354 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



boat carefully placed in the reduction tube, where it was heated in a 

 current of moist hydrogen until the fumes of hydrobromic acid ceased to 

 come off. The tube was then swept out with dry hydrogen, and when 

 cool the boat was quickly replaced in the weighing bottle coutaining dry 

 air, and was thus weighed after a suitable delay. In most analyses this 

 process was repeated until the weight of the cobalt ceased to change. 

 Cobalt reduced from the bromide is less constant in weight than nickel, 

 gaiuing several tenths of a milligram in weight in twenty-four hours. 



Fig. 1. Apparatus for ignitixg CoBALTOrs Bromide in ant desired 



iNIixTCRE OF Gases. 



Tlie use of rubber was confined to the fir.st part of this trnin, where it could do 



no harm (A B C D E F and A M N O P). 



For this reason the metal was always allowed to become thoroughly cool 

 in the atmosphere of hydrogen, and the weighing bottle was allowed to 

 come to perfect equilibrium with the atmospheric conditions inside a desic- 

 cator at the room temperature before receiving the boat. After half an 

 hour nickel treated in the same way had been found to come to constant 

 weight, and in half an hour the opportunity for oxidation of cobalt is so 

 slight as to be negligible ; hence this interval was the one which always 

 elapsed between the bottling and the weighing of the cobalt. In one 

 analysis, to see if exposure to the air affected the weight of the cobalt, 

 the boat was bottled in dry nitrogen in the bottling apparatus, after 



