52 THE GENERAL CHARACTERS OF THE PROTEINS 



100 c.c. The acid was in each case added gradually until the mix- 

 ture was only slightly opalescent and matched a given standard. 

 The amount of acid necessary to produce this given degree of opal- 

 escence was thereby determined. A large number of determinations 

 at different temperatures were carried out. If the mean amount of 

 hydrochloric acid necessary to produce this grade of solution of I 

 gram of globulin be taken as unity, the relative amounts of other 

 acids (given in equivalents) necessary to produce the same result is 

 given in the following table : 



Monobasic Acids. Dibasic Acids. Tribasic Acids. 



HC1 i-o H 2 SO 4 1-91 Citric acid 3-0 



HNO 3 0-995 Tartaric acid 1-994 H 3 PO 4 2-9 



CHC1 2 .COOH ro Oxalic acid i-g H,BO. Very large excess 



CC1 3 .COOH ro 



CH 2 C1 . COOH 1-05 



H . COOH 1-25 



CH 3 .COOH 5-2 



CH 2 .CH 3 .COOH 7-56 



It will be noticed here that the solvent power of strong acids is a 

 molecular function, and that HC1 - H 2 SO 4 = H 3 PO 4 . It may be 

 recalled that Osborne, in the case of edestin, also observed that 

 HC1 = H 3 PO 4 , and that salts of the type B . H 3 PO 4 are obtained. 

 The weaker acids require relatively far larger quantities to produce 

 the same grade of solution ; this is due to the readiness with which 

 salts undergo hydrolysis in dilute solutions. 



Generally the results obtained indicate that serum-globulin forms 

 salts of the same type as the amino-acids, i.e., salts in which a mole- 

 cule of acid and base combine to form additive compounds without 

 replacement : 



/NH 2 NH a .HCl 



CH 2 / + HC1 = CH 2 X 



\COOH \COOH 



Similar experiments were carried out with bases. Taking NaOH as 

 unity, the relative solvent actions may be represented by the following 

 figures : 



KOH i 



NaOH i 



NH 4 . OH 0-98 



Ba(OH) 2 2-008 



Urea and aniline also dissolve serum-globulin, but the quantitative 

 relationships were not determined. One point of considerable interest 

 appears from these numbers, viz., ammonia, which is a weak base, 

 has practically the same solvent power as sodium and potassium 

 hydroxides. Now the weak acids like acetic acid have considerably 

 less solvent power than the strong mineral acids, and these facts 

 indicate that serum-globulin has more decidedly marked acidic than 

 basic functions. In this respect it differs markedly from the plant 

 globulin edestin. 



In respect to its action on bases, the behaviour of globulin is some- 

 what peculiar in that i molecule of sodium hydroxide is equivalent 

 to i molecule of barium hydroxide. 



Measurements of the acidity and basicity of globulin by titration 

 in presence of indicators were also carried out. Freshly precipitated 

 and washed globulin reacts as acid *~ ^alysed litmus, gives no colour 



