> t 
 
m 
 
m 
 
ON 
 
 THE COTTON FIBRE, 
 
 AND ON THE 
 
 MANNER IN WHICH IT UNITES WITH COLOUEING MATTER. 
 
 [communicated to the chemical society.] 
 
 GLASGOW: 
 PRINTED BY BELL & BAIN, 15 ST. ENOCH SQUARE. 
 1863. 
 
Digitized by the Internet Archive 
 in 2013 
 
 http://archive.org/details/oncottonfibreonmOOcrum 
 
ON THE! 
 
 COTTON FIBEE, 
 
 AND ON THE 
 
 MANNER IN WHICH IT UNITES WITH COLOURINa MATTER. 
 By WALTER CRUM, F.R.S. 
 
 In the year 1843 I pablished a Memoir* on the manner in which 
 cotton fibre unites with colouring matter in the process of dyeing. 
 I endeavoured to show that tlie combination which there takes 
 place is not the result of chemical affinity, as was at that time 
 universally understood, but that the union is a mechanical one; 
 and, among other illustrations, I described various processes of 
 dyeing in which the mechanical union is in different ways effected. 
 
 Since that period much has been said in opposition to the 
 views then advanced, but generally with a very imperfect appre- 
 hension of them. I had indicated but a few of the facts which 
 led to the conclusions then arrived at, leaving unexplained other 
 facts and processes which have been supposed to contradict them. 
 
 The subject is sufficiently important to demand the more full 
 and systematic statement on which I propose now to enter, — 
 repeating, necessarily, some of the illustrations formerly adduced, 
 and taking advantage at the same time of certain new facts with 
 which I have since become acquainted. In this way I conceive 
 I shall best answer the particular objections, and correct the mis- 
 statements that have been made. I shall describe the processes to 
 be alluded to in such a manner that the chemist who may not 
 hitherto have attended to this technical branch of his science will 
 have no difficulty in following the statements ; and, from the new 
 light in which the subject is viewed, I trust they will not be 
 without interest, even to those who are already acquainted witli 
 the facts hitherto made known. 
 
 * " Proceedings of the PMlosophical Society of Glasgow," i., 98. " Phil. Mag ," 
 vol. xxiv., April, 1844. "Ann. Ch. Pharm.," Iv., 220. 
 
2 
 
 ON THE MANNER IN WHICH COTTON 
 
 In my original communication I gave a slight history of the 
 old mechanical and the chemical explanations of dyeing. The 
 early views entertained by Macquer, Hellot, and Le Pileur d'Ap- 
 ligny, with their theory of pores, incomplete and inconsistent as 
 they were, and wanting the support of facts which we now possess, 
 gave way at once to the chemical theory of Bergman. In his 
 treatise on indigo, in 1776, that chemist attributed to cotton the 
 power of elective attraction, which had just been promulgated for 
 acids and bases, and in this reasoning from analogy he was 
 followed by Macquer, Berthollet, and all other writers on the 
 subject. But no one who is at all conversant with the rationale 
 of the processes of dyeing, and with the laws of chemical combina- 
 tion as they are now understood, can examine the question with- 
 out arriving at an opposite conclusion. 
 
 Cotton wool in the bleached state — that is, when freed as much 
 as possible, by the action of alkalies, hypochlorites, and acids, 
 from foreign ingredients — may be considered as pure Avoody fibre, 
 or cellulose Ci2HioOio. It is one of the most inert of vegetable 
 bodies. In the textile fabric it is capable of having incorporated 
 with it, in all proportions, a multitude of different substances, 
 without changing its own or their physical or chemical characters, 
 except by holding them against mechanical efforts to wash away, or 
 otherwise to separate them, but yielding them up to their proper 
 solvents as readily as they could be taken from a surface of glass — 
 itself remaining unchanged. 
 
 We know only two examples of chemical combination into 
 which cotton wool, without total disintegration, is capable of 
 entering; — these are its compounds with nitric acid and with 
 potash or soda. When cotton wool is made to imbibe nitric acid 
 by the gun-cotton process, a true chemical combination is formed, 
 in equivalent proportions, but the characters of both constituents 
 are completely changed, and the cotton C12H10O10 has, as I find, 
 3H0 replaced by 3NO5, forming the compound C12H7O7, SNOg*. 
 Or the substitution may be stated thus : — 
 
 C12H10O10 + 3NO5 = 8H0 + Ci2H7(N04)30io 
 
 The combination with soda in mercerized cotton, if it does 
 exist, is not so stable, and the ultimate constituents of the cotton 
 
 * I have been represented, by Messrs. Porrett and Tescbemacher ("Mem. Chem. 
 Soc," iii., 261) as taking a mechanical view of the nature of gun-cotton, but I can- 
 
UNITES WITH COLOURING MATTER. 
 
 3 
 
 undergo no change; but, according to Dr. Gladstone, there is 
 a chemical combination O^q, KO, which, although decom- 
 
 posible by water and by carbonic acid, resists washing with 
 alcohol. All other substances with which cotton has been made 
 to unite, including those which form its various dyes, retain the 
 colour, and all the other properties which they possessed in a 
 separate state. Their union does not materially affect even the 
 degree in which they resist the external influences of light, or of 
 alkaline and other re-agents. 
 
 The attraction which is attributed to porosity or capillarity we 
 kiiow to be an attraction of surface ; but it is one in which, in 
 consequence of its structure, the absorbing body has its power of 
 attraction for that which it imbibes immensely increased. The 
 term capillarity gives but a faint idea of the disproportion between 
 the extent of surface of the cell which constitutes a pore in the 
 woody fibre and the almost mathematical line or point of matter 
 which that cell is capable of containing. From the experiments 
 of Saussure, we learn that boxwood charcoal absorbs a quantity of 
 carbonic acid 56 times greater than the capacity of its pores, which 
 implies the existence of a large proportion of it in the liquid state. 
 Other porous bodies have similar properties : raw^ silk, linen 
 thread, the dried woods of hazel and mulberry, although they 
 were found to condense but a small quantity of carbonic acid, 
 took up 70 or 100 times their bulk of ammoniacal gas ; and Saxon 
 hydrophane, which is nearly pure silica, absorbed 64 times its 
 bulk of that gas. The gas does not enter into combination with 
 the solid which absorbs it : the air-pump alone destroys their 
 union. 
 
 The power w^iich charcoal possesses of attracting to its surfaces 
 certain solid bodies which are dissolved in water is equally w^ell 
 known. Bone charcoal removes the colouring matter from the 
 brown solution of tartaric acid, and from syrup in the refining of 
 sugar. It precipitates lime from lime-water, and metallic oxides 
 from their solution in ammonia or caustic potash ; but no chemical 
 
 not discover on what grounds. In my paper on the Nitrates and on Gun-Cotton 
 ("Proc. Phil. Soc. of Glasgow," ii., 163, April, 1847. " Phil. Mag.," vol. xxx., June, 
 1847. " Ann. Ch. Pharm.," Ixii., 233) I assign to it the constitution in the text, as 
 the result of my own experiments. I have always attributed the difference between 
 my analyses of gun-cotton and those of others to the purifyhig process to which, in 
 the former case, the cotton was subjected. 
 
