D6 Lord Bayleigh. On the Character of the 



for u preliminary heating of the, large generating vessel and its charge, 

 with the result that the excess r of weight was raised to 55 milligrams, 

 or about 2J per cent, of the whole. In any case heat is developed 

 during the reaction, and the heavier weights of some of the earlier 

 trials probably resulted from a more rapid generation of gas. 



In seeking to obtain evidence as to the nature of the impurity, 

 the most important question is as to the presence or the absence of 

 carbon. The former experiment has been more than once repeated, 

 with the result that the baryta showed a slight clouding. Parallel 

 experiments in which C0 2 was purposely introduced, indicated that the 

 whole carbon in a charge of gas weighing 30 milligrams in excess was 

 about 1 milligram. It is possible (though scarcely, I think, probable) 

 that this carbon is not to be attributed to the gas at all, and in any 

 case the amount appears to be too small to afford an explanation of 

 the 30 milligrams excess of weight. If carbon be excluded, the range 

 for conjecture is much narrowed. As to oxygen, only traces were 

 found in most of the samples examined, whereas enormous quantities 

 would be needed to explain the excessive weight. It should be noted, 

 however, that the extra heavy sample, showing 55 milligrams excess, 

 gave evidence of containing a more appreciable quantity of oxygen. 



It seems difficult to suggest any other impurity than nitrous oxide 

 which could account for the anomalous weight. Unfortunately there 

 is no direct test for nitrous oxide, but so far as the examination has 

 been carried, the behaviour of the gas is consistent with the view that 

 this is the principal impurity. The gas as collected has no smell. The 

 proportion of nitrous oxide indicated by the refractometer is nearly 

 the same as that deduced from the weight. For example, the refrac- 

 tivity was observed of some of the gas which weighed 55 milligrams 

 in excess. The proportion by volume (;) of N 2 in the whole 

 required to explain the excess of weight is given by 



22 2-299 + 0-055, 



**U + l - X " -T299" 

 whence x = 0*042. 



The refractivity (referred to air as unity) of the same gas was deter- 

 mined by two independent sets of observations as 1"047, 1*048; 

 mean, 1*0475. If we assume that there are only nitrogen and nitrous 

 oxide present, the proportion (x) of the latter can be deduced from 

 the known ref inactivities (/*-!) of nitrous oxide, nitrogen, and air, 

 which are respectively 0-0005159, 0-0002977, 0*0002927, the number 

 for air being kss than for nitrogen. Thus, 



a; x 5159 + (1- a-) x 2977 - 1-0475x2927, 

 giving w = 0-0408. 



The slight want of agreement can be explained by the presence of a 



