1. Silica, 62·8%; potassa, 22·1%; lime, 15·5%; alumina (with traces of oxide of iron and manganese), 2·6%. Crown-glass of Bohemia, according to Dumas. Very beautiful.
2. Silica, 72·5%; soda, 17·75%; lime, 9·75%. English crown-glass; excellent quality, but not so white as the last.
b. Materials used:—
1. Finest white siliceous sand, 64%; purified potashes (dry), 23%; lime, 12%; white arsenic, 3⁄4%; oxide of manganese, 1⁄4%. Said to be used in Bohemia.
2. (Schweigger.) Pure sand, 57%; dry sulphate of soda, 281⁄2%; quicklime, 111⁄2%; powdered charcoal, 3 or 4%. Corresponds to a, 2, above (nearly).
3. Pure sand, 40%; soda ash, 24%; lime, 5%; white ‘cullet,’ 31%, Rather superior to the last.
Crystal, Crystal glass. The ‘crystal glass’ of England is flint glass’ of superior quality; that of Bohemia is noticed under Table glass.
Glass, Flint, Crystal. Sp. gr. 3·000 to 3·620.—
a. By analysis:—
1. (Berthier.) Silica, 59·19%; oxide of lead, 28·68%; potassa, 12·13%; oxides of iron and manganese, traces. Finest colourless English crystal.