SO, + H2O -= Sulphur Water. Sulphuric Trioxide. Acid.
The standard method has been to bring the sulphurous fumes into great leaden chambers and there to effect a union with oxygen by means of oxides of nitrogen, which are ulti mately recovered. This must be done in the presence of water so that the resultant acid or °chamber acid" as it is called is weak, and the excess water must be boiled off.
A later method of producing the anhydride of sulphuric acid (SO,) is accomplished by what is known as catalysis, whereby a foreign body causes a chemical action to take place between others without apparent change in itself. For instance, if the fumes of burn ing sulphur or sulphur dioxide are brought to gether with air, which contains one-fifth oxy gen, in the presence of platinum sponge, under the proper conditions, then great clouds of sulphuric anhydride or SO, (the trioxide) will fall to the floor of the apparatus. This is the principle of the contact process and it is in wide use wherever the anhydride is especially needed. The old chamber process, however, has also been improved, so that it is not clear which process is cheaper to make an acid of 93-95 per cent concentration. Chamber acid is more cheaply produced in the old way than by making SO, and then adding dilute acid to it. (No one would think of adding water to SO, in practice because the reaction would be too hot and lively for convenience).
A notable change in the industry in the United States within the last few years has been the enforced manufacture of sulphuric acid by copper and zinc smelters in order to get rid of the sulphurous fumes from the roasting of their ores, which vitiated the air for miles around the smelters, ruined vegetation, killed farm crops and are conceeded to be inimical to health. It was made possible by the invention of Dr. Frederick G. Cottrell. He found that by the conduction of high tension electric cur rents through vapors under proper conditions, suspended bodies were precipitated from the air as the currents pass through them, along with any excess of moisture contained in Cie air. This saved the day for many cop per smelting corporations that were in im mediate danger of being compelled by law to shut down, owing to the fumes which they pro duced. A considerable part of the sulphuric acid produced in the United States is now made from smelter fumes. The Cottrell process has been partially worked out with reference to other problems, such as the smoke nuisance in cities, and with reference to fog at sea. The method proposed for overcoming fog is to sail an electrically operated small aeroplane, merely large enough to carry the necessary apparatus, attached to the bow of a ship. Then with one pole on the aeroplane and the other at the bow of the ship, the high tension currents would pass between them and the intervening fog should be precipitated. It is interesting to record that Dr. Cottrell turned over all the proceeds from his patents on electrolytic pre cipitation to be expended for research in the advancement of science.
Nitrogen This has been one of the fields of greatest achievement of late years. Nitrogen, of which four-fifths of the air is composed, is needed in combination for fertilizer, for food, for the manufacture of dyestuffs, ex plosives, medicines,— in short, nitrogen in com bination is needed constantly for a vast number of purposes. Formerly the only source of supply was the great beds of nitrate of soda found in Chile, but not only will these be ex hausted within 100 to 150 years at the present rate, but in the event of war, a blockade of the Chilian ports makes the production of explo sives impossible. For despite the inexhaustible volume of it all around us, it will not enter into chemical combination except at the temperature of the electric arc or, until lately, under condi tions unknown to man. Leguminous plants,
such as clover, cowpeas, alfalfa, etc., take up nitrogen from the air and not only use it but enrich the soil with it when they are ploughed under. Other plants do not accomplish this and neither do laboratories or factories to this day, save in a roundabout way. The industry started at Niagara Falls under the invention of an American chemist, Charles S. Bradley. The product proved too expensive to persuade the investors in the enterprise that it was worth while, and the work was discontinued. Then two Norwegians, Birkeland and Eyde, took it up and have developed an enormous industry. With the great water powers of Norway, avail able to industry, they develop electric currents and produce nitric oxides from the nitrogen and oxygen of the air. These oxides, brought into combination with lime, produce a fertilizer which is sold all over the world. The process calls for vast quantities of power, and in Ger many, with the war on and the supplies of nitrate of soda approaching an end, and the ports all closed, and no great water power de velopment available in the country, something had to be done if the war was to continue. Without fixed nitrogen, no explosives may be made. At this point the process of two chem ists, Haber, a German, and Le Rossignol, a Frenchman, was used whereby anunoma was produced by causing nitrogen of the air to unite with hydrogen. They knew, as chemists have long known, that if three volumes of hydrogen gas and one vol ume of nitrogen are enclosed in a vessel and an electric spark is passed through the mixed gases, a little ammonia will be formed. Am monia is a combination of three atoms of hydrogen with one of nitrogen. Not much am monia is formed, though, because at that tem perature it is not a stable compound and it dissociates into its components, nitrogen and hydrogen. They sent the gases, instead, through tubes under varying conditions of heat and pressure, bringing them into contact with various metals with a view to getting them to act as catalysts. In other words, they were after a contact process. They succeeded with the metals osmium and uranium, and by 1913 there was erected in connection with one of the industrial establishments a $10,000,000 plant which operated successfully. But ammonia gives with water an alkaline reaction, and while i incalculably useful in the arts of peace, it will not do to make munitions. So a late discovery of Professor Ostwald was availed of, whereby ammonia, brought together with oxygen, under catalysis, produces nitric acid and water. This solved the problem. Another process to pro duce ammonia by contact was developed in the research laboratory of the General Chemical Company of New York and turned over to the United States government for war purposes. It is an improvement over the German method. Still another in wide use consists in treating calcium carbide at a high temperature with nitrogen gas, which combines with it and pro duces what is called calcium cyanamide, CaChi*, a favorite nitrogen fertilizer. Then calcium cyanamide treated with super-heated steam pro duces calcium carbonate, which is the composi tion of limestone and ammonia. Prof. John E. Bucher of Providence, R. I., has patented a method whereby steam and powdered coal and soda are brought together in the presence of iron; and as air, which is four-fifths nitrogen, is passed through at a moderately high tem perature, sodium cyanide is formed. But this poisonous substance, when treated with steam, goes over into bicarbonate of soda and am monia.