RUBY-GLASS. * 27 



of copper, and 80 pts. iron scales (smithy slack), for 12 hours, 

 and suflfered the fused mass to cool slowly. The oxide of cop- 

 per is reduced by the iron, which latter forms a silicate that 

 scarcely tinges the glass, while the minute crystals of metallic 

 copper, suspended in the glass, impart to it its peculiar ap- 

 pearance. 



Ssematinone is the name of a beautiful, red, opake glass, 

 employed by the ancients in mosaics. Analysis showing its 

 coloring matter to be copper, Pettenkofer asserts that he has 

 succeeded in producing it, and that it can be made in quantity. 

 A similar glass is not unfrequently obtained in testing copper 

 with borax by the blowpipe. 



Ruhy-glass. — H. Rose has examined gold-glass and gives 

 the following views on it. (Verhandl. d. Berl. Acad, and 

 Journ. f. Pract. Chem. xliii. 75.) When colorless gold-glass is 

 gently ignited, it become ruby-red, still retaining its trans- 

 parency, whether heated in oxygen or carbonic acid. The red 

 glass fuses in the flame of the hydroxygen blowpipe to color- 

 less drops, which do not redden again by heat. Splittberger 

 thinks that the colorless glass contains peroxide of gold, and 

 that this is reduced to protoxide, which precipitates and colors 

 the glass red. Rose holds that the peroxide is not contained 

 in the glass, because it is a very feeble base, if a base at all, 

 and because the reddening may occur in oxygen. But as the 

 protoxide is a base, forming salts, some of which are quite fixed 

 at a high temperature, (as the purple of Cassius, which Ber- 

 zelius regarded as stannate of protoxide of tin and protoxide 

 of gold,) Rose assumes a protosilicate of gold in the colorless 

 glass, from which heat precipitates the protoxide and gives 

 the red color. He compares it to glass colored red by sub- 

 oxide of copper, which is colorless after fusion and becomes 

 red by reheating, and that this change takes place even when 

 the colorless copper-glass is covered on both sides .by common 

 flint-glass. He further supports his view by the similar atomic 

 composition of suboxides of copper and gold. The brownish 

 color of gold-glass, too highly heated, he refers to a reduction 

 of oxide of gold to the metallic state. 



