58 HYDROGEN AND OXYGEN. 



In proportion as the combustion proceeds, water is 

 deposited in the internal surface of the vessel ; the 

 quantity of this water gradually increases, and it 

 unites itself intolarge drops, which run down the sides 

 of the vessel, and are collected in the bottom of it. 



In making this experiment, proper means were 

 taken to ascertain the weight of the gases em- 

 ployed. Before the experiment, the vessel was 

 weighed ; and, by weighing it after the operation, 

 the weight of the water that had been formed was 

 obtained. Here, then, is a double proof; on the 

 one hand, the weight of each of the gases em- 

 ployed ; and, on the other, the weight of the water 

 formed ; and these two quantities were found to 

 be equal within a two hundredth part. It was thus 

 found that 85 parts by weight of oxygen, and 15 

 parts also by weight of hydrogen, are required to 

 compose 100 parts of water. 



These phenomena of the decomposition and 

 recomposition of water are continually effected be- 

 fore our eyes, by the temperature of the atmos- 

 phere, and the agency of compound affinities. It 

 is this decomposition which gives rise, at least in a 

 certain degree, to the phenomena of spirituous fer- 

 mentation, to those of putrefaction, and to those 

 of vegetation. 



Pure water is perfectly transparent, and has no 

 taste nor smell. It is not liable to change. It can 

 absorb a variety of gases ; and when exposed to 

 the atmosphere, it always contains a small quantity 

 of common air, which may be separated by boiling, 

 or by the air-pump. Rain-water is the purest which 

 we see in nature ; but, for delicate chemical pro- 

 cesses, it is distilled in glass vessels. Spring- water 

 generally holds some salts in solution, which gives 

 it various properties. 



