SALTS OF ALBUMIN AND ACIDS 



77 



the variation in optical activity with increasing addition of 

 acid on the other hand, it is clear that not only the viscosity 

 maximum, but also the combination with the greatest quantity 

 of the acid employed and the ionisation maximum are coinci- 

 dent. The peak of the rotation curve does not coincide but 

 lies rather on the part representing the general decrease in the 

 viscosity. It is not, apparently, a difference in the rotation of 

 the ions and the neutral molecules of the protein salts, but 

 rather an effect of higher acid concentration on the constitu- 

 tion of the acid-albumin that here determines the characteristic 

 course of the curve for rotation. 



C. Schorr's * work on the precipitation by alcohol of the 

 acid albumins of different acids gives the same interesting 

 difference, which, for hydrochloric acid and acetic acid, lies 

 entirely in the comparison with the viscosity curves in the two 

 cases. In the first instance the maximum of viscosity corre- 

 sponds to one of precipitation ; in the second case the increase in 

 the alcohol precipitate only appears in higher concentrations of 

 the acid. With albumin sulphate low viscosity corresponds 

 well with greater precipitation by alcohol, so much so that to 

 show the variation in precipitation decrease and subsequent 

 increase with continuously increasing acid concentration it is 

 necessary to employ a 45 per cent, alcohol in place of the 96 per 

 cent, alcohol used in the work with hydrochloric acid. The ioni- 

 sation effect is then clearly seen. Albumin trichloracetate falls 

 quite outside any connection between viscosity and alcohol 

 precipitation, as it is entirely precipitated in analogy with 

 albumin chloride. The viscosity in this case indicates a great 

 difference in the hydra tion (Table 24). Here the strength of 

 the acid is clearly expressed in a corresponding difference of 

 ionisation of the albumin salt, as shown by the effect of addi- 

 tion of alcohol. In general, the precipitation by alcohol, as 

 shown by the researches which have been quoted, is an indi- 

 cator of the dissociative properties of the salt examined in this 

 way. 



A comparison of the viscosity values in concentration of 

 acid of 0-05 N and the precipitation of the albumin by acids is 

 * Biochem. Zeitsch., 1911, 37, 424. 



