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INDUSTRIAL A N D ENGINEERING CHEMISTRY
approximately 21rrdr. If unit length of the cylinder is considered, this may also represent volume. If h is the specific heat of the rubber, and D is density, the heat stored in the rubber when the maximum tem’perature is reached will be found by
which reduces to
TrDhR2 tal.
This amount of heat is, then, lost when the rubber returns to bath temperature, and, since the temperature-rise curve and cooling curve each cover the same range of temperature, the heat lost must be proportional to the time in.each case. If A is the time required to reach the maximum temperature after the temperature of the bath has been reached, and B is the cooling period, the total heat liberated will be
This figure is for unit length of cylinder and must be reduced to unit weight or volume. In the following calculations the last flat part of the cooling curve was eliminated because no such condition exists in the heating curves. It is evident that such figures can be only rough approximations. No account is taken of heat that might be liberated before bath temperature is reached, and it is considered that the reaction is finished a t the highest temperature. The figures of greatest accuracy will, therefore, be obtained from the reactions of greatest velocity, because here loss of heat will be reduced to a minimum. The following are some of the calculations made:
Stock 1
2 6
5
Sulfur Content 10
10 10
14
Vol. 15, No. 3
ACCEI,ERATOR None Piperidylthiuramdisulfide “Hexa” ZnO None
+
Bath Temperature Cal./G. 175 7.5 175 10.2
176 176
8.2 17.2
Both the assumption that the temperature gradient is a straight line and the fact that we consider only a limited portion of the curve will tend to reduce the value obtained, and there is no doubt that these figures are much too low; yet, they serve to show that the amount of heat liberated is small.
FURTHER EXPERIMENTS Since there was a possibility that the thermal changes noticed might be due to some reversible action, a calorimeter was constructed and experiments run as described above. The success of the experiment depends upon obtaining the correct balance between rate of heating and radiation loss from the calorimeter. Several different stocks, both accelerated and unaccelerated, with varying sulfur contents were run, with similar results. Fig. 6 shows a typical curve obtained when using this calorimeter. It will be noticed that the curve obtained with the rubber and sulfur separated is perfectly regular, while that obtained with the mixture rises above for a time and then drops below the first curve. After this it rises regularly until an equilibrium temperature is reached, which is the same as that of Curve 1. The two cooling curves are identical, which fact shows that there is no reversible reaction taking place. These curves show that during vulcanization both an exothermic and an endothermic reaction are taking place, the latter being less intense since it is only noticed after the first action is nearly complete. This is another factor which will tend to lower the calculated value of the amount of heat liberated, as shown above.
A Resource of Millions of Tons of Fertilizer It has long been known that the greensand marls of New Jersey contain small quantities of potash, lime, and phosphatethe elements of a good fertilizer. For more than a hundred yeaYs they were dug and marketed for use as fertilizer, and in the late sixties the quantity so used annually amounted to nearly 1,000,000 tons. With the introduction of prepared fertilizers the greensand-marl industry gradually dies, but here and there in New Jersey small quantities of greensand are still dug and used. It has been considered commercially impracticable to extract the potash from greensand because the mineral in which the potash is locked up-glauconite, a silicate of iron and potassium-is relatively insoluble. Of late years, however, many experiments have been made with the view of devising a process of extracting potash from silicates, and the greensand marls of New Jersey have attracted attention because of their accessibility, abundance, and the relative ease with which they may be mined. The scarcity of potash caused by the shutting out of German supplies during the World War gave impetus t o these experiments and encouraged the hope that a potash industry might be established in the United States, in which event the New Jersey greensands would be of high value. The greensand-marl belt of New Jersey extends across the state from the vicinity of Sandy Hook a t the northeast to Delaware River near Salem a t the southwest, a distance of about 100 miles. It ranges in width from nearly 14 miles in Monmouth County to 1 mile or less in parts of Gloucester County. It is crossed a t many places by railroads and by streams that flow into Delaware River.
During the World War, just before the armistice, the United States Geological Survey, in cooperation with the Department of Conservation and Development of New Jersey, began an investigation to determine the potash content of the greensand marl in this belt. Five type areas were explored by borings and the results were used to obtain specific estimates. These areas are a t Salem and Woodstown, in Salem County; Sewell, in Gloucester County; Somerdale, in Camden County; and Elmwood Road, in Burlington County. The data thus gathered were supplemented by published and unpublished well records and by information on file in the state offices a t Trenton. Moderate estimates show that the New Jersey greensands contain 256,953,000short tons of potash (KzO) that could be mined from open pits-enough to supply the needs of the United States, as shown by the pre-war importation, for nearly a thousand years. Limesand also has been found in probable commercial quantities as far north as Wrightstown. Several companies have undertaken to produce potash from hTewJersey greensand, and some of the companies have marketed small quantities of potash, though none are now actually producing. A detailed report on this investigation, entitled “Potash in the Greensands of ATew Jersey,” by George R. Mansfield, has just been published by the United States Geological Survey as Bulletin 727. The report includes several maps and other illustrations, as well as numerous mechanical and chemical analyses of greensand and an account of its commercial development and use, and notes on the possibility of further development.
