S70 



due to the actual solution of the copper in the metallic state, 

 the glohules of copper imbedded in the mass having been 

 deposited from a state of solution, upon coohng. To deter- 

 mine this, I mixed in different proportions with powdered 

 glass, iron, lead, copper, silver, bismuth, antimony, tin, gold, 

 platinum, in a minute state of division; and found that glass, 

 when mixed with iron filings, will oxidate and dissolve 

 almost as much iron, when mixed with it in the metallic state, 

 as if it were mixed with it in the state of oxide. Of 

 copper, only a small proportion is oxidated and dis- 

 solved, imparting a green colour to the glass, while the rest 

 remains disseminated throughout tlie glass in globules of 

 copper and red streaks, which are probably the protoxide ; 

 whereas lead (for whose oxide glass has such a strong 

 affinity) oxidates but a small portion, when mixed with it in 

 the metallic state, the rest being found imbedded in globules 

 throughout its mass. Tin, antimony, and bismuth are more 

 easily oxidized and dissolved than lead. Gold, when fused 

 with glass, imparts to it a light greenish tinge, increasing in 

 depth with the relative proportion of silica in the glass, — pro- 

 ducing a deeper colour with the bisilicate than the silicate of 

 potash, and still deeper when German glass (which contains a 

 large proportion of silica) is employed ; globules of gold are 

 found (as in the analogous cases of lead and copper) dissemi- 

 nated throughout the mass. If the heat be increased, and 

 the crucible containing the gold be left for some hours in the 

 furnace, the glass assumes a pinkish hue, which is the colour 

 imparted to it by the protoxide of gold. When platinum 

 sponge is fused with glass, it sinks to the bottom of the cru- 

 cible unaltered, owing to its infusibility. When charcoal is 

 heated with glass, a large proportion is oxidated, the remain- 

 der presenting the appearance of a mechanical mixture. 



** From these experiments it appears that glass, at high tem- 

 peratures, not only has the property of oxidating the metals, 

 and forming a chemical compound with the oxide, but 



