498 M. Regnault on the Specific Heat of Simple Bodies, 



which had been in contact with the air was cut off and the 

 cylinder immediately covered with tinfoil, the weight of which 

 had been previously determined. It could then be weighed at 

 leisure, and the experiment for determining its calorific capacity 

 be arranged. I have thought it necessary to determine it, at 

 temperatures below degree, in order to avoid the anomalies 

 proceeding from the successive softening which sodium suffers at 

 more elevated temperatures. 



In order to subject the substance to a uniform temperature, 

 and susceptible of an accurate determination, I used the appa- 

 ratus represented at fig. 2, which may serve also for higher 



Fig. 2. 



temperatures. Tlhis apparatus is composed of an oblong trough, 

 C D E F, resting on a support M N. An inclined tube of 

 brass traverses this trough, and its two open extremities pro- 

 ject at the exterior. It is in the middle of this tube that the 

 substance is kept which has to be raised to a fixed temperature. 

 In the present case, the cylinder of sodium, K, was fixed by silk 

 threads w^hich traversed the two orifices of the tube AB, and 

 were maintained by the two caps which closed them. A ther- 

 mometer, T, the bulb of which is inserted in the central hole of 

 the sodium cylinder, is fixed by means of a stopper on the cap A. 

 The trough is filled with a mixture of pounded ice and crystal- 

 lized chloride of calcium, which is constantly agitated. The 

 temperature gradually descends, but some time is necessary 

 before the minimum is reached, which then rests stationary for 

 ten or fifteen minutes. It is at this time that the calorimetric 

 experiment is made. 



In the calorimeter, V, a determinate quantity of naphtha 

 was placed, which had been previously distilled over metallic 



