhood, there exist 
 many beds of clay containing a sufficient quantity of silica. 
 Stone ware is glazed by throwing common salt into the kiln, 
 after the ware has been brought to a white heat. This becomes 
 volatile', and thus comes in contact with every part of the surface, 
 where a silicate of soda is formed, which fuses. 
 
 To form vessels of clay, an apparatus called the potter’s wheel 
 is employed. This, in its original form, was a circular table mount- 
 ed upon a vertical spindle. Bars project from the spindle, within 
 reach of the foot of the workman, who by successive blows gives 
 the bar a rotatory motion. If a ball of clay were laid on the table, 
 it would spread out into the form of a circular plate. But, if its 
 outward motion be restrained, it may be made to take the form of 
 a hollow vessel. This is effected by the hands of the workman. 
 
 The first improvement of the potter’s wheel consisted in 
 bending the spindle, so as to form a crank ; and applying to the 
 crank a connecting rod attached to a treddle. By applying the 
 foot to this treddle, the required rotatory motion is given to the 
 spindle. To render the figure of the vessel more perfect, tools 
 made of sheet metal are employed. These are cut to the shape 
 intended to be given to the outside of the vessel. 
 
 Shallow vessels are made by means of mo'ulds of plaster of 
 Paris. These are set upon small potter’s wheels of the original 
 form. The clay is rolled out into a thin sheet, which is applied 
 to the mould and pressed down upon it by means of a wet sponge, 
 while the wheel revolves slowly. To give a more perfect form to 
 vessels made in either way, they are, after being partially dried, 
 applied again to the potter’s wheel, upon which they are caused 
 to revolve, while a cutter of sheet metal is applied to the sur- 
 face. A more perfect form may be given by the use of the turn- 
 er’s lathe. 
 
 When the required figure is irregular, it is made by applying 
 thin sheets of clay to moulds of plaster, and uniting the several 
 pieces by a liquid mixture of clay and of water (slip). In this 
 way the spouts of vessels are made and attached. Rods may be 
 made by forcing clay through a hole in the bottom of an iron 
 
ALUMINUM. 
 
 41 
 
 box. These rods may be cut and bent, and of them the handles 
 of vessels are formed. By placing a mandril in the box, hollow 
 pipes may be made. 
 
 The kiln used in burning the cheaper kinds of ware is an 
 oven, whose floor is inclined. A fire is made at the lower end, 
 and the smoke and heated air aj^e directed through the kiln by 
 an opening in the opposite extremity and smaller ones in the 
 vault. 
 
 The kilns used for the better kinds of pottery are cylindrical 
 chambers, covered by a dome. Around the base of the chamber 
 a number of fire-places are arranged at equal distances, each 
 having an opening communicating with the chamber. Below 
 each of these openings a passage is formed in the floor of the 
 kiln, leading to an opening in the centre of the floor, and above 
 each of the openings is a vertical flue. To provide for the escape 
 of the smoke, a large opening is made in the middle of the door, 
 and small openings around its circumference. To create a 
 draught, a hollow cone is built upon the walls which inclose the 
 kiln. Formerly, a much larger conoidal chamber was built 
 over and around the kiln. In the French potteries several kilns 
 have been built over each other ; by this means all loss of heat is 
 prevented, and by placing furnaces on floors corresponding to the 
 divisions of the kilns, the lower portions may be permitted to 
 cool, while heat is applied to those above. 
 
 4. Delft ware may be made of any kind of clay, and is usually 
 made of that which takes a red color. The surface is rendered 
 white and opaque by glazing it, when in the state of biscuit, with 
 an opaque white glass. This kind of ware was known to the 
 Bomans, and was made in the middle ages at Faenza in Italy. 
 It was long manufactured at the place whence it obtains its 
 name, but has been superseded for about a century by Queen’s 
 ware. 
 
 5. Queen’s ware is made of a mixture of pipe-clay and pow- 
 dered flints. They are ground together with such an excess of 
 water that the mixture may be passed through a bolting-cloth. 
 The excess of water is removed by boiling in a pan formed of 
 large glazed tiles. Some difficulty is experienced in removing 
 
42 
 
 ALUMINUM. 
 
 the cavities formed by the bubbles of vapor. The ware is fash- 
 ioned on the potter’s wheel, and afterwards turned on a lathe. 
 Of late the potter’s wheel used in this manufacture has been 
 driven by steam, which it was once considered impossible to 
 substitute in this case for human intelligence. The dried ware 
 is converted into biscuit in a kiln of the improved form. 
 
 The biscuit is coated with the materials of the glaze, by being 
 dipped in a vessel, in which they are kept in a state of suspen- 
 sion in water by agitation. The materials of the glaze are car- 
 bonate of lead and powdered flints. 
 
 Great care must be taken to apply the heat gradually to the 
 raw ware, and the heat is at last carried to whiteness. This op- 
 eration always requires several days, and when the pieces are 
 large, may occupy a week or two. No such precaution is ne- 
 cessary in glazing, and the vitrification may be completed in a 
 few hours. 
 
 Bituminous coal is the only fuel that has been employed in 
 making Queen’s ware. To prevent the ware from being dis- 
 colored by the smoke of this fuel, it is inclosed, both in burning 
 the biscuit and in glazing, in vessels called saggers. These are 
 set one upon the other, and their joints are luted with tempered 
 clay. The saggers used in glazing must be themselves glazed, 
 or dipped in the materials of the glaze. To prevent the several 
 pieces from adhering while the glaze is vitrified, they are sepa- 
 rated from each other by crowsfeet, made each of three strips of 
 tempered clay. 
 
 Queen’s ware is often embellished with colored figures. These 
 are composed of enamels, and are sometimes applied to the sur- 
 face of the glaze, at other times to that of the biscuit. The 
 colors are ground with gum or glue, and may be laid on with a 
 hair-pencil. This method is too costly for any but rude figures. 
 More perfect figures are applied by 'printing. In printing, en- 
 gravings on copper are employed. By means of them impres- 
 sions are taken in the engraver’s press on well sized paper. The 
 paper, after being moistened, is pressed upon the surface of the 
 ware. A great part of the paper is removed by rubbing it with 
 the finger, and the remainder is burnt away, when the ware is 
 
ALUMINUM. 
 
 43 
 
 exposed in a kiln to a heat sufficient to vitrify the enamel color. 
 The favorite color is blue, obtained by means of the oxide of co- 
 balt ; and the blue printed Queen’s ware is known among us as 
 Liverpool China. 
 
 6. Porcelain is distinguished from other ware by being trans- 
 lucent. It is of so ancient a date in China, that vessels with 
 Chinese characters have been found in the catacombs of Egypt 
 of a date certainly earlier than the Persian conquest. It is 
 made of even better quality in Japan, and is also manufactured 
 in Persia. 
 
 When porcelain was first brought from China into Western 
 Europe, it was inferred that it must be composed of two sub- 
 stances, one of the nature of clay and infusible, the other fusible. 
 To imitate it, pipe-clay was mixed with powdered glass. It was, 
 however, found necessary to add so much of the latter material, 
 that the mixture lost its plasticity, and could not be fashioned on 
 the potter’s wheel. This defect was partially remedied by using 
 a marly clay, and tempering the mixture with water rendered 
 viscid by soap. The latter was the composition of the ancient 
 porcelain of Sevres. The same composition is also still employed 
 in some of the French manufactories, and in the ware styled Iron 
 Stone by the English. The glaze was powdered glass. Porce- 
 lain made of these materials is brittle, both when struck and 
 when suddenly heated or cooled, and it is easily fused. 
 
 The clay used by the Chinese was brought to Europe ; but 
 although a similar material was soon found, the discovery was of 
 no value, for want of a knowledge of the other materials. Fi- 
 nally, specimens of the other material used in the body of the 
 Chinese ware was sent to Europe, and found to be the abundant 
 mineral, felspar. 
 
 The best French porcelain is now made of China clay, mixed 
 with powdered felspar. After being burnt into biscuit, it is 
 coated with a glaze of felspar, by dipping in a vessel containing 
 water in which that material is suspended by means of gum. In 
 the Dresden China, besides these two materials, sulphate of baryta 
 is mixed with the body of the ware. The glaze is the same as 
 that of the French. 
 
44 
 
 ALUMINUM. 
 
 At Worcester, in England, no less than seven different earthy 
 minerals are used in the body of the ware. The material em- 
 ployed by the Chinese in their glaze, has been recently ascer- 
 tained. It is a transparent and colorless sulphate of lime. 
 
 At Sevres and Dresden, it requires a higher and longer con- 
 tinued heat to vitrify the glaze than to bake the biscuit. 
 
 7. The body of Wedgewood ware is composed of clay, powder- 
 ed flints, and sulphate of baryta. The materials of the glaze do 
 not appear to be known, 
 
 8. The Hessian crucibles are made of a refractory clay, mixed 
 with a pure quartzy sand. 
 
 In Wedgewood crucibles the raw clay is mixed with clay that 
 has been previously burnt, and reduced to powder. In black- 
 lead crucibles the clay is mixed with plumbago. In general the 
 quantity of raw clay is no more than will cause the material to 
 adhere. Crucibles, therefore, are usually made in moulds com- 
 posed of a hollow vessel of brass and a solid piece of the same 
 material attached to a rod, and applied to ram the tempered clay 
 into the space between it and the vessel. 
 
VII 
 
 CALCIUM. 
 
 1. MINERALOGY OF LIME. 
 
 Species 1. — Carbonate of Lime. 
 
