THE PROTEOSES AND PEPTONES. 49 



cially the biuret test, where the resulting color is a reddish 

 pink. They do not coagulate on boiling, and, unlike the 

 other albuminous substances, will pass through a parch- 

 ment or animal membrane. They cannot be precipitated 

 by ammonium sulphate or with potassium ferrocyanid. 

 Tannin or alcohol precipitates them from their solutions. 



A number of different classes have been described, two 

 of the principal ones being those designated by the prefixes 

 anti, which resist the action of ferments and are not 

 easily decomposed further; and Tiemi, which are more 

 easily decomposed. Thus we have antialbumoses and hemi- 

 albumoses, and antipeptones and hemipeptones. The other 

 classes differ principally in their solubilities. 



In the dry state the proteoses form an amorphous 

 powder. The peptones also have an amorphous form, but 

 are extremely hygroscopic, dissolving, to a resinous mass, 

 in the water which they absorb from the air. Their taste 

 is unpleasant. 



115. PREPARATION or PROTEOSES. Boil for twelve 

 to fifteen hours about 10 grammes of fibrin or coagulated 

 egg-albumin with three to four times its weight of 4 per 

 cent, sulphuric acid. Keep the volume constant by the use 

 of an inverted condenser or by the addition of water. The 

 liquid turns violet, then brownish. If on testing a 

 small sample by neutralizing with sodium hydrate much 

 acid albumin is precipitated, continue the heating until 

 such a precipitate is no longer produced or is but slight. 

 Then filter off any insoluble matter, neutralize with am- 

 monium hydrate, and saturate the liquid with ammonium 

 sulphate. The proteoses are precipitated. Filter and 

 wash them with a saturated solution of the last reagent. 

 Then dissolve the proteoses in a little water, place this 

 solution in a dialyzer, and dialyze until the outer liquid 



