B. B. Biggs — Separation of Magnesium Chloride, etc. 103 



Aut. 5 IV. — The separation of Magnesium Chloride from 

 the Chlorides of Sodium and Potassium by means of Amyl 

 Alcohol ; by E. B. Eiggs. 



This separation depends on the insolubility of the chlorides 

 of sodium and potassium and the solubility of magnesium 

 chloride in amyl alcohol. That the alkaline chlorides are in- 

 soluble in this reagent has already been shown by Gooch in his 

 paper* on the separation of sodium and potassium from lithium 

 by the action of amyl alcohol on their chlorides. In the same 

 paper attention is also called to the solubility of anhydrous 

 magnesium chloride. The difficulty, if there be any, lies in 

 dehydrating this chloride. Attempts to dehydrate magnesium 

 chloride by direct heat result in a more or less complete de- 

 composition. This is also found to be the case where the salt, 

 in a solution containing no free acid, is rendered anhydrous by 

 means of boiling amyl alcohol. The amount decomposed, in 

 this latter case, is however relatively small. The decomposi- 

 tion products are the oxide and hydrochloric acid. It is there- 

 fore necessary either to introduce conditions which will pre- 

 vent such decomposition or to find a means of redissolving any 

 oxide that may be formed. The use of hydrochloric acid gas 

 was deemed impracticable. To use the acid solution was 

 regarded as objection ablef because, in so doing, water, the 

 very substance to be driven out, would be brought into the 

 solution. Experiments were made in which, after the water 

 of the maguesium chloride solution had been nearly or quite 

 expelled by boiling with amyl alcohol, a few drops of benzyl 

 chloride were added and the dehydration completed. The 

 salt dissolved without leaving a residue. So little benzyl 

 chloride was used that it did not seem probable that its use 

 could materially affect the solubility of the chlorides of potas- 

 sium and sodium. Working on this supposition a series of 

 separations were made the results of which are given below. 



Standardized solutions of the several salts were used. The 

 solution of magnesium chloride was prepared from the carbo- 

 nate, which had been twice precipitated from moderately 

 strong solutions of the chloride. The chloride thus made was 

 free from alkalies and wholly soluble in amyl alcohol. The 

 strength of this solution was found by treating weighed por- 



*Am. Chem. Jour., vol. ix, p. 33. 



f This objection was afterwards found to be groundless. 



