48 CALORIFIC POWER OF FUELS. 



regulated so as to compensate approximately for the probable 

 use, and thus avoid corrections for influence of external air. 

 This cylinder was put into another, also of glass. A rotary 

 motion imparted to the cylinder aided circulation in the 

 liquid during combustion, which usually lasted thirty-five 

 seconds. 



Andrews also applied his calorimeter to combustion of 

 solids, but judging from the low results he did not have per- 

 fect combustion. The results obtained with some of the 

 gases, on the contrary, are quite reliable, notwithstanding the 

 imperfections of the apparatus. 



CALORIMETRIC BOMB OF BERTHELOT AND VIELLE. 



Of all the calorimeters known to-day, the calorimetric 

 bomb of Berthelot is that which offers the most advantages, 

 as much from its ease of operation as from the precision of 

 its results. Only one operator is needed ; the combustion is 

 perfect ; the gaseous products need not be analyzed to deter- 

 mine the combustible substance ; no weight save that of the 

 substance used is needed ; and it is as applicable to solids and 

 liquids as to gases. 



True, its use requires oxygen under high pressure ; but 

 this pressure (25 atmospheres) may be readily obtained with a 

 compression-pump, which is easily procured; and at the 

 present time oxygen may be bought sufficiently compressed 

 for the purpose. Berthelot states that as much as 5 or even 

 10 per cent of nitrogen is allowable, but that the latter limit 

 must not be exceeded. 



Mahler used compressed oxygen, and obtained good 

 results with that bought in the Paris market. This gas is 

 furnished in steel tubes and under 120 atmospheres pressure. 

 The cylinders contain sufficient gas to make a large number 

 of experiments before the pressure falls too low, i.e., below 

 25 atmospheres. 