 The carbonate of lime is a very abundant natural product. 
 It occurs in many different forms, of which the following are the 
 most important. 
 
 1. Crystallized, the primitive form being a rhomb, and the 
 secondary forms more numerous and varied, than those of any 
 other mineral. When transparent it is doubly refracting, and 
 when colorless as well as transparent, it is called Iceland spar. 
 
 2. Granular. When the grains are fine, it is said to be sanha- 
 roid, and this when of a pure white color is called, from its use, 
 statuary marble. Of this, the only localities that have been much 
 quarried are those of Paros, and Carrara. When of coarser 
 grain it is used as a building stone, being a material of great 
 beauty, and one of the few’ that withstand the severity of our 
 climate. Of this variety the Parthenon and several other build- 
 ings at Athens are specimens, 
 
 3. Stalactite hangs from the roof of caverns. Stalagmite 
 collects on the floors of caverns, and travertine forms in stagnant 
 waters. All of them are deposited in proportion to the quantity 
 of the excess of acid that escapes.' Stalactite when cut across 
 exhibits the several layers of its deposition, distinguishable by dif- 
 ferent shades of color, and takes a high polish. It is also, often 
 
46 
 
 CALCIUM. 
 
 translucent, and when it possesses both properties is used in the 
 manufacture of ornamental slabs and vases. It is included by 
 the Italians, under the name of labastro^ or alabaster. When a 
 similar deposit takes place in a bed of sand, calcareous sandstone 
 is formed, and when the deposit takes place in beds of pebbles, 
 the conglomerate is called breccia or pudding-stone. When the 
 pebbles take as high a polish as the carbonate of lime, the breccia 
 is a fine marble. Of this a fine description has been used in the 
 pillars of the Houses of Congress, at Washington. 
 
 4. Compact. When this is free from other earthy matter, it 
 takes a high polish, and comprises the greater part of the mar- 
 bles. The difference among them arises, in part, from colors 
 given by metallic oxides. These are variegated by veins of white, 
 or patches of other colors. Organic remains also occur in them, 
 as petrifactions of a difterent hue from the general mass. When 
 the marble is black, the coloring matter is carbon. When mixed 
 with other matter, the compact carbonate is of little use except 
 in the manufacture of lime, or as a building stone. When mixed 
 with argillaceous matter it is the basis of an hydraulic cement. 
 
 5. Oolite, occurring in spherical concretions. 
 
 6. Chalk. 
 
 Species 2. — Arragonite. 
 
 This is also a carbonate of lime, differing from the preceding 
 species in its crystalline form, and in being harder. It is com- 
 paratively rare, occurring in crystals, either detached or in groups 
 on the surface of ores of iron. It also forms a translucent stalac- 
 tite of even greater beauty than the former, of which the finest 
 specimen extant is the sarcophagus of an Egyptian king, now at 
 Cambridge, England. 
 
 Species 3. — Sulphate of Lime. 
 
 A hydrate of that salt, which occurs in crystals called selenite, 
 in white granular masses, which are translucent, and to which 
 the name of alabaster is usually restricted in our language ; of 
 dark colors, granular, earthy, and compact, in which forms it is 
 called gypsum, or from its use, plaster of Paris. 
 
 V 
 
CALCIUM. 
 
 47 
 
 Species 4. — Phosphate of Lime, 
 
 This has hitherto been a very rare mineral, but has recently 
 been found in tolerable abundance at two localities, in the Atlantic 
 States. 
 
 Species 5. — Magnesian Carbonate of Lime. 
 
 A compound of the carbonates of two' earths. When found 
 in crystals it is called bitter spar ; when granular, dolomite ; and 
 when compact, magnesian limestone. The granular variety oc- 
 curs in great abundance mixed with granular carbonate of lime in 
 the white marbles of Westchester Co. When of sufficiently 
 firm structure, these are not only the most beautiful, but also the 
 most durable of our building stones. The magnesian limestone 
 of England has by the experience of centuries been found to be 
 the most lasting material employed in that country. 
 
 2. MANUFACTURE OF LIME. 
 
 Lime may be made of any mineral of which its carbonate 
 forms the principal part. It is prepared in kilns of two kinds, 
 the common and perpetual. 
 
 The common kiln is a pyramidal building, the chamber within 
 which is sometimes egg-shaped, but more frequently conical. On 
 one side of the chamber is a low door. The limestone is broken 
 into pieces, none of which should exceed six inches in length. With 
 the largest of these, an irregular vault is built over the door, and 
 upon this vault the rest of the lime is thrown and heaped upon 
 the upper opening. The space beneath the vault serves as a fur- 
 nace, into which the fuel is admitted through the door. Any 
 fuel which burns with fiame may be employed, and when coal or 
 turf is used, an iron grate must be placed beneath the vault. 
 The only precaution necessary is, that the heat should not be 
 raised too suddenly. When the whole of the carbonic acid is 
 driven oft’, the fire is extinguished and the lime removed. 
 
 Perpetual kilns will make a given quantity of lime with much 
 
48 
 
 CALCIUM. 
 
 less fuel ; they are of two kinds, the one adapted to bituminous 
 coal, the other to anthracite. When bituminous coal is to be used, 
 the body of the kiln is’ a chimney 20 or 30 feet in height. Ad- 
 joining to the base, a furnace is built having grate bars, and an 
 ash-pit. From the furnace there is an opening into the kiln 
 above the fuel, and the furnace is covered with an iron door. 
 Another opening is made between the ash-pit and the kiln, and 
 the ash-pit is also furnished with a door. In lighting the fire, 
 the ash-pit is left open and the upper door is closed, but as soon 
 as the fuel is ignited the ash-pit is closed, and the upper door 
 opened. As fast as the lime is finished, it is raked out through 
 an opening at the base of the kiln, and the space thus left filled 
 by throwing limestone in at the top. For anthracite coal, the 
 kiln has the form of the common kilns, but is of much greater 
 height. Instead of the door it has a small opening near the base. 
 To set it in action, wood is thrown in and covered with coal. 
 Upon the coal is thrown a layer of limestone ; this is covered with 
 a layer of coal, and thus alternately until the kiln is filled. The 
 lime when finished is raked out from beneath, and fresh layers of 
 limestone and fuel are thrown in above. 
 
 3. MORTAK. 
 
 When hydrate of lime is mixed with water to the consistence 
 of paste, and exposed to the air, the lime which is in solution 
 receives carbonic acid from the atmosphere and is precipitated. 
 The water dissolves more lime which in its turn is precipitated, 
 and thus the operation will go on until the whole of the lime be- 
 comes carbonate, or until all the water has evaporated. In this 
 way an aggregate of carbonate of lime is attained of about the 
 hardness of chalk. If silica be present, the carbonate of lime -will 
 be precipitated upon it, and the aggregate will be much firmer 
 than in the former case. After a considerable time, the lime ap- 
 pears to be converted into a silicate, but this may not take place 
 completely until after the lapse of centuries. We therefore find 
 in old buildings, mortar not only harder than limestone, but ca- 
 pable of striking fire with steel. 
 
CALCIUM. 
 
 49 
 
 To make mortar of lime which slakes readily, sand is piled 
 in such a manner as to form a shallow hasin. In the basin the 
 lime is laid and water is thrown upon it. As the lime slakes, 
 water is added and the lime agitated until the mixture becomes 
 nearly liquid. In this state it is incorporated by degrees with 
 the sand until the whole becomes uniformly mixed with five 
 times its bulk. 
 
 To incorporate so large a quantity of sand, requires much 
 labor ; but the greater the quantity that can be added, the better 
 will be the mortar, up to the limit of plasticity. 
 
 When limestone contains carbonate of magnesia, the lim ^ 
 slakes slowly and cannot be treated in this manner. In ordcx' 
 to make a good mortar of this description of lime, a cavity is 
 formed in the ground, in which the lime is placed with a proper 
 quantity of water. Upon these the proper quantity of sand is 
 heaped, and the whole is left at rest until the lime is completely 
 reduced to powder. When the limestone contains silicate of 
 alumina, the lime will not slake ; it may however be reduced 
 to powder by mechanical means. The mortar made from it has 
 hydraulic properties, or, even when it has not, will set more 
 rapidly than mortar made from a purer lime. 
 
 4. HYDRAULIC CEMENT. 
 
 The material first used in the preparation of an hydrsLulie- 
 cement was puzzolana. This substance was used by the Ro- 
 mans. To prepare the cement, puzzolana, which has the ap- 
 pearance of ashes, is mixed, as in common mortar,, with pure 
 slaked lime. The attraction of the materials is so powerful, 
 that when prepared in small quantities, the cement will set in a 
 few minutes. It therefore will not only resist water, but will set 
 under water. By means of it, walls may be built at considerable 
 depths. The space intended to be occupied by the wall, is in- 
 closed by a wooden partition. The cement is mixed with an 
 equal bulk of angular fragments of stone, and is permitted to lie 
 in a heap until it sets at the surface. It is then agitated until 
 it resumes its former consistence, without adding water. The 
 4 
 
50 
 
 CAl.CiUM. 
 
 mixture is then plunged to the bottom of the space by means of 
 a cubical box whose bottom is hung on hinges. When a uni- 
 form bed has been thus spread, angular pieces of stone, about six 
 inches in length, are thrown upon it. Upon these is plunged 
 another layer of the mixture. When the water becomes too shal- 
 low for the use of the machine, the mixture is thrown in from 
 baskets, and the operation is continued until the surface of the 
 water is reached, from which level the wall may be carried up- 
 wards in the usual manner ; but so long as the stones are within 
 reach of water, the joints must be filled with the same cement. 
 