4 
 
 ON THE MANNER IN WHICH COTTON 
 
 union has ever been supposed to exist between the charcoal and 
 these gases or solid matters. It is well known to be chemically 
 indifferent to all such bodies. 
 
 Mitscherlich calls the force which produces such remarkable 
 effects upon the gases an action of contact, or an attraction of 
 surface, and he calculates the extent of surface, in proportion to 
 the mass which it attracts, as a measure of the force which -it 
 exerts. But it is something more, or, at least, the fact may be 
 more strikingly stated. The same, or even a larger amount of 
 surface unenclosed, does not exert an equal power. Saussure, in 
 his valuable paper on the absorption of gases, informs us that 
 charcoal from boxwood in the solid state absorbs twice as much 
 common air as when reduced to powder. The condensation of 
 gases in the solid charcoal goes on, he conceives, in the narrow 
 cells of which it is composed, and is analogous to the rise of 
 liquids in capillary tubes. But when we pulverize a body 
 containing such cells, we open and destroy a large portion of 
 them. While, therefore, we increase the actual amount of sur- 
 face, we increase in a much larger proportion the amount of the 
 fluid on which it acts, and thereby diminish the intensity of the 
 action. 
 
 It was these remarkable facts, as described by Saussure, 
 Graham, Bussy, Mitscherlich, and others, and not the crude 
 mechanical theories of the last century, that drew my attention to 
 the similarity of the action of cotton-wool in several of the pro- 
 cesses of dyeing. 
 
 The cotton fibre was first figured and published by Mr. Thom- 
 son, of Clitheroe, in 1834, in his interesting work on the " Mummy 
 Cloth of Egypt," from drawings by Mr. Bauer.* These drawings 
 gave an idea of the flax and of the ripe cotton fibre sufljciently 
 true for Mr. Thomson's purpose ; but in many respects they were 
 most inaccurate. When, some time afterwards, the defects were 
 pointed out to Mr. Thomson, he employed Mr. Varley, of London, 
 again to subject these fibres to the microscope, and have figures of 
 them engraved, intending, besides, to write a continuation of his 
 memoir on the mummy cloth. This he did not live to complete, 
 but some engravings were made, and published in No. 2 of the 
 " Classical Museum," together with a copy of the first paper. Mr. 
 
 * " Annals of Philosophy," for June, 1834, and "Ann. Ch. Pharm.," for January, 
 1849, Ixix., 128. 
 
UNITES WITH COLOURING MATTER. 
 
 6 
 
 Bauer represented the cotton fibre in the unripe state as a perfect 
 cylindrical tube; and, when ripe, as a hollow cylinder collapsed 
 longitudinally in the middle and twisted. 
 
 The mature cotton fibre is an irregular, partially twisted stem, 
 of about Twuth of an inch at its greatest diameter ; and if we take 
 the middling American at inch long, a cord of |^-inch diameter 
 and 13 feet long would give an idea of its relative dimensions. 
 It is not, however, of equal thickness. Towards the end farthest 
 from the seed it gradually diminishes, in many cases, like the 
 tape-worm, to about one-fifth of its greatest diameter ; and 
 there its form is cylindrical and straight. In other cases the 
 tapering is not nearly so great. The apex is always rounded and 
 closed. 
 
 Under the microscope the walls of these tubes do not exhibit 
 openings of any kind which can be taken for lateral passages ; but 
 it is a well-known property of vegetable membrane that fluids 
 pass through it with great facility, though no visible pores or 
 apertures can be detected in it. 
 
 Substances applied to cotton as dyes, or for the purpose of 
 attracting dyes, become fixed in the cotton fibre in two different 
 ways.* 
 
 I. They are attracted and precipitated from their solutions 
 
 by the pores of the cotton. Or, 
 II. They enter these pores in combination with an acid or 
 other solvent, and in a state of solution; and are there 
 fixed, not by an effect of porosity, but by the subsequent 
 removal of their solvent, or by other means which render 
 them insoluble in water. 
 
 Class I. — Attraction by Porosity; or, processes depending 
 * essentially upon attraction of surface. I shall describe, as 
 an example, — 
 
 The Indigo Dye. — When a pound of finely divided indigo, mixed 
 with a hundred and fifty pounds of cold water, is kept for some 
 time in contact with hydrated protoxide of iron and quicklime, 
 the indigo is gradually dissolved, and there is formed an olive- 
 yellow solution, from which the indigo may be reproduced and 
 
 * Pigments and other colouring matters which are fixed upon cotton by means 
 of albumen, oils, &c. , are not here treated of. 
 
6 
 
 ON THE MANNER IN WHICH COTTON 
 
 precipitated in its original blue state by oxidation, through 
 exposure to the atmosphere. 
 
 When a piece of cotton cloth is immersed in a solution of any 
 salt, or other substance which is indifferent to it, the solution is 
 imbibed by the ordinary hydrostatic capillary force; and when 
 the cotton is withdrawn, the same quantity of salt adheres to it 
 whether the period of immersion be long or short. But when a 
 similar piece of cloth is dipped in the solution of indigo just 
 described, there is also exercised a power of decomposition and 
 precipitation by which the indigo is gradually attracted to the 
 cotton from the solution around it, so that, if the immersion be 
 continued for a quarter of an hour, it becomes loaded with ten 
 times as much indigo as another piece which has been withdrawn 
 immediately after its immersion. If successive portions of cotton 
 be employed, the solution becomes robbed in this way of all its 
 indigo. Before exposure to the atmosphere (which, by oxidizing, 
 restores its blue colour) the indigo is attached to the fibre in its 
 yellow insoluble state. 
 
 The force here exerted appears to be analogous to that which 
 enables charcoal and dried wood to precipitate bodies in similar 
 circumstances; and there seems no greater reason for supposing 
 that a chemical union has taken place in the one case than in the 
 other. 
 
 Other examples of the first class will be given after the second 
 has been described. 
 
 Class II. — Processes where the mordant or dye has entered and 
 become fixed within the fibre, independently of attraction. 
 Example : Madder colours, with mordants of acetic solutions 
 of iron or alumina. 
 It is proper here to premise that no substance can be made to 
 adhere effectively to cotton which has not originally been applied 
 to it in a state of solution. However impalpable the insoluble 
 powder or the precipitate which we employ, mixing it with gum 
 or other mucilage, and so placing it upon the cloth, it cannot be 
 fixed; — the washing which removes the gum removes also the 
 insoluble matters which accompanied it. 
 
 The substance which produces the madder purple colour upon 
 cotton is a lake, or black substance, which b}^ great attenuation 
 becomes purple. Being insoluble in water, it cannot, as we have 
 
UNITES WITH COLOURING MATTER. 
 
 7 
 
 seen, be made, ready formed, to attach itself to cotton. But it is 
 composed of two ingredients — viz., oxide of iron, which can be 
 dissolved in water by the intervention of an acid, and the colour- 
 ing (or rather colourable) matter of madder, which is itself soluble 
 in water. The method is, first to apply the iron in solution, and 
 when that is rendered insoluble in the fibre, to place it in the 
 solution of madder, which, passing also through the membrane, 
 comes in contact with the iron within, and there forms with it the 
 insoluble compound. 
 
