I’. Gaffield on the action of Sunlight on Glass. 323 
ale lavender, into the lilac, mulberry, flesh, amethyst, rose, 
violet, pink and deep purple. ave produced, or seen speci- 
mens, showing all shades of the yellow, from the brownish yel- 
low, up to the brightest gold color, and I have several series of 
Specimens, in which the green has gradually changed into the 
yellow, and the yellow gradually run into the pink and purple. 
elouze, in an article in the Comptes Rendus, of Jan. 14th, - 
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8 In reference to glass made violet color by sunlight, he says, 
~The coloration seems to be due to the fact that the peroxyd of 
| Ton gives up a part of its oxygen to the protoxyd of manganese 
} “nformably to one of the two following equations. 
Fe?0?+MNO=2(FeO) +MNO? 
or Fe?02+2(MNO)=2(FeO)+MN?O0*. 
The reheating of glass, that is to say, the action of a temper- 
_ 4ture of red heat, produces an inverse reaction, which explains 
_ “€ decoloration. In which we have 
2(FeO)+Mn?20?=Fe?0*+2(Mn0),” 
temps, in an interesting article in the Comptes Rendus of 
Feb, 4th, 1867, attributes the changes in color to the presence of 
°xyd of manganese. He also remarks that he thinks that the 
_ Nolet color occurs only in glass in which the silicates have a 
base of potash, and the yellow in cases where soda is used. I 
: doubt the correctness of ‘this opinion, as I am quite sure T 
iy 