 In the Low Countries, an hydraulic cement was prepared 
 from a stone found on the banks of the Rhine. This is a trapp 
 rock. It is prepared by heatiug to redness, and grinding to 
 powder. When mixed with pure lime, it does not set under 
 water ; but when mixed with hydraulic lime, it will. This sub- 
 stance is called Trass. In Holland an artificial trass is prepared 
 from the mud taken from the bottom of the canals. This is 
 moulded and burnt, like brick, and is then reduced to powder. 
 Roth descriptions of trass must be kept in tight casks, for they 
 a ttract moisture rapidly from air. 
 
 Hydraulic cement may also be prepared from the limestones 
 containing silicate of alumina. These possess hydraulic proper- 
 ties in very different degrees ; when in the highest, they must be 
 mixed with pure sand ; when in moderate degrees, with trass or 
 other silicate of alumina possessing moderate hydraulic proper- 
 ties. Puzzolana is a pure silicate of alumina. Trass contains 
 iron ; if, in its preparation, the iron is converted into peroxide, 
 the properties of trass are impaired. The artificial trass owes its 
 good properties to the presence of organic matter in the mud, by 
 which the iron is prevented from becoming a peroxide. The 
 brick is also burnt in close kilns. The most powerful hydraulic 
 lime is prepared from a substance called septaria, found in the 
 London clay. The prepared article is called Roman cement. 
 An inferior cement is prepared from poor calcareous ores of iron. 
 When the Roman cement is to be exposed to the air, it ought to 
 be mixed with a large quantity of sand. 
 
 An artificial cement was formerly prepared in this city by a 
 mixture of pure quicklime, powdered brick, and forge scales. 
 
CALCIUM. 
 
 51 
 
 An artificial cement may Ibe prepared wherever lime and clay 
 can be obtained, by mixing the claywith carbonate of lime in powder, 
 forming the mixture into brick, and burning it at a temperature 
 less than that at which the mixture fuses. If the clay have a 
 red color it ought to be mixed with organic matter, and the 
 brick should, in all cases, be burnt in a close kiln. When chalk 
 or tufa can be obtained, it is mixed with the clay, but when the 
 limestone is hard it is made_ into lime and exposed to the air un- 
 til it falls to powder. It is then said to be air slaked, and is 
 a carbonate. 
 
 5. USE OF LIME IN AGKICULTUKE. 
 
 Lime is of great value as a manure. Its uses in agriculture 
 may be in part explained on the following principles : 
 
 1. Soils may contain so much clay that water will not sink 
 into them, and may in dry weather become so stiff that they can- 
 not be tilled ; a mixture of lime will diminish both of the defects. 
 
 2. Sandy soils permit water to pass through them ; a mixture 
 of lime will remedy this defect. 
 
 3. Some soils contain an acid, which may be neutralized by 
 lime. 
 
 In the first two instances, the lime ought to be in a caustic 
 state ; in the third, it may be a carbonate, 
 
 4. Soils often contain organic matter that will not decompose. 
 The decomposition may be effected by the application of quick- 
 lime. 
 
 5. All the seeds used in making bread, contain the sulphate 
 and phosphate of lime, and will not grow upon a soil that does 
 not contain that earth. Soils on which wheat is grown, however 
 rich in other respects, may cease to bear it unless lime be added 
 from time to time. The lime used in this case ought to be in 
 the state of carbonate, for quicklime will destroy the organic 
 matter in the soil. 
 
 6. All loose earths have the power of absorbing the gases 
 which are generated by putrefaction. But carbonate of lime pos- 
 
52 
 
 CALCIUM. 
 
 sesses this quality in the highest degree. These gases are the 
 most important part of the food of plants, and are not only found 
 in greater abundance, but are retained for a longer time in cal- 
 careous soils., 
 
 These gases are chiefly the carburets of hydrogen and am- 
 monia, the latter being derived from animal manures. 
 
 The proper mode of applying putrescent manures, would be 
 to bury them as deeply as possible ; and of applying the carbonate 
 of lime, to lay it upon the surface. 
 
 The cases in which quicklime can be applied, have been stated. 
 In all other cases the lime ought to be in the form of carbonate. 
 This is sometimes found mixed with clay, under the name of 
 marie, which is a valuable manure. When chalk can be procured 
 it will fall to pieces when exposed to frost, and may also be em- 
 ployed without preparation. Shells not only contain carbonate of 
 lime, but also organic matter. The best mode of preparing these 
 is to crush them. When limestones are to be used, the cheapest 
 mode of reducing them to powder is by burning and slaking. 
 But the powder ought to be exposed to the air, until it is satura- 
 ted with carbonic acid, before it is spread over the soil. 
 
 When lime contains magnesia it must be used with great cau- 
 tion, and it will be rarely safe to apply more than 20 or 30 bushels 
 per acre, and this at intervals of several years. In Great Britain 
 as much as 600 bushels of slaked lime have been applied to stiff 
 clay, and from 200 to 300 to sand. These quantities should not 
 be applied at less intervals than 20 years. 
 
 The most economic mode of using lime is practised in France. 
 Here quicklime is mixed in regular layers with sods. The mixture 
 is stirred several times and permitted to remain where placed, until 
 all the lime is carbonated. Seven bushels per acre is sufficient, 
 but it ought to be repeated with every grain crop. 
 
 Sulphate of lime is also used in agriculture, under the name 
 of plaster. The hydrated sulphate is prepared by being ground to 
 powder, and a single bushel per acre is sufficient, while a quan- 
 tity as great as 5 or 6 would be injurious. There are certain 
 plants, the ashes of 'which are chiefly composed of sulphate of 
 lime > those of red clover contain little else. The latter plant. 
 
CALCIUM. 
 
 53 
 
 will not grow in any soil that does not contain this sulphate. 
 It is therefore applied first to obtain a large crop of clover, 
 which draws the rest of its nutriment chiefiy from the atmos- 
 phere, Permanent fertility may be obtained by ploughing in 
 such crops of clover ; but where, at least, one crop of clover is 
 not ploughed in, the use of plaster injures instead of improving 
 the soil. Sulphate of lime would produce no effect in soils which 
 already contain it, or in soils containing oxalic acid. When the 
 latter is present it may be neutralized by the application of the 
 carbonate of lime, and soils on which plaster has ceased to act 
 may thus be rendered sensible to its action. 
 
 The phosphate of lime is of even more value as a manure 
 than the sulphate, for, although larger quantities may be neces- 
 sary to produce an effect, it is a substitute for other manures of 
 animal origin. The phosphate of lime has been most usually ap- 
 plied in the form of pulverized bones, but the mineral sources 
 that have been heretofore spoken of will, probably, hereafter be 
 resorted to. 
 
 The phosphate of lime as found, either mineral or in bones, is 
 insoluble. It may be converted into a soluble salt by the addi- 
 tion of sulphuric acid. In this state it acts much more rapidly, 
 and therefore may be used in less quantities, although it will re- 
 quire to be more frequently repeated. 
 
VIII. 
 
 SALTS OF COMMERCE. 
 
 ' 1. COMMON SALT. 
 
 The sources of common salt are the water of the ocean, brine- 
 springs, and geological formations, where it exists in a solid form 
 called Rock Salt. In one particular case, viz. near Cracow in 
 Poland, rock salt exists in such plenty as to require no other pre- 
 paration than crushing. In order to prepare it for carriage, it is 
 cut into blocks of the shape of a barrel, and these are surrounded 
 by staves and hoops. In most other cases the rock salt is mixed 
 with insoluble earthy matter as well as rendered impure by other 
 soluble salts. It therefore becomes necessary to dissolve it. 
 The insoluble matters which subside, may be separated by decant- 
 ing the solution. At the salt mines in Cheshire in England, 
 brine springs issue from the salt formations, and the rock salt is 
 dissolved in the water of these. The rock salt is also carried to 
 Liverpool, where it is dissolved in sea water. Erom such solu- 
 tions, as well as from the waters of the ocean and brine springs, 
 salt is obtained by evaporation and crystallization. 
 
 The preparation of the salt in all three cases rests upon the 
 same general principles. The substances contained in these 
 waters besides common salt are, 1 st, the carbonates of iron and 
 lime, held in solution by excess of acid ; 2d, sulphate of lime ; 
 3d, sulphate of soda; and 4th, chlorides of calcium and magnesia, 
 which are usually known under the name of earthy muriates. 
 
SALTS OF COMMERCE. 
 
 55 
 
 The carbonates of iron and lime may be precipitated by a mod - 
 erate heat, or by merely permitting the liquid to remain at rest 
 in contact with the air. They may then be separated by decant- 
 ing. Of the remaining salts, the sulphate of lime alone is less 
 soluble than common salt ; but when the sulphate of soda is also 
 present a double salt' is formed, which, although more soluble 
 than sulphate of lime, is much less soluble than common salt. 
 When therefore a saline water is evaporated, either artificially or 
 spontaneously, the double sulphate of lime and soda will be de- 
 posited early in the process, and collect in a hard crust upon the 
 vessels or natural basins which contain the liquid. Common 
 salt will next be deposited in crystals, and these are loose. It 
 may therefore readily be separated from the liquid even while 
 the evaporation is going on. When the crystals are large, this 
 may be performed by rakes. The earthy muriates have a bitter 
 taste. The evaporation, therefore, ought not to be continued be- 
 yond the point at which this taste begins to be sensible in the 
 salt. The remaining liquid which goes under the name of bit- 
 tern, is thrown away. 
 