 The iron employed in this way to attract the dye-stufi* is 
 called a mordant. Metallic iron dissolved in pyroligneous acid 
 is the particular preparation used as a mordant for a madder 
 purple dye. It is essentially an acetate of protoxide of iron. 
 When a solution of this salt is applied to cotton, it is received 
 into the pores of that body by common capillary attraction ; but 
 its oxide is not appropriated by the fibre, as indigo is. A stream 
 of water being sufficient to remove it, it is evident that cotton 
 has not the power of separating the protoxide from its acid, even 
 when that acid is the acetic. But if, after the solution of pyro- 
 lignate of iron has been applied to the cotton fabric, it be allowed 
 to dry, and then exposed to an atmosphere slightly warm and 
 moist, the acetic acid gradually escapes, in proportion as oxygen 
 is absorbed, and the iron, in the state of an insoluble hydrated 
 peroxide, remains. 
 
 But as insoluble matters cannot pass into the interior of the 
 fibre from without, so, when a substance has once entered that 
 fibre or its pores in a state of solution, and has become precipi- 
 tated within these enclosures, it is equally impossible for the 
 precipitate to return. It is entrapped within the body of the 
 fibre, or its tissue, and becomes fixed there. 
 
 It will be seen that this precipitation and imprisonment of the 
 oxide is no case of attraction, either chemical or mechanical. It 
 is a case of chemical decomposition, in which the cotton acts the 
 part only of a vessel to receive the materials. The same solution, 
 spread thinly over glass, and placed in similar circumstances, 
 undergoes the same decomposition. The greater subdivision of 
 the salt may, indeed, in the case of the vegetable fibre, accelerate 
 its decomposition; but a slight elevation of temperature in the 
 other case is sufficient to compensate for the greater exposure in 
 the cotton fibre. 
 
3 
 
 ON THE MANNEE IN WHICH COTTON 
 
 The inferences that may be drawn are, — 
 
 Is^. That the pores, whether larger or smaller, receive the solu- 
 tion of iron by ordinary hydrostatic capillary attraction. 
 
 2d. That while within these cavities or vessels, whatever be 
 their form, the salt is peroxidized and decomposed; and 
 
 Sd. That the result of the decomposition — an insoluble oxide 
 — is left there by the volatile acid, which, by its solvent power, 
 had enabled it to take that position. 
 
 In pursuing the process, the cloth which is thus furnished with 
 its mordant of iron is first passed through hot water, with certain 
 precautions which need not here be detailed, and washed, to 
 remove any unfixed mordant; after which it is ready to be dyed. 
 For that purpose it is made to traverse for a couple of hours a 
 vessel of water, throughout which madder in powder has been 
 distributed. Heat being gradually applied, the colouring matter 
 of the madder dissolves, slowly indeed, and Ify little at a time, 
 but, being soluble, it has no difficulty in passing into the fibre 
 which encloses the oxide of iron, and there uniting with it. The 
 resulting compound is the purple lake. 
 
 This last step of the process is a purely chemical one, in which 
 the oxide of iron forms a true combination with the colourable 
 matter of the madder, the cotton attenuating the iron to a pro- 
 digious extent, and placing it in circumstances the most advan- 
 tageous for forming a lake with this dye-stuff! 
 
 Having thus received the dye, the fabric is subjected to a 
 process of soaping in boiling water, by which its colour is much 
 reduced in depth and brightened in shade. 
 
 Having formed the idea that no portion of the dye but that 
 which is held most firmly within the cotton fibre could bear the 
 severe soaping operations to which this class of prints is sub- 
 jected, I formerly described a piece of dyed cotton as consist- 
 ing of a set of colourless bags, containing coloured substances, 
 and in so far resembling the cells of natural flowers; but the 
 statement was incomplete, and the proof rested to some extent 
 upon theoretical considerations, until the opportunity occurred of 
 observing the effects of the same process upon " dead cotton^ 
 And as the behaviour of this substance, in such circumstances, 
 throws much light upon the question we are now discussing, T 
 shall proceed to give some account of it. 
 
 Dead Cotton. — In May, 1848. Mr. Thomson, of Primrosf^. 
 
UNITES WITH COLOURING MATTER. 
 
 9 
 
 received from Mr. Daniel Koechlin, of Mulliouse, some specimens 
 of a purple-ground printed calico, each of them containing a por- 
 tion of cotton which was white, although it had been subjected to 
 the same treatment by which the rest of the cloth, and even the 
 threads which crossed the white ones, were uniformly dyed. The 
 white part of the thread was usually thicker than the rest, and 
 little more than a quarter of an inch long. The whole fabric had 
 been thoroughly bleached before printing, so that its white thread 
 contained no grease or other impurity that could have mechani- 
 cally resisted the mordant. Mr. Koechlin at the time suggested 
 that it might consist of unripe cotton, and might want the 
 hollow of the perfect fibre. Both in France and in this country 
 it is called " dead cotton^ Mr. Thomson kindly transmitted 
 me the specimens for examination, and my first observations 
 on the subject were published in 1849, in the " Proceedings of 
 the Philosophical Society of Glasgow."* 
 
 On placing it under the microscope, I found the cotton which 
 had thus resisted the dye to consist of very thin and remarkably 
 transparent blades, some of which were marked or spotted, while 
 others were so clear as to be almost invisible, except at the edges. 
 These fibres are readily distinguishable from those of ordinary 
 cotton by their perfect flatness, not having the vestige of a cavity 
 even at tlie sides, and by their uniform as well as great trans- 
 parency. They are broader than the usual fibre, and they show 
 numerous folds, both longitudinal and transverse. 
 
 On afterwards searching among the motes, or hard portions, 
 called droppings, which are rejected by the picking machine in the 
 preparation of raw cotton wool for spinning, I found what proved 
 to be the same fibre, in the form of a small matted tuft of a 
 shining silky lustre, several of which enclosed the fragment of a 
 seed, or perhaps an imperfectly formed seed. The fibres are short, 
 and have little tenacity. Small tufts, however, do occasionally 
 pass the sifting process of the picking machine ; and then these 
 fibres, being too short to be teased out in the carding engine, or 
 properly drawn into threads in the subsequent operations of 
 cotton-spinning, remain as minute lumps, or knots, entangled 
 among the fibres of the thread of good cotton, giving great annoy- 
 ance to the spinner of fine yarns, and appearing as white specks 
 upon a woven and dyed fabric. 
 
 In the month of June, 1862, I was favoured by Mons. Le Play, 
 
 * Vol. iii., p. 61 ; also " Philosophical Maofazinc," ^^ol xxxv., November, 1849. 
 
10 
 
 ON THE MANNER IN WHICH COTTON 
 
 at the request of Dr. Playfair, with a number of specimens of 
 the dried fruit of the cotton plant in various stages of maturity, 
 from the Algerian collection in the International Exhibition, and 
 was thereby enabled to ascertain the real nature of the peculiar fibre. 
 
 1st. I found that the contents of every capsule which had not 
 opened, and of those which had but slightly opened in drying 
 after having been cut from the plant, consisted in each cell of a 
 closely packed solid mass, without elasticity, which, however, 
 could be teased out into fibres, presenting under the microscope 
 the flat, glassy, broad appearance exhibited by the dead cotton 
 fibre already mentioned. 
 
