Bauhaus-Universität Weimar

The Art of Projecting. A Manual of Experimentation in Physics, Chemistry, and Natural History with the Porte Lumière and Magic Lantern
Dolbear, A. E.
I58 the art of projecting. 
To water made slightly acid, add enough litmus 
solution to turn it red and project it ; then drop a lump 
of carbonate of aihmonia into it. It will dissolve 
rapidly with effervescence, and the solution will be 
made blue about the crystal, and if there is enough of 
it the whole solution will ultimately become blue. 
The gradual solution of substances in water may be 
nicely shown by filling the tank with pure water and 
dropping a crystal of alum or sulphate of zinc or sul¬ 
phate of copper into it. Where the substance is dis¬ 
solved the solution will be denser, and its refractive 
powers changed, which will be manifest by gently stir¬ 
ring it with a glass rod. 
A dilute solution of copper sulphate may be placed 
in the tank. With a pipette, force into the solution 
some ammonia water : A dense precipitate will at first 
be formed, which will afterwards be dissolved if am¬ 
monia enough has been added, leaving the solution a 
beautiful blue color. A few drops of sulphuric acid 
will reproduce the precipitate and destroy the color; 
and when the solution again becomes clear, a few drops 
of ferrocyanide of potassium added will produce a 
brownish-red bulky precipitate, which will present a 
fine appearance upon the screen. 
In like manner all of the characteristic reactions of 
inorganic chemistry may be projected, and often with 
much less expenditure of materials than would be used 
if large vessels were employed to demonstrate the 
same things. One who has projected a number of 
these phenomena will find no difficulty in projecting 
any reaction that may be observed in a test-tube. 
Pictures of chemical apparatus, of processes, etc., 
will be very convenient for projection when instruction 
is given in chemistry.


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