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Heating, Lighting, and Refrigeration: Fasten

Plain rubber tubing or flexible gas pipe is suitable for this purpose. The longer, the better. Fasten to the removable screw top by means of wire a glass bottle containing sulphuric acid and having a glass stopper. Fasten another wire about the neck of this stopper, let it protrude through the cover, and end in a ring by means of which the stopper may be withdrawn. But care must be taken to use wires strong enough so that, should the stopper stick, the bottle may be broken off if need be without removing the screw top of the can. When required, carry the extinguisher to the vicinity of the fire, pull out the stopper, and shake the can to mix the oil and soda solution. Turn the stopcock and direct the resulting stream of water charged with carbonic-acid gas upon the flame.

Or an ordinary pair of pliers or nippers used to handle wire may be set in the screw top of the can to hold the neck of the bottle of acid between their teeth. Then by closing the handle of the nippers the neck of the vial may be broken, allowing the acid to drop into the soda solution. This should be a little below the mouth of the can, so that the pliers themselves will not be immersed. They may be protected from rust by coating with rust-proof varnish.

Or get a cylinder or pipe of tin, zinc, or other suitable material, and by means of a perforated partition near one end divide into two compartments, one much larger than the other. Fit the opposite end with a stopcock, a flexible tube, and a nozzle.

The larger compartment contains the solution of bicarbonate of soda in water; the smaller contains sulphuric acid in the form of a dry powder or crystals too coarse to pass through the perforations in the partition. This cylinder when not in use must, of course, be kept upright so that the soda solution will not come in contact with the acid; when required for use it must be inverted, the soda solution will then fall through the perforations upon the dry acid, and the mixture will produce carbonic-acid gas.

Or the partition may be operated by means of a plunger which will knock it out of the way so that the dry soda will fall into the soda solution. Any tinsmith or person of mechanical ingenuity can construct at a very nominal cost either of these devices and charge it with the same matcrials as are used in the most expen sive fire extinguisher upon the market But take care to use a strong receptacle or to open the stopcock so as to give the mixture a vent by means of a suitable tube and nozzle as soon as the acid and the soda solution are brought into combination. This will prevent an explosion. Take care also to combine the materials in the right proportion.

The proportions in which sulphuric acid and bicarbonate of soda unite to form carbonic-acid gas are 5 parts of sulphuric acid and 6 parts of bicarbonate of soda (which is ordinary baking soda), by weight. Commercial bicarbonate of soda requires 13 times its weight of water to fully dissolve it. Hence a sufficiently large receptacle would require 6 pounds of baking soda dissolved in 78 pounds of water and 5 pounds of sulphuric acid so arranged as to be poured into the soda solution when required.

To fill a smaller tank in the same proportions, place the tank on the scales and note its weight. Now fill about two thirds or more with water.