ELECTROLYTES AND THEIR ACTION 



221 



With regard to proteins, we have seen in dealing with them from the colloidal 

 point of view how the effect of acid and alkali on the sign of their electrical 

 charges is explained by their nature as amphoteric electrolytes. A further proof 

 of this fact is afforded by the measurements of the freezing points of their salts 

 with acid and alkali, as obtained by Bugarszky and Liebermann (1898, p. 72). 

 In the table below, the first column gives the number of grams of egg albumin 

 added to 100 c.c. of the acid, base, or salt in 0'05 molar concentration, and the three 

 remaining columns give the depressions of the freezing point in each of these cases. 



It will be seen that there is a considerable diminution of A in the cases 

 of acid and base, due to formation of salts with the protein. In the case of the 

 neutral salt there is no such effect. The contrary effect, a rise of A with the 

 sodium chloride, is, in fact, due to the albumin itself, since 6-4 g. of the 

 protein in 100 c.c. of water gave a freezing point depression of 0-022 ; this, added 

 to 0-183, gives 0-205, as in the table. 



ACTION OF ELECTROLYTES IN EXTREME DILUTIONS 



The powerful effect of hydrogen and hydroxyl ions in traces has been 

 exemplified in the case of the heart. Further instances will occur in the course 

 of this book. 



One or two striking cases of the action of inorganic salts in minute quantities 

 may be referred to here. 



Elissafoff (1912) showed that the effect of the quadrivalent thorium ion on 

 the surface charge of quartz was such as to lower it by 50 per cent., when the 

 solution contained only one gram ion in a thousand million grams of water. 



The extraordinary effect of zinc in traces on the growth of moulds was 

 discovered by Raulin (1870, 1 and 2), as also that of manganese. This observer 

 was doubtful whether the effect of manganese salts was not due to traces of zinc, 

 and the matter was further worked out by Bertrand and Javillier (1912). They 

 found that manganese itself actually has an effect of this kind. One part of 

 manganese in one million of the culture solution raises the crop of Aspergillus 

 from 0*610 to 0-631 and the effect continues to increase even up to one part in 

 100. In further work it was found that the combination of zinc with manganese 

 was more effective than either alone. To take an example : 



Control 



With Zn, 1 : 500,000 

 With Mn, 1 : 5,000- 

 With both together 



Weight of Crop. 

 1-45 

 4-10 

 2-79 

 4-35 



The data also show the really astonishing effect of zinc alone. In another 

 experiment, indeed, we find that the addition of one part of zinc to twenty-five 

 millions of solution increases the crop from 3'00 to 4'54, that is, by more than 

 50 per cent., and one part in ten millions nearly doubles it. 



The authors point out how important is this function of elements present only 

 in traces ; they regard it as being of a catalytic nature. We shall have occasion 

 later to return to the question of the effect of substances, not only inorganic ones, 

 which, although present only in infinitesimal amount, are, as it seems, absolutely 

 indispensable to the normal functional capacity of protoplasm. 



