31 Experiments on the Yolk of Wool. 



ceptible by its odour. Concentrated sulphuric acid black-* 

 ens the thickened yolk, and disengages from it some vapours 

 of muriatic acid. 



2d, Lime water renders the solution of yolk turbid and 

 milky ; but it forms in it no coagulum, as in a solution of 

 common soap. 



3d, Neither caustic alkalies nor quicklime show the pre- 

 sence of ammonia. 



4th, Nitrate of silver produces in it a yellow precipitate, 

 which adheres to the sides of the vessel in the manner of a 

 greasy substance. This precipitate dissolves in a great part 

 in nitric acid. 



The part of yolk insoluble in alcohol has still a salt taste, 

 but fainter than the portion soluble in that reagent. After 

 being thus treated with alcohol, it does not redissolve en- 

 tirely in water ; there remains a glutinous matter of a gray 

 colour, which effervesces with acids : this announces the 

 presence of an alkaline carbonate. The portion which re- 

 tains its solubility in water, communicates to it a reddish 

 colour and a salt savour : its solution is not rendered turbid 

 by acids, as it was before being treated with alcohol. Caustic 

 alkalies do not disengage from it ammonia ; muriate of ba- 

 rytes forms in it a very abundant depot, the greater part of 

 which dissolves in water ; nitrate of silver occasions in it 

 also a precipitate which partly dissolves in nitric acid. Al- 

 cohol precipitates this matter under the form of a mucilage, 

 which is speedily deposited. 



Nitrate of iron mixed with the solution of this substance 

 formed in it a brown precipitate, and the liquor at the end 

 of some days furnished a pretty large quantity of nitrate of 

 potash. 



The filtered liquor of yolk decomposed by dilute nitric 

 acid blackens by evaporation, exhales vapours of sulphuric 

 acid, and becomes carbonaceous in proportion as the con- 

 centration of the sulphuric acid takes place. The residuum 

 being then washed with water, and the solution properly 

 evaporated, furnishes crystals of neutral sulphate of potash ; 

 but there remains a great deal in solution in consequence of 

 the superabundant acid, which reduces it to the state of 

 acidulous salt ; by longer evaporation this salt crystallizes 

 in needles, and into laminae of a white pearly colour. During 

 the course of these successive evaporations, another kind of 

 salt presents itself under the form of flattened needles of a 

 satin white colour and without any taste. 



This salt, when carefully examined, appeared to me to be 



nothing: 

 5 



