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II. Chemical Science. 

 § Chemistry, Electricity, Sj-c. 



1. Oxides of Manganese, — Dr. Forchhammer, in addition to 

 his remarks on the acids of manganese, has published an ac- 

 count and analysis of the different oxides, the preparation and 

 composition of which will be briefly noticed below. 



The manganese was obtained free from other metals, by heat- 

 ing the black oxide with sulphuric acid till all excess of acid 

 was driven off, by making a solution, and then by precipitating 

 the coppei: and iron from that solution by hydro-sulphuret of 

 ammonia, they fall down of a black colour ; when the precipi- 

 tate becomes grey, the solution is to be heated to the boiling 

 point, and, if sufficient hydro-sulphuret has been added, will 

 precipitate white with a farther addition of it. From the solu- 

 tion thus precipitated the carbonate is obtained, and from that 

 the other preparations of manganese. 



Another process for preparing pure manganese may be found 

 at page 358, vol. VI. of this Journal. 



Dr. F. obtained protoxide of manganese by heating the deut- 

 oxide very gently in a glass tube, and at the same time passing 

 a current of hydrogen gas over it. The brown powder became 

 of a light yellow colour, and whilst cooling, white; the cold 

 oxide was of a beautiful light green colour ; by mere exposure to 

 the air it absorbed oxygen, and began to turn grey. 



Several analyses of this oxide were made, one from among the 

 rest gives its composition as 100 manganese + 30.24 oxygen, 

 and Dr. F. thinks that the true quantity of oxygen, combined 

 with 100 of manganese, is between 30.18 and 31.29. 



The deutoxide of manganese is prepared by heating pure 

 protoxide in the air, at a temperature between the boiling point 

 of water and of mercury, it takes fire and burns slowly with a 

 reddish light, into deutoxide. The composition of this oxide is 

 100 manganese with 42.04 oxygen. 



When this deutoxide is boiled in dilute nitric acid a part is dis- 

 solved, and an insoluble peroxide remains. It is black, and inso- 

 luble in acids or alkalies. The latter when slightly heated with 

 it form deutoxide and manganeseous acid, the latter being dis- 

 solved. It is a conductor of electricity. It maybe formed, also, 

 by exposing carbonate of manganese to air, at a temperature 

 of 500° Fahr., and, washing it with weak cold muriatic acid, 

 its composition is 63.749 manganese 4- 36.351 oxygen when 

 dry, but it is when prepared as above, always a hydrate, and con- 

 tains manganese 30 + oxygen, 16 -|- water 9. 



The oxide obtained, by exposing the nitrate to moderate heat, 



