356 On the Cause of Chemical Proportions. [Mat, 



21. Colaltum, cohalt (Co). — By analogous experiments to those 

 made with nickel, Mr. Rolhoff found that 100 .parts of muriatic 

 acid are neutralized by 137*345 of the oxide of cobalt, ilence it 

 follows that this metal combines with 27*3 of osygtn. Mr. RolbofF 

 found likewise that 100 parts of peroxide of cobalt exposed to heat 

 lose from \)'b to 99 of oxygen, and are reduced to the state of 

 protoxide. Hence the peroxide contains 1^ times as much oxygen 

 as the protoxide. Hence the protoxide is Co -J- 2 O, and the 

 volume of cobalt weighs 732-61. 



It is a very remarkable circumstance that these two metals, nickel 

 and cobalt, wiiicli so frequently accompany each other in nature, 

 have, not only in their gaseous state, but likewise when in a solid 

 form, an equal specific gravity. 



22. Bi'imiithum, Insmulh (Bi). — Mr. Lagerhjelm has found that 

 this metal combinei with 11-275 of oxygen for the 100 of bismuth. 

 I have found tiiat this mttal when exposed to the air forms a purple 

 coloured protoxide. Hence the known oxide must be at least 

 Bi + 2 O. In that case the volume of bismuth will weigh 1774. 



The analogy between antimony and bismuth led me to expect 

 that it would be converted into an acid when heated with nitrate of 

 potash ; but 1 obtained only the common oxide, which even when 

 in a state of fusion did not mix with the fused nitre. 



23. Plumhum, lead (Pb). — I have found that 1 00 parts of this 

 metal combine in its three known oxides with 77? 11'55, and 15'4 

 of oxygen. But these numbers are to each other as 2, 3, 4. I 

 have endeavoured to prove that the tarnished and blackish surface, 

 which lead acquires when exposed to the moist air, is a protoxide of 

 ,hat metal. Hence it follows that the yellow oxide must be Pb + 



O. The volume of lead then weighs 2597"4. 



24. Slaiini/}?!, tin (Sn). — 1 have proved in another memoir that 

 tin has three degrees of oxidation, and that the protoxide is com- 

 posed of 100 metal and 13-6 oxygen, while the peroxide contains 

 twice that quantity. As these three oxides are all salifiable, it is 

 probable that their respective quantities of oxygen are to each other 

 as the numbers 2, S, 4, and not as the numbers 3, 4, 6, because 

 this last progression belongs to the oxides vyhich have acid proper- 

 ties, as those of antimony, arsenic, and chromium. Besides, the 

 progression of oxidation of a metal ought to be the same as that of 

 its different degrees of sulphuration ; and I have proved that tin has 

 three sulphurets, in which the sulphur is as the numbers 2, 3, 4, 

 and the two extremes of which are proportional to the protoxide and 

 peroxide of tin. Hence the intermediate sulphuret and oxide must 

 have a proportional composition. From these observations it follows 

 that tlie three oxides of tin are Sn + 2 O, Sn + 3 O, Sn + 4 O, 

 and that the volume of this metal weighs 1470*49. 



25. Ferrum, iron (Fe). — I have found that the purest hammered 

 iron contains always about half a per cent, of carbon, and that it 

 produces 14.V5 of red oxide, which of course contains only 99*5 of 

 iron : 100 of iron, then, combine with 44*25 of oxygen. The 



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