pure, recrystallized potassium permanganate, by heating in an apparatus 
which was completely of glass, and leading the gas over heated plati- 
nized asbestos. The apparatus which had served the same purpose 
in Comm. N°. 78 § 44, had been improved by Dr. C. A. CROMMELIN 
when reconstructed, in that the tubes for drying and for absorbing 
the carbon dioxide had been replaced by an arrangement which 
allowed the gas to be condensed by cooling with liquid air and the 
liquid obtained to be re-evaporated (comp. Comm. N°. 117). A deserip- 
tion of the apparatus will be given on a future occasion. 
The nitrogen was prepared in the Pharmaceutical Laboratory 
under the supervision of Professor van ITaLti, to whom we hereby 
express our hearty thanks. The method of preparation was by boiling 
a solution of sodiumnitrite and sodiumsulphate with ammonia; the 
nitrogen was then led over sulphuric acid in order to keep back 
ammonia that might be carried over. 
The purity of both substances was checked by condensation expe- 
riments (comp. Comm. N°.145d), when it appeared that the vapour- 
pressure between the beginning and the end of the condensation 
did not rise by more than a few hundredths of an atmosphere, 
§ 3. Results. The results are contained in the following tables. 
TABLE 1. 
Vapour pressure of oxygen. 
gtje) PERE pin dn 
| 
—154.91 C. 118.18 K. 9.096 
149.29 123.80 12.506 
138.98 134.11 21.328 
138.95 134.14 21.342 
135.99 137.10 24.528 
130.67 142.42 30.914 
125.31 147.78 38.571 
121.36 151.73 45.138 
121.35 151.74 45.142 
| 121.33 151.16 45.217 
120.04 153.05 47.258 
118.70 154.19 49.640 
Eren TOER Pikes iid a! 
