128 



ELEMENTS OF LABORATORY WORK 



consequently contain the same amount of water or hydrogen 

 sulphate vapour ; but they are evidently not in the same con- 

 dition with regard to pressure. To remedy this the tubes 

 should be raised or lowered, in another vessel if necessary, 

 until the gas is in each case counterbalancing the pressure of 

 the atmosphere. 



If the pressure of the atmosphere be now read from the 

 barometer, and the temperature be taken, the volumes of the 

 gas, now found to correspond with the known quantities of the 

 metals, may be subsequently utilised. So far, we are only con- 

 cerned with the difference which is shown in the -extent of 

 the action of different kinds of matter upon hydrogen sul- 

 phate. When other equal quantities are taken, the same ratio 

 is maintained in the volumes of gas liberated. 



The gas which is set free in each 

 of the tubes may be shown to be in- 

 flammable. That it is the same gas 

 we have not yet proved, although a 

 little research would be sufficient to 

 prove this. 



The same operation may be carried 

 out with the substitution of hydrogen 



Fig. 43. 



Fig. 44. 



chloride for hydrogen sulphate, and the same observations 

 may be made. The ratio which is observed in one reaction 

 is maintained in another. 



