352 Memoir upon Hair. 



I succeeded in dissolving them without alteration in 

 Papin's digester, by regulating the heat properly. If in this 

 operation a certain degree of temperature is exceeded, the 

 substance of the hair is decomposed in whole or in part ; a 

 circumstance demonstrated by the ammonia, carbonic acid, 

 and the fetid empyreumatic oil found in the solution, to 

 which the oil communicates a deep yellow colour. 



In the one or the other case, sulphureted hydrogen gas 

 is liberated in great quantity, which acted strongly upon the 

 copper of the digester, which it blackened : more was found 

 when the heat was raised; which seems to indicate that this 

 substance is produced during the operation. 



If we operate upon black hair, or if the heat is not suffi- 

 cient to decompose it, there remains a black matter, which, 

 on account of its minute division and the consistency of th« 

 solution, is deposited very slowly. This matter is princi- 

 pally composed of a black oil, as thick as bitumen, little 

 soluble in alcohol and the alkalis of iron and sulphur per- 

 haps united with each other. Red hair leaves a yellowish 

 red residue, containing plenty of oil, sulphur, and a little 

 iron. 



The solutions are almost entirely colourless when they are 

 filtered ; the concentrated acids make them turbid, the 

 weak acids produce no change : an excess of fhese agents 

 restores the liquor its former transparency. Tincture of 

 galls and the oxygenated muriatic acid form abundant preci- 

 pitates. Silver is blackened in it; the acetate of lead is 

 precipitated from it brown. These solutions, evaporated 

 with every necessary precaution, were not jellied, and only 

 furnished a viscous and gluey matter; whence I concluded 

 that the substance of hair is not gelatinous. 



The acids form precipitates more abundant and higher 

 coloured in a solution of hair made at a higher temperature, 

 for this reason, that they decompose an ammoniacal soap, 

 which does not take place in the former case. 



I likewise dissolved black and red hair in water contain- 

 ing onlv four per cent, of caustic potash. During this solu- 

 tion hydrosulphurct of ammonia is liberated : which seems 

 to announce a commencement of decomposition in black 



hair, 



