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to run fast (at 150 revolutions per minute), and could hence be of 
small dimensions and inexpensive. 
With pressures up to 10 atmospheres the disadvantages of the 
lubricant used, in connection with a drying apparatus presently to be 
described (in v) are so unimportant that I hope before long to obtain 
by means of this apparatus liquid hydrogen. The vacuum pump 
which I considered necessary for this in Comm. N°. 23 § 5 will 
soon be in regular work. 
The connection, whenever the mercury pump and the auxiliary 
compressor work together, is shown by IL (PI. III). The mercury 
pump and auxiliary compressor are regularly used for the oxygen- 
circulation of the cryogenic laboratory (comp. comm. N°. 14) 5, in 
the manner described. 
The gas from the auxiliary compressor passes first through the 
eg. drying tower for gas under high pressure. This is a steel 
bottle 7 (see Pl. IIT and Pl. VI, fig. 3. A front view of Z was 
already given in Comm. N°. 51, Pl. II, as D;) closed at the upper 
end by means of a nut with flat sides and an overpipe with packing 
I,. The tube is made very wide so as to secure a slow motion of 
the gas. It is designed to stand a higher possible pressure (150 
atm.) than that allowable in the drying tubes described in Comm. 
N°. 51 (§ 3 and fig. 6 Pl. III.) 
The drying agent (phosphorous pentoxide, or sometimes sodium 
hydroxide) is not immediately introduced into this heavy tube, but 
is in a thin-walled brass tube Z,, which is so fastened in the drying 
tower that the gas is obliged to flow through the drying agent. It 
is exhausted by the pump itself, the cocks N33 and O, being 
used. When the tube J, is filled with the substance through which 
the gas must pass mixed with glasswool or dried asbestos, and closed 
at the upper and the lower ends with the sieves Js; and 74» (fastened 
to it by screw-threads) we may allow the rim Jas to rest on the 
wall of the drying tower itself and then screw up the bottom 745 
by means of the bar J4;, which causes the packing to expand and 
press against the wall of J. 
The bent tube Js; serves to let out the drops of glycerine that 
might be carried along from the auxiliary compressor, the cock Is: 
is used to remove them, to exhaust the apparatus, and to introduce 
or draw off gas. 
1) Comp. Mathias |. c, Pin 
