MOHR AND REDWOOD'S PRACTICAL PHARMACY. 127 
"The gas-furnace of Mr. Rickets, noticed in Chap. I. is 
equal to a charcoal fire for many of the purposes of the 
pharmaceutist, and can be conveniently arranged at the 
working counter. A set of the shorter cylinders, from one to 
four inches in diameter, should be at command — made of 
tinned iron — one end covered with fine brass wire gauze, 
simply crimped over the edge, and a piece of copper wire 
twisted around it. When no means of protection are used, 
the gauze requires to be renewed, if constantly in use, at 
intervals of one or two months ; especially if corrosive sub- 
stances are allowed to come in contact with it from the boil- 
ing over of liquids. It may be protected by having a short 
cylindrical cap, covered with coarse iron wire gauze, slipped 
over the end of the cylinder, and the space between the two 
wire tissues filled with granular pumice-stone, free from 
dust, 
"The following arrangements are adopted in the laboratory 
of the Pharmaceutical Society, where they were originally 
introduced. 
" Gas-Bumers. — The gas-burner generally used is that 
represented in fig. 19. It consists of a perforated ring (a) the 
diameter of which is two inches and three quarters ; this is 
supported on a foot (b,) and attached by a flexible tube to 
the gas-pipe, so that it may be moved to any part of the 
work-table, to suit the arrangement of other apparatus. 
" Fig. 20 represents a larger gas-burner, the diameter of 
which is six inches, but this is rarely required excepting in 
some particular cases, in which it may be wished to have 
the heat diffused over a large surface. The smaller burner 
affords heat enough to boil a gallon or more of water in a 
metallic vessel. 
" Gas-Furnaces. — The gas-furnace, (fig. 21) is used to 
confine the heat of the flame from the gas-burner, to protect it 
from being blown about by currents of air, and at the same 
time to form a support for the vessel containing the liquid 
to be heated. This furnace consists of a slightly conical 
