Horry Furnace, showing Carbide just removed.[5]
The actual ingot of good commercial carbide is nearly pure—ninety-six to ninety-nine per cent—but the ingot is surrounded by a crust of carbide mixed with unchanged material, containing forty to seventy per cent of carbide. Foreign makers break and blend ingot and crust to standard size, the best makers guaranteeing their carbide ninety per cent pure, giving five cubic feet of acetylene per pound (pure carbide gives 5.89 cubic feet). Eight to nine pounds of carbide per horse power in twenty-four hours, averaging five cubic feet of acetylene, is considered satisfactory work. The Union Carbide Company, which controls the sale of carbide in the United States, is selling graded carbides under guarantee, the first grade being the nearly pure ingot, the lower grade the crust.
As the moisture of the air decomposes the carbide, it must be broken up as soon as made, and packed in air-tight tin cans, varying in size from one to four hundred pounds.
The present price of carbide abroad averages $96.80 in large lots, and $7.26 per hundredweight in small lots, packing included; in the United States, $70 per ton in large lots, and $4.50 per hundredweight in small lots, packing included. In 1898, 4,650 tons are said to have been made in the United States and Canada, and a much larger amount abroad. The output for 1899 is estimated at 12,000 tons for the United States, with a capacity in the new works in erection at Sault Ste. Marie and at Niagara Falls of 41,000 tons. The new works building in Europe, to be finished in 1899-1900, have a capacity for making 80,000 metric tons. These figures will justify the statement made at the beginning of this article, that the new industry has found ample capital.
The statement is still current that acetylene attacks copper and brass, forming an explosive compound. This is not true. Exhaustive experiments by Moissan and by Gerdes, keeping these and other metals in contact with acetylene for months at a time, have shown that the metals were not affected. The conditions under which the explosive copper acetylide is made in laboratories can not well occur in generators or gas holders. It has been said that acetylene is very poisonous; the experiments of many observers, and especially those of Gréhant, do not confirm this statement. Gréhant experimented on dogs, causing them to breathe mixtures of acetylene, air, and oxygen, which always contained 20.8 per cent of oxygen, this being the percentage of oxygen in pure air. By this device he was able to discriminate between the poisoning caused by acetylene and suffocation caused by insufficient oxygen. A mixture containing twenty per cent acetylene inhaled for thirty-five minutes did not seem to trouble the animal. A sample of the dog's arterial blood contained ten per cent of acetylene. A dog which inhaled a mixture containing forty per cent of acetylene died suddenly after fifty-one minutes, having inhaled one hundred and twelve litres of the mixture; the arterial blood contained twenty per cent acetylene. Gréhant proved that acetylene simply dissolves in the blood plasma, while carbon monoxide forms a compound with the hæmoglobin of the blood. A dog breathing a similar mixture of air, oxygen, and illuminating gas containing only one per cent of carbon monoxide quickly showed convulsive movements, and died after ten minutes; its blood contained twenty-four per cent of carbon monoxide. Thus acetylene, while slightly poisonous, is less poisonous than coal gas, and vastly less than water gas, which contains a high percentage of carbon monoxide.
A pressure of thirty-nine atmospheres and three quarters at 20° C. converts acetylene into a liquid weighing one third as much as the same volume of water, while one cubic foot of the liquid when released from pressure gives five hundred cubic feet of gas.
Hitherto acetylene is used only as a source of heat or as a source of light; yet with very cheap carbide it would prove useful in many ways in chemical industry, and its use would have the most wide-spread effect on industry and agriculture. For instance, a method of making alcohol from acetylene is patented abroad, and by another patented process it is proposed to make sugar from acetylene. With the present prices of alcohol, sugar, and carbide, these processes have no commercial value.
Acetylene may be made from the carbide in gas works and delivered to the consumer through mains like ordinary illuminating gas; or it may be liquefied at a gas works and delivered to the consumer in the liquid form under pressure; or the consumer may purchase carbide and generate acetylene for his own consumption. All three of these methods are in use.
To understand the attitude of insurance companies and of consumers toward liquid acetylene it will be well to examine its record for the last few years. Those interested in methods for liquefying acetylene, and for reducing the pressure of the liquid at the place of consumption so that the consumer actually uses it as a gas under a water pressure of six inches or less, may find processes described in detail in the Progressive Age, and in other technical journals. Suffice it to say that the methods in use in this country and abroad are simple and effective. The purified acetylene is delivered in strong steel cylinders, which may be placed in a special building or case and need not be handled by the consumer. It has been proved by the exhaustive experiments of the eminent French chemist Berthelot that liquefied acetylene in cylinders can not be exploded by blows or shocks to the closed cylinder. If it is exploded, however, by causing a spark within the cylinder, the explosive force is very great, being about equal to that of gun cotton.