266 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



Wt.H. At.Wi. {H = l). 



.041234 26.898 



.042051 26.889 



.040362 26.907 



.084614 20.872 



.081595 26.891 



.7541 936.4 .084156 26.882 



Mean, 26.890, ± .0034 



Hence Al = 37.099, when = 16. 



The closing series of experiments was made with larger quantities of 

 aluminum than were used in the foregoing set. The hydrogen, evolved 

 by the action of the caustic alkali, was dried by passing it through two 

 drying tubes containing pumice stone and sulphuric acid, and two others 

 containing asbestos and phosphorus pentoxide. Thence it passed through 

 a combustion tube containing copper oxide heated to redness. A stream 

 of dry nitrogen was employed to sweep the last traces of hydrogen into 

 the combustion tube, and dry air was afterwards passed through the 

 entire apparatus to reoxidize the surface of reduced copper, and to 

 prevent the retention of occluded hydrogen. The water formed by the 

 oxidation of the hydrogen was collected in three drying tubes. The re- 

 sults obtained were as follows. The third column gives the amount 

 of water formed from 10 grammes of aluminum. 



2.1704 grm. Al gave 2.1661 grm. H„0. 9.9802 



2.9355 " 2.9292 " 9.9785 



5.2632 " 5.2562 " 9.9867 



Mean, 9.9818, ± .0017 



Hence Al = 27.073. 



From the last two series of experiments an independent value for the 

 atomic weight of oxygen may be calculated. They give = 15.895, when 

 H = l. The closeness of this figure to some of the best determinations 

 affords a good indication of the accuracy of Mallet's work. 



In connection with Mallet's work it is worth noting that Torrey' 

 published a series of measurements of the H : Al ratio, representing 

 determinations made under his direction by elementary students. These 

 measurements are thirteen in number, and calculated with Eegnault's 

 old value for the weight of hydrogen, range from 26.661 to 27.360, or in 

 mean, 27.049, ±.323. Corrected by the latest value for the weight of H, 

 this mean becomes 26.967, when H = l. This figure, of course, has only 

 confirmatory significance. 



1 Amer. Chem. Joum., 10, 74. 1888. 



