THE ANALYSIS OF CADMIUM CHLORIDE. 9 



had been expelled. After the salt had cooled, the hydrochloric acid was dis- 

 placed by pure dry nitrogen and this in turn by dry air. Next, by means of a 

 glass rod, the boat was pushed into the weighing-bottle contained in the soft- 

 glass tube V, and the stopper was inserted without opening the apparatus or 

 interrupting the current of dry air by rotating the tube V slightly so as to 

 cause the stopper to roll from its position in the pocket of the tube into the 

 main tube. By means of the rod the stopper was readily pushed into place. 

 This bottling apparatus in its improved form was first used by Richards and 

 Parker in their work upon magnesium chloride.^ The bottle was transferred to 

 a desiccator and, after standing near the balance case for some time, it was 

 weighed by substitution for a counterpoise similar in weight and volume as 

 well as shape. 



Sublimation of the cadmium chloride always took place to some extent during 

 the fusion, and the subhmed salt occasioned some difficulty since it flowed down 

 the inside of the glass tube and, upon solidification, firmly cemented the boat 

 to the tube. Furthermore, the salt which adhered to the outside of the boat had 

 thus been fused in contact with glass, and hence may have been impure. Both 

 these difficulties were avoided by supporting the boat upon a carriage of heavy 

 platinum wire. While the salt was still warm and the current of hydrochloric- 

 acid gas was still passing, the boat was pushed out of the carriage by m.eans of 

 a long glass rod. Neglect to observe the latter precaution usually resulted in 

 the cementing of the boat to the carriage by the salt which had condensed upon 

 the outside of the boat. 



It has already been shown that barium and calcium chlorides when they have 

 been fused and allowed to solidify in an atmosphere of hydrochloric-acid gas, 

 occlude none of the gas,^ for they give neutral solutions; hence it is reasonable 

 to conclude that this is the case with cadmium chloride also. However, in order 

 to test this point, in analysis 9 the hydrochloric acid was displaced by nitrogen 

 while the salt was still warm, and in analysis 8 the salt was allowed to solidify 

 only when the hydrochloric acid had been almost completely displaced by 

 nitrogen. In one experiment where the hydrochloric acid had been completely 

 displaced by nitrogen, the boat became covered with a gray coating which 

 turned brown, and finally volatilized when the boat was ignited. This coating 

 undoubtedly consisted of metalHc cadmium, formed either by the dissociation 

 of cadmium chloride vapor or by the action of the small amount of hydrogen con- 

 tained in nitrogen produced by Wanklyn's method, owing to catalytic decom- 

 position of the excess of ammonia by the hot copper. The close agreement of the 

 results of analyses 8 and 9 with those obtained in the other analyses where the 

 salt solidified and cooled in hydrochloric acid, shows conclusively that no ap- 

 preciable amount of hydrochloric acid was occluded by the salt. 



' Loc. cit. 



^ Richards: Proc. Amer. Acad.,2g, 59 (1893); Zeit. anorg. Chem., 6, 93 (1894); Jour. Amer. 

 Chem. Soc, 27, 376 (1902); Zeit. anorg. Chem., 31, 273. 



