CALO RIME TRY. 1 3 



Carbon, which, before their time, had given only 7624 

 calories to Laplace, 7386 to Clement-Desormes, 7915 to Des- 

 pretz, 7295 to Dulong, and 7678 to Andrews, yielded to F. 

 & S. 8081 after correction for carbonic oxide in the waste 

 gases. This number has since been increased to 8140 by the 

 latest determinations of Berthelot. Berthelot and Vielle have 

 shown that by using oxygen under pressure complete com- 

 bustion can be attained v 



INSTALLATION OF APPARATUS. 



The apparatus should be placed in a room free from 

 sudden changes in temperature and consequently protected 

 from direct sunlight. If it is not entirely protected from 

 solar radiation, the apparatus may be set up on the north 

 side and shaded from the direct midday sun by a screen. 



The calorimeter cylinder with its accessories, as well as the 

 distilled water used, should remain in the room long enough 

 to acquire its proper temperature. The cylinder should be 

 protected as much as possible from radiation by envelopes 

 which vary according to circumstances. Favre and Silber- 

 mann used a cylinder with a double wall. The external one 

 was rilled with water, and between this one and the cylinder 

 proper swan's down was packed. The upper part of the 

 cylinder also had a layer of thick paper covered with down 

 on the under side. 



Berthelot states that the down is more troublesome than 

 useful, and that it may be omitted with advantage. The space 

 between the cylinder and its envelope forms a layer of air 

 which is an excellent non-conductor. In modern instruments 

 the down is replaced by a thick layer of felt. Berthelot even 

 omits this covering, stating that the great cause of loss of 

 heat was not from radiation, but due to evaporation produced 

 by the agitation of the water in contact with the air. He 

 surrounds his cylinder with a layer of air inside of the 

 envelope of water, and outside of all a layer of felt 0.8 inch 

 thick. By this means external influence is much reduced. 



