1813.] a Chemical Knowledge of Manganese. 179 



which is pure carbonate of manganese, and answers perfectly 

 to that mentioned above. 



There is only one combination of carbonic acid and manga- 

 nese, that, namely, in which the metal is in the state of prot- 

 oxide. When we endeavour to increase the proportion of oxy- 

 gen, as, for example, by the application of heat, a portion of 

 the carbonic acid is disengaged, and the whole peroxide pro- 

 duced remains behind when we attempt to dissolve the carbo- 

 nate in an acid. 



Carbonate of manganese, which has a reddish yellow or brown 

 colour, and yet contains no other metal mixed with it, must 

 therefore be considered as a mixture of brown oxide and car- 

 bonate of manganese. 



When oxymuriatic acid is brought in contact with carbonate 

 of manganese, the carbonic acid separates in the same propor- 

 tion in which the oxymuriatic acid is decomposed and manga- 

 nese oxydated. A solution of manganese in muriatic acid, 

 though mixed with abundance of oxymuriatic acid, is precipi- 

 tated, it is true, by the alkaline carbonates ; but the brown or 

 black precipitate in that case consists (obviously at the expense 

 of the oxygen in the oxymuriatic acid) of pure oxide, without 

 the smallest portion of carbonic acid. Neither precipitate ren- 

 ders lime-water in the least muddy when it is treated with an 

 acid in a small Woulfe's bottle, furnished with a bent tube, the 

 extremity of which passes into the lime-water. 



Pure carbonate of manganese appears in the state of a soft 

 snow-white powder. 



It is quite tasteless, and is not altered in the air at a tempera- 

 ture between 55° and 60°. Hence it may be kept with perfect 

 safety in a close vessel. 



I have found that it may with safety be dried in the tempera- 

 ture of 80°, without either attracting more oxygen, or losing 

 any of its carbui.ic acid. As I very frequently determine the 

 quantity of pure oxide in salts of this nature by the quantity of 

 carbonate, I chose, in order to avoid all inconvenience arisino- 

 from the presence of a greater or smaller quantity of water in 

 such carbonates, to dry them always ai the temperature of 80°. 

 The pure alkalies decompose the carbonate of manganese, com- 

 bine with the acid, and the white oxide, by exposure to the air, 

 attracts oxygen, and becomes brown. 



Carbonate of manganese may be considered as insoluble in 

 water, since eight ounces of that liquid scarcely dissolve half a 

 grain of it. Even water impregnated with carbonic acid c;as 

 dissolves it onlv in wry minute quantity, though recently preci- 

 pitated, and !-till moist Eight ounces of water, :is strongly 

 impregnated with carbonic acid as possible, dissolved scarcely 

 one grain of carbonate. To choose carbonic acid as a medium 



If 1 



