M. Wieland o^i the Fahrkatkm of ArUJicial PaHes S71 
M. Lan 9 on recommends the following mixture for a pure 
strass : 
Litharge, - - 0.540 
White Lead, - - 0.400 
White Tartar, or Potash, 0.054 
Topa %, — The imitation of topaz is difficult. It passes from 
the white of strass to sulphur-yellow, violet and red purple, ac- 
cording to circumstances which are not determined. The fol- 
lowing are two of M. Wieland’s recipes : . 
White Strass, 
0.95816 
0.99 
Glass of Antimony, 
0.04089 
Purple of Cassius, 
0.00095 
Oxide of Iron, 
0.01 
1.00000 
1.00 
These mixtures sometimes yield an opaque mass, translucent at 
the edges, and of a red colour in thin plates. By mixing it with 
eight times its w^eight of strass, and keeping the mixture in fu- 
sion for thirty hours in a potter’s furnace, the result is a fine 
yellowish crystal. This crystal re-melted by the blowpipe, pro- 
duces the finest imitation of eastern Ruby. 
Ruby . — A ruby less beautiful, and of a different tint, may 
be made thus : 
Strass, - 0.9755 
Oxide of Manganese, 0.0245 
1.0000 
Emerald . — This paste is very easily made ; and that which 
approaches the nearest to the mineral is the following : 
Strass, - 0.98743 
Green Oxide of Copper, 0.01200 
Oxide of Chrome, - 0.00057 
1.00000 
The following is M. Lan 9 on’s recipe for emerald : 
Strass, - 0.9905 
Acetate of Copper, 0.0080 
Peroxide of Iron, - 0.0016 
1.0000 
Peridot . — By augmenting the proportion of oxide of chrome 
and oxide of copper in the first composition of emerald, and 
adding oxide of iron, we may vary the green shades, and imi- 
tate the peridot and deep coloured emerald. 
