ON ICE-MAKING AND ICE MACHINES. 
273 
•can in a most unexpected way be made available for industrial 
purposes. No one could have imagined that the liquefaction of 
gases could prove of any practical benefit to mankind, but we 
now know that such is the case, since M. Carre’s ammonia 
freezing machine depends upon the liquefaction of the gas by 
pressure, and its subsequent condensation in water after it has 
produced a low temperature by its evaporation. The operation 
is conducted without the application of any mechanical power. 
A hollow conical condenser of iron has a space bet ween its inner 
nud outer surfaces, which is connected by a tube with a boiler 
•containing ordinary liquid ammonia ; that is to say, a solution 
of about 700 volumes of ammoniacal gas in 1 volume of water. 
The conical condenser is immersed in a stream of cold water, 
while the boiler is heated over a fire or large gas-burner to a 
temperature of 270° F. During this operation the ammo- 
niacal gas is expelled from the water, and is condensed by the 
pressure of its own particles and the cooling action of the 
stream of water. If now fresh cold water be placed in the con- 
denser cone, and the heated boiler be cooled in water, the 
ammonia distils off at the expense of the heat in the water to 
be frozen, and finds its way back once more to the boiler, ready 
for another operation. 
Leslie’s famous experiment of causing water to be frozen by 
the rapid absorption of heat caused by its own evaporation has 
been modified by M. Carre, in such a manner that ice in small 
quantities, as, for instance, in water-bottles, may be made in a 
few minutes. The apparatus consists of an air-pump, to which 
the water-bottle is attached. As the handle of the pump is 
worked and the air exhausted, a quantity of oil of vitriol is 
agitated in a vessel, through which all aqueous vapour and air 
from the water-bottle must be drawn. The avidity with which 
the oil of vitriol absorbs the vapour as fast as it is formed so 
hastens the evaporation that in a few minutes a bottle of ice is 
the result. 
Perhaps of all machines the one of most interest is that 
invented by M. Kaoul Pictet, of Greneva, the striking feature 
in which is the employment of liquefied sulphurous acid as the 
absorbent of heat instead of ether. In all other machines there 
is a liability to a slight leakage, on account of the fact that the 
cylinder of the exhausting and condensing pump is kept air- 
tight to some extent by the lubricating material. Now as 
ether and all kinds of grease are solvents of each other, it 
is easy to account for a certain amount of escape, which will 
be difficult to avoid. Liquefied sulphurous acid does not dis- 
solve to any considerable extent in oil, and when free from 
moisture is without action on metals ; and although it might 
be expected that the packing of the piston might in time be 
