148 PHYSICAL CHEMISTRY IN MEDICINE. 



Let us now ask what will happen when we try to pre- 

 cipitate with neutral salts protein that has been rendered 

 electropositive through the addition of an acid. Theoret- 

 ically we would expect that under these circumstances 

 the negative ions of the salts would precipitate the pro- 

 tein, while the metallic ions would have an inhibiting effect. 

 And as an actual matter of fact, we find that when the 

 protein has been acidulated the formerly inhibiting 

 bromides, iodides, and sulphocyanates become powerful 

 precipitants, and those salts which formerly precipitated 

 now inhibit. In other words, the signs cf the above table 

 are reversed; only the precipitating effect of the negative 

 ions increases in the same order as their inhibiting effect 

 did formerly, while the order of the now inhibiting 

 positive ions is just the reverse of that given in the table. 



The following interesting fact has also been found. 

 The same reversal in ionic effects as is brought about 

 through acids can also be brought about through the 

 addition of the salts of the alkaline earths, Ca, Ba, and 

 Sr, to the native protein. One may conclude from this 

 that a change in the sign of the charge of the protein 

 solution from the negative to the positive occurs in this 

 case also. According to our conversion experiments, 

 however, uncharged protein does not assume an electrical 

 charge through the presence of the neutral salts of the 

 alkaline earths, and in consequence we have to discover 

 whether these do not bring about an acid reaction by 

 meeting with the salts contained in the animal fluids. 

 In order to answer this question, let us consider the 

 changes that are brought about through the addition of 

 calcium chloride to a solution of sodium bicarbonate 

 or disodium phosphate. As is well known, the two salts 



