﻿166 Prof. R. Bunsen's Calorimetric Researches. 



For the magnitudes in equation (2), 



p = > 



s w —s e 



we have therefore the values : — 



v =0-00007733, 

 s e =0-91674, 



s w =0*99988; 

 and thence 



p =0-00085257. 



The weight of melted ice (e) in grammes corresponding to T 

 corrected divisions on the scale is therefore 



e=0-00085257T (3) 



If the latent heat of liquidity of water be called I, a scale- 

 division pi corresponds to the unit of heat above defined. For 

 the amount of heat w, expressed in units of heat, which T scale- 

 divisions indicate, we have 



w=plT; 



or when we take for I the value 80-025 as found below, then 



w=0-068227T (4) 



Since the ice-cylinder surrounding the vessels weighs from 40 

 to 50 grms.,and on an average in each experiment only about 0*35 

 grm. of ice requires to be melted, which corresponds to some- 

 what more than four hundred scale-divisions, it is possible, with 

 the same ice-cylinder, to make one hundred calorimetrical re- 

 searches and to use the same apparatus (prepared once for all) 

 for a week, if only care is taken to renew the snow round the 

 instrument every night and morning. The ice cylinder is easily 

 produced by an arrangement represented in fig. 2. A is a tin- 

 plate vessel containing alcohol, and B an empty tin-plate vessel, 

 which are both cooled down in a freezing-mixture of salt and 

 snow to about —20° C. C represents the inner vessel (a, fig. 1) 

 around which the ice-cylinder is produced. On sucking at the 

 tube a, the cold alcohol of the vessel A is brought over into the 

 vessel B through the vessel C; and therefore, conversely, on 

 sucking at b the alcohol is brought back into the vessel A through 

 C. By alternate sucking at a^and b, the vessel C can, to the 

 level a, by means of fresh cold alcohol be kept at a temperature of 

 from —10° C. to —15° C, and thus the ice cylinder gradually 

 formed in the mass of water (b, fig. 1) surrounding the tube C. 



