108 Prof. Rcgnault on the Specific Heat of some Simple Bodies. 



desirable to determine the specific heat of metallic lithium. 

 M. Debray provided me with an opportunity, by placing- at my 

 disposal a small quantity of lithium which he had carefully pre- 

 pared by Bunsciv's method. It consisted of a large globule 

 weighing about a gramme, and of 12 grains of the size of a 

 small pea. I endeavoured in vain to fuse these small grains 

 into a single globule ; but the layer of oxide with which they were 

 coated prevented them from completely welding. I preferred 

 to operate solely with the large globule, which in the cold could 

 be readily worked by the hammer, and presented a very lustrous 

 surface. 



To preserve the metal from contact with the air during the 

 experiment, it was hermetically enclosed in a leaden box, repre- 

 sented in fig. 4. The globule of lithium was first formed into a 

 cylinder by pressure in a lapidary's steel mortar; while at the same 

 time a hollow leaden cylinder abed had been made, in which 

 the plunger of the mortar fitted, as well as a leaden piston P. 

 The cylinder of lithium L having been placed in the hollow 

 cylinder of lead, the piston P was inserted above it, and briskly 

 struck with a hammer in order to enclose the lithium completely. 



The weight of the lithium being known, as well as that of the 

 leaden vessel, the calorific capacity of the whole arrangement 

 was determined by experiment ; and as that of the lead is known, 

 it is easy to calculate the specific heat of lithium. For the sake 

 of greater accuracy, before placing the lithium in the leaden 

 vessel, several experiments were made with this vessel provided 

 wii;.h its piston : these determinations gave exactly the calorific 

 capacity found by calculation for the weight of lead in the vessel . 

 The following are the results of three experiments made with the 

 lead and lithium together : — 



M . . 



, . 0^*945 



0e r -945 



0& r -945 



Lead 



, . 109s r -985 



109s r -985 



109^985 



T . , 



, . 99°*27 



99°*57 



99°-77 



& . , 



, . 26°-56 



26°*89 



26°-83 



A0' . , 



■ . 2°-0856 



2°*0555 



2°-0588 



A . , 



, . 15ls r -55 



151e r -55 



151^-55 



C . 



. . 0-9412 



0-9405 



0-9407 



Mean .... 0*9408. 



The calorific capacity of lithium is very considerable, being 

 almost equal to that of water. Taking its atomic weight at 

 80*37, the number assigned by chemists to lithium, the product 

 of its specific heat into its atomic weight would be 75*61. JBut 

 assuming that the atomic weight is 40*18, which gives for lithia 

 the formula Li 2 0, we obtain the product 37-80, and lithium then 

 completely satisfies the law of the specific heats of simple bodies. 



