THE CHEMISTRY OF ALBUMINS 187 



ganate and determining the so-called ' albuminoid ammonia ' 

 evolved, a measure is obtained of the quantity of albumin sub- 

 stance removed from solution. It should be noted, of course, 

 that in a complicated substance like sewage other substances 

 besides albumins, notably e.g. fats, are carried down by this 

 process. 



Besides hydroxides of aluminium and iron, hydrated copper 

 oxide combines readily with albumin, and copper salts have 

 been used on a large scale in the treatment of water supplies, 

 more especially with the object of preventing the growth of 

 algae in reservoirs. It is probable that the toxic action of 

 copper in this respect, and also its analogous action as a germi- 

 cide, is due to the readiness with which insoluble compounds of 

 copper and albumin are formed. 



Albumin can be recovered from its compounds with 

 metallic oxides by treatment with acids, when the metal goes 

 into solution and the albumin is precipitated. By careful 

 treatment of a copper compound it has been possible to obtain 

 albumin in a form which is not crystalline, which is almost 

 completely soluble in alcohol and which does not coagulate 

 on boiling. The following description is given by Harnack 

 (Ber. XXII. ii. pp. 30-46) : A clear solution of albumin is 

 obtained by dissolving egg-albumin in water and filtering off 

 the globulin ; acetic acid is added and the precipitate obtained 

 filtered off. The filtrate is exactly neutralised and again 

 filtered ; in this way the remaining portions of globulin are 

 removed. The neutral solution is now precipitated with 

 copper sulphate and the precipitate thoroughly washed, then 

 suspended in water, dissolved in a few drops of caustic soda 

 and reprecipitated with acetic acid. The precipitate is again 

 washed, redissolved in caustic soda and precipitated with 

 acetic acid, and again thoroughly washed. It is then dis- 

 solved in excess of caustic soda and the dark violet-blue jelly 

 allowed to stand twenty-four hours, when it is precipitated 

 with hydrochloric acid, the copper in this case going into 



