Section III, 1919 [27] Trans. R.S.C. 



The Estimation of the Helium Content of Mixtures of Gases by the Use 



of a Katharometer^ 



By V. F. Murray, M.A., B.Sc. 



Presented by Professor J. C. McLennan, F.R.S.C. 



(Read May Meeting, 1919.) 



Introduction 



The katharometer instruments dealt with in this paper were 

 designed for use with mixtures of hydrogen and air. In view of the 

 use of helium in airships it seemed desirable to investigate whether 

 such instruments could be utilised for mixtures of helium with air, 

 helium with oxygen, and helium with nitrogen. 



Since the katharometer is based upon the thermal conductivity 

 of a gas mixture, it would be anticipated that the instrument, at least 

 in the case of high percentage mixtures of helium with the gases 

 mentioned, could be employed. Values for the thermal conductivity 

 of hydrogen at 0°C have been given as KXlO~^ = 327 (Winkelmann) ; 

 397 (Eucken)^; 416-5 (Weber)^; while that for helium at 0°C has been 

 found to be KX10~^ = 336 (Eucken) ; 338-6 (Schwarze); 343-8 

 (Weber)^. Thus the thermal conductivities of helium and hydrogen 

 are of the same order. 



On experiment it was found that the various instruments respond- 

 ed when helium mixtures were used, and they were therefore calibrated 

 for mixtures made with this gas and air, oxygen or nitrogen. 



Principle of the Katharometer 



Dr. G. A. Shakespear has supplied us with information on the 

 design and details of the instruments dealt with in this paper and we 

 are indebted to him for the greater portion of the material of the 

 description which follows. 



In a katharometer the measurement depends upon the cooling 

 of a platinum spiral on exposure to the gas mixture which is being 

 tested. This spiral, carried on a copper frame, is mounted in a copper 

 cylinder pierced at the end and with three small orifices to admit 



^ Communicated by Professor J. C. McLennan, F.R.S., by permission of the 

 Admiralty. 



^ Landolt-Bornstein Tab. 



3 Weber. Annal, d. Physik. Bd. 54, 1917. 



