SIR B. C. BEODIE ON THE CALCTJLUS OF CHEMICAL OPERATIONS. 831 



III. A=— . Phosphorus and arsenic : — 



4a*^ = 6 a -|- a*f*. 



This weight A, which may be regarded as the limit beyond which the chemical divi- 

 sion of the weight of unit of the elemental body cannot be effected, is, it will be observed, 

 half the atomic weight of the element on the most recent and approved system. And it 

 is further true, as a matter of observation, that if X be the weight of an elemental body 

 which is formed in the decomposition of the unit of volume of any chemical substance, 

 X is a multiple of A, so that X=NA, where N is a positive integer. The relation 

 which this weight holds to the thermal properties of the element will hereafter be 

 pointed out 



From these considerations a certain probability is raised in regard to the value of V, 

 where the value cannot be experimentally determined, in favour of the values V=A, 

 V=2A, V=4A. 



The smallest weight of carbon, A, which is formed by the decomposition of the unit 

 of volume of any chemical substance, in regard to which the point can be experimentally 

 ascertained, is that which is formed by the decomposition of the unit of volume of marsh- 

 gas, formic acid, methylic alcohol, and a few other substances. 



Now, the equation which asserts the identity of the unit of weight of marsh-gas with 

 the units of hydrogen and carbon into which it is resolved, is 



yaV=2ya+a;x*, 



whence 



A=-V. 



y 



There are, therefore, from these considerations, three hypotheses more probable than 

 others which may be made as to the value -• 



1. A=V,^=l,ar=l,3^=l:— 



