26 



PROCEEDINGS OP THE AMERICAN ACADEMY 



In Experiment 11 a hard glass tube with small rubber stoppers was 

 employed for the ignition of the baric bromide, but it was attacked 

 by the salt and gained 0.10 milligramme during the heating. 

 This gain corresponds to a loss of about the same weight of bromine, 

 assuming all the barium which combined with the glass to have 

 been converted to the oxide. For this reason the amount of hydro- 

 bromic acid recorded in the seventh column of the final table is 

 about 0.12 cubic centimetre too large. In calculating the corrected 

 weights of baric bromide, silver, and argentic bromide, allowance 

 is made for all these facts. Because of the complication of all these 

 little corrections, the glass tube was abandoned, and the platinum 

 crucible was again used. 



Data and Kesults. 



The first column of the final Table of Data. gives the number of 

 the experiment. The second column contains the weight of the 

 crystallized baric bromide, while the third contains the observed 

 weight of the ignited baric bromide. After this is recorded the 

 number of cubic centimetres of standard hydrobromic acid (of 

 which one litre corresponded to a gramme of silver) required to re- 

 store the small amount of bromine lost during ignition. This 

 quantity is divided into two parts, the upper one corresponding to 

 baric hj^droxide, and the lower to baric carbonate. Multiplying 

 the upper figure in this column by -^^-^ milligramme, and the 

 lower figure by -^% milligramme, and adding the two products to 

 the weight given in column III., we obtain the corrected weight of 

 the baric bromide which is recorded in the fifth column. The sixth 

 column gives the total weight of silver taken; the seventh, the 

 number of cubic centimetres of the same hydrobromic acid necessary 

 to titrate back to the mean end point; and the eighth, the weight 