 In the manufacture of salt from sea water, the evaporation 
 may be performed either by exposure to the air, or by artificial 
 heat, and even in the latter case the process may be made to as- 
 sume the character of a spontaneous evaporation. 
 
 There are certain places in warm climates where the sea 
 water is admitted at spring-tides into shallow natural basins. In 
 these, salt is often crystallized and may be raked from them. 
 Such natural basins exist at Turk’s Island, and at Key West. 
 In other places artificial basins are formed, called fialt-pans. In 
 order to form one of these, a portion of salt meadow is chosen 
 and inclosed by dykes. Within the outer dyke a sort of laby- 
 rinth is formed, in which the water is first concentrated and the 
 salt finally crystallized. The first part of this labyrinth is a large 
 basin or reservoir which communicates with the tide by gates. 
 The water is led from this through a canal which follows the 
 course of the outer dyke, thus forming three sides of a square, and 
 has a branch parallel to the reservoir, which nearly forms the fourth 
 side, and conveys the water almost back to the place where the 
 
56 
 
 SALTS OF COMMEECE. 
 
 canal first issued from the reservoir. Within the square thus 
 formed are two sets of rectangular basins. In the first of these 
 the water circulates, passing through them diagonally. From 
 these the water is admitted into the basins of the second set, in 
 each of which a portion of the water is shut up until the crystalli- 
 zation is completed, and after the salt begins to form in them it 
 is raked out. Salt is obtained in this way in large cubic crystals, 
 and is called Bay Salt. In this form it is found to be better 
 suited for preserving meat than when fine. Large crystals may 
 also be obtained by artificial heat, by taking care not to permit 
 the liquid to boil. When the boiling is rapid, the crystals are 
 so small as to be separately invisible, and the product is fine or 
 table salt. 
 
 If the artificial evaporation be carried on, as it frequently is, 
 until the whole of the liquid is evaporated, the earthy muriates 
 will be crystallized with it and give it a bitter taste. These 
 earthy muriates are deliquescent and very soluble. Hence they 
 are sometimes separated from fine salt, in the following manner. 
 The salt is packed in baskets, which are suspended over a pan 
 in which the artificial evaporation is going on. ^ The steam which 
 .rises is condensed in the salt, and dissolves these deliquescent 
 substances together with a portion of the salt. This portion 
 however is comparatively small, because the water has the boiling 
 temperature and will thus dissolve much more of the muriates 
 than when cold, although it takes little more of common salt. 
 The baskets are set by to drain, and then dried by artificial heat. 
 
 In very cold climates the water of the ocean has been con- 
 centrated by frost. When water containing salt freezes, the ice 
 is perfectly fresh, hence it is only necessary to separate the ice 
 as it forms, and the strength of the brine will be much increased. 
 This method is practised in the eastern part of Siberia. The 
 brine which remains is evaporated by artificial heat. 
 
 In the Dutch herring fishery, the best bay salt is employed, 
 but before this is used it is dissolved in sea water, and purified 
 by a second crystallization. 
 
 The water of brine springs may be evaporated by artificial 
 heat in the same manner as that of the ocean. Large rectangu- 
 
SALTS OF COMMEECE. 
 
 57 
 
 lar vessels of sheet iron are the best for this purpose, but in this 
 State, and generally in the U. S., cast-iron boilers of the form of 
 potash kettles are employed. In these, the evaporation is ofte 
 carried to dryness, and thus the salt is impure. It will howeve, 
 purify itself if permitted to drain ; for the earthy muriates will 
 deliquesce, and the solution thus formed will drain off. The 
 purification may be performed more rapidly by adding a thou- 
 sandth part of its weight of boiling water to the salt. In order 
 to perform the draining more effectually the salt should be placed 
 in bins, the bottom of which is inclined and pierced with small 
 holes. 
 
 In this State a method called Solar evaporation has been 
 used to obtain coarse salt. Brine is poured into shallow wooden 
 troughs. Each of these is furnished with a cover which runs 
 upon a railway, so that it may be placed over the trough when it 
 rains, and removed when the weather is fine. The principal ob- 
 jection to this method is the great extent of valuable ground re- 
 quired for this purpose. 
 
 At some of the salt springs in Europe, a greater extent of 
 evaporating surface is obtained within a very small space. The 
 methods used for this purpose are three ; that of hurdles, that of 
 tables, and that of ropes. In the method of hurdles a number 
 of bundles of the twigs of a thorny shrub are piled in a frame 
 building. Over the hurdles is situated a trough, into which the 
 brine is pumped. This trough has notches cut on its sides 
 through which streams of the brine pass and fall upon the twigs. 
 The quantity of brine is regulated by means of two sliding boards 
 in which similar notches are formed. 
 
 In the method of tables, a number of surfaces of wood are 
 arranged one over the other in a lofty building. Each table is 
 slightly inclined, and the alternate tables are inclined in opposite 
 directions. Brine being admitted upon the upper table will 
 therefore flow slowly over the surface of them all 
 
 In the method of ropes, cords are stretched between two 
 troughs, one of which is situated immediately over the other. 
 The upper trough being filled to overflowing, the brine will trickle 
 over the surface of the ropes. This method has been found 
 
58 
 
 SALTS OF COMMEECE. 
 
 especially advantageous for causing the crystallization of salt from 
 a boiling and saturated solution. 
 
 2. NITEE. 
 
 The greater part of the nitre of commerce is obtained from 
 soils in which it is spontaneously formed. It may also be obtain- 
 ed from artificial nitre beds composed "of earth, and specially 
 prepared for the purpose. The soils in which nitre is formed 
 spontaneously are found wholly in warm countries, and Bengal 
 at this moment supplies the greater part of the world with nitre. 
 Nitre cannot be formed in a soil which does not contain potassa^ 
 but the other nitrates may be formed in any soil which contains 
 their base. No nitrate will, however, be formed in a soil which 
 does not contain animal matter ; and it was at one time supposed 
 that the whole of the nitrogen in the nitric acid was derived from 
 the animal substance. It is now, however, known that the quan- 
 tity of nitre is much greater than can be thus accounted for. It 
 is therefore inferred that the animal matter acts only as a fer- 
 ment, and that when the process is once commenced, both the 
 nitrogen and oxygen are derived from the atmosphere. The soil 
 of Bengal and Ceylon contain, besides nitre, the nitrate of lime, 
 which may be converted into nitre, and other saline matters 
 which crystallize with it and render it impure. These salts are 
 separated from the earth by lixiviation. If wood ashes be pre- 
 viously mixed with the earth, the nitrate of lime will be converted 
 into nitre. The same change may also be effected by adding 
 potash to the liquid. In some countries all the nitrate of lime is 
 lost. 
 
 Artificial nitre beds were at one time formed in France in 
 calcareous soils, and in places abounding in animal matter. The 
 neighborhood of shambles and burying grounds was chosen for 
 the purpose. The earth was trenched to a considerable depth, 
 and frequently turned over to expose fresh surfaces to the air. 
 When this supply was exhausted, calcareous earth was exposed 
 to the draining of stables. The process is tedious, and requires 
 several months for its completion. 
 
SALTS OF COMMERCE. 
 
 59 
 
 The only country in Europe where artificial nitre heds are 
 still used is Sweden. There the calcareous earth is charged 
 with animal matter by folding sheep upon it. In the United 
 States, in the war of 1812, a considerable quantity of nitre was 
 manufactured from a cave in Kentucky. In all these cases the 
 earth was lixiviated, and potash added to the liquor. 
 
 Purification of Nitre . — Crude nitre contains about 25 per 
 cent, of other substances, which may be considered as impurities. 
 These are partly organic, derived from the animal and vegetable 
 matter which exists in the soil, and partly saline. In order to 
 fit it for its most important uses in the arts, it requires to be 
 purified or refined. This is effected by two successive solutions 
 and crystallizations. In the first solution, water having one-fifth 
 of the weight of the nitre is employed. This is put in a copper 
 boiler and heated. The nitre is gradually added as the water 
 grows warm, and when it boils the whole will be dissolved. The 
 organic matter being lighter than this solution, will rise to the 
 surface, and may be skimmed off. In order to facilitate the for- 
 mation of a scum, a small quantity of glue dissolved in water is 
 added to the solution. The solution is then poured into copper 
 basins, which are covered with wooden lids in order to render 
 the cooling more slow. In these basins a quantity of nitre, equal 
 to the difference between that which is soluble in cold and in 
 boiling water, will crystallize. A mass resembling a sugar loaf 
 is thus formed. This is placed on shelves and permitted to drain. 
 The water which flows from it still contains nitre, and the greater 
 part of the saline impurities. But some of the latter will also 
 remain adhering to the crystals. Hence the necessity of a 
 second solution. The quantity of water used in this is equal to 
 one-third of the weight of the nitre. Glue is also employed, and 
 any scum which may form is removed. The crystallization is ef- 
 fected as before ; and after the loaves have thoroughly drained 
 the nitre is nearly pure. The liquor which drains off in these 
 processes is concentrated by boiling, and yields by crystallization 
 a considerable quantity of nitre. 
 
