144 APPENDIX II. 



all experimentally determined, and was added to the 

 increase of temperature observed in each experiment. 

 The amount of heat carried away by the escaping 

 gases after issuing from the water may be divided 

 into two items, viz. : 



a. The amount of heat rendered latent by the 

 water which is carried off by the gases in the form 

 of vapour. 



b. The amount of heat carried off by these gases 

 by reason of their temperature being above that of 

 the water from which they issue. 



It was ascertained that a stream of dry air when 

 passed through the water of the calorimeter, at 

 about the same rate and for the same period of time 

 as the gaseous products of combustion, depressed the 

 temperature of the water by only 0< 02 C. 



By placing a delicate thermometer in the escaping 

 gases, and another in the water, no appreciable 

 difference of temperature could be observed. Both 

 these items may therefore be safely neglected. 



The two remaining corrections can be best con- 

 sidered together, since a single careful determina- 

 tion eliminates both. When a combustible sub- 

 stance is burnt in gaseous oxjsgen, the conditions 

 are essentially different from those which obtain 

 when the same substance is consumed at the expense 

 of the combined or solid oxygen of chlorate of pot- 

 ash. In the first case the. products of combustion, 

 when cooled to the temperature of the water in the 

 calorimeter, occupy less space than the substances 

 concerned in the combustion, and no part of the 

 energy developed is therefore expended in external 



