MA HLER S CAL ORIME TER. 



59 



The calorimeter is of thin brass, and is quite large on ac- 

 count of the size of the combustion-chamber. It contains 

 2200 grams (4.85 Ibs.) of water, thus eliminating the causes of 

 error due to the loss of a few drops by evaporation.* The 

 agitator of Berthelot is supplanted by a very simple and gentle 

 cinematic combination called a drill 

 movement, and which can be worked 

 without fatigue. The source of elec- 

 tricity is a Trouve" bichromate pile (P, 

 Fig. 23) of 10 volts and 2 amperes. 



The oxygen used is that furnished by 

 the Compagnie Continentale d'Oxygene. 

 This company supplies oxygen free from 

 CO,, but containing from 5 to 10 per 

 cent of nitrogen. This means of supply 

 simplifies the manipulation ; it also ob- 

 viates the introduction of grease, as 

 happens with oxygen compressed by a 

 pump in the laboratory, f 



The cylinders vary in size, and con- 

 tain gas at a pressure of 120 atmospheres. 

 The average content is about 1200 litres 

 (about 40 cubic feet) compressed. They FlG> 24> 



have a uniform top, and hence the copper pipe connecting the 

 bomb with the manometer and the cylinder, once adjusted, 

 will fit all of them. 



The method of working is very simple. 



Weigh i gram of the substance to be tested in the cap- 

 sule. Fasten a small weighed iron wire (English gauge 26 or 

 30) to the electrode and to the support of the capsule. Put 

 the end in the bomb and fasten in the cover, which should be 

 held in a vise. Put the conical stop-cock in connection with 

 the oxygen cylinder, and open it carefully so as to allow suffi- 



* The evaporation never exceeds a gram per hour, 

 f This gas is also compressed by pumps at the works. 



