238 



ELEMENTARY GENERAL SCIENCE 



CHAP. 



We have now a means of obtaining hydrogen in considerable 

 quantity, and have observed that it is a colourless, odourless 

 gas, considerably lighter than air, which does not support com- 

 bustion, but which burns itself, and which with air forms a 

 highly explosive mixture. 



Production of Oxide of Hydrogen. We must next endeavour 

 to obtain and to examine the compound which is produced by 

 the burning of hydrogen, that is, the oxide of hydrogen. 



EXPT. 244. Arrange a flask as before for the production of 

 hydrogen. Pass the gas through a tube containing chloride of 

 calcium in order to thoroughly dry it. Allow it to burn under 



FIG. 123. Production and Collection of Oxide of Hydrogen (Water). 



a retort which is kept cool by a stream of water flowing in at 

 the tubule and out at the end of the neck (Fig. 123). Observe 

 the formation, on the side of the retort, of a clear liquid 

 which collects and drops into a beaker placed to receive 

 it. By this means sufficient of the liquid can be obtained to 

 identify it, especially if a number of students all work together 

 and add the liquids. 



EXPT. 245. Take the density, freezing point (a mixture of 

 sodium sulphate and hydrochloric acid forms a very convenient 

 freezing mixture), and boiling point of the liquid. You will 

 find these are 1, C., and 100 C. respectively, a result which 

 is sufficient to enable us to state that the liquid is identical 

 with pure water. 



