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and flow out through an exit tube a t the top, or it may be drained periodically and fresh distilled water added. The most suitable voltage to apply a t the electrodes will vary with the nature of the sol being electrodialyzed, and with its content of electrolyte. It is generally best t o keep the current under one ampere in order to avoid too much heating. This can be done by controlling the line voltage or, more conveniently, by using an adjustable rheostat connected in series with the cell. A line voltage of 100 to 220 volts is commonly used. Rate of Electrodialysis
The comparative rate of electrodialysis of different ions through parchment membranes is shown in Figure 2. Tencubic centimeter samples of solutions of KC1, KzSO?, and KH2P04,all normal in potassium content, vere placed
Vol. 20, No. 1
in 500 cc. of water in the middle chamber of the electrodialysis cell and 100 volts d. c. applied a t the electrodes. The anolyte and catholyte were siphoned off every 10 minutes and titrated with standard acid or base. I n every case the cation is removed much more quickly than the anion. The rate of removal of the cation is influenced by the nature of the anion with which it is combined, while the rate of removal of the anions is in the order C1>SO4>HzPO4. I n every case the cation is removed quantitatively within 20 to 40 minutes. The anion can also be removed quantitatively, but the time required is greater, especially in the case of the phosphate ion. The rate of removal of anions should be facilitated by the substitution of a positive membrane for the negative parchment membrane on the anode side. L4 satisfactory positive membrane has not yet been found, although the chromated gelatin membrane2 has proved helpful in certain cases.
Present Status of Coal By-Product Nitrogen' Mildred S. Sherman FIXEDNITROGENRESEARCH LABORATORY, BUREAU OF CHEMISTRY A N D SOILS, WASHINGTON, D. C.
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ITHIN the last fifteen years coal has been a T-ery influential factor in wresting the world nitrogen monopoly from Chilean nitrate. Power for the manufacture of fertilizers is obtained from coal; 85 to 90 per cent of the hydrogen required for the synthetic fixation of nitrogen will be produced in 1927 through coal, either from water gas or by-product coke-oven gas; and Aikman, Ltd. (London), estimates that of the world consumption of 1,315,000 tons of nitrogen in the year ending June 30, 1927, 24 per cent, or 310,000 tons, were produced as a distillation product of coal. This figure of 310,000 tons of nitrogen from by-product ammonium sulfate shows an increase over the figures of 300,000 and 275,000 tons for the two previous years and on the basis of 850.40 per ton (2000 pounds), the average price of ammonium sulfate for that period, was worth $73,745,280. While there have been no startling new developments in the processes for treating coal by-products within the last year, the industry has made steady progress and developed its operating technic along lines already established. However, three decided tendencies have become apparent. Rigger and more efficient ovens are being built. The trend of the industry is for larger unit coke-oven capacity. I n America the average oven holds a charge of 12 tons of coal. There is an increasing number of plants having 16-ton ovens and the Carnegie Steel Company a t Clairton, Pa., is now constructing three hundred and forty-eight ovens of the Koppers-Becker type, whose individual capacities will be 19.13 tons of coal per charge. It is estimated that this new group of ovens will produce 2,721,000 tons of coke annually, so that this new plant alone will potentially be able t o recover 45,000 tons of ammonium sulfate per year. The city gas companies are becoming more closely allied to the by-product coke-oven interests. I n the United States five of the eleven companies which placed new by-product coke ovens in operation in 1926 were connected with public utilities companies and will market their surplus gas through these systems. City gas works thus owned 27 per cent of the new ovens opened up in the past year, and these ovens will manufacture 22 per cent of the additional estimated annual coke output. Furthermore, the keen competition due to the increased 1
Received October 13,1927.
production of synthetic nitrogen is forcing the by-product companies to convert their ammonia liquor to sulfate. &lore and more industries needing highly pure ammonia are looking to the synthetic plants t o supply their wants and the output of the coal industries will be converted. into fertilizer materials. A study of the statistics2 for the United States for the year ending June 30, 1927, will give an accurate picture of the condition of the industry. On that date there were seventy-seven active by-product coke-oven plants and one idle one, and these plants were producing slightly more than 82 per cent of their capacity. These plants had about 12,000 ovens in actual use. During the year eleven companies placed 679 new ovens in ~ p e r a t i o n from , ~ whose estimated annual production of 3,794,470 tons of coke it will be possible, using present methods, to recover 12,920 tons of nitrogen. On December 31, 1926, fourteen companies were constructing 945 new ovens, whose annual coke production capacity will be 6,304,250 tons of coke with the corresponding recovery of 21,450 tons of nitrogen. Table I s h o w there has been a steady increase in the nitrogen produced from by-product coke ovens in the United States in the last three years. I n addition to these figures, the gas works have recovered, as the three-year average, 5300 tons of nitrogen per year. T a b l e I-Kitrogen Recovered f r o m By-Product Coke Ovens COALCONAMMOXIUM YEARENDING SUMED IN BYSULFATE hTITROGEN JUNE30 PRODUCT OVENS EQUIVALENT EQUIVALENT Tons Tons Tons 595,050 126,150 1925 51,525,000 700,774 148,564 1926 60,653,000 738,772 156,620 1927 63,963,000
During the calendar year 1926 the nitrogen needs of the United States were such that it was necessary to import 155,200 tons of nitrogen in the form of Chilean nitrate valued a t $42,781,400. Additional 22,880 tons of nitrogen mere imported in the form of other salts, showing that our consumption was 178,080 tons greater than our domestic production. Although our synthetic-nitrogen plants will probably produce a t least 23,000 tons of nitrogen in 1927, 2
Taken from Weekly Coal Reports of U. S. Bureau of Mines. Steel Plant, 16, 41 (1927).
