548 Dr. E. J. Mills 



on the 





pp. 151, 2: 







Zn 19-688 65-079. 

 Zn H 80-312 1 



Hence 



15-95 

 H 1 



p. 290 : 







Fe 2 O3 _ 55-608 29*992. 

 H 2 Fe 2 1 * 70-008 



Hence 



15-88 

 H 1 



pp. 179, 180 : 







Al 2 3H 2 53-780 9-9818. 

 H 2 Al 2 " 2 10 



Hence 



15-89 

 H 1 



I regard these ratios as very important, because they are 

 now for the first time disclosed^ and could not have been 

 obtained intentionally. There is thus a residual uncertainty 

 about O : H. 



As regards the methods employed, it is open to question 

 whether a current of gas can be dried ; at any rate, I have 

 not succeeded in drying a current of air. Glass globes, and 

 other glass apparatus, must resemble thermometer-bulbs in 

 undergoing progressive contraction. Hydrogen (according 

 to Dittmar and Henderson) decomposes sulphuric acid at the 

 ordinary temperature — presumably in presence of light. 

 Phosphoric anhydride (according to Crookes) is apt, unless 

 previously heated, to give up matter to hydrogen, and, one 

 would suppose, to other gases. Hydrogen made from metals 

 is likely to contain carbonic impurity (Morley). Mercury 

 is a nearly certain impurity in most gases ; its presence 

 reduces the relative gravity of oxygen by about "02. 

 Bottger's important observation (Cliem. Centr. 1878, p. 574) 

 that the mixture H 2 : 0, when exploded, always produces 

 some peroxide, seems to have been almost entirely over- 

 looked : and the same remark applies to Richardson's dis- 

 covery (Proc. Chem. Soc. 1889, p. 134) that water forms 

 peroxide on exposure to light. A quantity of peroxide 

 amounting to *05 p. c. of the water would reduce the value 



yj by about '06. 



The preparation of hydrogen by electrolysis of baryta- 

 water, and its subsequent occlusion by palladium, is a great 

 step in advance, as enabling hydrogen to be weighed instead 

 of measured. Scott's use of argentic oxide, also, has pro- 

 bably resulted in the production of oxygen of improved 



