206 METALLOIDS. 



distant from the aspirator* is first filled with oxide of 

 copper, and then heated while a current of hydrogen 

 gas is drawn over its surface. The heated hydrogen 

 carries with it the oxygen of the copper, and passes 

 into the second tube, as vapor of water. Here it is re- 

 tained by potassa, or some substance of similar proper- 

 ties. Both tubes are afterward weighed, and their gain 

 or loss determined, by comparison with their weight 

 before the commencement of the process. 



508. The loss of weight in the one tube. 



How are the 



results calcu- expresses the weight of the oxygen which 

 it has furnished for the formation of water ; 

 the gain in the second tube, gives the weight of the water 

 thus formed. The difference of the two, gives the 

 weight of the hydrogen which has been appropriated 

 in its passage, and now makes part of the newly formed 

 water. For every nine grains of water thus produced, 

 it is found that eight grains of oxygen, and one of hy- 

 drogen have been consumed. Its precise composition 

 is thus demonstated, by another and quite distinct pro- 

 cess. 



What is said 5$> SOLUTION. Water is a very gene- 

 of solution ? ra i so i ven t. The disappearance of salt, or 

 sugar, in water, is an example.f Transparency is es- 

 sential to a solution. Where the particles of a solid 

 are distributed throughout a liquid, as when chalk is 



* A vessel employed, as in the present instance, to produce a current 

 of air or gas, is called an aspirator. 



t Water also di-solves many gases. The ammonia of the shops is 

 prepared by passing gaseous ammonia in water. 



