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 han dle 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 com partments, 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 solu tion. Any tinsmith or person of me chanical ingenuity can construct at a veiy nominal cost either of these de vices and charge it with the same ma terials as are used in the most expen sive fire extinguisher upon the market. But take care to use a strong recep tacle 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 bicar bonate 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 recep tacle would require 6 pounds of bak ing 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. Note the total weight and subtract the weight of the tank. Divide this amount expressed in pounds by 13, and the result will be the number of pounds of soda required. The weight of acid required will be five sixths the weight of the soda. Dissolve the soda in the water and place the sul phuric acid in a glass bottle so ar ranged that when required for use the bottle may be turned over by a crank or otherwise and the acid spilled into the charge of soda water. Carbonic-acid gas will be generated at once under strong enough pressure to force the whole contents with con siderable power through a nozzle di rected against the fire.
Or dissolve copperas or ferrous sulphate, 5 parts; ammonium• sul phate, 90 parts, in water, I25 parts.
Or dissolve in 75 parts water, cal cium chloride, 90 parts; salt, 5 parts.
The two last may be kept conveni ently at hand for use with a hand pump.
Hand Fire Extinguisher.—Another device consists of a mixture of suit able substances combined in a glass vessel, which must be thrown upon the fire with sufficient force to break the glass. To make hand grenades or fire extinguishers of this sort take pint or quart fruit jars or any large bottles and charge them with a mixture of equal parts of sugar of lead, alum, and common salt, dissolved in water. Keep these tightly corked in various parts of the house. To extinguish a fire throw one or more of these bot tles into or just above the burning parts, so that the liquid will fall upon the wood or flames.
Or charge these bottles with a mix ture made of e pounds of common salt, 1 pound of muriate of ammonia, and 3 quarts of water. Dissolve, bot tle, cork, and keep at hand in various parts of the house for emergency. Throw the bottles into the fire with force enough to break them.
Or dissolve pearlash, soda, wood ashes, or common salt in the water which is being dashed upon the flames from pails or pitchers, or in which are soaked cloths to beat out the flames.