282 



ANNUAL OF SCIENTIFIC DISCOVERY. 



The equivalent of Cu has been here taken at double that usually employed, 

 or that which results from taking the first oxide of copper as CuO, a view 

 formerly entertained by Berzelius, L. Gmelin, and other distinguished chem- 

 ists.* 



The second number in the above series, l-52'o, does not correspond with 

 the equivalent of any known element, and, like the number 104, which occurs 

 twice in the nitrogen series, may represent the equivalent of some element- 

 ary body as yet unknown. 



The same relation may also be extended, with more or less approxima- 

 tion to the platinum group, which naturally divides itself into two families; 

 rodium, ruthenium, and palladium; and platinum, iridium, and osmium; 

 and the difference between the equivalents of the two groups approaches 

 to 45. 



So, also, if we take Gerhardt's equivalent of carbon == 12, the sum of the 

 equivalents of carbon, boron, and silicium, amounts to 44 exactly. 



From these and other examples, which Mr. Lea develops at considerable 

 length, it is evident that the number 44 4-3 plays an important part in the 

 science of Stoichiometry; and the relations which depend upon it are sup- 

 ported, in some cases at least, in a remarkable manner, by analogies of 

 atomic volume. That such analogies are a support, becomes evident from 

 the following considerations. 



Solids and liquids are very far from being governed by the laws which 

 determine the combinations of gases, in volumes either equal or having some 

 simple relation to one another. Therefore, if we find that in some few in- 

 stance's such a relation does hold good with solid substances, we may natu- 

 rally expect to find a close relationship existing between those substances 

 thus united. We may even be permitted, by way of hypothesis, to advance 

 a step further, and finding that a given volume of silver unites with a given 

 volume of oxygen, and that the same volume of gold unites with precisely 

 the same volume of oxygen, to conjecture that gold may differ from silver 

 only by a third substance, which unites with the silver without increasing 

 its volume, or affecting the amount of oxygen which it is capable of sat- 

 urating, but which, on the other hand, alters its chemical equivalent, its 

 specific gravity, and other physical characters. 



Moreover, if we find that by subtracting from the chemical equivalent of 

 silver half the difference between the equivalents of silver and gold we 

 obtain the equivalent of a third metal, copper (Cu = 63'4), which also, under 

 equal volumes, combines with a quantity of oxygen expressed by a very 

 simple relation with that capable of saturating gold and silver, we may at 



* In the cases of nitrogen, tin, and lead, the equivalents are taken with a negative 

 sign, as before explained. 



