1318.] the Atoms of Chemical Bodies. 347 



"Weight nf an atom. 



55 Peroxide of lead 15-000 



56 Tin 7-375 



57 Protoxide of tin 8-375 d 



58 Peroxide of tin 9-375 



59 Copper 8-000 



GO Protoxide of copper 9-000 



61 Peroxide of copper 10-000 



62 Bismuth 8-875 



63 Oxide of bismuth 9-875 e 



64 Mercury 25-000 



65 Protoxide of mercury 26-000 



66 Peroxide of mercury 27-000 



67 Silver 13-750 f 



68 Oxide of silver 14-750 



69 Gold 24-875 



70 Protoxide of gold 25-875 s 



71 Peroxide of gold 27-875 



72 Platinum 22-625 



73 Protoxide of platinum 23*625 h 



d This number is deduced from the experiments of John Davy, 

 which are a mean of those of Gay-Lussac and Berzelius, and 

 make protoxide of tin a compound of 100 tin + 13*55 oxygen. 

 This gives 7375 for an atom of tin, and 8*375 for an atom of 

 protoxide. There can be no doubt, from the experiments of the 

 same chemists, that peroxide of tin contains twice as much 

 oxygen as protoxide. Hence the weight of an atom of it must 

 be 9*375. 



e This number almost coincides with Lagerhj elm's analysis of 

 oxide of bismuth, which I think the most accurate analysis. 

 He found it a compound of 100 bismuth + 11-275 oxygen. 

 Now 11-275 : 100 :: 1 : 8-869. This number differs very little 

 from 8-875, which, being a multiple of -125, has been adopted. 



f This number is derived from the analysis of chloride of 

 silver, which, according to Dr. Marcet, is composed of 24*53 

 chlorine + 75*47 silver; according to Gay-Lussac, of 24*75 

 chlorine + 75*25 silver : the mean of these is 24-64 chlorine 

 + 75-36 silver. Now 24-64 : 75-36 :: 4*5 : 13-75 very nearly. 



B The weight of an atom of gold and of its oxides are derived 

 from the analyses of the oxides of gold by Berzelius. I have no 

 great confidence in these numbers, because 1 have doubts how 

 far the accuracy of the method followed by Berzelius is to be 

 depended on 



" The weight of the protoxide of platinum, and consequently 

 of platinum itself, is founded upon the analysis of protoxide of 

 platinum by Mr. Cooper, the discoverer of it. He found that 



