W. G. Mixter — Thermal Constants of Acetylene. 15 



hydrogen at the latitude of New Haven. The oxygen used 

 was free from water, hydrogen, and carbon compounds, con- 

 taining, however, about one per cent of nitrogen. After each 

 of the calorimetric tests the silver dissolved as nitrate was pre- 

 cipitated as chloride. The amount, however, was so slight that 

 no correction was made for the oxidation of nitrogen. 



To Professor H. A. Bumstead the writer is indebted for the 

 following method of reducing the results. 



The general formula for reducing the heat of combination, 

 found under the condition of constant volume, and between 

 the temperatures t x and t, to that found at 0° and under con- 

 stant pressure, is easily obtained by imagining the mixed gases 

 to be carried through two different processes from the same 

 initial state to the same final state, and equating the losses of 

 energy in the two processes. 



First Process. — M grams of mixed gases at p^V x t° are cooled 

 and compressed or expanded to^? V 0°. By Joule's law energy 

 given out is MC^ where G v is the sp. ht. (const.-vol.) of the 

 mixed gases. It is then burned at constant pressure, p , giving 



out Q calories, its volume simultaneously diminishes by ^ Y , 

 and work is done upon it equal to — ^-=- - calories. 



.*. Loss of energy = Q + MC^ 1 

 Final state is (p , — V , 0). 



7 J 



7 



Second Process. — M grams are burned at const, vol. V x , 

 temperature rising from t x to t giving out Q' calories; we have 

 now to reduce the mixture of C0 2 , water and water vapor, to 



4 . 



p ,—V , 0° to bring it to the same final state as by the previous 



process. No matter what the details of the process, the energy 

 given out by the C0 2 in this operation will be (Joule's law) 

 mc v t / where m and c v are the mass and specific heat of C0 2 . 

 We may therefore consider the water vapor separately. Sup- 

 pose it first compressed at constant temperature t until it is 

 wholly condensed ; the work done on the vapor will be 



— =-* calories 



o 



when 7r t is the pressure of water vapor at t°. The latent heat 

 given out will be cr t L t V 1 where <r t and L e are the density and 

 latent heat per unit mass at t. Let the water now be cooled 

 to degrees ; the heat given out is m w t, where m w is the mass 

 of the water formed. 



