955 
refer to the communication quoted above. For the sake of comple- 
teness we will mention two small improvements *) : 
1. The tube of the glass compression vessel a, was made much 
longer in order to preclude all danger of the mercury when it rises 
quickly penetrating into the metal capillaries. 
2. In the connection between the small high-pressure reservoir a 
and the compression vessel a,, (by the taps c,,, ¢,,, &,, and k,,) a 
glass pipette of about one litre was introduced by means of a 
T-piece, so as to make it possible to transfer the nitrogen to the 
compression vessel in measured quantities. 
These two improvements have added considerably to the certainty 
and convenience with which the apparatus could be manipulated. 
§ 3. As regards the method of conducting the experiments we 
may also in the main refer to the previous paper. 
The vapour-pressure measurements, which are needed for the 
calculation of the corrections, were not made during the diameter- 
determinations this time, but in a separate series of experiments, 
which will form the subject of a separate communication by one 
of us. *) 
The temperature was again measured and at the same time kept 
constant by means of two platinum-thermometers /P¢,, and Pt, 
which had been compared shortly before the measurements with 
the standard platinum-resistance-thermometer /%';. The latter had 
not long ago been once more very carefully compared with the 
hydrogen-thermometer*), so that the temperature-measurement in 
our determinations must have satistied very high requirements. The 
agreement of the two resistance-thermometers used left indeed nothing 
to be desired. In these measurements we were assisted by Mr. P. G. 
Carn, phil. nat. cand., whom we gladly hereby express our thanks 
for his coöperation. 
4. Calculations. As regards these we may again refer to the 
previous communication. The reductions for tie dead spaces at low 
temperature could not be made with the same certainty as in the 
case of argon; for the latter substance extensive series of observations 
of isotherms for low temperatures‘) were available, whereas for 
nitrogen the same data are at present entirely lacking. We were 
1) Comp. fig. 1 which is the improved form of the right-hand part of fig. 1 in 
Comm. NO. 1314. 
2) CG. A. CROMMELIN, This number of the Proc, Comm. N°. 145d. 
3) KAMERLINGH ONNES and G. Horst, Proc. Sept. 1914, Comm. NO. 141a. 
4) H. KAMERLINGH ORNEs and C. A. CROMMELIN, Proc. Dec. 1910, Comm. 
N'. 1185, and C. A. CROMMELIN, Dissertation, Leiden. 1910. 
