COMPOSITION OF OXIDE OF ZINC. 51 



the ten thousandth part of the whole. The 

 accuracy of the process, indeed, is only limited 

 by the delicacy of the balance made use of in 

 the experiments. And my balance enabled me 

 to weigh to within less than one hundred thou- 

 sand part of the weight. 



It has been demonstrated by Gay-Lussac and 

 Humboldt, that water is a compound of oxygen 

 and hydrogen gases, in the proportion of one 

 volume of the former, to two volumes of the 

 latter. It occurred to me that by a very careful 

 analysis of water, the relation between the vo- 

 lumes and the weights of these gases might 

 perhaps be determined. These experiments 

 were made by means of zinc, and before their 

 accuracy can be appreciated, it will be necessary 

 to know the exact composition of the oxide of 

 zinc. I shall therefore divide this chapter into 

 three sections. In the first section, we shall de- 

 termine the composition of oxide of zinc ; in 

 the second, the specific gravity of oxygen gas ; 

 and in the third, the specific gravity of hydrogen 

 gas. 



SECT. I. 



OF THE COMPOSITION OF OXIDE OF ZINC. 



I SHALL be under the necessity to state in this 

 section a variety of facts, which may seem at 

 first sight foreign to the subject in view ; but 



D2 



