416 Contributions to the [June, 



Properties of the crystallized Salt. 



The shape cf the ciystais is a rhomboidal table, having com- 

 monly two of its opposite angles truncated. They have a red 

 colour, are transparent, are not altered by exposure to the air, and 

 have a peculiar hut weak mctrillic taste, uith a certain degree of 

 astringeiicy. ''i'iiey are soluble both in water and in alcohol. At 

 the common temperature tliey require about 3i times their weight 

 of water to dissolve them. 



When heated they exhibit the same phenomena as succinate of 

 manganese. The solution of tliis salt in water is decomposed by 

 the alkaline carbonates, prussiates, molybdates, and arseniates, hut 

 not by the alkaline liorates and oxalates. Arsenic acid produces a 

 precipitate of arseniate of manganese, 



Tliis salt analysed in the same way as the preceding salt, was 

 found to consist of 



Oxide 30 



Acid and water ... 70 



100 



ACTION OF CHROMIC ACID. 



a. On the Metal. 



Chromic acid acts but slowly on manganese. However, by the 

 application of a moderate heat, water is decomposed, hydrogen gas 

 evolved, and the oxide gradually unites with the acid and is dis- 

 solved. 



I'. On the green Oxide. 



Chromic acid dissolves the green oxide with tranquillity, and the 

 carbonate v/ith efrervcscence. The solution is never completely 

 neutral, but always contains an excess of acid. When concen- 

 trated it has a dark cliesniit brown colour, and a sharp metallic 

 taste. The cbromate of manganese cannot be obtained in a 

 metallic form. When evaporated the manganese absorbs oxygen, 

 and falls in the state of a black po'.vdcr, united- witii a small por- 

 tion of chromic acid. Jf the solution be repeatedly evaporated, 

 and then diluted with water, the manganese gradually |)recipitates, 

 and the chromic acid remains united to a very small proportion of 

 the oxide. 



The solution of chromate of manganese is decomposed by the 

 alkaline carbonates and prussiates. The prt-cipitate obtained con- 

 sists of carbonate or |)russiate of manganese. If nitrate of silver 

 be dropt into t'^.e solution af this salt, a fine black pieciiiitaie iiills, 

 consisting of chromic acid and oxide of siher, united vviih 

 ^ome oxide of ir)anganese. Nitrate Of manganese remains in solu- 

 tion. 



ACTION OI" TUNGSTIC ACID. 



Ijy digesting a mixture of powdered manganese and tungstic acid 