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January, 1928
IliDUSTRIAL AhTDEh'GIh'EERIA'G CHEMISTRY
as compared with about 12,800 tons in 1926, and although their output will be further increased in the next five years, the nitrogen demand of the United States will be so great that the coke industries will have no difficulty in disposing of all of their nitrogen by-products. Owing to the growth of the by-product coke industry caused by the increased demand for both coke and gas, and also to the adoption of new processes, such as the Bergius process for the hydrogenation of coal (which recovers 50
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per cent of the coal's nitrogen by conversion into ammonia as compared with less than 20 per cent recovery by present practices), the nitrogen derived from coal is bound to remain an important factor in the nitrogen situation of the United States. Thus, in spite of the probability of a lower selling price resulting from the competition of the direct synthetic processes, the quantity of by-product ammonium sulfate produced in this country is likely to increase in the next decade.
Brittleness Tests for Rubber and Gutta-percha Compounds' G. T. Kohman and R. L. Peek, Jr. BELL TELEPHOKE LABORATORIES, INC, 463 WEST S T . , NEW
I-ORK,
s.Y
An insulating material compounded of rubber, guttaholds the sample in the temSELDOM nientioned percha, or of similar substances becomes brittle at a perature bath. To test, this property of rubber and temperature characteristic of the material, below support is raised sharply and, gutta-percha comwhich it may not be used if liable to mechanical stress. as it brings the sample from pounds, which is yet of conAn apparatus has been designed for determining this the bath, automatically trips siderable importance in their temperature by giving the sample a sharp bend through a hammer which bends the use for insulating purposes, is a fixed angle. The highest temperature at which fracsample through a fixed angle t h e t e m p e r a t u r e a t which ture occurs in this test (the brittle temperature) has (about 45 degrees). they become hard and brittle. been found to be nearly independent of the bending Raw rubber, when quickly reApparatus angle and the sample's dimensions provided the rate moved from a bath of liquid of bending is maintained at a nearly constant (high) 4 photograph of the apair in which it has been held rate. A modified form of the apparatus is also deparatus is shown in Figure for a minute or so, and struck scribed with which the brittle temperature may be de1. S i s t h e s a m p l e held with a hammer, will shatter termined when the material is under high hydrostatic against the movable support like glass. The same effect pressure. The constancy of the brittle temperature A by the clamp C. The hammay be observed at any temwhen determined under different conditions suggests mer H , operated by the spring perature up to about -60" C. that it marks a change in the structure of the material. h similar behavior is shomi B, is shown in the tripped position, in which it has bent by gutta-percha compounds cooled to temperatures below -30" C. Insulatuig materials the sample as shown. \Then the hammer is locked by Gems compounded of these substances may be brittle a t higher tem- of the catch D:the sample and support can be lowered into peratures, and it is obviously necessary that this brittle tem- the Dewar flask F , in which is a temperature bath of perature be below the lowest temperature to which the ethyl alcohol. The temperature i s adjusted by means of a insulation may be subject, if it is likely in use to come under small heating coil (not shown) and by additions of liquid any strain. The insulation of a submarine cable, for instance, air. The bath is stirred mechanically by a glass stirrer must not be brittle a t sea-bottom temperature, which is as (dismounted, to simplify the photograph). Temperatures low as 0" C. over large areas. are measured by means of potentiometer readings on a Brittleness is a phenomenon which can only be defined thermocouple, the fixed junction of which is held in steam, in an arbitrary manner, as it refers to a combination of proper- thus giving readings conveniently over any range below ties which produce a fairly definite practical effect, but whose 100" c. inter-relations vary in different materials and are in no case Determination of Brittleness Temperature ~ e r yclearly known. This practical effect is fracture under moderate deformation quickly applied. The simplest method The sample in the form of a strip approximately 0.050 of nieasurement is in terms of the sudden bending of a strip. inch (1.3 mm.) and 0.3 inch (7.6 mm.) wide is inserted beneath The shattering of a sheet of material under a hammer blow, the clamp C in such a way as to project beyond the end of another common condition under which brittleness is appar- the support A far enough to be struck by the toe of the ent, involves similar strains along the radii of the circle hammer when the latter is tripped. The support is then struck, combined with compressive strains. lowered into the bath and held there for about 2 minutes I n a test developed by the authors the bending of a strip to allow the sample t o reach the bath temperature. The is used, and the highest temperature a t whirh the strip support A is then sharply raised, tripping the hammer, will fracture under fixed conditions determined. The de- and the sample examined for signs of fracture. If the sample pendence of this temperature on the sample dimensions breaks the operation is repeated a t a higher temperature, if and on the rate and character of the deformation will be it does not break, a t a lower; and this is repeated until the discussed below. The other factor in the design is that of highest temperature a t which the sample will fracture has temperature control and measurement. To provide for these, been located, as can generally be done, within 2" C. The and a t the same time to avoid having the mechanism subject determination first made is checked by repeating the proceto the varying resistance of the viscous bath liquid, the dure, starting with a temperature slightly higher than the sample is held on a sliding vertical support, which normally brittle temperature found in the first determination, and changing the temperature in the opposite direction. 1 Received September 27, 1927.
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