CHEMICAL SCIENCE. 233 



rine remain dissolved in the water. The chlorine, which gives the liquid a 

 yellow color, is disengaged as soon as the bottle is opened. To produce a 

 more rapid disengagement, the liquid is poured into flat plates, so as to offer 

 a large surface for evaporation. 



ON COLORS OBTAINED FROM COAL-TAR PRODUCTS. 



The following paper was recently read before the London Society of Arts, 

 by Mr. Grace Calvert : 



In November 1854, in a paper read to this society, I stated that, ere long, 

 besides carbo-azotic acid, some valuable dyeing substances would be pre- 

 pared from coal-tar. This expectation has now been fulfilled. Messrs. 

 Perkins & Church have obtained several blue coloring substances from the 

 alkaloids of coal-tar, and one from napthaline, named by them Nitroso- 

 phenyline and Xitroso-naphthyline, etc. 



Mr. Perkins has lately taken a patent for the commercial application of 

 some of these beautiful purple-blue colors, which he has succeeded in fix- 

 ing on silk, a sample of which I have the pleasure to lay before you. This 

 fine color, which rivals the delicate and admired color of orchil, has this 

 great advantage over it, that it is not destroyed by light; Mr. Perkins has, 

 therefore, solved one of the problems of the art of dyeing, viz., the produc- 

 tion of a fast color similar to the fugitive one of orchil. Mr. Perkins's pro- 

 cess consists in dissolving in water the sulphates of aniline, of cuminine, and 

 of toluidine, and adding a quantity of bichromate of potash sufficient to 

 neutralize the sulphuric acid in these sulphates. The whole is left to stand 

 for twelve hours, when a brown substance is precipitated, which is washed 

 with coal-tar naptha, and then dissolved in methylated spirits. This solu- 

 tion, with the addition of a little tartaric oxalic acid, forms the dyeing 

 liquor of Mr. Perkins. 



Mr. Charles Lowe and myself have lately been fortunate enough to obtain 

 from coal-tar products having a most extraordinary dyeing power, and 

 yielding colors nearly as beautiful as safflower-pinks and cochineal-crim- 

 sons; and what increases the interest of this coal-tar product is, that, by the 

 process we have discovered, we can obtain with it, on a piece of calico mor- 

 danted for madder colors, all the various colors and shades given by this 

 valuable root violet, purple, chocolate, pink, and red. The only thing 

 which prevented us from introducing into the market the crown-red, inodor- 

 ous product which we prepare, has been, that it is as yet too expensive to 

 compete with this extraordinary color-giving root; but we intend pursuing 

 our researches in the hope of employing it as a substitute for safflower or 

 cochineal, two coloring matters, the price of which is sufficiently high to 

 induce us to continue our investigations. We may add, that our imitation of 

 safilower stands soap and light, whilst safflower colors do not. 



I shall now draw the attention of the meeting to the preparation, dye- 

 ing, and printing of a magnificent crimson color, called murexide, obtained 

 from guano, a substance which, until lately, has been entirely imported 

 for agricultural purposes. The interesting application of this color to calico- 

 printing has been, like many valuable chemical discoveries, progressive, and 

 htis only been brought to successful commercial application by successive 

 discoveries, made by various persons. 



Prout was the first chemist to remark that if the fasces of serpents were 

 healed with nitric acid, and a little ammonia added, a beautiful purple color 



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