1249 
through the drying spiral Sp, cooled 
in liquid air to the reservoirs R, was 
condensed in the calorimeter flask /” 
(Fig. 2). The heat capacity of this 
flask (provided with heating and ther- 
mometer wires) with the condensed gas 
in it was then measured by the method 
of electrical heating in a high vacuum 
(ef. Comm. N° 143, these Proc. De- 
cember 30, 1914). 
The capacity of the steel reservoirs 
(together about 45 L., the same 
reservoirs which served for the mea- 
surement of the heat of vaporization 
of hydrogen, Comm. N°. 187e), and of 
the connections as far as necessary, 
was accurately determined by the vo- 
lumenometrie method, using two glass 
bulbs (together 4.5 LL.) calibrated with 
water. The quantity of gas, which was 
condensed in 4, was calculated from 
the pressures of the gas in FR before 
and after, taking into account the gas 
which remained in the connections. 
For a check after the measure- 
ments the gas was collected from the 
Fig. 2. calorimeter into /? and measured again. 
The spiral Sp,, which was cooled in liquid air, serves for retaining the 
last traces of moisture and other vapours. To prevent a deposition 
of solid nitrogen in the glass inlet tube 5, (continued by the copper 
tube d,, internal diameter 3 mm.), and to get the calorimeter properly 
filled, the cooling was performed very slowly from below upwards. 
The, condensation process was checked with the manometer J/ and 
for the measurements on solid nitrogen was continued until at the 
triple point the nitrogen, as calculated from the volume of the 
calorimeter and the density of the liquid, filled the flask /’to a little 
below the top. For safety a second tube b,d, was provided, by which 
the gas, if 6, or d, sbould become obstructed, can escape through the 
safety tube v (provided with a strike-back safety-valve v, for the 
mercury and a U-tube wv, cooled in liquid air for protecting the 
calorimeter from mercury vapour), or else be led back to £ through 4, 
Through the bottom a chamber is let in into #, into which the 
