HEAVY METALS 



139 



dissociated AgNO 3 , the concentration of the cation being assumed 

 to be equal to that of the anion. 



Calling C g the total concentration of silver nitrate, then C = 

 C g Ck, and we have 



= [CW> i + C k fo 



where C is the molecular concentration of the protein-silver-nitrate 

 in saturated watery solution (a quantity which naturally, cannot 

 be measured directly) and C' is the molecular concentration of the 

 protein-silver-nitrate in the AgN0 3 solution. 



Assuming that the molecular weight of the compound, in saturated 

 solution, is always the same, whether excess of silver nitrate be present 

 or not, .we can take C' as the percentage concentration of the com- 



Ql 



pound, since the ratio ^- will then not involve the molecular weight 



of the compound. 

 Putting 



1 2 m <f>Qi 2m 



~logC" a; IT'logC"^' "R" 



we have, from the above equation, 

 alogC' + 0(V 



logC 



1=0, 



in which a, 0, and 7 are constants, and C 1 ', C g , and C k are all directly 

 measurable. The following results of Galeotti's demonstrate the 

 validity of this equation, the most probable values of the constants 

 (a = -1.507; = +37.27; 7 = -72.06) having been determined 

 from all the observations by least squares. 



From this result we^may draw the following conclusions: 

 (a) The substance precipitated is a compound and not the free 

 protein, since the value of a in the above equation indicates a 



