to the Knowledge of Chemical Bodies. 



325 



Here there is such an exact agreement in 5 out of 6, that 

 the density multiplied by the oxygen gives one constant 'num- 

 ber. Iodine is the only exception, the product of which is 

 much greater than it should be: but as iodine was only dis- 

 covered in 1812, as there is only one of its combinations with 

 oxygen (iodic acid) known, and as all the others combine 

 with oxygen in more than one proportion, I have strono- 

 hopes that future investigations will cause this anomaly to 

 disappear; particularly as chlorine, which is very similar in 

 many respects to iodine, combines in such proportions as 

 would with iodine give the true number, viz. 1 atom chlorine 

 + 1 atom oxygen. 



A familiar example of the combination of oxygen with a 

 metal, and the condensation resulting, will serve to give a 

 clear idea of what I conceive to be another law. — Oxygen in 

 uniting to a metal has its bulk reduced to a small measure of 

 the balk of the metal. 



Lead, the density of which at 62° when perfectly pure and 

 allowed to cool gradually, is 11-352, water being 1-, takes of 

 oxygen, to form its protoxide, 7'692 to 100 metal : that is, a 

 cubic inch of lead, weighing 2886^ grains, unites with 222 

 grains or 655 cubic inches of oxygen gas; but the 656 cubic 

 inches are now reduced to very nearly l£ cu hi c inch, for the 

 oxide would only displace that quantity of water, having a 

 density of 9-277; therefore, we must suppose the cubic inch 

 of lead to have condensed the 655 cubic inches of oxygen to 

 M of its own bulk, or to l-2036th part of the space it occupied 

 in the state of gas. The following list will show that the 

 same law obtains with the other metallic oxides. 



Lead 



