On the Method of Condensation in Calorimetry. 361 



glass ; it was found that such bulbs will not stand the internal 

 pressure otherwise obtaining at steam temperature. 



Its weight is now 15'930 grams. It is estimated that its content 

 is altogether 16'5 c.c. ; this quantity of air at 760 mm. and 11°, as 

 above, weighs very closely 0'020 gram. The deduction for the 

 weight of the glass envelope in order to deduce the weight of con- 

 tained water is, then, 2-084 — 0*020 affording W=13'866. 



In subsequent experiments with this bulb of water, it is necessary 

 from the precipitation obtained to deduct w, as ascertained by experi- 

 ments (1) and (2), above, diminished however by the quantity of 

 precipitation to be ascribed to the calorific capacity of the contained 

 air present in those experiments. Taking the specific heat of air as 

 0"2389, this retrenchment calculates to be nearly 1 mgrm. of precipi- 

 tation, and it is taken as such as it probably contained still some 

 moisture. This leaves the deduction as 0'115 for a range of 89'2°. 

 Although the nearly constant displacement difference of the bulb 

 from air to steam is here included, this quantity may without sensible 

 error be recalculated for variations in temperature range as the cor- 

 rection on the large condensations subsequently obtained. The 

 further process of experiment is the same as previously described in 

 the case of zinc. 



In this way, the six experiments contained in the following table 

 have been carried out : — ' 



Table of Experiments on Distilled Water. 



So. 



W. 





t 2 °. 



X. 



w. 



Sp. heat. 



1 



13 866 



11-20 



99 -90 



536 • 56 



2 



•3125 



1 -0087 



2 



jj 



11-70 



99-45 



536 -90 



2 



•2760 



1-0044 



3 



>j 



8-80 



99 -55 



536 -80 



2 



•3610 



1-0074 



4 





9-70 



99-50 



536 -80 



2 



•3320 



1 -0055 



5 





9-47 



100 00 



536-50 



2 



3530 



1 -0055 



6 





8 80 



100-10 



536-40 



2 



•3740 



1-0059 





Mean . . 



10° 



100° 







1 -0062 



Between same limits, according to Kegnanlt, specific heat = 1 "0055. 



The last four experiments in the table were carried out in such a 

 way that the rate of precipitation was much retarded, in fact the 

 conditions were altered to those prevailing in the case of a very badly 

 conducting body. This was effected by shielding the glass bulb from 

 direct contact with the steam by a loose fitting copper-foil box, an 

 intervening air-jacket being left around the bulb. With this arrange- 

 ment precipitation was hardly completed in 15 minutes ; the naked 



2 B 2 



