§§ 92, 93, 94. ESTIMATION OF ALBUMEN. 79 



the property ti albsorbing aniline-violet (protoplasm generally 

 assuming a bluish-violet, the cell-nucleus a reddish tint), carmine, 

 cochineal, picro-carmine, etc. Note' should also be taken of the 

 form in which the albumen occurs, whether crystalline or 

 amorphous, etc. (See also §§ 74, 90, 95, 194.) 



Protoplasm is coagulated . by absolute alcohol and by glycerine. 

 It becomes clear with solution, of caustic potash, -cloudy with 

 acetic acid. Nttdei are generally stained more deeply than pro- 

 toplasm by aniline-violetj etc., and by iodine. They are coloured 

 deep blue by a solution of hsematoxylin (1 : 30) and alum (1 : lO) ; 

 the former alone also produces the same eifect if the section has 

 been previously treated with picric acid and the excess of the 

 latter completely removed (Schmitz). Crystallbids dissolve in 

 dilute potashj ammonia, and acetic acid. 



PTecipifyition. — Albuminous substances are precipitated by ferro- 

 cyanide of potassium and acetic acid, by aqueous colution of 

 trichloraicetic acid, and by solution of xanthogenate of potassium. 

 The precipitate produced by the last reagent becomes ilocculent 

 on heating to 30° (Zeller). (See also ^ 95,. 231, 232.) 



§93. Estimation of Legwmin and Ghiulin. — Part of the filtrate 

 (25 to 50 cc.) is acidified with hydrochloric acid in the cold. By 

 this means such substances as leguvtin are precipitated ; they 

 should be collected on a tared filter, washed first with water 

 acidified with hydrochloric acid, then with 40 per cent, spirit, 

 dried and weighed, deducting ash (§ 225 et seq.). If hydrochloric 

 acid has caused a precipitate, a fresh portion of the filtrate should 

 be tested for globulin by saturating with carbonic acid. It should 

 also be ascertained microscopically whether the precipitate (if any) 

 is crystalline or amorphous. (Cf. §§ 226, 227.) 



§94. Eslimation of Albumen. — To the filtrate from the legumin 

 (without. the spirit- washings), to 10 cc. of a concentrated solution 

 of chloride of sodium are added, together with enough acetate 

 of soda to remove all the hydrochloric acid, and the whole 

 raised to the boiling-point. If flocks of albumen separate they 

 must be collected, washed iirst with boiling water, afterwards 

 with 40 per cent, .spirit, dried and weighed, deducting ash. 



In the absence of legumin 25 cc. of the aqueous extract may 

 be mixed with 5 cc. of a concentrated solution of chloride of 

 sodium and a few drops of acetic acid and treated as described 

 in the foregoing paragraph. (See also § 230.) 



