ATOMIC WEIGHTS 21 



Second Series. — Electrolytic Hydrogen, Dried hy Phospliorus Pentoxide. 



Mean, 15.8893, ± .0014 



At the end of this series it was found that the hydrogen contained a 

 trace of water, estimated to be equivalent to an excess of three milli- 

 grammes in the total hydrogen of the six experiments. Correcting for 

 this, the mean becomes = 15.899. 



Fourth Series. — Electrolytic Hydrogen, Dried over Freshly Sublimed 

 Phosphorus Pentoxide. 



Wt.ofH. Wt.ofO. Ratio H:0. 



1.0444 8.3017 15.898 



.7704 6.1233 15.896 



.8231 6.5421 15.896 



.8872 7.0490 15.890 



.9993 7.9403 15.892 



1.1910 9.4595 15.885 



Mean, 15.8929, ± .0013 



The mean of all the twenty-four determinations, taken as one series, 

 with the correction to the third series included, is = 15.8966, ±.0017. 

 In sum, there were consumed 18.5983 grammes of hydrogen and 147.8145 

 of oxygen; whence = 15.8955. 



Dittmar and Henderson,* who effected the synthesis of water over 

 copper oxide by what was essentially the old method, begin their memoir 



^ Proc. Roy. Soc. Glasgow, 22, 33. Communicated Dec. 17, 1890. 



