Ammonia and Carbonic Acid Gas.
To the Editor of FIRE AND WATER:
In your issue of May 23 F. M. Mahan, of Chicago, desires the writer “to show to the firemen of the country how far he is able to handle the question of ammonia gas as a fire extinguisher.” He also propounds several questions upon the theory of putting out fires by either ammonia or carbonic acid gas, but as to the facts in regard to the advocacy or adoption of ammonia gas engines by the large fire departments of the country he has not a word to say. Our firemen, caring so much more for the practical than the theoretical views of these matters, would not wish for a lengthy dissertation upon the latter, and it would not do to tire them of the subject before the appearance of the thesis with which Mr. Malian is going to settle these questions once for all.
Briefly, therefore, in carbonic acid gas engines the gas is generated by the mixing of acid and an alkaline solution in a tank, and there is neither gas nor pressure until the moment that both are required. This gas is both the propelling and the extinguishing agent, and, when in service, is sufficiently controlled by suitable devices. When a stream is thrown upon a fire by these means the “percentage of gas” reaching the burning surfaces is great enough to make the fluid a most powerful extinguisher, not only in theory, but in practice as well, and this we know not alone from tests on open sheds filled with kindling wood, but also from the hearty indorsement of hundreds of firemen in cities, towns and villages everywhere.
In ammonia gas engines the fluid has no expansive or propelling power as it lies in the tanks. A pump is used first to force the solution into the tanks, and then to generate a heavy pressure of compressed air which, it is claimed, will remain in the cylinders indefinitely. Whether the machine stands unused for months, or runs out two or three times a day at a break-neck pace over rough streets, this great pressure must maintain itself if any service is expected on reaching the scene of the fire. The ingredients of the fluid used are not for the general public to know, and, so far as the ammonia gas is concerned, we have the proprietor’s statement for it that this element is generated when the stream strikes the fire, and not until then. As they stand alarmingly close to the flames when giving their interesting exhibitions, they can, of course, see what may be invisible to the spectators.
For lack of space Mr. Malian’s questions on combustion will be passed at present, particularly as the answers may be found in any good elementary book upon chemistry. Instead of these, some mention of the process of recharging chemical engines will be made. Carbonic acid gas machines carry with them soda, for the alkaline solution, in small carriers, and acid in handy receptacles, both in the proper quantities. With these packages ready, the only other ingredient required is water, and this may be procured from any hydrant, well or cistern, or, as once happened in the writer’s experience, from a puddle in the road. The engine can thus be easily and quickly recharged, and, in case of a long-continued fight, even more soda and acid can be carried by men or boys from the engine house or the nearest drug store.
As the fluid for an ammonia gas machine must lie mixed in bulk, or bought in quantity ready prepared, no extra charges can be carried on the engine. If the fire be such as to require more than the original contents of the tanks, the whole quantity used in reloading must be prepared in advance and hauled to tile scene in barrels or tanks, which would be a slow matter in case of bad roads even were horses and wagons available. Any trifling mishap to the pump would render reloading impossible, just as a slight leakage in some one of the numerous pipes or valves might let the compressed air out with a whiz at a vital moment. A small town depending entirely upon a chemical engine for protection, wouid be likely to have tiieir first real fire get away from them entirely while they were sending for material and recharging an ammoniacal gas engine.
Mr. Mahan evades the writer’s suggestion of April 7, which was to place an ammonia gas engine in the department of some city like Detroit or St. Louis and let it remain in hard service two or three years to find out its usefulness. In his last letter he makes a proposition of his own desiring a carbonic acid gas engine to go into service alongside of his favorite machine in any city except Chicago. F-videntiy the fire authorities of the second city in this country think very little of ammonia gas. This proposition was hardly necessary because it might not be easy to find a first-class city prepared to use two chemical engines under such conditions and pay for the men and horses required.
Mr. Malian can find in almost any city or large town in this country enough carbonic acid gas engines to give him all the comparative tests in regular service that he may care for, if he can only induce the chief of one of these to try an ammonia gas engine for the year that he mentions. He has told us that the judgment of the Chicago firemen is against him, but why not try Cincinnati, Denver, Detroit or some other city where the chief is also an acknowledged authority on fire matters ? HARRY W. BRINGHURST. SEATTLE, Wash., June 6.