 2d. In capsules more fully developed, the ordinary cotton ap- - 
 peared where it had pushed its way outwards, and assumed the 
 woolly form ; while the seeds in the same cell nearer the calyx, and 
 still confined, were clothed with the solid mass, chiefly consisting 
 of the glassy though somewhat less transparent fibre. 
 
 Sd. The glassy fibre frequently appeared in pods of ripe cotton, 
 in spots where discoloration showed that an injury had taken 
 place before maturity. 
 
 4ith. Small portions, glazed and satiny, which proved to be dead 
 cotton, though not discoloured, were seen, but rarely, on the outer 
 part of the wool of a well-clothed ripe cotton seed. 
 
 5th. We must add to these sources of dead cotton the small 
 glazed tuft already mentioned as found in cotton bales, and 
 appearing to have separated from the stem through which it de- 
 rived nourishment, while the other seven or eight seeds in the 
 same cell went on to maturity. 
 
 6th. The glassy fibre is broader — often one-half broader — some- 
 times even twice as broad as the ripe fibre. 
 
 7th. A distinct gradation is perceptible under the microscope in 
 different specimens, from the pure and spotless glassy fibre in the least 
 mature cotton, to the comparatively dense and opaque ripe cotton. 
 
 I shall describe four of these varieties of the cotton fibre as 
 they are found in the dried state in commerce. I shall afterwards 
 describe their behaviour with mordants ; and, in doing so, I have 
 to acknowledge my obligations to my assistant, Mr. M'Farlane, for 
 his valuable co-operation in the preparation of materials and dyes. 
 
 1. Mature cotton. 
 
 2. A cotton ^vhich I shall call three -fourths ripe. 
 
 3. Half-ripe cotton. 
 
 4. The youngest cotton found in commerce. 
 
UNITES WITH COLOURING MATTER. 
 
 11 
 
 Mature Cotton. 
 
 Plate I. gives a view of various forms of cotton fibre in a state 
 of maturity, mounted dry, and magnified about 400 diameters. 
 They have often been represented before, and are produced now 
 principally that they may be compared with the unripe fibres 
 shown in Plate II. 
 
 After numerous attempts, which were but partially successful, 
 to observe the interior of the cotton fibre, I was enabled, by the 
 instructions of Mr. Kennedy, of Glasgow, to procure in great per- 
 fection abundance of transverse sections, exhibiting in the most 
 interesting manner the nature of its contents. 
 
 From the drawings of these sections in Nos. 1 and 2, Plate III., 
 it will be observed that the cotton fibre is not a hoUow tube or 
 bag filled with air, as it has been hitherto represented to be, but 
 a nearly solid stem, with a very small cavity in the centre. A 
 few of these slices are nearly circular, representing cylinders, 
 but the greater part are irregularly oblong or oval shaped, with 
 a central marking or aperture of corresponding form. They 
 resemble the liber fibres of hemp or flax, as these have been 
 delineated by Mr. Tuffen West in the "Micrographic Dictionary." 
 
 Unripe Cotton. 
 
 The youngest or least ripe of the fibres of cotton, as it is im- 
 ported, are those of the small glazed tuft found among the 
 rejected portions of cotton wool in its preparation for spinning. 
 They are identical wdth the white specks I have already often re- 
 ferred to, which occur upon dyed fabrics, and to which the name of 
 dead cotton has been given. Plate II. contains specimens of these 
 fibres, viewed lengthways and mounted dry. In glycerine jelly 
 they appear still more transparent, and in Canada balsam they 
 are scarcely distinguishable from the surrounding medium. At 
 No. 8, Plate III,, are transverse sections of the youngest fibres as 
 mounted in glycerine jelly. They are so thin that they can only 
 be made to stand upright where the section is bent. In many of 
 them the sides adhere to each other so firmly that no line can be 
 detected to mark a division between the walls, for even the rough 
 treatment of the knife does not always serve to separate them. 
 Others, however, have a slight mark between the two outlines, 
 
12 
 
 ON THE MANNER IN WHICH COTTON 
 
 chiefly at the end of the section, and then they somewhat resemble 
 the thinnest of the half-ripe fibre. 
 
 Plate II. contains also side views of the cotton which I propose 
 to call half-Tijpey or in the second stage of maturity, mounted dry. 
 This is the wool contained in an Algerian pod pulled green, and 
 slightly open when dry, and I have found it the most interesting of 
 the unripe cottons for the purposes of this inquiry. No. 4, Plate 
 III., shows the microscopic appearance of transverse sections of 
 this half-ripe cotton mounted in glycerine jelly. A line is always 
 to be observed in the centre, pointing out that the flat blade con- 
 sists of two walls, and that it is a flattened bag or tube. 
 
 I have found a distinctly marked third stage, which I have 
 called three-fourths ripe, in a pod of Orleans cotton of the same 
 external appearance as the Algerian pod containing the half-ripe 
 wool. The walls of this fibre are considerably and uniformly 
 thickened, but the fibres themselves are comparatively flat, and 
 none of them are cylindrical. It is represented in transverse 
 section at No. 6, Plate III. 
 
 Commencing with the thin and flat blade (of dried cotton), 
 whose section shows no apparent opening, the ripening of the fibre 
 thus goes on, by the gradual thickening of its walls, until it 
 assumes the more or less cylindrical and solid form of ripe cotton, 
 exhibited in Plate III., Nos. 1 and 2. On first observing that fact, 
 there did appear to me some authority for applying the generally 
 understood principle of a formation of new and separate matter in 
 the process of ripening ; but I am inclined to doubt that explana- 
 tion, after having observed that the substance of the thin wall, as 
 it exists in the half-ripe fibre, and after being removed from the 
 plant and dried, is itself, as I shall now relate, capable of expan- 
 sion, so as not only to give the fibre the cylindrical form, but to 
 fill up a great part of the interior of the cylinder. 
 
 Of the Half-ripe Cotton artificially Expanded. — When the half- 
 ripe but stiU perfectly flat and thin dried fibre (No. 4, Plate III.) is 
 soaked in a solution of caustic soda of specific gravity ] 300 or 
 1*400, it at once assumes the round solid form of ripe cotton, 
 differing from the naturally matured fibre only in being smaller, 
 more generally cylindrical, and in having a larger aperture in the 
 centre. It is represented at No. 5, Plate III. 
 
 To produce tliis change, it is best to soak the unripe fibre in 
 water before dipping it in the strong caustic soda, without which 
 
UNITES WITH COLOURING MATTER. 
 
 13 
 
 precaution it is apt to become matted together, and less fit for 
 subsequent operations. After the soda, it is washed in water, 
 then treated with a weak acid, and again washed. 
 
 It is well known that mercerized cotton, as the ordinary cotton 
 wool when so treated has been called, retains, after washing, none 
 of the alkali that had swelled it. The increase of magnitude which 
 the half-ripe fibre thus acquires is due, therefore, altogether to an 
 expansion of the cell wall, or a separation from each other of the 
 inner and outer surfaces of that wall. 
 
 The youngest fibres do not seem to become rounded by caustic 
 soda. 
 
