Royal Irish Jcademi/. 227 



colour uniformly diffused throughout the mass, so deep as to render 

 the glass nearly opake. The experiment originated from a work- 

 man in the glasshouse having dipped a heated copper ladle into a 

 pot of fused glass. The copper ladle was melted ; the casting and 

 annealing of the plates were proceeded with as usual ; and on their 

 completion the workmen Avere surprised to find, that not only were 

 grains of metallic copjDer imbedded in the substance of the glass, 

 but bands uniformly coloured of a fine bright red, were distributed 

 throughout the mass. 



" The experiment of Guy ton Morveau, being but a repetition of 

 the accidental one made by the workman, seems to have but little 

 engaged his attention, the colour being conceived to be due to an 

 imperfect state of oxidation, as oxide of copper imparts to glass a 

 greenish colour. 



" It appeared to me, at first sight, that the red colour was due to 

 the actuEil solution of the copper in the metallic state, the globules 

 of copper imbedded in the mass having been deposited from a state 

 of solution, upon cooling. To determine 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 dis- 

 solve 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 dissolved, imparting a green 

 colour to the glass, while the rest remains disseminated throughout 

 the 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 me- 

 tallic 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, — producing 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) 

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

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

 nace, 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 crucible unaltered, owing 

 to its infusibility. "When charcoal is heated with glass, a large 

 proportion is oxidated, the remainder presenting the appearance of 

 a mechanical mixture. 



" From these experiments it appears, that glass, at high tempera- 

 tures, not only has the property of oxidating the metals, and form- 

 ing a chemical compound with the oxide, but moreover, when the 

 chemical affinity is satisfied, of dissolving the oxides, and probably 

 the metals themselves when in a state of fusion ; the latter, on the 



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