312 Mr. Haldane Gee and Dr. A. Harden on 



Another principle of obtaining the volume of a sub- 

 stance, which, so far as we are aware, has never before been 

 applied, is embodied in the apparatus of Fig. 7. 



Fig. 7. 



The glass vessel A and its tubes up to B and Bj (Fig. 7) 

 are calibrated. The substance of unknown volume is then 

 placed in A, the air of the vessel displaced by pure, dry 

 carbon dioxide, which is led in at the three-way tap B 

 and out at Bi, and the weight of carbon dioxide in the 

 apparatus determined by sweeping the gas out by a current 

 of dry air passed in at D, and absorbing it in a weighed 

 solution of caustic potash. The vessel A is immersed in 

 water, which keeps its temperature constant, and the latter 

 and the height of the barometer are both noted. From these 

 data the volume of carbon dioxide present is calculated, and 

 hence by subtraction from the known volume of the vessel, 

 the volume of the substance introduced. 



The experiments hitherto made show that the volume 

 of carbon dioxide can be easily estimated to within '3 per 

 cent of its calculated value, no allowance being made for 

 the small proportion of air always present (the gas was 

 generated by the action of diluted hydrochloric acid on 

 marble and dried by sulphuric acid). The following results 

 were obtained by gauging the volume of a vessel by this 