 It may now appear not improbable that, by the natural process 
 of ripening, an eff'ect is produced similar in character to that which 
 is given to the unripe fibre by artificial means, and that the natu- 
 ral expansion may be ascribed, not to the importation of a new 
 kind of matter, coating the interior of the original cell wall, but to 
 a strengthening and rendering elastic of the membrane already 
 existing of the wall itself, so as to produce the separation from 
 each other of the cells or laminae, or other structure of which it 
 must consist. 
 
 The singular effect of strong alkaline solutions upon cotton 
 woven fabrics was discovered by Mr. John Mercer, and patented 
 by him in 1850. From the transverse section of the mature fibre 
 thus altered, as shown at No. 3, Plate III., it will be seen that the 
 action of the soda completes the cylindrical form of that fibre, at 
 the same time greatly enlarging its volume, and filling up almost 
 entirely the central cavity. The twisting of the fibre is also much 
 increased, as shown at B, Plate IV., and there is a consequent 
 shortening of it, sufficient to account for the shrinking in length 
 and breadth, and the thickening of any woven fabric which is 
 made to undergo the mercerizing process. Diagonal lines are 
 sometimes seen in these ripe mercerized fibres, giving the im- 
 pression of a spiral structure ; but they are evidently the creasing 
 or corrugating effect of extreme twisting. Diagonal lines, appar- 
 ently also from the effect of creasing, may occasionally be detected 
 in the original fiat unripe fibre, Plate II. They seem to cross 
 each other where the two sides of the fibre can be viewed in the 
 same focus. 
 
 I have made many attempts, by the use of Ross's J, and Powell 
 & Lealand's Ts^-inch object glasses, to discover how the wall is 
 
ON THE MANNER IN WHICH COTTON 
 
 built up in the mature cotton fibre, but without success. Some 
 concentric rings in cross sections, sketched in Plate VII., are apt 
 to be mistaken for internal structure. They will be recognized 
 as an optical effect, obtained by placing the illuminator out of 
 focus, and especially when using gas-light. 
 
 Mordanting with the Acetates of Iron and of Alumina. 
 
 Plate IV., A, shows side views of the ordinary cotton fibre 
 which has been made to imbibe the pyrolignate of iron in the 
 manner described at page 7, and then dyed in madder and soaped. 
 The compound of madder and iron which forms this purple dye 
 is so uniformly distributed over the cellular matter which it 
 colours, that we can scarcely detect any point of the full-grown 
 fibre which it does not pervade. On the other hand, although 
 the greater part of the dark markings of these fibres are due to 
 irregularities of the surface, corresponding with those of the undyed 
 fibres, Plate I., there are other markings to be found in the centre 
 of almost every fibre, which, after examining the cross sections 
 of the same preparation at D, Plate VIIL, and observing the clots 
 which occur in the centre of many of them, will readily be 
 recognized as accumulations of the black lake of madder and 
 iron. 
 
 We must assume that in this process every cavity of the fibre 
 has been filled with the iron solution, and we know that when 
 that solution is evaporated to dryness, the acetate is gradually 
 decomposed and converted into the hydrated peroxide of iron, 
 which, by combining with madder, becomes the black or purple 
 lake already alluded to. The cavity in the centre (D, Plate VIII.) 
 is sufficiently capacious, and admits solution enough to exhibit to 
 us this lake in the form of a bulky black clot collected into one 
 mass, altogether separate from, and sometimes scarcely touching 
 the bag which contains it. It is not too much to infer that, in 
 each of those innumerable though invisible cavities which exist 
 throughout the body of the fibre, a similar process goes on, and that 
 each enclosure, after imbibing its fill of the iron solution, contains 
 first a parcel of the dried acetate, which soon becomes a clot of 
 the hydrated peroxide, as distinct in its degree from the wall which 
 surrounds it as that which we are enabled to see in the central 
 cavity. I need not repeat that the substance which is seen under 
 
UNITES WITH COLOURING MATTER. 
 
 15 
 
 the microscope to be black in the central opening is the same 
 with that which, in a state of still greater subdivision, gives a 
 purple colour to the body of the fibre. At B, Plate IV., and at 
 E, Plate VIII., are shown the effects of the same process applied 
 to mature cotton pre viously mercerized. When acetate of alumina 
 is employed, instead of the iron solution, the only difference in the 
 appearance is the substitution of red for purple. 
 
 Plate VI,, No. 1, shows transverse sections of the ordinary 
 cotton fibre mordanted with acetate of alumina and dyed red. In 
 depth of colour they are extremely unequal, of which the chief 
 cause, no doubt, is the variety in the thickness of the slices ; but 
 there are always present also fibres comparatively unripe; and 
 even well-formed fibres differ in the amount of the colour they 
 receive. This inequality is nowhere more remarkable than in the 
 cross sections and the side views of the most beautifully dyed 
 turkey-red yarn, notwithstanding its perfectly uniform appear- 
 ance to the naked eye in the aggregate. 
 
 Deep red specks, which are evidently clots of the red lake of 
 alumina and madder, are seen occasionally occupying the other- 
 wise void space in the heart of the fibre mordanted with acetate 
 of alumina ; but these occur to a much greater extent in cotton 
 mordanted with mono-muriate of alumina, as will presentlj^ 
 appear. 
 
 No. 2, Plate VI., shows the appearance of a fibre mordanted 
 with acetate of alumina, and not fully dyed — that is, a fabric to 
 which a sufiicient quantity of madder had not been given to 
 saturate all the alumina wliich it had received. It is only as the 
 outer portions of the mordant become saturated that they allow 
 the madder to pass inwards ; and until that takes place the fibre 
 remains uncoloured in the centre. 
 
 Whether Thickening impedes the Entrance of a Mordant into 
 the Cotton Fibre. — I shall here remark, that whether the mordant 
 be applied to a piece of calico in the fluid state, or made nearly 
 solid with an amylaceous or other thickening substance, it finds 
 no difficulty in traversing the whole fibre. I have examined 
 threads which have been soaked with a solution of acetate of 
 alumina altogether fluid — comparing them with other threads 
 which had been printed with the same solution made into a thick 
 mucilage with gum-arabic, and with others again made into a paste 
 with the flour of wheat, so thick that when applied to one side 
 
16 
 
 ON THE MANNER IN WHICH COTTON 
 
 of a piece of bleached calico it did not pass through to the other 
 side ; and on examining transverse sections of dyed specimens of 
 these fibres, I found that such of them as had been reached l^y the 
 mordant were in all these cases equally penetrated. The white 
 centre was always due to a want of dye-stuff. 
 
 I am glad to be able to establish this fact — an apparent impos- 
 sibility, — which has been a stumbling-block to several of my 
 friends. It is difficult, no doubt, without direct examination, to 
 conceive of a capillary power so great, or that a solution rendered 
 so tenacious as to require considerable force to drive it through 
 an opening of an inch in diameter, should be able, without any 
 pressure at all, to pass into the interior of the cotton fibre, the 
 pores of which cannot be detected by the most powerful micro- 
 scope. In the latter case we have reason to believe that the solu- 
 tion leaves its farinaceous accompaniment at the entrance, and 
 passes on; but a similar effect cannot be so readily supposed 
 in the case of a mucilage. 
 
 Plate VII., B. — The youngest fibre bleached and mordanted 
 with acetate of alumina, then dyed with madder, and afterwards 
 soaped. A. The youngest fibre unbleached and similarly treated. 
 
