44 RESEARCHES UPON ATOMIC WEIGHTS. 



ANALYSIS OF MANGANOUS CHLORIDE. 

 PURIFICATION OF MATERIALS. 



MANGANOUS CHLORIDE. 



Portions of the pure material employed in the experiments upon manganous 

 bromide served also for the preparation of manganous chloride. Two speci- 

 mens of chloride were made. Sample B corresponds in its purity to Sample B 

 of manganous bromide, since both were made by dissolving the same specimen of 

 manganous carbonate (page 35). This carbonate had been made from potas- 

 sium permanganate which had been crystallized ten times. The solution of the 

 carbonate in hydrochloric acid was evaporated to dryness in a quartz dish and 

 was heated to 200° in an electric oven. Then the filtered aqueous solution was 

 evaporated to crystaUization in a platinum dish and the first crop of crystals 

 was twice recrystallized (Sample B). 



The mother-liquors of the manganous nitrate used in preparing Samples B 

 and D of bromide (page 35) were combined and crystallized six times, three 

 times in glass vessels, three times in platinum vessels, and from this pure ni- 

 trate Sample E was prepared by precipitation of the carbonate with distilled 

 ammonium carbonate, solution in hydrochloric acid and crystallization as with 

 Sample B. 



HYDROCHLORIC ACID. 



The hydrochloric acid was purified by boiling the "chemically pure" acid for 

 some time, after the addition of a small quantity of potassium permanganate. 

 Then it was distilled in glass, the middle portion only being collected, and finally 

 once with a quartz condenser shortly before use. 



SILVER. 



The same samples of pure silver were employed as in the work with mangan- 

 ous bromide (page 37). 



DRYING OF MANGANOUS CHLORIDE. 



The salt was prepared for analysis by fusion in a current of hydrochloric-acid 

 gas and then the chlorine content was determined gravimetrically as silver 

 chloride and by titration against a weighed amount of silver in solution. 



The apparatus employed for the fusion was identical with that described in 

 the paper on cadmium chloride (see page 8), the hydrochloric-acid gas in 

 which the fusion took place being dried by passing through four towers con- 

 taining concentrated sulphuric acid. In a few preliminary experiments the 

 hydrochloric-acid gas was passed over freshly sublimed phosphorus pentoxide, 

 but this drying agent was subsequently eliminated since it was found to intro- 

 duce volatile phosphorus compounds into the hydrochloric-acid gas, and thus 

 into the manganous chloride, if the latter was moist. This diflficulty has been 