 A method has recently been introduced, which enables us to 
 dispense with the second solution. The nitre being dissolved as 
 
60 
 
 SALTS OF COMMERCE. 
 
 before, in one-fifth of its weight of water, the solution is treated 
 with glue and skimmed. The liquor is permitted to cool to 1 90°, 
 at which temperature it is kept ; and after about twelve hours 
 is poured into a vat, the bottom of which is formed by two in- 
 clined surfaces. Here the liquid will cool further, and the nitre 
 tends to crystallize. The formation of large crystals is prevent- 
 ed by stirring the water, and the nitre which is deposited takes 
 the form of a fine powder. This powder is placed in a vessel 
 with a false bottom, and is alternately washed with water and a 
 solution of nitre. 
 
 Manufacture of Gunpowder . — The nitrate of potassa is de- 
 composed by heat. In this decomposition its elements enter into 
 new combinations, all of which are either vapors or gases. When 
 carbon in any of its forms is mixed with the nitre, the decompo- 
 sition of the latter is so rapid as to be attended with explosion. 
 This explosion, however, does not take place except at high tem- 
 peratures. A substance has therefore been sought which pos- 
 sesses the properties of taking fire at a low heat, and of generating 
 a high heat by its combustion. Sulphur is a substance having 
 these properties, and gunpowder is a mixture of sulphur, charcoal, 
 and nitre. The proportions do not vary materially from 75 per 
 cent, of nitre and 12^ of each of the other substances. 
 
 The materials used in the manufacture of gunpowder ought to 
 be of the best quality. The nitre is therefore refined, the sul- 
 phur purified by sublimation, and the charcoal is prepared by dis- 
 tillation in iron cylinders. The charcoal which is preferred is 
 made from the softest woods, and the alder, the poplar, and the 
 willow, are principally used for the purpose. In Spain the char- 
 coal is prepared from the stalks of hemp. The three materials 
 are pulverized separately. The charcoal and sulphur are then 
 mixed, and the nitre is gradually added. The operations of pul- 
 verizing and mixing were originally performed in wooden mor- 
 tars. The pestles were also of wood, and moved by machinery. 
 At present, the materials are ground and mixed in cylinders or 
 drums, revolving on a horizontal axis. So long as they are not 
 mixed, the grinding is performed by means of balls made of an 
 alloy of copper ; but when the nitre is added, tin balls are em- 
 
SALTS OF COMMEECE. 
 
 61 
 
 ployed. In order to lessen the danger of explosion, the mixture 
 is kept in a moist state. 
 
 The gunpowder in this stage has the form of a fine powder or 
 meal, in which state it burns slowly for the want of free access of 
 air. It therefore requires to be formed into grains when it is to 
 be used explosively. These grains had originally the form of 
 those of rice, and were obtained by pressing the moist meal 
 through a sieve. At present spherical giains are preferred. 
 These are prepared by placing very dry meal in a revolving drum. 
 A shower of drops of water is permitted to fall upon the surface 
 of the gunpowder while the drum is revolving rapidly. The 
 water does not sink into the dry mass, but the drops roll over 
 the surface and each drop becomes the nucleus of a solid sphere, 
 composed of moistened gunpowder. The grains are then care- 
 fully dried. 
 
 Gunpowder sometimes has a polished surface and is said to 
 be glazed. It is glazed by the mutual friction of its grains, 
 which are made to rub against each other by putting them into 
 a revolving drum. 
 
 When the materials of which gunpowder is made are good, 
 and it is perfectly dry, the whole mass is converted by explosion 
 into gas or volatile matter. Hence the quality of gunpowder 
 may be tested by flashing it from a sheet of white paper, on which 
 if of good quality it will leave no stain whatever. If the quality 
 be inferior, a part of the carbon will remain unconsumed and 
 blacken the paper. 
 
 3. BORAX. 
 
 The principal source of borax is a lake in Thibet, in which 
 impure crystals are found that go by the name of Tmcal. This 
 contains beside the sub-borate of soda, an oil which is supposed 
 to be of vegetable origin, along with other salts of the same acid. 
 In order to purify the tincal it is ground to powder and thrown 
 upon a filtering cloth. Here it is washed with a dilute solution 
 of carbonate of soda. The washing is continued until the liquid 
 
62 
 
 SALTS OF COMMERCE. 
 
 runs off clear. By this action the oil is converted into a soap 
 and dissolved in the water. The matter which has been washed 
 is then dissolved in boiling water, and to the solution twelve 
 parts of carbonate of soda are added for each hundred of the 
 tincal. This serves to decompose the other salts. As some of 
 these have insoluble bases, the solution requires to be filtered. 
 The filtered liquor is concentrated by boiling and permitted to 
 crystallize. The crystallization is performed in vessels having the 
 form of a truncated pyramid, which are lined with sheet-lead. 
 
 There are springs in Tuscany which contain boracic acid. 
 A solid acid may be obtained from these by evaporation and 
 crystallization ; in this form it is carried to France, where, after 
 being redissolved, it is made to combine directly with soda by 
 adding the carbonate of that alkali to the solution. 
 
 4. ALUM. 
 
 Alum was originally obtained from Bocca (Edessa) in Syria, 
 hence the best alum is to this day often called rock alum. The 
 manufacture was carried thence to Tolfa, in the States of the 
 Church, and it is hence often called Roman alum. At these two 
 places the double sulphate of alumina and potassa is formed 
 spontaneously. When the chemical composition of alum was 
 discovered, means were found for converting the sulphate of 
 alumina, which is sometimes formed spontaneously by the decom- 
 position of pyrites in a slaty rock, into alum. There are also 
 some slates which contain pyrites that does not decompose spon- 
 taneously. The decomposition of these may be effected by arti- 
 ficial heat. It has also been found possible to form a sulphate of 
 alumina by the direct union of its elements, and to convert this 
 into alum. When the alum is already formed in the rock it is 
 only necessary to lixiviate it and to cause the solution to crys- 
 tallize. When a sulphate of alumina is formed spontaneously, 
 the rock is lixiviated and potassa added to the solution. When 
 the pyrites does not decompose spontaneously, the slate is formed 
 into heaps along with some description of fuel by the combustion 
 
SALTS OF COMMEKCE. 
 
 63 
 
 of which a decomposition is effected. The whole mass is then lix- 
 iviated. If wood have been the fuel, its ashes will supply potassa, 
 and when coal is the fuel, ammonia will have been generated by 
 its combustion, which will have combined with the sulphate of 
 alumina. 
 
 In order to prepare alum^by the direct union of sulphuric 
 acid and alumina, clay is roasted for several hours in a furnace. 
 During this time it is continually stirred, and is thus prevented 
 from uniting into a solid mass. The clay being thus converted 
 into a dry powder, is formed into a paste with dilute sulphuric 
 acid. This paste is exposed for several days to the waste heat of 
 the furnace. The paste is then laid aside for about a month ; at 
 the end of this time it will be found, that a sulphate of alumina 
 has been formed which may be separated by washing. This may 
 be converted into alum by the addition of an alkaline substance. 
 The paste is therefore lixiviated and an alkaline carbonate added 
 to the solution. 
 
 5. ACETATE OF ALUMINA. 
 
 One of the most important uses of alum is in the art of dye- 
 ing. The earthy base is precipitated to serve as a mordant. 
 The sulphuric acid being thus set free is apt to injure the tex- 
 ture. For this reason it is frequently converted into an acetate 
 of alumina, before it is employed. This acetate is prepared by 
 dissolving three parts of alum with one part of acetate of lead, in 
 eight parts of water. A small quantity of chalk and pearlash is 
 then added to the solution. The mixture is occasionally stirred, 
 and after a few hours' is permitted to settle. A clear liquor is 
 decanted and will contain a solution of the acetate of alumina 
 with sulphate of potassa. The latter salt has no effect either ad- 
 vantageous or disadvantageous. It is therefore unnecessary to 
 separate it. The acetate of alumina does not crystallize. The 
 solution is therefore preserved in a liquid state. 
 
64 
 
 SALTS OF COMMEKCE. 
 
 6. SULPHATE OF IRON. 
 
 This salt is sometimes formed spontaneously by the decom- 
 position of rocks containing the sulphuret of iron. These rocks 
 must not contain clay or slate, otherwise sulphate of alumina will 
 be generated. The sulphuret of iron may also be converted into 
 the sulphate by roasting it. There are also sulphurets of iron 
 found in many places, which are rapidly converted into the sul- 
 phate by the action of water. One of the most remarkable cases 
 of this kind is at Strafford, Yt. Here the sulphuret of iron can 
 be obtained in large quantities. The rock is broken into pieces 
 and piled into heaps, containing hundreds of tons. Water is 
 sprinkled over these heaps until the sulphuret is actually ignited. 
 When the fire has exhausted itself, a stream of water is directed 
 against the base of the heap. This carries away at first both the 
 insoluble and the soluble substances, but the stream being caused 
 to fiow in a channel of small inclination, the former are deposited. 
 The clear liquor which contains the solution is concentrated, and 
 permitted to crystallize. 
 
 7. ACETATE OF IRON. 
 
 The sulphate of iron, which is much used in dyeing black, is 
 liable to the same objection as the sulphate of alumina. Hence 
 for dyeing articles of the best quality, an acetate of iron is often 
 prepared. This is manufactured by steeping fragments of rusty 
 iron in vinegar, or pyrolignous acid. This, like the acetate of 
 alumina, does not crystallize, and must therefore be preserved in 
 its liquid form. 
 
IX. 
 
 METALLURGY. 
 
 The useful metals are found : native, usually in the form of 
 alloy ; combined with oxygen and other supporters of combustion ; 
 combined with sulphur and other combustibles ; and in the state 
 of salts. These metallic compounds are usually mixed and ag- 
 gregated with earthy minerals, and to the aggregate we give the 
 name of Ores. 
 
