( 177 ) 

 XIII. The preparation of liquid air hy means of the cascade process. 



§ 1. Efficiency of the regenerative cascade method. In none of 

 the communications there was as yet occasion to treat more in 

 detail of the preparation of liquid air by the Leiden cascade pro- 

 cess. In the description of the preparation of liquid oxygen (in Comm. 

 N°. 24, Dec. '94) I have said that especially the ethylene refri- 

 gerator had been constructed very carefully, and that the principle 

 after which various cycles operating in the regenerative cascade can 

 be made was embodied there. 



When the new methyl chloride circulation (comp. Comm. X". 87, 

 March '04) was ready and the inadequate methyl chloride refrigerator 

 was replaced by one constructed after the model of the ethylene 

 boiling vessel with application of the experience gained, it was possible 

 to prepare a much larger quantity of liquid oxygen (10 liters per 

 hour easily) with the same ethylene boiling vessel. This quantity 

 will still increase when the regenerator in the ethylene boiling vessel 

 will be enlarged so much as our experience with the new methyl 

 chloride regenerator has again taught to be desirable and when the 

 exhaust tube of the ethylene boiling vessel will have been replaced 

 by one of greater width than could be used originally. The intro- 

 duction of a nitrous oxide and of a methane cycle, which in '94 

 stood foremost on our programme, has dropped into the background 

 especially when, also for other reasons (in order to obtain the tem- 

 peratures mentioned at the end of XII § 1), it appeared desirable to 

 procure vacuumpumps of greater displacing capacity ('96) and these, 

 being arranged for operations with pure gases (described in Comm. 

 N°. 83, March '03) had become fit to be introduced into the ethylene 

 and the methyl chloride cycles (wiiile in general for the cryostats 

 these two cycles were sufficient, cf. the end of XII § 1). Larger 

 quantities of oxygen could be used in consequence, for which (as 

 mentioned in '94) a Brotherhood compressor was employed (comp. 

 the description of the installation for operations with pure gas in 

 Comm. N'\ 51 § 3, Sept. '99). A picture of the cascade method in 

 this stage of development accompanies a description of the crvogenic 

 laboratory by H.H. Francis Hyndman in "Engineering" 4 Mrch '04. 



This picture represents how the oxygen cycle is used to maintain 

 the circulation in the nitrogen cycle, described in Comm. N". 83, 

 March 1903. In the same way as nitrogen we also liquefy air with 

 the oxygen cycle. When it is drawn off the liquid air streams from 

 the tube in a considerable jet; about 9 liters of liquid air are collected 

 per hour, so that iji one day we can easily prepare half a hectoliter. 



