On the Density of Nitrou* 0,dde. 181 



" On the Density of Nitrous Oxide." By LORD KAYLEIGH, O.M. 

 F.RS. Eeceived September 1, 1904. 



In the ' Proceedings,' vol. 72, p. 204, 1 897,* I have given particulars of 

 weighings of nitrous oxide purified by two distinct methods. In the 

 first procedure, solution in water was employed as a means of separating 

 less soluble impurities, and the result was 3'6356 grammes. In the 

 second method a process of fractional distillation was employed. Gas 

 drawn from the liquid so prepared gave 3 '6362. These numbers may 

 be taken to represent the corrected weight of the gas which fills the 

 globe at C. and at the pressure of the gauge (at 15), and they 

 correspond to 2 "6276 for oxygen. 



Inasmuch as nitrous oxide is heavier than the impurities likely to be 

 contained in it, the second number was the more probable. But as I 

 thought that the first method should also have given a good result, I 

 contented myself with the mean of the two methods, viz., 3*6359, from 

 which I calculated that referred to air (free from H 2 and C0 2 ) as 

 unity, the density of nitrous oxide was 1 '52951. 



The corresponding density found by M. Leduc is 1-5301, appreciably 

 higher than mine ; and M. Leduc argues that the gas weighed by me 

 must still have contained one or two thousandths of nitrogen, f Accord- 

 ing to him the weight of the gas contained in my globe should be 

 3*6374, or 1'5 milligrammes above the mean of the two methods. 



Wishing, if possible, to resolve the question thus raised, I have lately 

 resumed these researches, purifying the nitrous oxide with the aid of 

 liquid air kindly placed at my disposal by Sir J. Dewar, but I have not 

 succeeded in raising the weight of my gas by more than a fraction of 

 the discrepancy (1*5 milligramme). I have experimented with gas 

 carefully prepared in the laboratory from nitrate of ammonia, but as 

 most of the work related to material specially supplied in an iron 

 bottle I will limit myself to it. 



There are two ways in which the gas may be drawn from the supply. 

 When the valve is upwards, the supply comes from the vapourous 

 portion within the bottle, but when the valve is downwards, from the 

 liquid portion. The latter is the more free from relatively volatile 

 impurities, and accordingly gives the higher weight, and the difference 

 between the two affords an indication of the amount of impurity present. 

 After treatment with caustic alkali and sulphuric acid, the gas is 

 conducted through a tap, which is closed when it is desired to make 

 a vacuum over the frozen mass, and thence over phosphoric anhydride 

 to the globe. For the details of apparatus, etc., reference must be 

 made to former papers. The condensing chamber, which can be 



* Or ' Scientific Papers,' vol. 4, p. 350. 

 t ' Recherches sur les Gaz,' Paris, 1898. 