 An ore takes its name from the metal which exists in it in 
 greatest abundance, except in the case of the precious metals, 
 when it takes its name from the substance of greatest value. 
 
 Ores occur in alluvial or diluvial formations; in beds in 
 stratified rocks ; and in veins that traverse both stratified and 
 unstratified rocks. 
 
 To obtain the useful metals from their ores, various processes 
 are necessary, which may be arranged under the three heads of 
 Mechanical, Physical, and Chemical. 
 
 1. MECHANICAL PROCESSES. 
 
 1 . — Ticking and Sorting. 
 
 When ores have been extracted from the mine, they are in 
 the first place picked and sorted. For this purpose they are 
 broken with a hammer, in such manner as to expose the interior 
 5 
 
66 
 
 METALLUEGY. 
 
 of the mass, and separate any external earthy matter. The 
 broken pieces are usually arranged in three parcels, the first of 
 which is rich enough to be worked ; the second, undergoes a sec- 
 ond picking and sorting ; the third is too poor to be profitably 
 worked. 
 
 2 . — Stamping and Crushing. 
 
 Stamping is performed by machines moved by water, or other 
 convenient power. The apparatus is composed of a number of 
 heavy beams, set vertically in a frame. From each beam a tooth 
 or caoi projects. An axle revolves in the neighborhood of the 
 beams, on which teeth are arranged in the form of a helix. These 
 teeth taking hold of the cams on the beams, raise them in suc- 
 cession, and when by the revolution of the axle, the teeth cease 
 to lock, the beams fall by their own weight. The beams are shod 
 with iron, and the ore is laid on a bed of iron or stone. The bed 
 may be dry, in which case, the fineness of the ore is regulated by 
 sieves ; or it may be placed in a trough, through which water is 
 continually flowing. The fineness of the ore is in this case regu- 
 lated by the force of the current. 
 
 Crushing is performed by causing the ore to pass downwards 
 between rollers. Of these, there are several pairs, the uppermost 
 of which have the greatest space between them. After passing 
 the upper rollers the ore falls upon a sieve, whose bottom is in- 
 clined, and which is continually shaken by the same force which 
 turns the rollers. 
 
 3. — Washing and Concentration. 
 
 When ore in fine powder is mixed by agitation with water, the 
 heavier particles sink first, and the less dense may be removed 
 by discharging the water before it ceases to be turbid. As me- 
 tallic is usually heavier than earthy matter, the greater part of 
 the latter may by a process founded on this principle, be separa- 
 ted from the former. Washing may be performed by hand in 
 bowls, or even in a common frying pan, and various machines 
 
METALLUEGY. 
 
 67 
 
 have been planned for performing it on a large scale . The 
 character of the machine will differ according to the nature of the 
 metal contained in the ore. 
 
 In concentration, the powdered ore is mixed by agitation with 
 a large quantity of water, and then left at rest. For the same 
 reason as before, the metallic portions tend to sink first, and the 
 earthy matter last. The water is removed after it has become clear, 
 and the paste which remains beneath is separated by horizontal cut- 
 ting into three portions. The upper portion is rejected, the mid- 
 dle portion is concentrated a second time, and the lower portion 
 is ready for the subsequent processes. 
 
 2. PHYSICAL PROCESS. 
 
 Roasting. 
 
 Roasting is the only important physical process. It consists 
 in exposing the stamped and washed, or concentrated ore, to a 
 heat sufiicient to separate its volatile parts. In this way, water, 
 carbonic acid, sulphur, arsenic, &c., may be separated from the 
 metals with which they are combined. 
 
 Roasting of ores that do not contain pyrites in large quanti- 
 ties, may be performed in large heaps, by placing the ore and fuel 
 in alternate layers ; in kilns composed of three walls ; in kilns re- 
 sembling lime-kilns ; and in reverberatory furnaces. In some 
 cases, arsenic and sulphur are separated in quantities sufficient 
 to defray the expense of collecting them. For this purpose, the 
 kilns may be placed under sheds, or the deposit may be formed 
 in the chimneys of the reverberatory furnaces. 
 
 Pyritical ores may be roasted by means of a single layer of 
 fuel forming the base of a large pyramidal heap. The sulphur 
 which is separated by the combustion of the fuel from the lower 
 part of the heap, serves as fuel for the upper portions. 
 
68 
 
 METALLURGY. 
 
 3. CHEMICAL PROCESSES. 
 
 1. — Smelting. 
 
 In smelting, the earthy matter of the ore is converted by 
 fusion into a vitreous substance. In some cases the earthy mat- 
 ter is fusible without addition. More frequently, it becomes ne- 
 cessary to add some other earthy mineral, which is called a Flux. 
 When the ore contains little or no silica, some silicious mineral 
 must be added, with or without another flux. When the ore 
 abounds in silica, limestone, or quicklime, is added. The vitreous 
 matter is less dense than the reduced metal, and they do not mix 
 with each other. 
 
 2. — Reduction. 
 
 To separate oxygen from a metal, it is heated in contact with 
 carbonaceous matter. Charcoal and coke are employed for this 
 purpose, and in some cases wood or even coal. The processes of 
 smelting and reduction, although very difirerent in principle are 
 performed together in furnaces. 
 
 The furnaces in which ore is smelted and reduced, are of two 
 kinds. In the first, air is supplied to the burning fuel by the 
 draught of a chimney. These are called air or wind furnaces. 
 In operations on a small scale, the ore may be placed in crucibles 
 On the large scale the ore is placed on a hearth in a chamber, 
 which is placed between the furnace proper, and the chimney. 
 A furnace of this character is styled Reverberatory. 
 
 In the second kind of furnaces, air is supplied by a blowing 
 machine. Of these, the most familiar is the common bellows. 
 To furnaces thus supplied with air, the epithet of Blast may be 
 given as the generic name. They may be of various kinds from the 
 Forge fire.^ which is kindled in a shallow cavity, to the blast fur- 
 nace used in making Fig iron^ some of which have been 70 feet 
 in height. 
 
METALLUKGY. 
 
 69 
 
 1. METALLUKGY OF IKON. 
 
 1 . — Ores of Iron. 
 
 All the useful ores of iron are either oxides or carbonates. 
 The protoxide probably occurs in the crystallized ores of Elba, 
 and at Peru, in the State of N. Y. The magnetic oxide is found 
 in grains, and in crystals aggregated in masses in primitive rocks, 
 the usual form of its crystals being the octoedron. 
 
 The peroxide, occurs in the form called from its appearance 
 micaceous and specular iron ; and in combination with water in 
 the haematites, and the bog and meadow ores. 
 
 The carbonate of iron occurs in crystals, and crystalline mas- 
 ses of great purity. It also occurs mixed with carbonate of lime, 
 clay, or other earthy matter, in some coal formations, where it is 
 known as Iron-stone. 
 
 2. — History. 
 
 Iron is mentioned in the oldest writings, both sacred and pro- 
 fane. It is, however, among the most difficult of the metals to 
 obtain from its ores, and the methods are so far from perfect that 
 they are receiving improvements almost daily. It would appear 
 that the first iron used by man was found native, as it is still oc- 
 casionally found at the present day, and is ascribed to meteoric 
 origin. In this state, it appears from a passage in scripture, to 
 have been abundant in Palestine. The earliest workers of iron 
 from its ore, seem to have been the Chabybes, a nation of Asia 
 Minor, called Chaldeans by Xenophon, in whose original seats 
 iron is still worked. 
 
 From this people, the Grreeks learnt the art, if not of making 
 iron, certainly of making steel, as appears from the Greek name 
 of that substance. Elis in Greece, was the seat of an extensive 
 iron manufacture, and Homer refers to a traffic in which the iron 
 of Greece was exchanged for the bronze of the Tyrrhenians. 
 
 The art of smelting iron, was carried by Greek colonies 
 
70 
 
 ' METALLUEGY. 
 
 throughout the shores of the Mediterranean, and by one of them, 
 the mines of Elba were opened 3 or 400 years B. C. These 
 mines are still worked, the ores being smelted in Tuscany and 
 Catalonia, by methods apparently identical with the ancient 
 Steel was probably obtained accidentally, and the iron in the 
 original process passes through a state of combination identical 
 with steel. Steel may also be obtained with certainty from the 
 crystallized carbonate of iron. 
 
 Cast-iron is usually said to have been accidentally discovered 
 in Alsace, towards the close of the 15th century, but it would ap- 
 pear that the Chinese have possessed the art of making it for 
 ten or twelve centuries. 
 
 3. — Blooming. 
 
 Wrought-iron maybe obtained directly from its ores. Those 
 best suited for the purpose, are rich, and contain earthy matter 
 which when combined with a small quantity of oxide of iron, is 
 easily fusible. 
 
 The ore, after being picked and sorted, is stamped into a 
 coarse powder. The apparatus employed is a forge fire, the 
 fuel charcoal. Some ores may be reduced in a common smith’s 
 forge, but one of larger size and specially constructed, is generally 
 employed. The fire is lighted in a shallow cavity in the hearth 
 of the forge, and is heaped into a conoidal mass against the wall. 
 The blowing apparatus is a pair of bellows, each composed of 
 two pyramidal boxes of wood, usually driven by a water-wheel, 
 and acting alternately. When the heap of charcoal is fully igni- 
 ted the bellows are set in action, and a layer of ore is strewn 
 over the fuel. Upon this another layer of charcoal is laid, which 
 is followed by another layer of ore, until as much as can be acted 
 upon has been introduced. 
 
