dipped into the bath, leaving them afterward to dry. If the bath becomes
of a yellowish color, it must be renewed. This bath has for its object
to remove the coating of bichromate, so as to allow the color to adhere
to the glass, from which it has been separated by the layer of glucose
and bichromate, which would prevent the vitrification. The bath has also
for its object to render the light parts of the picture perfectly
pure and capable of being easily retouched or painted by hand. The
application of variously colored enamels and the heating are then
effected as in ordinary glass painting. The same process may be applied
to marble, wood, stone, lava, canvas prepared for oil painting,
earthenware, pure or enameled iron. The result is the same in all cases,
and the process is the same as with glass, with the difference only that
the above named materials are not dipped into the bath, but the liquid
is poured over the objects after the latter have been placed in an
inclined position.

* * * * *




PREPARATION OF HYDROGEN SULPHIDE FROM COAL-GAS.

By I. TAYLOR, B.A., Science Master at Christ College, Brecon.


Hydrogen sulphide may be prepared very easily, and sufficiently pure
for ordinary analytical purposes, by passing coal-gas through boiling
sulphur. Coal-gas contains 40 to 50 per cent, of hydrogen, nearly the
whole of which may, by means of a suitable arrangement, be converted