Cobalt by Hydrochloric Acid. 397 



cyanide, and neither the apple-green hydroxide nor the black 

 sulphide, prepared by the usual methods, showed any trace of 

 cobalt in the borax bead. It is obvious, therefore, that nickel 

 chloride is not fully precipitated under these conditions and 

 that the green color of the solution is due to nickel in solution 

 and not to traces of iron, as Pinerua has supposed.* A second 

 experiment similar to the first showed a solubility of the 

 nickel chloride represented by 0*0018 gm. of metallic nickel. 

 It is evident, then, that the solubility of nickel chloride in this 

 mixture of aqueous hydrochloric acid and ether thoroughly 

 saturated with hydrochloric acid gas is not far from an amount 

 represented by 0-0020 gm. of metallic nickel for every 14 cm * of 

 solution. 



Still another experiment, in which nickel chloride repre- 

 senting 0*0020 gm. of metallic nickel was treated with ll cm3 

 of the ether-hydrochloric acid solution and the whole saturated 

 for one hour at a low temperature with hydrochloric acid gas 

 without precipitation, showed the same thing. 



When the nickel chloride remaining on the asbestos was 

 washed with about 40 cm3 of a mixture of equal parts ether and 

 aqueous hydrochloric acid saturated with hydrochloric acid gas, 

 the washings evaporated with sulphuric acid and treated by the 

 battery gaveadeposit of metallic nickel weighing 0*0027 gm. — 

 an amount proportionately less than that found in the filtrate 

 proper. 



Although employing a mixture of aqueous hydrochloric acid 

 and ether saturated with gaseous hydrochloric acid for the 

 precipitation, Pinerua has advised the use of pure ether sat- 

 urated with gaseous hydrochloric acid for the washing. In my 

 experiments with such a mixture I find that in it the hydrous 

 nickel chloride is practically insoluble and that 30 cm3 of the 

 washings of the precipitated chloride with such a mixture gave 

 no deposit of nickel by the battery. It seemed possible, 

 therefore, that by reducing the water present to the lowest 

 possible amount necessary to dissolve the chlorides to be treated 

 the precipitation of the nickel might be made more complete. 

 The experiments of the following table were made to put this 

 idea to the test. 



Solutions of the pure chlorides of nickel and cobalt, carefully 

 purified and freed from other metals and each other, were, 

 after conversion to the form of the sulphate, standardized 

 by the battery. Weighed portions of these solutions were 

 taken in a small beaker, evaporated to dryness, the dry salts 

 dissolved in as little water as possible (about l cm3 ), 10 to 15 cm3 

 of ether added, and the whole saturated with hydrochloric-acid 

 gas, the beaker being meanwhile immersed in running water 



* Loc. cit. 



