222 E. IF. Morley — Volumetric Composition of Water. 



little impurity as one part in fifteen thousand. In the autumn 

 of 1888, Scott* stated that the volume of hydrogen required 

 seemed to decrease when it was evolved continuously from the 

 same apparatus; and that the variation showed some impurity 

 at present undetected, fle published the results of four ex- 

 periments giving values varying from 2*001 down to 1'995. 



My own experiments on this matter are a part of one of my 

 processes for determining the ratio of the atomic weights of 

 oxygen and hydrogen. In this determination, the ratio of the 

 densities of the two gases under ordinary conditions is one 

 factor, and the ratio of their combining volumes under the 

 same conditions is a second factor. Since it is difficult to free 

 hydrogen from nitrogen, I hoped to obtain it free from every 

 other impurity, and to determine the amount of nitrogen con- 

 tained in it, so that I could compute a numerical correction to 

 the observed density. I have now finished the determination 

 of the combining volumes of the gases unless some as yet unde- 

 tected error should necessitate further investigation. I have 

 been able to reduce the mean error of a determination to less 

 than one half of that which I ventured to predict early in the 

 volumetric studies preliminary to the actual determinations. f 

 As the degree of accuracy which I hope it will be found that 

 I have attained is very considerably greater than in determina- 

 tions of the same kind by others, I have thought it needful to 

 give a somewhat minute account of the details of the work, in 

 order that those interested in the matter may better judge 

 what degree of confidence may fairly be reposed in the result, 

 or may be in a position to suggest improvements or corrections 

 needed in my processes. Though some parts of the work go 

 back for many years, yet, thoroughly agreeing with the expres- 

 sion of Ostwald that he undertakes a heavy responsibility who 

 publishes values of constants, I have made public no figures 

 obtained till I have done the best that I know how to do. 



Preparation of pure hydrogen. — The preparation of pure 

 hydrogen has been difficult. I tried long to obtain it by the 

 action of dilute acids on zinc. It is in this way not difficult to 

 obtain the gas free from arsenic and sulphur (or chlorine), and 

 easy to obtain it free from oxygen by passing the hydrogen 

 over heated copper; but two difficulties remain, one of which 

 is serious. The amount of hydrogen which can be obtained 

 from a given weight of materials is not always enough to 

 sweep out all the nitrogen present in the apparatus or con- 

 tained in the liquids used and still leave much of the gas to be 

 utilized. Perhaps, by constructing the apparatus so that it 

 can be repeatedly exhausted, this difficulty could be overcome. 



* Br. Assoc. Trans.. 1888. p. 631. 



f Am. Chem. Journal, vol. x. p. 23. 1888. 



