Chemistry and Physics. 391 
would be 136° and the amount of heat absorbed 2982-2 units. 
Evidently then less than one-half of the heat of hydration is due 
to this cause. M. Ditte has also determined the solubility of 
e 
thermometer, but it was found possible to simplify very greatly 
the details of the process without seriously impairing the accu- 
ble investigation of the boiling point of s at different 
emperatures, the observations of temperature are undoubtedly 
accurate to this extent, but Regnault’s own n of these 
own more accurately; for even when withim the range of a 
mercury thermometer an observation of a g point to be 
accurate to a tenth of a centigrade de attentio 
The glass thermometer bulb used in our bi sc age is repre- 
sented in the accompanying figure of one-hal the 
‘its linear dimensions. The longer stem was made of fine ther- 
mometer tube, and a shorter stem was added to the opposite end 
of the bulb in order to facilitate the cleaning, drying, filling, or 
emptying of the interior—all of which was easily accomplished 
by the aid of a Bunsen pump. The shorter stem was of course 
sealed after the bulb Kad been dried and made ready for use, and 
before it was immersed in the medium whose temperature was to 
measured. After an equilibrium had been established at this 
unknown temperature T°, the protruding end of the longer stem 
