90 



CHEMISTRY. 



Hydrogen dioxide is applied with special ad- 

 vantage in the treatment of Indian tusseh silk. 

 Atmospheric oxygen in presence of oil of tur- 

 pentine has been applied to the bleaching of 

 feathers and some other materials of animal 

 origin. A very useful improvement, when 

 properly managed, is the combination of chlo- 

 rine and air-bleaching. Linen goods and some 

 of the higher grades of cotton cloth, having had 

 most of the color removed by a preliminary 

 bleaching with chlorine, are then exposed to 

 the sun and air after the old fashion, for the 

 completion of the process. In this method the 

 rapidity of bleaching by chlorine is combined 

 with the exemption from injury to the fabric 

 of air-bleaching. 



The more recent features in the manufacture 

 of dyestuffs are the introduction of organic 

 colors in great number and variety, which has 

 marked the progress of the last twenty years, 

 and the reproduction of natural organic colors 

 by artificial means, which has been successfully 

 carried out and greatly extended within the 

 last ten years. More recently, the introduc- 

 tion of artificial alizarine has been followed by 

 a falling off in the production of madder and 

 its preparations. Ammonia, instead of lime, 

 has been applied with advantage to the extrac- 

 tion of indigo in Java ; and in India an increase 

 of the product, amounting to as much as 25 per 

 cent., has been obtained by increasing the tem- 

 perature of the steep- water to 110. The crude 

 material of many long-known vegetable dyes 

 has been replaced by concentrated extracts; 

 and a considerable improvement has taken 

 place in the solubility and tinctorial power of 

 the extracts. 



A most important change in the preparation 

 of the original so-called aniline colors consists 

 in the application on a great scale of Coupler's 

 process, or a modification of it, for making 

 aniline red (rosaniline salts) without the use of 

 arsenic, by heating together in the presence of 

 an acid nitrobenzene and commercial aniline 

 oil of high boiling-point, rich in toluidine. The 

 researches of Dale and Schorlemmer have es- 

 tablished a fall connection between phenol and 

 the whole series of aniline colors. Better pro- 

 cesses have been employed in preparing violet, 

 blue, and green. The soluble aniline blacks 

 " indulines " and " nigrosines " have come 

 into use for general dyeing purposes, particu- 

 larly in some forms adapted to silk goods. Ali- 

 zarine from anthracene, which has to a great 

 extent replaced madder, has become recognized 

 as in the front rank of artificial coloring mate- 

 rials. Numerous new colors of greater or less 

 value have been obtained from this and other 

 bases. The " Oachon de Laval " of Croissant 

 and Bretonniere is a material of much practi- 

 cal value. It is made by heating in close ves- 

 sels to 250 or 300 0. various waste forms of 

 vegetable fiber, such as sawdust, spent dye- 

 woods, rags, paper refuse, and the like, with 

 caustic alkali and sulphur. The product is 

 obtained in various colors, chiefly of tints of 



brown, and is remarkable for the firmness with 

 which it attaches itself to cotton cloth, particu- 

 larly when fixed with bichromate of potash, 

 while it produces a satisfactory modifying 

 effect upon the brighter coal tar dyes, and is 

 cheap. 



Attempts to generalize our knowledge of or- 

 ganic colors, and to determine some definite 

 relation between their composition and tincto- 

 rial power, have been attended by only a very 

 limited success. 



New processes have been introduced for fix- 

 ing colors upon cloth, which are dependent 

 severally upon the employment of silicic acid, 

 chromic hydrate, precipitated sulphur for cer- 

 tain colors, albumen, "lactarine," tannic acid 

 with or without the addition of an antimony 

 salt, lead acetate, and calcium phosphate, with 

 some of the dyes. 



The coal-tar colors have been introduced in 

 calico-printing on a large scale, and with re- 

 markable brilliancy and variety of effect ; and 

 pigments of mineral origin attached to the cloth 

 by the aid of albumen, have been used in sur- 

 face printing with similar results. Colors may 

 be used in these processes which are not avail- 

 able in general dyeing among them the insol- 

 uble aniline black of Lightfoot on account of 

 the difficulty of attaching them uniformly over 

 a large surface of cloth. 



The improvements in tanning have not been 

 extensive or important, and relate chiefly to 

 the superior quality of the extracts and the 

 greater purity of the solutions which are used, 

 and their more extensive substitution for crude 

 materials. The results of the rapid processes 

 in ordinary bark-tanning have not been satis- 

 factory, for the saving of time is apparently 

 always attended with deterioration in the qual- 

 ity of the leather. A method of dyeing and 

 at the same time partly tanning raw hide has 

 been introduced in the United States, the prod- 

 uct of which, in some respects resembling hard 

 vulcanized India-rubber, is susceptible of a 

 high polish, and is adapted to uses in which 

 flexibility is not required. In the process, the 

 hide, having been properly cleansed, is immersed 

 in solutions containing infusion of logwood, 

 nut-galls, cupric sulphate, vinegar, and a salt 

 of iron. 



For the manufacture of India-rubber, the 

 supply of crude caoutchouc has been greatly 

 increased by the fruits of a systematic search 

 for it in different countries, and the use of new 

 plants affording it. The preparation of vul- 

 canized rubber has been adapted to the pro- 

 duction by means of an intimate mixture of 

 caoutchouc and calcined magnesia of a hard 

 rubber of high grades which may be used as an 

 imitation of ivory for billiard-balls, piano-keys, 

 and similar articles. A plan has been pro- 

 posed, but not yet tested by experience, for 

 giving a certain degree of porosity to rubber 

 by mixing in it, before the vulcanizing process 

 is applied, a certain amount of vegetable fiber, 

 with the expectation of producing a material 



