9 o COLLOID CHEMISTRY OF THE PROTEINS 



soluble both in small quantities of acid and also in alkalis. It 

 is prepared by treating albumin with hot dilute acid, but the 

 alteration in chemical constitution in the albumin induced by 

 this treatment is not at present known. The measurement of 

 the capacity for combination with acid, however, gives a hint 

 as to what has happened. As the following results show, this 

 property is markedly greater than in the natural albumin : 



Table 39. 

 Acid-albumin (0-62 per cent.) -f- HC1. 



According to Pauli and Hirschfeld, an albumin in 0-63 per 

 cent, concentration takes up a maximum of i-o X io- 2 N HC1. 

 per litre ; and although i gm. serum albumin combines with a 

 maximum of 1-66 x io- 3 gm. equivalents of acid, the value 

 for i gm. acid-albumin is 2-06 x io- 3 N HC1, or some 20 per 

 cent, higher. We can conclude from this result that heating 

 with dilute acid makes about one-fifth more of the basic valencies 

 of the albumin operative, and that these remain permanently 

 available for combination with acids. This type of alteration 

 plays an essential part in the irreversible transformation which 

 the acid-albumin has undergone. The capacity for combination 

 with alkalis, on the other hand, remains unchanged by the 

 transformation into acid-albumin. One gram of serum albu- 

 min combines with 2-4 X io- 3 gm. equivalents of alkali (see 

 Chapter VII.), while measurements on acid -albumin give 

 2-5 X io- 3 N, or practically the same value. 



If the degradation of the protein is carried beyond the stage 

 of acid-albumin, greater changes in physico-chemical properties 

 take place. Bugarsky and Liebermann (loc. cit.) made electro- 

 metric measurements on the capacity for combination with 



