Volume 23 — ICE MACHINES.

Ice machines are constructions designed to employ the heat generated from coal in extracting the heat stored up in water at the ordinary temperature. One ton of coal will make 15 tons of ice, and yet only about 1 per cent. of the power used is utilized, these machines being especially wasteful of heat. The work is done through the medium of some volatile fluid, like ether or ammonia, or by the use of previously cooled air. Raoul Pictet, who advocates the employment of another fluid—sulphurous acid solution—says that every machine must comply with five conditions: 1. Too great pressure must not occur in any part of the apparatus. 2. The volatile liquid employed ought to be so volatile that there will be no danger of air entering. 3. It is necessary to have a system of compression which does not require the constant introduction of grease or of foreign materials into the machine. 4. The liquid must be stable, it must not decompose by the frequent changes of condition, and it must not exert chemical action on the metals of which the apparatus is constructed. 5. Lastly, it is necessary, as far as possible, to remove all danger of explosion and of fire, and for this reason the liquid must not be combustible. The only substance, in his opinion, that answers these requirements is sulphurous acid. This subject is a very important one. If the utilization of heat could be carried to 3 per cent., as in most machines, it might be possible to make ice cheaper in New York than to gather, store, and transport it.