366 Mr. E. Cleminshaw’s Lecture-Hxperiments 
stances in question may be conveniently introduced into the 
flame. Bunsen made hydrogen in a bottle containing a strong 
solution of sodium chloride with zinc and hydrogen sulphate, 
passed coal-gas into the bottle in order to increase the size of 
the flame, and to assist in the mechanical carrying-over of 
the spirtings of the sodium-chloride solution, and burnt the 
mixed gases in a description of Bunsen burner. 
Instead of burning the mixed gases in air, I propose to 
burn them in an atmosphere of oxygen, by which I find a 
sufficiently bright flame can be obtained to show the spectra 
on the screen. . 
The mixed gases are burnt from a jet consisting of two 
concentric brass tubes, the inner of which passes into the gas- 
generating apparatus, and the outer is connected with a supply 
of oxygen; the inner tube is from }—,3, inch diameter, and 
may with advantage be wider at the bottom. A better result 
is obtained by passing hydrogen into the bottle, since it is 
not easy to render the coal-gas perfectly non-luminous by the 
oxygen. 
A rapid evolution of hydrogen is necessary for a good 
result. The lens or lenses should be arranged so as to obtain 
as bright an image of the slit as possible, even at the expense 
of some spherical aberration. 
The light obtained with sodium chloride is perfectly mono- 
chromatic and very bright. I venture to recommend this - 
method of obtaining a bright monochromatic flame for lecture- 
demonstrations. 
With a strong solution of lithium chloride the red band 
(Li a) can be shown, and on adding some strong solution of 
sodium chloride the yellow band of sodium. 
For showing the spectra of the alkaline earths I use a 
saturated solution of the chlorides and generate hydrogen 
with zinc and hydrogen chloride. With two OS,-prism 
bottles a red, orange (Sra), and blue (Sr 6) can be shown 
on the screen; and, if the slit is narrow, the yellow band 
of sodium is clearly shown as soon as some sodium-chloride 
solution is introduced into the gas-generator. If a strong 
solution of lithium, sedium, and calcium chlorides are used, 
with two CS.-prisms five bands can be shown on the screen, 
including the orange, green, and violet bands of Ca. 
The above method is applicable for all compounds which 
can be volatilized in the oxy-hydrogen flame, and which are 
not reduced by the nascent hydrogen. 
If hydrogen gas is passed into the bottle, or sufficient 
oxygen used to destroy the luminosity of the coal-gas, no trace 
of a continuous spectrum can be seen An occasional addition 
