ON MANGANESE 103 



'(I) When mixed with a large quantity of common 

 enamel, consisting of siliceous powder and litharge fused 

 together, so as to form a clear yellow glass, and exposed to 

 a stream of air in a close crucible for a quarter of an hour, 

 the roasted powder (/) yielded only a clear olive-coloured 

 glass, in which many little grains of reduced lead were to be 

 observed. That it did not assume a garnet colour, I 

 ascribe to the too great violence of the heat. The reduction 

 of some of the lead indicates the presence of phlogiston in 

 the pulverised manganese. 



(ra) Some of this roasted manganese was rubbed in a 

 glass mortar with a quantity of the above-mentioned enamel, 

 to which a little more siliceous powder and some fixed alkali 

 were added. With this mixture a piece of Cologne clay 

 burnt white was covered, then placed in a heated assay- 

 furnace, and taken out as soon as the enamel began to melt. 

 It had acquired a clear and more beautiful colour than I 

 could have produced with other manganese. 



(n) One part of the roasted powder, mixed with two of 

 siliceous powder, and four of w r hite potashes, fused in a 

 crucible, placed before the bellows, in seven minutes. It 

 effervesced at first with violence, and afterwards yielded a 

 clear violet-coloured glass, with which the crucible was like- 

 wise glazed. 



The small quantity of which I was possessed, and the 

 shortness of the time, would not permit me to make any 

 more experiments. From those which I have related, it 

 appears that this species has nearly the same properties with 

 that examined by Mr. Scheele. There are, however, some 

 points of difference to be noticed : as its showing the same 

 phenomena as zeolite under the blowpipe without addition ; 

 its containing in all probability but little iron ; and its yielding 

 a very beautiful violet-coloured enamel, for which, and 



