156 CALORIMETRIC APPARATUS. 



longed shaking over mercury with its own volume of acid 

 cuprous chloride. 



Its composition was verified ; 102 vols. of this gas, burnt in 

 the eudiometer by a slight excess of oxygen (360 vols.), produced 

 200 '5 vols. of carbonic acid. The total diminution of the 

 volume after explosion and absorption of carbonic acid, amounted 

 to 451 vols. ; the remainder, deprived of the excess of oxygen by 

 hydrosulphite, yielded two volumes of nitrogen. 



According to the formula C 2 H 6 -f 7 = 2C0 2 + 3H 2 0, 

 100 vols. of combustible hydrocarbon should have produced 

 200 vols. of carbonic acid, occasioning a total diminution of 450 

 vols. 



The gas analysed was therefore ethane, containing only two 

 hundredth parts of nitrogen, which have no appreciable influence 

 on the heat of combustion. 



The foregoing results show that the gas employed is really 

 ethane, and that its combustion by a slight excess of oxygen is 

 total. However, it has appeared useful to prove that the com- 

 bustion is effected in the same manner in the calorimetric 

 bomb, that is to say, that the above equation is applicable to 

 the measurement itself. 



With this object, the bomb was filled with the mixture of 

 ethane and oxygen in suitable proportions, placed in the water 

 of the calorimeter, and the gases exploded ; then the whole of 

 the gases contained in the bomb were extracted by the aid of 

 a mercury pump, passed into a large test-tube, in which the 

 carbonic acid was absorbed by potash and the excess of oxygen 

 by hydrosulphite. 



It is known that this reagent does not act either on carbonic 

 oxide or on hydrocarbons. The residuum thus obtained under- 

 went no diminution of volume by cuprous chloride, it was not 

 combustible, and, mixed with half of its volume of oxygen, it 

 did not explode under the influence of the electric spark. In 

 another trial, for greater certainty, the analogous residuum was 

 mixed with its own volume of electrolytic gas after adding 

 oxygen to it, in order to burn the last traces of combustible 

 gases, if such existed. But this test showed that there remained 

 in the residuum nothing but nitrogen. The combustion of 

 the ethane- in the calorimetric bomb had therefore been total, 

 as well as in the eudiometer. 



The following are the figures of a calorimetric experiment 

 performed on October 28, 1880. 



200 cub. cms. of ethane and 720 cub. cms. of pure oxygen 

 were mixed over mercury, and the mixture was passed, with the 

 aid of a system of suitable tubes, into the calorimetric steel 

 bomb lined with platinum, shown on p. 152, a vacuum having 

 previously been created in the bomb with the aid of the mercury 

 pump. The cock of the bomb was closed, and the latter was 



