ON RENDERING SUBSTANCES INCOMBUSTIBLE. 83 
reaction, but cannot be burned completely upon platinum 
foil and do not neutralize acids. When they are digested 
with dilute sulphuric acid, a layer of oil separates on the 
surface, which after sufficient washing dissolves readily in 
hot alcohol, and communicates to the solution an acid reac- 
tion. On cooling, the substance separates from the alcohol 
partially in a butyraceous state. It dissolves readily in 
carbonate of soda, and furnishes a soap. The supposed 
crotonine is consequently nothing more than a magnesia 
soap with an alkaline reaction. — Chemical Gazette^ Sept 
15, 184 9, from Liebig's *dnnalen f lxx. p. 255. 
AET. XXIL—ON A MODE OF RENDERING SUBSTANCES 
INCOMBUSTIBLE. 
By Robert Angus Smith. 
I have often been surprised that, considering the number 
of materials which will not burn and the small number 
which do burn, we should be compelled to build houses so 
liable without constant watchfulness to instantaneous de- 
struction; that we should go also to sea in vessels made of 
a most combustible substance filled with enormous fires,, 
frequently under the care of ignorant men. I think, there- 
fore, I may be excused when I endeavor to add to a 
knowledge of the mode of rendering substances incombus- 
tible, or the theory of the mode to be sought after, even if 
the addition which I make be but a very small one. 
Silicate of potash has been considered good. It is a soluble 
glass which was expected to cover the fibre of cloth or 
wood, and so protect it from heat. This does act to some 
extent; probably in the same manner as stones do when 
put into a fire of wood or coal ; they take heat but give 
none, and are also bad conductors. If silicate of potash 
remained as a glass, it would act also by keeping out the 
