ON MANGANESE 



99 



diminished, and was as dark as at first ; but of the small 

 globules dispersed around upon the charcoal some were clear 

 and colourless, others were white and opaque. 



I attempted to give them colour by means of the blow- 

 pipe alone, but without success. 



(7) In one experiment I had taken a much larger 

 quantity of manganese in proportion to the borax, and 

 happening to give it a very violent heat, so as to cause an 

 explosion of small particles, I found that the larger globule 

 constantly retained a red colour, till at last it likewise grew 

 clear and transparent during the blowing. On stopping 

 suddenly, the glass was clear as long as it remained warm ; 

 but as soon as it began to grow cold, a dark cloud made its 

 appearance upon the surface, which by degrees spread over 

 the whole. On melting it suddenly anew, it recovered its 

 transparency ; but as it grew cold the same phenomenon as 

 before appeared; and the oftener I repeated this, the more 

 cloudy appeared the globule. As soon as it had become 

 cold, I observed that it had lost its glassy splendour, and 

 had assumed a very dry appearance, and was of a greyish 

 red colour. The same thing happens likewise with glass of 

 borax and lime ; if the latter be added in too large quantity, 

 the glass of borax loses its glassy appearance nearly in the 

 same manner. 



That the small globules separated by the violent heat 

 (6) remained colourless, though the great globule became 

 red, seems to show that manganese, or at least its colouring 

 part, has a strong attraction for a small portion only of 

 borax ; and that by means of a violent heat the superfluous 

 part may be separated, and the rest unite more closely with 

 the earthy particles. The same thing happened likewise 

 with the small globules which sometimes remained after the 

 mass was taken away, fixed to the charcoal by the violence 



