Chemical Science. 199 



dition of ammonia, a precipitate took place, which was collected by a 

 filter and dried. Narcotin was thus obtained in the form of white 

 and beautiful silky crystals, which were readily soluble in sulphuric 

 ther. 



* When we consider how often opium has been dissolved in proof 

 spirits by chemists and pharmacopists, it is surprising that crystalline 

 principles, so easily evolved, as are morphia and narcotin, by the pro- 

 cess above described, should have escaped observation until lately, 

 when Sertuerner, by a much less obvious route, had the honour of 

 discovering them*.' 



25. COLOURATION OF AZOTED BODIES BY NITRATES OF MERCURY. 



M. Lebaillif remarked that when certain vegetable and animal sub- 

 stances were moistened with a solution of mercury in nitric acid, 

 they became of a red or amethystine colour, but the effect did not 

 take place with the protonitrate or pernitrate of mercury separately. 

 He and M. Lassaigne investigated this action, and found that a solu- 

 tion containing both prot and per nitrate always produced the effect. 

 Such a solution is always produced when mercury is dissolved by 

 moderate heat in nitric acid ; the production of colour is so ready, 

 that if a piece of animal matter, as dried white of egg, caseum, 

 horn, &c., be moistened with the mercurial solution, it will be red- 

 dened in eight or ten seconds, and if warmed (as upon platina foil, 

 six or eight inches above a candle), will take a rich purple red 

 colour. The effect may be produced even with milk, mucus or 

 dissolved gelatine. 



Organic substances containing azote were such as, in this way, 

 became coloured. Thus starch was not coloured. Gluten was 

 readily coloured, and it was found easy to find out very small quan- 

 tities of gluten in starch by the rose tint then acquired : but still 

 all organic azoted substances were not coloured. Fibrin and the 

 varieties of albumen, including caseum, horn, wool, milk, mem- 

 branes, &c., gelatine, silk, vegetable albumen, wheat flour, sweet 

 almond, *and some other substances, became coloured. Urea, uric 

 acid, osmazome, picromel, sugar of milk, sugar, starch, lignine 

 quinia, morphia, and the vegetable acids, were either not coloured 

 at all, or only pale yellow. 



A solution made of one part of mercury in two parts of nitric 

 acid was boiled for four or five minutes, to convert part into per- 

 nitrate, then diluted with its bulk of water, and silk or wool im- 

 mersed for ten or fifteen minutes, at temperatures from 113 to 

 122 Fah. : it was thus dyed of an amaranth colour, more or less 

 deep, and which, upon the silk, withstood the action of light, and 

 of weak sulphuric acid or alkaline solution. The colour appears 

 due to a combination of the mercurial salt, for the silk becomes 

 brown by a solution of hydrosulphuret ; and 100 parts of white silk 

 increased by 17 or 18| parts during dyeing t- 



* Sillimau'g Journal, xvi. 365. f Auuales tie Chimie, jdv, 435* 



