Dr. E. J. Mills on the First Principles of Chemistry. 13 



be legitimate. Here no assertion is made that water is a com- 

 pound body. 



((3) The use of such symbols will depend upon the object in 

 view. One instance of their application has been given in (7), 

 where the effect of one variable (calcic chloride) on another 

 variable (baric sulphate) is thereby expressed. The logarith- 

 mic and hyperbolic curves of Esson, in which are shown 

 the relations of changing substance to change produced, also 

 make use of such symbols. These are representations of the 

 chemical process. 



But we require to use symbols for other purposes. Suppo- 

 sing that, in Debus' s investigation, baric iodide had been used 

 instead of baric chloride, what weight of the former would 

 have done the same work as the latter ? The answer to this 

 question gives us the real or dynamic equivalent of baric iodide 

 in terms of baric chloride. In other words, if * stand for baric 

 iodide and c for baric chloride, it is a solution of the equation 



i=fc. 



It was after such numbers that Bergman sought in vain ; but 

 he was the first who clearly saw their immense importance. 

 In memory of him we may term them Bergmannics. For the 

 few that are known I refer to the Proceedings of the Royal 

 Society, vol. xviii. p. 348, and this Journal (IV.), vol. xliv. 

 p. 506*. Thus, if N stand for thallous, argentic, or plumbic 

 nitrate reduced to the unit (N0 3 ), and P stand for potassic 

 nitrate, the bergmannic is 



N=fP; 



if S stand for sodic nitrate, 



S = 1P. 



Diffusion bergmannics were obtained by Graham (Phil. Trans. 

 1850, p. 46), who proved that they -are not by nature atomic, 

 but either equal weights or multiples of equal weights. Such 

 questions are of the highest importance. The manufacturer, 

 for example, who is required by alteration of prices or other 

 economical reasons to substitute one substance for another, 

 ought to have such numbers ready to hand. Should the agri- 

 culturist desire to use potassic instead of sodic nitrate on a 

 grass crop, he ought to know what weight of grass will be pro- 

 duced by one as compared with the other. The physician 

 should know what weights of quinine, cinchonine, and strych- 

 nine, &c. do the unit of work. All this, and more, is not only 

 attainable but near. 



* See also Chizynski, Ann. Chem. Pharm. Suppl. vol. iv. p. 226. 



