192 ROYAL SOCIETY OF CANADA 



ing way. The volume of the reservoir was 7 litres, so that it contained 

 7 m grams of gas at standard temperature and pressure, m being the 

 mass of one litre. Hence by Boyle's Law, for every millimetre fall of 

 pressure 7m/760 grams of gas must have escaped. The calibration of 

 the gauge was checked by means of a mercury manometer, and its read- 

 ings reduced to millimeters of mercury. In an experiment with atmos- 

 pheric air for which m=1.293 the quantity of air which issued from the 

 reservoir was calculated for a series of different pressure falls and the 

 results of this calculation are exhibited in Fig, 5. In this figure the 

 ordinates represent the quantities of air which escaped when the pressure 

 fell to zero from uie values indicated by the corresponding abscissae. 



(3) The Calorimeter. 



The bore of the capillary tube of the calorimeter was calibrated by 

 filling it with mercury and then running it out a little at a time and 

 weighing the parts run out. From this the mass of mercury occupying 

 each division was found for different parts of the tube. 



The number of calories required to cause a displacement of one 

 gram was found as follows: — 



Data : — 



1 gram of water gives out 80.025 calories on freezing. 

 1 gram of water occupies 1.00013 c.c at 0°C. 

 1 gram of ice occupies 1.090 x 1.00013 c.c at 0°C 

 1 gram of mercury occupies .073553 c.c at 0°C. 



Solution : — 



80.025 calories used in melting ice cause a change in volume of 



1.00013 \ 1.090 - 1 [ c.c. and therefore cause a displacement of 



1.00013 ] 1.090 - 1 I X 1 grams of mercury. 



^ ^ .073553 



Hence a displacement of one gram of mercury means the using of 

 .073.^53 X 80.025 calories = 65.4 calories. 

 1.U0013 (1.090 - 1) 



From this value the number of calories causing a displacement of 

 one division at different parts of the scale was found. The results of 

 this calibration are illustrated by Fig 6, which shows at any point the 

 number of calories corresponding to a displacement of the mercury from 

 zero of the scale to that point. 



