308 Progress of Foreign Science. 



of oxygen to become molybdic acid. It follows that for 

 molybdenum, there is between the sulphur and the oxygen of 

 the acid a ratio analogous to that which we have found, for the 

 sulphuret and the acid of arsenic ; that is to say, the sulphuret 

 of molybdenum is proportional to a degree of oxidation inferior 

 to that of the acid." Now, this proposition is true no doubt, 

 but very much mystified in the enunciation. The sulphuret of 

 molybdenum is evidently a compound of one atom metal + 2 

 atoms sulphur ; or is a bisulphuret : and the acid is like all the 

 well-marked metal acids*, a compound of one atom metal + 3 

 atoms oxygen. Hence the ratio of 4, (=2 x 2) to 3 as found 

 by Bucholz. 



Ten grammes of nitrate of lead, equivalent to 6.731 oxide of 

 lead, yielded of molybdate 11.068 grammes, according to Ber^ 

 zelius. He then proceeds : " By a very simple calculation we 

 find that the molybdate of lead is composed of — 



Molybdic acid . 39.185 . 100.0 



Oxide of lead . 60.815 . 155.2 



Now, 155.2 parts of oxide contain 11.129 parts of oxygen, which 

 are a submultiple of 50 (the quantity of oxygen absorbed by 

 100 of molybdenum, in the experiments of Bucholz,) by 3 ; for 

 11.129x3=33.387. It follows thence that, in the neutral 

 molybdates, the acid contains three times as much oxygen as 

 the base. It is then composed of— 



Molybdenum . 66.613 . 100.00 



Oxygen . 33.337 . 50.12 



Now, this marvellous prolixity and obscurity of induction^ 

 might have been all saved, by referring molybdenum directly to 

 its place in that general scale of equivalents of which oxygen is 

 the radix, or modulus. He would also have avoided the un- 

 warranted position with which the quotation concludes, of the 

 acid containing three times as much oxygen as the base ; for 

 molybdic acid forms an insoluble precipitate with some of the 

 deutoxide salts of copper, which compound consists, in all pro- 

 bability, of an atom of acid to an atom of base ; and therefore 

 the former will contain a quantity of oxygen, to the latter in the 

 ratio of 3 to 2, and not, as he says, of 3 to 1. Again, when 

 treating in the same paper of the composition and the capacity of 

 saturation of chromic acid, Berzelius says, " It thence follows 

 that the chromate of lead ought to be composed of— 



Chromic acid . 31.853 . 100.000 



Oxide of lead . 68.147 . 213.924 



* Thus, as to the acids of Chromiutn, Manganese, Arsenic, Tungsten, 

 consist each of one atom metal -J- 3 atoms oxygen. Selenic acid has two 

 atoms, but its base can hardly be called a metal. Antimonic acid has 

 also probably two ; but it resembles an oxide more thau an acid. 



