chap, xxxviii.] CALORIMETRY. 479 



This form is called the WATER CALORIMETER. In the 

 ICE CALORIMETER the body whose specific heat is to 

 be measured is placed in a receiver made of thin 

 sheet copper. It is placed in an outer vessel con- 

 taining broken ice at the melting point, the space 

 between the two vessels being entirely filled with the 

 broken ice. The heat from the body melts the ice, 

 and is measured by the quantity of water produced. 

 As we have seen, it takes always a definite quantity 

 of heat to convert 1 pound of ice at the freezing 

 point into 1 pound of water at the same temperature. 

 The water produced trickles down through the ice, 

 and escapes through a tube at the bottom of the 

 vessel into a vessel placed to receive it. To ensure 

 that all the ice is melted by the heat of the body, 

 and none by the heat of the surrounding air, a third 

 vessel also containing broken ice surrounds the other 

 two. The heat of the surrounding air is intercepted 

 bv this outer ice jacket, and the water produced is 

 caused to flow into a different vessel from that which 

 catches the water produced in the calorimeter. This 

 form of calorimeter was constructed by Laplace and 

 Lavoisier. 



The construction of the calorimeter will be 

 understood by reference to Fig. 196. It shows the 

 water calorimeter employed by Favre and Silbermann 

 to measure the quantity of heat produced by the com- 

 bustion of different substances. (See page 460.) It 

 consists of a vessel K in which the substance to be 

 burnt is placed. K is enclosed in a chamber L, in 

 which it is completely surrounded with water. The 

 chamber L is supported on feet in a larger chamber M, 

 the space betw-een the two being packed with a non- 

 conducting material An outermost vessel N tilled with 

 water encloses the whole. The heat given off by the 

 burning substance in K is communicated to the water 

 in LJ raising its temperature the non-conducting 



