472 Intelligence and Miscellaneous Articles. 



with }?ermissible approximation. To render this expression calcu- 

 lable I substitute for I and L their values according to Clapeyron's 

 formula, and obtain 



c?Q = L 1- 



The addition of a weight x — x^ of water will evolve a quantity of 

 heat given by the integral 



Q=l( [l-^Aclv. 



M cii J 



^ dt ' 



/, r, L are given by the experiments of M. Eegnault ; and from 



them we deduce — and — . Besides, if x—x^ is slight, we readily 

 ctij etc 



perceive that the mean value of the element (which varies with 



X — x^) of the integral is obviously the mean of the values taken by 



elf 



the ratio — . after the addition of the weights x^ and x of water. 



This being admitted, what is the quantity of heat evolved, for 

 example, when H^ is mixed with SO^ IT^ + H^ ? M. Pfaundler's 

 formula gives 3048 calories. M. Kirchhoff's relation gives the fol- 

 lowing figures : — 



Temperatures. Calories. 



10 4554 



20 3168 



21 2887 



22 2648 



24 2420 



M. Pf aundler's measure was probably taken in the vicinity of 20°. 



The above Table shows the influence of temperature in calome- 

 tric determinations of this order, and sets forth what is wanting 

 for a complete investigation of the question. However, M. Kirch- 

 hofE's relation, presented under the foregoing form, and conse- 

 quently rendered quickly calculable, may be considered sufficient 

 until direct measurements are obtained. — Comjotes Bend us de VAca- 

 demie des Sciences, Oct. 1, 1877, tome Ixxxv. pp. 617-619. 



