The liquid extinguishing agent has seen little change since 1907. In 1914 it was modified so that it injures nothing with which it comes in contact. It puts out fires originating in oily wastes, turpentine and shellac, and fires resulting from the ignition of gasoline, benzine or acetylene gas, on which ordinary chemicals and water are useless. It extinguishes electrical fires without injuring insulation or apparatus and without injury to the operator. A stream of this liquid has been directed upon a circuit of 110,000 volts without the least harm to the operator. A German originated the soda and acid type of extinguisher from tests made in Denmark between 1830 and 1835. The enterprising Teuton divided a hogshead into two parts. He filled one part with a solution of alcohol and water; the other division was partly filled with sulphuric acid. His problem was to unite the two when he wanted to put out a fire. This was accomplished by fastening a charge of gunpowder in such a way that when exploded it would break the partition and mix the solutions. French ingenuity added slight improvements a short time later. [Illustration] Alexander Graham, of Lexington, Virginia, applied for patents on this type of extinguisher a number of times between 1844 and 1849. He was unable to patent his invention. A fire extinguisher company in Chicago and one in Baltimore obtained patents on what was known as the “bicarbonate of soda and sulphuric acid” extinguisher by a special act of Congress in 1865. These patents were known as the Graham patents, and both extinguishers were called the “break-bottle type” because the soda and acid were mixed when a glass bottle containing the latter was broken. The “up-set” type of soda and acid extinguisher was adapted by Meyerose in St. Louis in 1891. The improvement lay in the vessel containing the acid being upset instead of broken. This extinguisher was of copper construction and had a capacity of three gallons. One fire extinguisher company improved upon the original type of “up-set” extinguisher in 1893 by lining the extinguisher with lead which the acid did not affect. Since 1893 there have been no improvements of consequence on the soda and acid extinguisher. It consists of a cylindrical container with a solution of sodium bicarbonate. Over the bicarbonate is suspended a vessel containing sulphuric acid. When in use the acid is tilted over and comes in contact with the bicarbonate. This liberates carbon dioxide. The pressure generated is sufficient to throw a stream of the bicarbonate solution forty feet. The chief disadvantages of the soda and acid type of extinguisher are that its weight makes it cumbersome to operate and it cannot be safely used on electrical fires until the current has been turned off. * * * * * How is Gold Leaf Made?