 The ore being heated, the earthy matter combines with a part 
 of the oxide of iron to form a compound known from its charac- 
 ter as the vitreous oxide. The rest of the oxide of iron, enveloped 
 in an atmosphere of carbonic oxide is reduced, and the result- 
 ing iron in contact with carbon, forms with it a compound analo- 
 
METALLUEGY. 
 
 71 
 
 gous to steel. To separate the carbon, the iron is raised up, and 
 exposed to the blast, under whose action the carbon burns away. 
 The iron finally subsides into the cavity of the hearth, where by 
 pressure it takes the form of a spongy mass, whose cavities are 
 filled with the vitreous oxide, and which is called a Loop. The 
 loop being taken from the fire, is beaten on an iron fioor with 
 wooden mallets, by whose action a large proportion of the vitreous 
 oxide is separated. It is then replaced in the furnace, and brought 
 again to a welding heat. 
 
 The loop is next placed on an anvil and beaten with the Forge 
 Hammer into the form of an irregular polygonal prism, which is 
 called the Shingle. The forge-hammer is made of cast-iron, hav- 
 ing a shape somewhat resembling the letter D. It weighs several 
 cwts., and is mounted on one end of a strong beam of wood, the 
 opposite end of which rests on gudgeons. To lift it, an axle 
 driven by a water-wheel, revolves close to the beam, having cams 
 projecting from it which apply themselves near the head of the 
 hammer, and lift it with such force as to throw it against a beam 
 or wooden spring, whence it rebounds towards the anvil. 
 
 The shingle is reheated and beaten into the form of a paral- 
 lelopiped called the Bloom.^ from which the process takes its 
 name. 
 
 The bloom, or as much of it as is sufficient to form a bar of 
 the desired size, was formerly thrice reheated and beaten to draw 
 it into a bar. At the present time, blooms are often reheated 
 only once, and are drawn into bars by passing them between roll- 
 ers. The reheating of the bloom is also performed in an oven 
 or reverberatory furnace, instead of a forge fire. By both me- 
 thods much fuel and labor may be saved. 
 
 Poor ores may also be converted directly into iron. Instead 
 of a forge fire, a furnace, whose depth is three or four times as 
 great as its diameter, is employed. The ore, mixed if necessary 
 with a flux, is placed in the cavity with charcoal in alternate 
 strata. When the charcoal is burnt away, a loop may be found 
 in the cavity, but it often contains a liquid mass of carburet of 
 iron. This process is no otherwise interesting, than as that in 
 which cast-iron was originally discovered. 
 
72 
 
 METALLUKGY. 
 
 4. — Cast-Iron. 
 
 Cast-iron is manufactured in a furnace to which the name of 
 Blast Furnace is usually restricted. 
 
 A blast furnace has usually the external form of a square 
 truncated pyramid. The height has varied from 18 ft. to 70 ft. 
 The pyramid is usually pierced on all its sides with arches, which 
 support the masonry above ; one of these afibrds a place of dis- 
 charge for the metal and vitrified earths. Through the others, 
 pipes pass that convey the air from the blowing apparatus. The 
 cavity of the furnace is inclosed in a lining of fire-brick, or re- 
 fractory stone. The cavity has a shape which may be described, 
 by supposing two truncated cones to be joined to each other at 
 their greater bases, and that the lower cone rises from a square 
 truncated pyramid, differing but little from a prism. The lower 
 or pyramidal portion is called the Crucible; the wide space at 
 the junction of the two cones, the Boshes ; the opening at top, 
 the Trundle-Head. The space between the outer pyramidal wall 
 and the lining is filled with sand, for the purpose of preventing 
 the outer wall from being broken by the expansion of the lining. 
 
 The blowing apparatus was originally composed of two wooden 
 bellows, like those described in the preceding section. Various 
 other forms were subsequently employed, until finally a double 
 acting cylinder of cast-iron has superseded all others. 
 
 So long as bellows were used, the quantity of air, and the 
 pressure at which it was introduced were limited. More iron 
 was therefore made in winter than in summer, because the vol- 
 ume of air being limited by the power of the blowing apparatus, 
 the absolute quantity was greater in cold weather than in warm. 
 With a double acting cylinder propelled by a steam engine, the 
 volume of air can be increased beyond what can possibly be 
 needed. In this way an equal weight of air can be introduced, 
 whether its temperature be high or low. It has, therefore, be- 
 come possible to introduce air artificially heated. This has been 
 done, and has been attended with great advantages. 
 
 1. The quantity of iron made will be equal, whatever be the 
 external temperature. 
 
METALLURGY. 
 
 73 
 
 2. The height of the furnace is limited not by the force of the 
 blast, but by the nature of the fuel. With charcoal made from 
 soft wood, it may be as great as 28 or 30 ft., with charcoal from 
 hard wood, from 36 to 40 ft., and with coke from 40 to 48 ft. 
 
 By an increase in the dimensions of the furnace, the interior 
 may be kept at a higher temperature with a given consumption 
 of fuel. In this way either more iron may be made, or iron of a 
 higher quality. 
 
 Cast-iron may be either composed of an aggregate of separate 
 grains of carbon and iron, of a definite compound of carbon and 
 iron, of a white color, or of a mixture of iron, carbon and differ- 
 ent carburets of iron. The highest quality or No. 1, is of the 
 first description, and No. 3 is the definite white compound of 
 iron and carbon, usually called forge-pig^ because it is of little 
 use except to convert into wrought iron. To obtain the highest 
 quality of No. 1, the heat of the furnace must be sufiicient to melt 
 wrought iron, and the liquid metal must cool slowly. By rapid 
 cooling the highest quality may be rendered white. 
 
 3. The consumption of fuel may be lessened. 
 
 4. Raw coal and wood may be used in part, instead of char- 
 coal and coke ; and anthracite, which could not be used when the 
 blast was not heated, may be employed as fuel. 
 
 To set a blast-furnace in action, a fire is lighted under one 
 of the arches for the purpose of drying the furnace. This fire is 
 made of brush or other fuel burning with much flame. A fire is 
 next lighted in the bottom of the furnace, called the Hearth. 
 The hearth is composed of a large flat stone, and inclosed on the 
 side whence the metal is to be withdrawn, by the Dam and 
 Tymp. The dam rests on the hearth, and was formerly of stone. 
 It is now usually a hollow block of cast-iron, kept from melting 
 by the passage of a stream of water through it. Between the 
 dam and tymp is an opening, through which the excess of vitre- 
 ous matter may flow. 
 
 Under the dam is a passage for the flow of the metal, which 
 is usually closed with a plug of tempered clay. To draw off the 
 metal, the furnace is tapped by breaking through the clay with 
 an iron tool, pointed with steel. When the furnace has been 
 
74 
 
 METALLUEGY. 
 
 thoroughly dried, fuel is gradually added to that in the hearth, 
 until the whole cavity is filled with ignited fuel. The blowing 
 apparatus is then set in action, and the charging of the furnace 
 commences, by throwing charges in at the trundle-head. A 
 charge is composed of a constant quantity of charcoal, and a mix- 
 ture of ore and flux in constant proportions. The quantity of 
 this mixture is small as first, and is gradually increased until the 
 furnace assumes a regular state of working, and can be tapped at 
 regular intervals of 12 hours. The charges are repeated at regu- 
 lar intervals, until the stock of materials is exhausted, or the 
 furnace ceases to be in working order. 
 
 As the charge descends in the furnace, the earthy part of the 
 ore, the flux, and a part of the oxide of iron, unite to form a glass 
 called the Cinder. The cinder being liquid descends to the 
 hearth, where the heat is suflacient to keep it fluid. The oxide 
 of iron enveloped in an atmosphere of carbonic oxide is reduced, 
 and being in contact with carbon, unites with it, thus becoming 
 fusible. The carburet of iron melts, and follows the cinder to 
 the hearth, where from its superior density it sinks beneath it, 
 and is protected by it from the blast. A part of the earths also 
 is reduced, and their bases united with the carburet of iron. 
 
 Cast-iron is therefore, a very complex substance, containing 
 not merely carbon and iron in various modes, but also the me- 
 tallic bases of earths, and the metalloid silicon. Its quality is, 
 perhaps, as much affected by the character of the earthy bases 
 with which it is alloyed, as by any other circumstance. 
 
 To receive the iron drawn from the furnace by tapping, 
 trenches are cut in a floor of sand. One of these is of considera- 
 ble length ; the others are arranged at right angles to it, and hold 
 each about 1 cwt. of iron. The iron which flows into the long 
 trench, and thence into those at right angles, is called the soiv 
 andy?zg-5. Hence the name oi pig-iron. 
 
 Castings may be made of pig-iron as it flows from the blast- 
 furnace by receiving it into moulds. They are more usually 
 made from remelted pig-iron. Pig-iron, and old castings, may 
 be melted for the purpose, either in reverberatory furnaces or in 
 low blast furnaces, called Cupolas. 
 
METALLURGY. 
 
 75 
 
 The moulds may be made of three dilFerent materials, called 
 green sand, dry sand, and loam. Moulds of either description of 
 sand are made in iron frames or boxes, by the aid of a pattern 
 made of wood or metal. The box is of such form that the mould 
 may be made in at least two pieces, so that it may be opened to 
 remove the pattern. The pattern being supported within the 
 box, sand is rammed around it. The surfaces at which the box 
 is to opened, are dusted with powdered coke to prevent adhesion. 
 After the several parts of the box have been filled with sand, the 
 box is opened and the pattern is taken out, leaving a cavity hav- 
 ing exactly its own shape. Grreen-sand moulds contain a small 
 quantity of water and of clay, to render the sand adhesive. The 
 presence of water may be dangerous. Hence, for large castings, 
 the sand is mixed with a larger quantity of tempered clay, and 
 the water is evaporated by placing the moulds in a heated oven. 
 
