in the immediate future need not cause anyone great worry. So long as the war lasts, chemists will be in demand and remunerations will run high. Now is the time, however, to raise their social status. Lest anyone should doubt that we are still unknown soldiers, let him ask any of his friends how many chemists he knows; if he can name three, I shall be greatly astonished. Let him look over the lists of prominent men being polled by newspapers on questions of the day ; how many chem ists will he find? Who knows or cares to know who gave to the world aspirin,
Magnesium
ethyl gas, or concrete? People talk glibly about insulin and sulfa-compo Jids, vita mins, and plastics, but h^v p j rer inquire who the chemists are w . *>ted these products, nor do I reme* >s seeing their pictures in any advertising literature. If history repeats itself and chemists come again to the fore in this war, I hope the
AMERICAN
CHEMICAL
SOCIETY
will
do its utmost, not only to emphasize chemical achievements, but also to pub licize the names of the men behind them. Perhaps we shall yet see the day when schools, parks, or streets are named after
from Dolomite
chemists rather than after dead real estate speculators. If we chemists wish to better our lot, we must dig down to the roots of what ever evils we are afflicted with. Unless we do so, we shall continue to harvest sour fruits. Above all, we should at last be recognized, socially and financially, as one of the highest rating professions in our present social order. If we slip up on our chance this time, we shall have no one to blame but ourselves. We may not be given another chance like this in our generation.
by Ferrosilicon
Reduction
D. H. Kiileffer, Contributing Editor, 60 East 42nd St., New York, Ν. Υ. TVVTOUNTING demands for magnesium for war purposes continue to em phasize interest in new processes for its production. Latest of these employs ferrosilicon to reduce calcined dolomite to free metallic magnesium which is then dis tilled from the reacting mass. Production of the light metal in the United States has so far been limited to the electrolysis of magnesium chloride obtained from natural brines and from sea water [ N E W S EDITION, 19, 1189 (Nov. 10, 1941)] together with small amounts from the Hansgirg process based on the reduction of calcined magnesite with carbon [NEWS EDITION, 19, 839 (Aug. 10, 1941)]. A new ferrosilicon process has been developed by L. M. Pidgeon, of the Cana dian National Research Council. Pidgeon found that the reaction between ferro silicon and magnesium oxide proceeds smoothly at practicable temperatures under vacuum in the presence of calcium oxide. Metallic magnesium distills readily at the reaction temperature and con denses in extraordinary purity as a crystal line lining in a condenser tube connected with the reaction retort. The process consists of briquetting ground ferrosilicon (75 per cent or higher silicon content is preferred) with dead burnt dolomite and heating these briquets in an alloy steel retort to about 1,150° C. T h e retort is constructed with an integral condenser tube into which a removable, tubular steel lining fits. The retort and condenser are evacuated to low pressure (a fraction of a millimeter), and as the reaction proceeds, pure metallic mag nesium condenses in the lining of the con denser. At the end of the run—including time for evacuation, the cycle is about 6 hours—the condenser liner is removed with its accumulated magnesium. Differ ential contraction of the steel and mag nesium breaks the two apart and the mag nesium "pipe" is ready to go to the foundry V O L U M E
2 0,
NO.
6
»
»
without further purification or treatment. The retorts used resemble those of the zinc industry and can be heated in any con venient manner, using gas, coal, or electric heat. The advantages claimed for this process are several. The process equipment is comparatively simple: cast alloy steel retorts which embody a minimum of ma chine finishing, furnaces for heating the retorts, and vacuum pumps to evacuate them. Dolomite is plentiful and easily calcined in standard lime-kiln equipment. Ferrosilicon is made in this country on a huge scale in standard electric furnace equipment from plentiful raw materials. The reaction proceeds smoothly without hazard. No evolution or handling of gases is involved, and when the retorts are opened, the magnesium is in solid massive form precluding the possibility of explosion or fire. Special emphasis is placed on the relatively low investment in plant re quired and on the speed with which units can be built in the present emergency. Furthermore, pilot plant operation to date has amply proved the process, and construction of production plants is al ready under way. Several companies have become actively interested in putting this process to work. In Canada, Dominion Magnesium, Ltd., is operating a pilot-scale plant. This operation is in process of being enlarged to 10 tons per day. The process depends on the simple reaction between magnesium oxide and elementary silicon contained in ferrosilicon : 2MgO + Si = 2Mg + SiOj Subsequent reaction between the S1O2 formed and the calcium oxide of the charge forms infusible dicalcium silicate that can be easily removed from the retort at the end of the run without slagging. N o gas M A R C H
2 5,
1942
is evolved or involved in the process. Based on this reaction, each pound of silicon in the charge should theoretically produce 1.73 pounds of metallic mag nesium. In terms of 75 per cent ferro silicon, each pound of magnesium pro duced requires practically 1 pound of alloy The simplicity of the operation depends further on the fact that a powerful reduc ing agent, ferrosilicon, is supplied to the process. This must be manufactured else where, and although the raw materials required for it are plentiful, the energy needed is high and the demand for the product by the steel industry is great. Production of ferrosilicon of all grades in the United States in 1940 was 406,699 net tons. The average silicon content of this entire output was 28 per cent. Included in the total are alloys containing as little as 7 per cent and as much as 95 per cent elementary silicon. The lower grades were produced in blast furnaces, whose total output was 190,310 tons. Electric furnace operation supplied 219,141 tons of higher concentration alloys and 248 tons were produced as a by-product of electric furnace abrasives. Present rate of pro duction is over 700,000 tons per annum. Because of the need for ferrosilicon in war work, the present fixed price ceiling for the 75 per cent grade is $135 per net ton. On this basis and assuming that ferrosilicon of the required" grade is avail able in sufficient quantity, the cost of magnesium by the Pidgeon process should be well below the present market price of 22.5 cents per pound. When these facts are considered with the obvious advantages of the process and the further consideration that the opera tion can be carried out in relatively small and widely distributed units, the desira bility of utilizing ferrosilicon as a reducing agent with dolomite in the expanded magnesium program at once becomes patent. 369
