1 30 Wokt Colour of Glaft. [Book VI. 



acid, abfiracting part of its oxygen. The manganefe 

 feparated from its folution in acids by alkalies, is in 

 the form of the white or imperfect calx, which, how- 

 ever, becomes black by being heated in contact with 

 air. 



In the dry way the calx of manganefe combines 

 with fuch earths and faline fubftances as are capable of 

 undergoing fufion in a ftrong heat. The violet co- 

 lour which it communicates to glals is liable to be de- 

 ttroyed by eombuftible fubftances. From this cir- 

 cumftance we may conclude, that the property of 

 colouring glafs depends on the calciform ftate of this 

 metal, and that it is loft when any body abftracts its, 

 oxygen and reduces it to a regulus. 



Manganefe in its metallic form will not unite with 

 fulphur, but melts readily with moft of the metals. 

 Gold and iron are rendered more fufible by a due addi- 

 tion of manganefe, and the latter metal is rendered 

 jmore ductile. 



Manganefe has hitherto been ufed chiefly by glafs- 

 makers and potters ; but the important difcoveries of 

 the effect of oxygenated muriatic acid, prepared by' 

 means of manganefe, in bleaching, will no doubt ex- 

 tend its utility to feveral other manufactories. 