 Plate v., B. — The half-ripe fibre unbleached, mordanted with 
 acetate of alumina, dyed with madder, and soaped. When 
 bleached, a great many fibres of the half-ripe cotton remain alto- 
 gether colourless after having undergone the dyeing process, and 
 the whole are much paler than the unbleached. C. The same 
 half-ripe fibre bleached and mercerized, and then similarly treated. 
 
 The fibre three-fourths riije, whether bleached or unbleached 
 (judging from the small specimen at my command), takes a dye, 
 after mordanting with acetate of alumina, little, if at all, inferior 
 to the mature cotton. 
 
 Mordanting with Mono-Muriate of Alumina. 
 
 To prepare this solution, the sulphate of alumina (known as 
 concentrated or cake alum) is decomposed by chloride of calcium, 
 and the fluid purified from iron by means of ferro-cyanide of 
 potassium. For that purpose a solution of the ferro-cyanide is 
 added to the impure muriate of alumina so long as any precipitate 
 is formed ; and as the deposit does not separate by filtration, it is 
 left to subside. Small floating particles, however, remain after 
 the principal part of the prussian blue has gone down, and these 
 
UNITES WITH COLOURING MATTER. 
 
 17 
 
 are separated hy albumen, a very small quantity of which collects 
 them in the usual way of clarifying. The product is then divided 
 into three equal parts. Two are decomposed by ammonia, and 
 the precipitated alumina, after being filtered and washed, is added 
 to the third portion, which re-dissolves it. 
 
 The mono-muriate of alumina thus formed has usually been 
 employed for these experiments of a specific gravity 1-125, at 
 which it is strong enough to be converted into a thick magma by 
 the addition of ammonia. The cotton is left to soak several 
 hours in this solution, after which it is washed in water, dyed in 
 madder, and soaped. I shall describe the action of this compound 
 upon the various fibres more particularly than its industrial 
 importance would seem to merit, because it represents what 
 appears to me to be an additional character not before recognized 
 in the action of mordants upon cotton. 
 
 The Youngest Fibre, when bleached, takes no alumina from the 
 solution of the mono-muriate. I have given a sketch, however 
 (D, Plate VII.), for comparison, of fibres which have been sub- 
 jected to the process. The same fibre unbleached (C, Plate VII.) 
 takes exceedingly little. Many of the unbleached fibres remain 
 destitute of colour, and others, probably more mature, take up a 
 very small quantity of alumina, and they all take it in the pecu- 
 liar way there represented — a layer of alumina between the walls 
 of the fibre. 
 
 It is the cotton, however, in what I have called the half-ripe 
 stage, that furnishes the most remarkable example of the peculiar 
 manner in which alumina is deposited in the fibre by immersion 
 in the basic solution of that earth. I have endeavoured to pic- 
 ture its microscopic appearance in Plate V., A, the fiat fibres being 
 the same as those shown without dye in Plate II. The same 
 preparation is represented in transverse section, Plate VI., No. 7. 
 Unlike the youngest fibre, the half-ripe ceUs are in such a state of 
 growth that their walls readily separate to admit of the introduc- 
 tion of the fluids in which they may be immersed. When after 
 two or three hours of such immersion the cotton is washed in cold 
 water, a quantity of hydrate of alumina is found separated from 
 its solution, and retained by the fibre. 
 
 The circumstances are these : — The young fibre, an empty flat- 
 tened bag, is placed in the basic solution, which soaks and more 
 or less completely fills it. It is then put into water, or what Mr, 
 
 B 
 
18 
 
 ON THE MANNER IN WHICH COTTON 
 
 Graham has called an atmosphere of water. The bag or cell wall 
 acts the part of the septum described by him in experimenting on 
 similar fluids, and the salt is decomposed. The crystalloid por- 
 tion — the muriate of alumina — diffuses through the septum into 
 the surrounding water, and the colloid hydrate of alumina re- 
 mains within, gelatinized, no doubt, either spontaneously or by 
 the traces of saline matter which are always present. The fibre 
 itself, through which the aluminous solution has passed and re- 
 passed, retains no trace of the presence of alumina. It may be 
 called a microscopic dyalizer. 
 
 Many of these fibres seem as if a thin film of alumina had 
 originally been deposited within them over their whole length 
 and breadth ; and in all of them there is evidence of the deposit 
 having shrunk to a great extent in both directions in the process 
 of dyeing. It is remarkable that the alumina should adhere so 
 slightly to the membrane which contains it as thus to shift with- 
 out difficulty from one part of it to another in the act of shrink- 
 ing. The same remark applies to the clots found in the centre of 
 full-grown cotton, whether the mordant of iron or alumina be 
 applied from an acetic solution, or as in the case before us. 
 
 By previous bleaching of this fibre the quantity of alumina 
 which it can receive is much diminished ; but enough is admitted 
 to form with it a most interesting microscopic object. In all cases 
 the cell remains beautifully colourless and crystalline, enclosing 
 its flakes of carmine ; and the variety in the distribution of these 
 flakes is infinite. 
 
 Along with these drawings are placed representations (D, Plate 
 V.) of the same half-ripe fibre in the unbleached state, and swelled 
 out by strong soda, previous to receiving the mordant ; and they 
 form examples not less remarkable of the action of the cotton fibre 
 upon this salt. The opening in the centre appears to have been 
 entirely filled with the clot, which (as it does with other fibres) 
 has shrunk both in length and breadth in the subsequent pro- 
 cesses. In the corresponding transverse sections (Plate VI., No. 8) 
 pieces of the clot may often be seen scattered over the slide, 
 having dropped out of their places, and lying near the aperture 
 which had contained them. 
 
 When the half-ripe cotton is bleached previous to being mer- 
 cerized, and then mordanted with mono-muriate of alumina and 
 dyed (E, Plate V.), not only is the body of it much paler than the 
 
UNITES WITH COLOURING MATTER. 
 
 19 
 
 unbleached, but no such masses of colour reach the centre. In 
 some instances a colourless fibre encloses a quantity of the red lake. 
 
 The effect of bleaching, in diminishing the power of cotton 
 to receive mordants, is to be attributed to the boiling in weak 
 solutions of quicklime and carbonate of soda to which the cotton 
 is subjected, and not to the hypochlorite of lime, which is very 
 sparingly used in the process of bleaching, nor to the sulphuric 
 acid, which does not affect the mordanting. Hot alkaline solu- 
 tions, though weak, mat together the young fibres, and close 
 their passages against the admission of mordants. They have a 
 similar tendency when applied to riper cottons, while that of strong 
 caustic alkaline solutions is, as we have seen, to open them. 
 Hypochlorites in excess also open the pores of ripe cotton, and, by 
 enabling them to admit more mordant, greatly increase the inten- 
 sity of the dye. 
 
 At No. 8, Plate VI., are cross sections of ordinary cotton, mor- 
 danted with mono-muriate of alumina. Like the unripe fibres, 
 they show that tlis salt had passed into the centre of the tube, 
 and had been there decomposed- 
 
 Mordanting with Oxychloride of Iron. 
 