 Every mould must have at least two openings, one for the ad- 
 mission of the heated metal, the other for the escape of air and 
 vapor. The discharge through the latter may be accelerated by 
 setting fire to the hydrogen, which escapes from it. This hydro- 
 gen is furnished by the decomposition of the water of the mould. 
 
 Loam moulds are made by laying brick in an earth of that 
 character, plastering the brick with the same material, and giving 
 to the interior cavity of the mass the shape required. The mould 
 is finally dried by lighting a fire within it. 
 
 5. — Refining. 
 
 In refining, cast-iron is converted into wrought-iron. The 
 apparatus is a forge fire similar to that used in blooming, except 
 that an opening is left in the wall, over the cavity of the hearth, 
 for the purpose of introducing the pig of iron. The fuel is char- 
 coal, and the [chemical part of the process consists in burning 
 away the carbon. The metallic iron collects, with vitreous oxide, 
 in the hearth, in the form of a loop. The subsequent processes 
 are the same as in blooming. 
 
 Refining may be used to advantage wherever large bodies 
 of woodland exist The absolute cost of refined iron in fuel 
 
76 
 
 METALLURGY. 
 
 and labor, is less than that of bloomed, but it may be impractica- 
 ble to employ the process of refining. 
 
 A blast furnace in which charcoal is used, will require all the 
 wood that can be furnished by successive growth on 7000 acres 
 of woodland. It will supply material for 5 or 6 refineries, each 
 of which requires at least 2000 acres of woodland to keep it in 
 action. 
 
 Refined iron made from ore of equal quality, is better than 
 bloomed iron, being more homogeneous and free from wiry fibres 
 of steel. But as cast-iron can be made from ores very inferior to 
 any that can be used in blooming, and as any cast-iron may be 
 refined, the average quality of refined is inferior to that of bloomed 
 iron. 
 
 If the pig iron contain the bases of earths, they are oxydated 
 in the process of refining, and concur to form the vitreous oxide 
 which collects in the cavity of the loop. 
 
 7 . — Rolling and Slitting. 
 
 To obtain small bars either round or rectangular, by heating 
 in a forge fire and beating with the forge hammer, would be very 
 costly. Hence only large bars are made either in the processes 
 of blooming or of refining. To reduce these bars to a smaller 
 size they are heated in an oven to a welding heat, and are then 
 passed between rollers driven by water or steam. To make round 
 iron, a large round bar is passed through grooves cut opposite to 
 each other in the rollers, each having the section of a semicircle. 
 The grooves diminish in size, in succession, until the bar acquires 
 the proper size. To make small rectangular bars, a large flat bar 
 is drawn between rollers having rectangular grooves cut in them 
 in such a manner that the projection on one. roller corresponds to 
 the cavity in the other. The bar is thus slit into many pieces at 
 a single operation. 
 
 This method is now of little importance except historically. 
 
 6. — Puddling. 
 
 When coke is used instead of charcoal in a refinery fire, the 
 cast-iron does not lose enough of its carbon to cease to be fusi- 
 
METALLURGY. 
 
 77 
 
 ble. It therefore will not collect in a loop, or come to nature. 
 The carbon may be removed by heating cast-iron in a reverbe- 
 ratory furnace, with free access of air. Both methods are now 
 combined in the process of puddling. Pig-iron is first heated 
 with^coke in a forge fire. The forge fire is now made so large as 
 to admit of several nozzles or tuyeres.^ for the admission of the 
 blast, and from three to nine pigs may be acted upon at a time. 
 The melted iron is removed by tapping the cavity of the hearth, 
 and is received on a plate of cast iron, where it cools rapidly. To 
 break it to pieces and render it brittle, it is sprinkled with wa- 
 ter while red-hot. The broken pieces are then stamped. 
 
 The stamped iron is placed in a reverberatory furnace, on a 
 hearth, composed at first of sand, and afterwards of vitreous ox- 
 ide. The hearth has also been made of rich magnetic ores of 
 iron. The fuel is bituminous coal. 
 
 When the iron has melted, it is stirred with iron tools, and 
 free access of air is permitted. The carbon is thus burnt away, 
 the bases of the earths, and some of the iron are oxydated, and 
 unite to form the vitreous oxide. Finally, the iron ceases to be 
 fusible, and becomes malleable. It is at this time in the form of 
 small grains, which, if pressed together adhere, and form balls or 
 loops. A thin bar of iron is introduced to form the nucleus of 
 each ball, and serves as a handle. The balls were formerly with- 
 drawn in succession, and passed between rollers, having grooves 
 diminishing in succession, until the required form of bar be 
 given. 
 
 In rolling, the vitreous oxide is pressed towards one end of 
 the bar, whence a part of it exudes, but cannot be entirely sepa- 
 rated. The forge hammer removes the vitreous oxide complete- 
 ly, but is so slow in its action, that a ball could not be both ham- 
 mered and drawn without being reheated. The advantages of 
 both hammering and rolling have been united, by the use of 
 hammers weighing several tons, and moving with great rapidity. 
 After these have compressed the balls to the utmost, they still 
 contain heat enough to permit them to be rolled. 
 
 Puddled iron is often of poor quality ; because iron may be 
 passed between rollers, even although it would fiy to pieces un- 
 
78 
 
 METALLURGY, 
 
 der the hammer. To render it merchantable, the bars are cut 
 into pieces of from 6 to 18 inches in length. Several of the bars 
 
 piled one upon the other. These piles are placed side by 
 side, and end to end, on the hearth of a reverbatory furnace. 
 On this layer of piles another is placed at right angles. In the 
 furnace the piles are brought to a |vhite heat, by which a large 
 quantity of vitreous oxide is formed, of which exudes like 
 sweat from the pile. The piles are then passed through rollers 
 of higher finish than the puddle rolls, and become merchant-bars. 
 
 In both puddling and reheating, the vitreous oxide is pressed 
 by the rolls towards one end of the bar. These ends are cut off, 
 piled, reheated, and rolled, furnishing iron of better quality. 
 Smaller scrap is heated in a puddling furnace, rolled into bars, 
 cut, piled, reheated, and again rolled, yielding iron of still higher 
 quality. 
 
 Iron made by the process of puddling with bituminous coal, 
 from American charcoal-made pig iron, is of better quality than 
 any imported. 
 
 The best iron made in England is used wholly in the manu- 
 facture of chain cables, and is never seen in this country in its 
 original form. The pig iron is melted in a forge fire, with char- 
 coal, run into plate iron, stamped, puddled with bituminous coal, 
 cut, piled, and reheated. 
 
 8. — Steel. 
 
 Steel; as has been seen, may be obtained directly from ores 
 containing crystallized carbonate of iron. The greater part of 
 the steel of commerce, however, is made from bar iron, and the 
 art is most extensively practised in England. The material 
 there employed is made solely at a few forges in Sweden. Rus- 
 sia formerly yielded iron for this purpose, but it is no longer ex- 
 ported. It has been supposed that the properties of the iron of 
 these forges depended on their extreme purity ; but this idea 
 has been set aside, and the precise reason of its superior value 
 remains to be investigated. One forge in New Jersey furnishes 
 iron, from which steel of the best quality may be made ; but, ex- 
 
METALLURGY. 
 
 79 
 
 cept in case of a war with England, this iron is of too much 
 value for other purposes, to he employed in making steel. 
 
 In making steel, the bar iron is placed in layers, in a rectan- 
 gular oven, and completely imbedded in powdered charcoal. In 
 this it is exposed to a red heat for several days. When removed, 
 it is found that the surface has distended and risen from the bar, 
 giving it an appearance which entitles it to the name of Blistered 
 Steel. 
 
 Blistered steel is richest in carbon at the surface. To render 
 it homogeneous, it may be brought to a welding heat, and beaten 
 with Tilt Hammers, when it is called Tilted Steel. It is now 
 more usually melted in crucibles, with the addition of powdered 
 charcoal and glass. The latter preserves it from burning, by 
 contact with air. When melted, it is cast into ingots, in moulds 
 of wrought-iron. The ingots are drawn into bars by the tilt 
 hammer, or by rollers. 
 
 Steel will combine when liquid, with a small portion of silver. 
 The compound is harder than common cast-steel. 
 
 A kind of steel called Wootz, is brought from India. On 
 analysis, it appears to contain aluminum. 
 
 Silver steel is distinguished by oval spots, and wootz by strim 
 of different lustre on its surface. 
 
 The same steel may have different degrees of hardness and 
 elasticity given it by Tempering. Tempering consists in heating 
 the steel to different temperatures, and cooling it at different 
 heats. When heated to the highest degree and suddenly cooled, 
 it is hard and brittle, when moderately heated and slowly cooled, 
 it is soft and elastic. 
 
 The proper degree of heat was formerly judged of, by the 
 color the steel assumed. It is now known, that the temperatures 
 necessary for the purpose are included between the boiling points 
 of water and mercury. Hence, tempering is now performed by 
 heating the articles of steel in a bath of mercury, and withdraw- 
 ing them in succession as the proper temperature is reached. 
 
 Before this discovery, the manufacture of particular articles 
 was restricted to particular places, and the art often died with 
 the workman. At present it may be considered universal.