Determining tJte Specific Heat of a Liquid. 103 



If water be used in both places and we neglect for the moment 

 the variations in the specific heat of water and assume it to be 

 unity, then 



or W = Wi(^i-£) 



The water-equivalent of the apparatus, exclusive of contents 

 is therefore 



w,(«,-«)_„_,V,. 



If the liquid of unknown specific heat o-q be now used in the 

 calorimeter, we have 



y^\{0-0) = {^^\ + ^v,a,) {0-6,) 



=w,{e-eo)+^yo<To{o-Oo) 



If the liquid of unknown specific heat be used in the spiral, 



we have 



^yMOi-0) = ^y{0-0,) 



^y{e-6,) 



Generally speaking, there will be corrections for the variation 

 in the specific heat of water and also corrections for losses of 

 heat by radiation, but their application is simple and requires 

 no special reference. 



I will now proceed to show in detail how each of the quantities 

 involved in the above equations is measured, and also what 

 degree of accuracy is to be attained in each measurement. 



^1 — the temperature of the hot liquid. About twenty to 

 twenty-three grams of the liquid are poured into a glass tube 

 (n) — see diagram — enclosed in a large tin vessel (/?) suitably 

 shaped and containing about twelve litres of water. This 

 vessel is well screened by two felt screens so as to intercept 

 as much as possible of its radiation and especially to screen 

 the calorimeter ; the water in it is kept at a temperature of 

 from 50° to 60°C. by means of a very small gas jet beneath it, 

 and its temperature can be kept constant within one-tenth of a 

 degree for hours together. As will be seen from the diagram, 

 the glass tube passes through the water-jacket diagonally, and 



