( 139 ) 
diameter 11 em. contained in a felt-coated copper vessel (height 14, 
width 12, 5 em.), which is packed with solid carbon dioxide. The 
condensing spiral is provided on both sides with a regulating-cock (for 
the model see SIERTSEMA, Comm. Suppl. No. 1, Pl. ILI, fig. 9) and 
To the latter of these a narrow discharging tube is fastened. 
5. Boiling nitrous-oxide in large quantities. Cycle of nitrous- 
oxide. If we wish to cool apparatus with larger volumes or capaci- 
ties for heat in a bath of nitrous-oxide, it will be necessary to 
receive the gas evolved by the liquid and to compress it by means 
of a compressor with or without cooling. As at Leiden a methyl- 
chleride-cycle is at hand, the proper way was not to compress the 
nitrous-oxide at the ordinary temperature, but in the methylchloride 
refrigerator (Comm. N°. 14 § 3, see also Pl. J, Maruras l.c.). As 
compressor a Brotherhood-pump could be used, arranged as described 
above § 3. 
If we condense the N,O at a very low temperature, the vapours 
escaping from the refrigerator are very rare andthe vacuum-pump, which 
sucks them up, can only move a small quantity of methylchloride. 
If we condense the N,O at a higher temperature, more methyl- 
chloride will certainly evaporate and more nitrous-oxide will be 
condensed, but the latter will evaporate to a much greater degree 
on flowing out than more cooled N,O0. Usually we operated at the 
temperature —45° C of the methylehloride-refrigerator and the 
safety-valve of the Brotherhood (see § 3) was adjusted for 25 atm. 
The separator in order to work well, should have a rather large 
capacity in which therefore a large stock of N,O would be stored 
up at high pressure. This alone would make it desirable not to 
proceed to too high pressures, and moreover at the discharge of 
the gas, which deviates strongly from Boyte’s law, from the 
separator water might be frozen and so cause accidents. 
Plate LV ') represents a scheme (the parts nearly 1/3; nat. size) of 
the arrangement of the apparatus in Dr. HasENOEHRL’s experiments 
with liquid nitrous-oxide (Comm. N®. 52) as an example of operations 
with the nitrous-oxide cycle. B is the Brotherhood-pump, with acces- 
sories, of which the principle may be understood from plates II and IIT 
together with ¢3. The compressed gas is conducted through the regu- 
lating-cock (ks Plate II) along D (Plate IV) to the methylchloride- 
refrigerator, where it is cooled first by the cold methylehloride vapours 
1) For simplicity a case was here selected for which the refrigerator had been 
formerly described; but a refrigerator, wholly independent of the triple-cascade 
might be used, 
