( .^8 ) 



tn determining the quantity of gas in the tube the latter is sunk 

 into the mercury so deep that the measuring of the volume and of 

 the pressure of the gas may be done with the same accuracy. Fitting 

 toünd the tube are elastic cylinders of thin sheet iron, provided 

 tvith sharp points, which are bent downwards. The needle is pointed 

 at the mercury surface, and the rim allows to read the divisions on 

 the glass tube. In doing this an india rubber stopper bearing a 

 glass water-jacket is fixed round the glass tube. By means of this 

 simple contrivance we know also the temperature of the gas to be 

 measured and so the volume may be reduced to 0° C and 1 atmosphere. 



In determining the quantity of the liquid-mixture and of the 

 vapour-mixture drawn off, we also take into consideration the portion 

 of the mixture which remains in the spaces A and B after the 

 flowing off under the barometric pressure. Especially for the vapour 

 at low pressure this should not be disregarded. 



As the measuring tubes were filled with mercury in the ordinary 

 way, there remained a small quantity of air in the theoretical vacuum; 

 this quantity was determined and taken into account. 



§ 8. Results. 



The plait on the «/^-surface of carbonic acid and methylchloride 