 The sesquichloride of iron, with the addition of an equivalent 
 of sesquioxide of iron, forms a solution (Feg CI3 -|- Fcg O3) cor- 
 responding, in its action upon the cotton fibre, with the mono- 
 muriate of alumina. It gives up its peroxide in a similar manner, 
 and thus forms a mordant which, when dyed with garancine, pro- 
 duces upon the cotton a black or a purple colour, in proportion as 
 the quantity of oxide which it has received is greater or smaller. 
 
 The oxychloride may readily be obtained by adding ammonia 
 to 100 parts by weight of nitrate of peroxide of iron of specific 
 gravity 1-55, washing the precipitate, and re-dissolving it in 37^ 
 parts hydrochloric acid of specific gravity 1-17. 
 
 The cotton is steeped for a couple of hours in this solution 
 reduced to the specific gravity of from 1*03 to 1'07; after which 
 it is placed in water, and washed before being dyed. The dye 
 for this preparation of iron is garancine, and it does not require 
 soaping. 
 
 The effects are shown in Plate VIII. The unripe fibre, A and A2, 
 acts the part of a membrane or dyalizer for decomposing the solution 
 
20 
 
 ON THE MANNER IN WHICH COTTON 
 
 when placed in water, and as a bag for retaining (without being 
 itself coloured by) the precipitated oxide, or its purple lake. The 
 same fibre, B and B2, while it has an equal power of admitting the 
 solution into its interior, has likewise, by the mercerizing process, 
 had cavities or enlarged pores formed in its wall ; and each of 
 these appears to have taken its propoi'tion of the iron, so as to 
 produce, when dyed, a purple tube — the larger quantity of iron 
 in the centre giving a black. With the ripe fibre, C and C2, a 
 quantity of the oxide has been retained in the hollow centre, 
 and but little by the walls themselves. 
 
 I shall now enumerate a few additional processes which belong 
 to the two different classes, of which I have already given examples. 
 
 Class I. — A. The indigo dye has been already described as the 
 type of those which cotton attracts by its porosity. 
 
 B. Bodies, such as safilower, turmeric, &c., which, like indigo, 
 are colours per se. 
 
 C. Bodies which, while they attach themselves to cotton as 
 indigo does, are not, like indigo, possessed of colour, but have the 
 power of attracting and uniting with other bodies, and of forming 
 with them coloured compounds. 
 
 a. Tannin is much employed in this way. When cotton is 
 immersed for some time in a wwm decoction of gall-nuts, or in a 
 solution of tannic acid, a considerable quantity of tannin is depo- 
 sited in the fibre; and if cloth so charged be subsequently im- 
 mersed in the solution of any metal with which tannin is capable 
 of uniting, it is attracted and deposited along with it in the fibre. 
 In this way a black dye is often produced with nitrate of iron. 
 The metallic solution becomes in that case the dyeing material, 
 and the vegetable body the mordant. Tannin attracts also the 
 violet colouring matter of Perkin. 
 
 b. Oxide of lead is readily fixed upon cloth on the same prin- 
 ciple. The cotton fibre, by mere immersion in the fluid, separates 
 lead from its solution in lime or in soda, as charcoal does; and 
 when cloth so loaded is treated with a chromic salt, a yellow chro- 
 mate of lead, or an orange dichromate, is produced. By treating 
 leaded cloth with protosulphate of iron, we obtain, instead of 
 oxide of lead, a deposit of peroxide of iron and sulphate of lead ; 
 and if the sulphate, by immersion in ammonia, be reconverted into 
 oxide, it becomes capable of fixing another equivalent of iron, and 
 
UNITES WITH COLOURING MATTER. 
 
 21 
 
 so on as often as we alternate the immersions in ammonia and 
 sulphate of iron. It is remarkable that leaded cloth attracts 
 scarcely any iron from the red salts of that metal. 
 
 D. Bodies which form mordants for attracting and uniting 
 with other mordants. 
 
 a. Tannin fixed in the manner just described is employed to 
 attract tin from an acid solution of tin, and in this way a com- 
 pound mordant is produced which is the most suitable, by sub- 
 sequent dyeing in Lima or Brazil wood, for producing what is 
 termed a fancy red — a dye at one time much used as an imitation 
 of turkey-red. 
 
 h. As subsalts of iron by themselves do not advantageously 
 deposit their excess of oxide in the cotton fibre when it is im- 
 mersed in their solutions, the intervention of tin is employed. 
 When cotton is soaked in a cold and weak solution of oxy- 
 chloride of tin, or still better, in a mixture of the bichloride and 
 protochloride, and when, after this preparation with tin, it is 
 immersed in oxj^chloride or oxy nitrate of iron, a large quantity 
 of iron is deposited, in the state, I presume, of a stannate of iron. 
 This mordant, when dyed in ferro-prussic acid, forms a prussian 
 blue of the greatest richness and brilliancy. 
 
 Varieties of Class II. — A. The acetate of iron has already 
 been mentioned as an example of this class. 
 
 B. Acetate of alumina acts in a similar manner, 
 
 C. From the manner in which the mono-muriate of alumina 
 acts upon cotton, it is evident that the process in which it is 
 employed must also be placed in the 2(i Glass, as defined at page 
 5 of this memoir, and not in the Is^ Class. The alumina is not 
 attracted by the pores of the tissue, as indigo is. When dissolved 
 in the termuriate, it passes into the interior of the fibre through 
 these passages by ordinary capillary force, and when the fibre, 
 with its contents, is subsequently placed in water, the alumina 
 remains in its enclosure, in consequence of the diff*usive character 
 of its solvent. 
 
 D. If we wish to fix upon cotton other oxides, as those of 
 copper, manganese, or chromium, which do not spontaneously, or by 
 difiusion, part with the acids wliich dissolve and carry them into 
 the fibre, we must employ an alkali to precipitate them there. The 
 acetate and nitrate of lead being also not spontaneously decom- 
 posible, cotton which has been charged with these salts has to be 
 
22 
 
 ON THE MANNEE IN WHICH COTTON 
 
 treated with ammonia or a carbonated alkali, or a sulphuric salt, 
 to fix the lead in the fibre. Aluminated potash is, in the same 
 way, treated with sal-ammoniac ; the stannate of soda, with weak 
 sulphuric acid; the sulphates and chlorides of manganese and of 
 iron, by caustic soda ; the salts of oxide of chromium, by carbonate 
 of soda, (fee, &c. 
 
 E. Steam colours, where mordant and dye mix together without 
 combining. The mixture, therefore, retains the solubility of its 
 ingredients, and enters the fibre as readily as either would do in 
 a separate state. Heating in steam of boiling water determines 
 the union and consequent precipitation within the fibre where 
 the mixture had been deposited. Decoctions of those vegetable 
 colouring matters which form lakes with aluminous salts are 
 chiefly here referred to. 
 
 F. Steam Prussian Blue. Ferro-prussic acid applied to cotton 
 and subjected to steam causes a deposition of white proto-cyanide 
 of iron, which is changed by the air into prussian blue. 
 
