ALBUMEN. 337 



is then dried, pulverised, and freed from fat by boiling alcohol and 

 ether. 



Wurtz* obtained a soluble albumen which, however, contained 

 acetic acid, by treating the albumen of hens' eggs with basic acetate 

 of lead, and removing the lead from the albumen by means of car- 

 bonic acid and sulphuretted hydrogen. This albumen reddens 

 litmus. 



Hruschauerf likewise obtained an albumen that reddened 

 litmus by precipitating albumen with sulphuric acid. After being 

 washed for a period of six weeks it reddened litmus; it was, 

 however, free, from sulphuric acid. 



Tests. The presence of albumen is in general very easily shown, 

 since the coagulability of a fluid by heat is usually regarded as a 

 proof of its presence; but when we consider that several other 

 substances (to be treated of in the sequel) likewise coagulate when 

 boiled, we must not adopt this property of albumen as the sole 

 means of its recognition, since, as has already been noticed, albu- 

 men under some relations either does not coagulate, or presents a 

 scarcely perceptible turbidity. We have already indicated the 

 methods by which the presence of albumen may be detected in 

 very acid or very alkaline fluids ; we either neutralise the fluid, or 

 we treat it with a strongly saturated solution of hydrochlorate 

 of ammonia, and then boil it. Many methods were formerly 

 recommended for indicating the presence of albumen, especially 

 when occurring only in very small quantities, among which we 

 may particularly notice nitric acid, corrosive sublimate, bi-chro- 

 mate of potash to which a small quantity of sulphuric acid has 

 been added, and tannic acid ; but these methods were only of value 

 when applied in addition to the coagulation test, since the greater 

 number of the protein-compounds are precipitated by them ; they 

 are, therefore, only regarded as conclusive when they yield re- 

 actions in a fluid in which no other protein-compound but albumen 

 is generally found. Thus, for instance, when urine coagulates on 

 being heated, and is likewise precipitated by nitric acid, corrosive 

 sublimate, chromic acid, and other means, we entertain no doubt of 

 the presence of albumen, although these tests yield the same 

 reactions with most of the other protein-compounds. As, however, 

 all these reagents collectively yield only a relative proof of the 

 presence of albumen, we can trust but little to the evidence 

 afforded by the mere coagulation of a fluid by heating, since animal 



* Compt. rend. T. 18, p. 700. 



t Ann. d. Ch. u. Pharm. Bd. 46, S. 348. 



Z 



