1824-3 the Oxidum Mangano$o-Manganicum. 27 1 



his Attempt to lay the Foundation of a new scientific System of 

 Mineralogy, p. 92. 



It remains now to ascertain how far the so called grey ore of 

 manganese and the crystallized varieties of that mineral usually 

 consist of manganese in the form of superoxide, or if they may 

 not consist of black oxide, which we have seen gives out oxygen 

 gas also when heated to redness. 



I. Crystallized Grey Manganmalm, from Udenas, in West 



Gothland. 



5*035 grammes of the pure crystallized ore was heated over a 

 spirit-lamp in a small retort, to the beak of which was luted a 

 glass tube filled with dry chloride of calcium. The matter, as 

 soon as the heat was applied, gave out much water, which by 

 degrees passed over, and was absorbed by the chloride. The 

 heat was continued as long as any moisture was perceptible in 

 the beak of the retort. The apparatus being now allowed to 

 cool was weighed, and the loss of weight amounted only to two 

 millegrammes, a loss so small that it may be overlooked. Thus 

 no gas had been extricated. The mineral by this exposure to 

 heat had lost 0*508 gramme, which may, therefore, be reckoned 

 the weight of the water contained in the specimen. The residue 

 amounted to 4*527 grammes ; of this 4*504 grammes were 

 exposed to a strong red heat in a platinum crucible : the loss of 

 weight amounted only to 0*022 gramme. Being exposed a 

 second time to as high a temperature as the fire could give, the 

 loss of weight was increased by 0*139 gramme. A third heating 

 diminished the weight by 0*016. When heated for the fourth 

 time no further loss of weight was sustained. The crystals still 

 retained their shape; but the colour had been changed from 

 black to reddish-brown, and the powder had a cinnamon-brown 

 colour exactly similar to the above described oxidum manganoso- 

 manganicum. The whole loss of weight amounted to 0*177 

 gramme. This, though only from 4*504 grammes, may be 

 taken without sensible error for the whole loss from 4*527 

 grammes, as the error only begins to be perceptible in the fourth 

 decimal place. 



Thus the mineral had given 



Water 0*508 or 10*08 



Oxygen 0*177 3*51 



Oxidum mang.-manganicum. 4*350 86*41 



5*035 100*00 



The small quantity of oxygen gas obtained shows evidently 

 that the mineral under examination cannot be a superoxide of 

 manganese ; and it seems plain that the manganese is in the 

 state of black oxide ; for we find by an easy calculation, that 

 the 86*41 parts of oxidum manganoso-manganicum obtained 



