160 THE ATOMIC WEIGHTS. 



B from the second portion, and series C from the third 

 portion : 



Series A. 



Mean, 82.455, ± -OOI 



Hence Al = 27.046, ± .061. 



The high probable error of this result is due to the high 

 probable error of the atomic weight of bromine. 



The experiments to determine the amount of hydrogen 

 evolved by the action of caustic soda upon metallic alumi- 

 num were conducted with pure metal, specially prepared, 

 and with caustic soda made from sodium. The soda solu- 



4 



tion was so strong as to scarcely lose a perceptible amount 

 of water by the passage through it of a dry gas at ordinary 

 temperature. As the details of the experiments are some- 

 what complex, the original memoir must be consulted for 

 them. The following results were obtained, the weight of 

 the hydrogen being calculated from the volume, by Reg- 

 nault's data corrected for the latitude and elevation of the 

 University of Virginia : 



Weight of Al. Vol. of H. Wt. of H. At. Wt. 



.3697 grm. 458.8 c. c. .04106 grm. 27.012 



•3769 

 .3620 



•7579 

 •73'4 

 •7541 



467.9 " .04187 " 27.005 



449.1 " .04019 " 27.022 



941.5 " .0S425 " 26.99S 



907.9 " .08125 " 27.006 



936.4 " .0S3S0 " 26.996 



Mean, 27.005, rt .0032 



