HEAT OF WATER, WITH EXPERIMENTS BY A NEW METHOD. 
21 
therefore, preferable to adopt a method of reduction depending on some assumed 
variation of the total heat. This appears at first sight a less direct method, but is 
peculiarly appropriate when the primary object of the experiment is to verify formulse 
already obtained by different methods. 
Variation of the 'Total Heat. 
The variation of the total heat is not so familiar as the variation of the specific 
heat, but since the change of total heat between given limits is the quantity actually 
measured in a calorimetric experiment, the total heat is generally the most useful 
quantity to tabulate for experimental purposes. The numerical value of the total 
heat h from 0° C. to t° C. in terms of a unit at 20° C. differs but little from t over the 
range 0° C. to 100° C. It is, therefore, convenient to write 
h = t + dh, .(8) 
where dh is the small excess of h over t at any temperature, which may appropriately 
be called “ the variation of the total heat.” 
The value of dh given by Ludin’s formula (5) is 
dh = 0-84 -3-8656 y + 6-588 f—Y-2-929 (— 
100 Vloo/ Vloo/ \ioo 
whence the value at 100° C. is 0-84 + 6-588 — 3-8656 —2'929 = +0-633. 
The corresponding formula for dh deduced from my formula (6) representing the 
results of the continuous-electric method is 
d/i = 1-1605 logio^^-1-464 -^+0-42 f—Y +0-30 f-^Y, . . (lO) 
^ 20 100 \100/ VlOO/ ^ ' 
whence the value at 100° C. is 0-903-r464 + 0-420 + 0-300 = +0-159, differing from 
Ludin’s formula by nearly 0-5 per cent. 
These two formulse are represented by the curves in fig. 6. In order to save space. 
