1887.] 



On the Composition of Water by Volume. 



397 



understood, but their deviations from it are in opposite directions ; 

 hence it can only be by the merest chance that at our ordinary 

 temperatures and pressures the combining volumes should be exactly 

 two of hydrogen to one of oxygen. Moreover, when, we consider 

 that it is more than eighty years since these researches were carried 

 out, that the instrument used in all the measurements was Volta's 

 eudiometer, and that the gases were collected and measured over 

 water and so contained impurities to the extent of 0*4 per cent, in 

 the oxygen and 0"6 to 0'8 per cent, in the hydrogen used, a redetermi- 

 nation of this ratio with the greatly improved means for attaining 

 accuracy now at our command seemed to be of extreme importance. 

 The exact ratio as given in the memoir referred to is 199*89 volumes 

 of hydrogen to 100 volumes of oxygen, and this the authors say is 

 almost exactly as 2 : 1. 



To arrive at greater accuracy the author of this note has given 

 especial attention to the following points : — 



(1.) The preparation of purer gases. 



(2.) The use of larger volumes. 



(3.) The measurement of both gases in the same vessel. 

 (4.) The analysis of the residue after explosion and determination 

 of the impurity in each experiment. 



