

GENERAL CHEMICAL CHARACTERS OF PROTEINS 4! 



hydrochloric acid was much greater than this : the diminution was 

 due to actual neutralisation, and not to mere increase in internal 

 friction. 



Sjoqvist determined the conductivity of the 0-05 N hydrochloric 

 acid solution after the addition of varying amounts of egg-proteins, 

 with the following results : 



Amount of protein in 100 c.c. o 0-72 1*08 2-16 3-03 4-09 4-70 



^pr .... 334'5 286-2 263-1 196-2 140-3 97-5 78-52 



Amount of protein in 100 c.c. 5*22 6-26 6-71 7-83 9-40 



^T .... 68-66 60-7 59-43 58-32 57-7 



It is evident from the above numbers that in the last determina- 

 tions far more protein was added than was necessary to neutralise 

 the hydrochloric acid. After making corrections for the increased 

 conductivity, due to the protein added, and the diminished con- 

 ductivity due to friction, Sjoqvist calculated that the molecular con- 

 ductivity of the hydrochloride of the egg-proteins in 0*05 N solution 

 was 53 x io~ 7 , and, by interpolation in the curve, that neutralisation 

 of 0*05 N hydrochloric acid solution was attained when 4*1 grams 

 of protein had been added to 100 c.c. From this the equivalent of 

 egg-protein was calculated to be 820. This number obtained with 

 sulphuric acid was found to be 840, and with nitric acid 720. The 

 average is not far removed from 800. 



There is one other factor in these experiments which deserves 

 mention. It was noticed that in the case of the neutralisation of 

 hydrochloric acid by ammonia the curve first descends, and then 

 suddenly becomes almost parallel with the abscissa, forming thus 

 two straight lines enclosing a sharp angle. In the case of the protein 

 hydrochloric acid neutralisation curve there is no sharp break, but 

 the curve is rounded off. This is due to the fact that hydrolysis 

 of the protein hydrochloride can take place according to the equation 



Alb. HCl + H 2 O = Alb. OH + HCl. 



This hydrolysis is suppressed in the presence of a large excess of 

 protein (i.e., in the calculations of conductivity given above). 



The amount of hydrolysis has been determined by Sjoqvist in 

 the following way. He calculated the molecular conductivity of a 

 solution produced by adding the inorganic constituents of 4 grams 

 of protein to 100 c.c. of 0*05 N hydrochloric acid (the quantity neces- 

 sary for " neutralisation," vide supra). Such a solution would con- 

 tain known quantities (which were determined by analysis) of free 

 HCl, CaCl 2 , H 3 PO 4 and H 2 SO 4 (produced by the action of a large 

 excess of HCl on the original salts CaSO 4 and Ca 3 (PO 4 ) 2 ). For such 

 a solution //, was found to be 3 14 x 10 ~ 7 . The conductivity was next 

 calculated for this solution when the free acids were neutralised by 

 egg-proteins without hydrolysis, and after making correction for 

 decreased conductivity due to viscosity. (The molecular conduc- 

 tivity of egg-protein hydrochloride was found as shown above to be 

 S3 x 10 ~ 7 , and that of the sulphate and phosphate were determined 

 in a similar way in other experiments.) //, for this neutralised solu- 

 tion was calculated to be 55*66 x 10 " 7 . The actual observed value 

 was 100*5. Now as 314 x io~ 7 represents the value for total 



