1892.J Prof. Dewar on Magnetic Properties of Liquid Oxygen. 695 



WEEKLY EVENING MEETING, 



Friday, June 10, 1892. 



The Eight Hon. Lord Kelyin, D.C.L. LL.D. Pres. E.S. 



Vice-President, in the Chair. 



Peofessor Dewar, M.A. LL.D. F.R.S. M.B.I. 



Magnetic Properties of Liquid Oxygen. 



(^Abstract.) 



After alluding to the generous aid which he had received both from 

 the Royal Institution and from others in connection with his 

 researches on the properties of liquid oxygen, and to the untiring 

 assistance rendered him by his co-workers in the laboratory, Prof. 

 Dewar said that on the occasion of the commemoration last year of 

 the centenary of the birth of Michael Faraday he had demonstrated 

 some of the properties of liquid oxygen. He hoped that evening to • 

 go several steps further, and to show liquid air, and to render visible 

 some of its more extraordinary properties. 



The apparatus employed consisted of the gas-engine downstairs, 

 which was driving two compressors. The chamber containing the 

 oxygen to be liquefied was surrounded by two circuits, one traversed 

 by ethylene, the other by nitrous oxide. Some liquid ethylene was 

 admitted to the chamber belonging to its circuit, and there evapo- 

 rated. It was then returned to the compressor as gas and liquefied, 

 and thence, again, into the chamber as required. A similar cycle of 

 operations was carried out with the nitrous oxide. There was a 

 hundredweight of liquid ethylene prepared for the experiment. 

 Ethylene was obtained from alcohol by the action of strong sulphuric 

 acid. Its manufacture was exceedingly difficult, because dangerous, 

 and as the efficiency of the process only amounted to 15 or 20 per 

 cent, the preparation of, a hundredweight of liquid was no light task. 

 The cycle of operations, which, for want of time, was not fully ex- 

 plained, was the same as that commonly employed in refrigerating 

 machinery working with ether or ammonia. 



The lecturer then exhibited to fhe audience a pint of liquid 

 oxygen, which by its cloudy appearance showed that it contained 

 traces of impurity. The oxygen was filtered, and then appeared as 

 & clear transparent liquid with a slightly blue tinge. The density 

 of oxygen gas at —182° C. is normal, and the latent heat of vola- 

 tilisation of the liquid is about 80 units. The capillarity of liquid 

 oxygen at its boiling-point was about one-sixth that of water. The 

 temperature of liquid oxygen at atmospheric pressure, determined by 

 the specific heat method, using platinum and silver, was — 180° C. 



Reference was then made to a remarkable experimental corrobo- 

 ration of the correctness for exceedingly low temperatures of Lord 