 I have thus endeavoured to illustrate two principles, on one or 
 other of which dyes can alone enter the cotton fibre. But dyes 
 are not always confined to the interior of the fibre. Previous to 
 the soaping which follows the application of the madder in the 
 madder-purple process, a considerable quantity of the dye remains 
 less firmly fixed than the rest; and in the case of the numerous 
 class of colours which do not require the soaping process, that 
 external dye is allowed to remain. Most colouring matters would 
 not bear so severe a cleansing ; and, besides, much richness of hue 
 and velvety aspect would be lost if a portion of them were not 
 left to cover the fibre and its occasional imperfections. All that 
 class of goods which are dyed with garancine, — the indigo dyes, — 
 all colours fixed by steam, and, indeed, the great majority of all 
 prints, are in this situation. 
 
 We can readily conceive of a tissue so subdivided as the cotton 
 fabric having passages less perfectly enclosed than those we have 
 been describing, and yet narrow enough to be capable of harbour- 
 ing more or less securely such insoluble matters as may be left 
 there by an iron or aluminous acetate, during its spontaneous 
 decomposition, and even of exercising to some extent a capillary 
 decomposing power over such a solution as that of indigo. We 
 know, besides, that in many dyes part of the colouring matter is 
 
UNITES WITH COLOURING MATTER. 
 
 23 
 
 attached only by cohesion, for which the spaces between the fibres 
 furnish ample opportunity. But all comparatively external adhe- 
 sions, although of great commercial importance, are only super- 
 additions to the greater amount of dye which is, or ought to be, in 
 all cases fixed within the fibre, on one of the two principles which 
 it has been my object to explain. 
 
 The "dead cotton" is still apparent in most of these dyes. 
 I have observed it principally in the indigo dye, the chrome- 
 orange dye, the aniline-violet fixed with tannin, and in the dyes 
 from the iron and aluminous mordants where these are attached 
 to the cloth by deposition from basic solutions of their salts. By 
 that method of fixing iron and alumina, white specks appear which 
 would not be discernible when the ordinary mordants are em- 
 ployed. But the " dead cotton " is also distinctly visible (more or 
 less tinged) in all garancine dyes, whether chocolate, black, red, 
 purple, or catechu, even when washing with water is the only 
 means employed to cleanse after dyeing; and it appears in all 
 steam colours that are well washed. 
 
 The " dead cotton " does not however refuse all colouring sub- 
 stances. On examining a safilower-pink dye, the " dead cotton " 
 seems to have attracted its full proportion of it, and the same is 
 the case with the prussian blue, which is produced from stannate 
 of iron. By repeated dips in the indigo-vat, too, the " dead 
 cotton " is concealed, if not otherwise dyed. 
 
 EXPLANATION OF THE PLATES. 
 
 Plate 
 
 I. Full-grown cotton, magnified about 400 diameters, as seen with 
 Ross's J-in. object-glass, and mounted dry. 
 II. Unripe cotton. — Half-ripe cotton taken from an Algerian pod, which, 
 when dry, was almost entirely closed ; and along with them fibres 
 in what I have described as the youngest stage. 
 
 III. Transverse sections of various conditions of the cotton fibre, as 
 
 there described, and all as they appear when mounted (except 
 No. 2) in glycerine jelly. 
 
 IV. A, Full-grown cotton prepared with a mordant of pyrolignate of 
 
 iron, then dyed in madder and soaped. At D, Plate VIII., will 
 be found transverse sections of A. 
 
24 
 
 HOW COTTON UNITES WITH COLOURING MATTER. 
 
 B, The same as A, but steeped before mordanting in a strong solu- 
 tion of caustic soda. At E, Plate VIII., are transverse sections 
 of B. 
 
 V. Half-ripe fibres with aluminous mordants, dyed in madder and 
 soaped. 
 
 A, Mordanted with mono-muriate of alumina. 
 
 D, The same, but mercerized in the unbleached state before mor- 
 danting. 
 
 E E, The same, bleached and mercerized previous to mordanting. 
 
 B, Mordanted with acetate of alumina without being bleached. 
 
 C, Mordanted with acetate of alumina after having been bleached 
 and mercerized. 
 
 VI. Transverse sections of the various fibres with aluminous mordants, 
 dyed in madder and soaped. 
 VII. A and B, The youngest fibre mordanted with acetate of alumina, 
 showing the effect of bleaching upon dead cotton in rendering it 
 less capable of receiving a d^^e. C and D, which are mordanted 
 with mono-muriate of alumina, give the same indication in an 
 equally remarkable manner. 
 
 Transverse sections of mature cotton dyed chrome-orange, as seen 
 with Powell & Lealand's irsth inch, showing concentric rings — 
 an effect of diffraction, not of structure. 
 VIII. A, The half-ripe fibre mordanted with oxychloride of iron, and dyed 
 with garancine. A2, Transverse sections of A, where the greater 
 part of the lake is seen to be lodged in the hollow of the fibre. 
 
 B and B2, The half-ripe fibre mercerized, and then mordanted with 
 oxychloride of iron, showing the effect of soda in opening the 
 pores to admit the mordant into the body of the wall, and 
 retain it there, as well as to allow of its passing through the 
 wall into the central cavity. 
 
 C and Ca, The full-grown cotton mordanted with oxj^chloride of 
 iron, and dyed in garancine. 
 
 D, Full-grown cotton mordanted with pyrolignate of iron, dyed 
 with madder and soaped. Side views of the same preparation 
 are given at A, Plate IV. 
 
 E, The same dye with mercerized cotton. Side views at B, 
 Plate IV. 
 
 BELL AND BAIN, PBINTKES, GLASGOW. 
 
PLATE 
 
 UNRIPE COTTON. 
 
 -o.rraler lieit 
 
Fl.AT'^ Til 
 
 TRANSVERSE SECTIONS OF COTTONS 
 
 1 . Mature Cotton 
 E- Mat^Jire Cc^tton, Mo-untecL Dry. 
 
 Q M9,ture Cotton, MercerisecL. 
 
 |) CE) e ® Q 9 9 
 
 4'. Halt Ri£e CottciL. 
 
 5. HaJf Ripe Cotton, Mercerised. 
 
 r ci' cf 
 
 CottozL "^/4- ths E-ipe, Mercerised. 
 
 Tiie Least Ripe Cottr 
 
 ivcdler Delt 
 
 Maciure & IvLaodotLalel Lxtk. 
 
PLArE IV. 
 
 ScimdLsr Delt 
 
4 
 
FLATE VL 
 
 TIONS "WITH THK ALUMINOUS L/J^E OF MADDER 
 
 MoTd4al( 
 
 :.ate of Ajumma 
 
 ^ . As 1^1 i>-ut deficiem m. t^aaXLi:!^-' of Madder. 
 
 4. Mature Cotton. Mercerised ,_ Asetate of A-luuairi.a, 
 
 • • • • O ® o • 
 
 Mature Cotton.- Meroerised, _ Mono Muriate of Ai-aminA 
 
 ?) , . r ^ (5) ^ # (J) ? 
 
 Half Ripe Cotton _ Mono Miu-iaLe of Aumma.. 
 
 ^ ^ 1 1 % / ^ i ^ J 
 
 & .- ifaat itipe Cotcoji Merce:. 
 
 icriTirii.er Xvca 
 
PLATE VUl 
 
 COTTON i'lBRES WITH ^L'l-ffi LAKE OP' IROIT AND MADDER 
 
GETTY RESEARCH INSTITUTE 
 
21