96 ANNUAL OF SCIENTIFIC DISCOVERT. 



rMrROVEMENTS IN DYEING. 



* 



New Apph'rafion of Tannin. — Not only are now anillno dyps 

 constantly disoovorofl, but now and more eonvoniont or oiTeclive 

 modes of applying them are obtained. Silk and wool are easily 

 dyed by means of them; vegetable matters, the affinities of which 

 for colors of all kinds are much weaker, not so c^asily nor so 

 ettbctively. It has hov.n discov(!red, however, tliat brilliant colors 

 may be imparted to flax or cotton by means of the aniline,d3^es, if 

 they are Ih-st impregnated with an alkaline solution of tannin. 

 Vegetable parchment, which acts like silk or wool with reference 

 to the aniline dyes, does notre(|uiro the use of tannin. When ordi- 

 nary paper is to be colored, the tint ol)tained is wonderfully im- 

 proved if it is coated with albumen before being subjected to the 

 action of tannin. 



Utilization of Aniline Djiat. — The beautiful colors derived from 

 aniline have already received a very general api)lication ; Ijut they 

 have been, hitherto, unsuitable to one pur])oso, which would be most 

 likely to Ijeneflt by the brilliant elFects they produce, — oil paint- 

 ing. They are now very likelj' to become extrouKdy useful in 

 this branch of art. It has been found that a solution of aniline is 

 capable of dissolving caoutchouc, and all the x-esins which have 

 acid properties, and also the aniline dye-stuffs. Tlie solution of 

 shellac, for example, in aniline, may be colored by the addition of 

 the concentrattul solution of aniline dye-stutf; the result being a 

 transparent paint, which answers admirably for glass, porcelain, 

 etc. This shellac solution may be mixed with any oil 2)aints that 

 contain no lead ; and thus an oil paint of extraordinary l)rilliancy 

 may be obtained. With the exception of fuschine, all the aniline 

 dyes may be dissolved in the aniline solution of shellac itself. 



Aniline. — It requires as many as two thousand tons of coal to 

 produce a small circular block of aniline twenty inches liigli l)y 

 nine inches wide. This quantity is sufficient to dye three hundred 

 miles of silk fabric. 



Aniline Black. — The discovery of a fine black, pi'oduced from 

 aniline, may almost be considered as completing the series of 

 magnificent colors obtained from that substance. This new dye 

 is the more valuable, since it may be associated with any kind of 

 madder color, and may be treated in subsequent processes like 

 logwood. It is obtained by dissolving hydrochlorate of aniline 

 in an aqueous solution of hydrofluosilicic acid (sjiec. gi-av. 8° B.) 

 which has been projierly thickened, and then adding chlorate of 

 potash, and printing or preparing the tissue with chlorate of pot- 

 ash, and afterward printing. On raising the temperature from 

 32° to 35° C, a beautiful and permanent black is produced. The 

 hydrofluosilicic acid required may be obtained by decomposing 

 a mixture of fluor-spar and sand with sulphuric acid. The 

 decomposition which takes i)lace during the process consists in 

 decomjjosition of the chlorate by the hydrofluosilicic acid, silicate 

 of potash being formed and chloric acid set free. A part of this 

 chloric acid acts on the hydrochloric acid of the hydrochlorate of 



