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INDUSTRIAL A N D ENGINEERING CHEMISTRY
A. It is assumed that the accelerator decomposes into inactive products. What they are I am unable t o say. Q. Was any work done on combinations of accelerators along that line? A. Not in this particular investigation. Q. For a stock t o be non-blooming with one of these accelerators, would the accelerator disappear during the cure? A. To make non-blooming stocks the sulfur would have t o be kept very low so that the free-sulfur ratio would not be more than about 1 per cent on the rubber. The accelerator would disappear regardless of the amount of sulfur present. Q. Have you been able t o apply this method to determine the best amount of sulfur to use in a stock with any given accelerator? It seems, since i t was discovered that the combined sulfur is not an index of cure, t h a t i t has been neglected more than it should have been. Although it (the sulfur coefficient) certainly cannot tell anything about the state of cure, i t is highly important t o determine the actual amount of sulfur combined by any given
Vol. 19, No. 9
accelerator. This paper seems t o be valuable in its suggestiveness of what may be developed along these lines. Q. Is i t not possible that the flattening of the curves is due to the mass action of the sulfur rather than t o the decompositions of the accelerator? A. No, i t has been established by a number of investigators t h a t mass action does not seem t o enter into i t a t all until the free sulfur is almost gone. It would make little difference whether the sulfur content were 5 or 10 per cent, the accelerator of this fugitive type would combine just about the same amount of sulfur. Q. What would be the effect of a change of temperature on these curves? A. I cannot exactly say, b u t I think a change of curing temperature would merely change the position of the curve but not its general shape, except possibly in the case of the xanthates, which are so unstable that if you attempted t o cure with them at high temperatures, there would be almost no cure a t all.
Heat of Solution of Paraffin Wax' By F. W. Sullivan, Jr., W. J. McGill, a n d A u g u s t F r e n c h STANDARD OIL COMPANY (INDIANA), WHITING, IND.
I
N CALCULATIONS concerning refrigeration require-
ments for the chilling of wax bearing distillates, 63.27 B. t. u. per pound is commonly used as the heat of solution of the wax. This figure seems to have been taken from the 1894 edition of Landolt-Bornstein's "Tabellen."* Graefe3 gives a value of 70.2 B. t. u. per pound; Batelli,4 63.0 B. t. u. per pound; Kozicki and Pilat,' 70 B. t. u. per pound for 126" F. (52.2' C.) melting point paraffin wax and 78.9 B. t. u. per pound for 149.6" F. (65.3' C.) melting point wax. I n making heat balances for refrigerating operations on wax distillate, discrepancies have been found which it was thought might be due to the use of this commonly accepted figure of 63.27 B. t. u. per pound. The heat of crystallization of the wax found in the wax distillate cut from midcontinent crude was consequently determined and found to be 72.5 B. t. u. per pound.
This stirrer mixed the contents of the calorimeter very thoroughly. The amount of heat developed thereby was negligible in these experiments. I n 45 minutes of stirring at room temperature in a vacuum bottle the temperature of the oil was raised only 0.1"C. The water bath was kept a t a constant level by means of tube, e , attached to a suction line. The bath was adjusted to any desired temperature by running in water from the hot-water line, h , or the cold-water line, f. The heating coil was operated by current from a 24-volt storage battery. The current consumed was measured by means of a voltmeter and ammeter which were read at 50second intervals. Materials
The oils were pressed distillate from midcontinent crude and a wax-free gas oil. With the latter it was possible to Apparatus work close to room temperature because of its greater solvent An adiabatic calorimeter was used in this work (Figure 1). effect for the wax. The wax was obtained by recrystallization of a slack wax The inner vessel, a, consisted of an old 1-quart, wide-mouth vacuum bottle, the vacuum of which had been broken. It until it was practically oil-free. This wax was ground in was left mounted in its original jacket. It was fitted with a food chopper into particles less than l/8 inch (3 mm.) in a thermometer, t, graduated in 0.2" C., a heating coil, c, diameter. These were formed into the shape of an easily of No, 24 nichrome resistance wire, a '/*inch (13-mm.) crumbled rod by plunging a cork-borer into 8 pile of the opening, 0, fitted with a glass tube for introducing the wax. wax particles several times and then ejecting the wax from and a stirrer, s. The stirrer was of the reciprocating type the cork-borer with one of the next smaller size. These consisting of two flat rings, r, mounted on two upright wires rods disintegrated readily upon being introduced into the and spaced above each other 2 inches apart. These rings oil so that the wax dissolved completely in a short time. were of sheet copper of about 2 inches outside diameter and Procedure 1 inch inside diameter and had l/d-inch (6-mm.) holes drilled Four hundred grams of the oil were weighed out into the about inch (13 mm.) apart midway between the two edges. The ends of the upright wires were sealed into narrow calorimeter. The motor driving the stirrer was started and glass tubing with cement. The glass tubing passed through the speed was adjusted by means of the regulator until the brass sleeves in the cork covering the inner vessel. The stirrer made 60 cycles per minute. The oil was brought t o stirrer was driven by a string which passed over a pulley, the desired temperature by means of the electric heating coil. p , actuated by a crank attached to a reducing gear driven Some of the first experiments were done a t higher temperatures, but the later ones were done close to room temby an electric motor. perature to reduce any possible errors due to radiation 1 Presented before the Division of Petroleum Chemistry at the 73rd losses. When the desired temperature was reached the Meeting of the American Chemical Society, Richmond, Va , April 11 t o 16, current was shut off and the stirring continued. Mean1927 2 Day, Handbook of the Petroleum Industry, Vol 11, p 823, John while the temperature of the water bath was adjusted by Wiley & Sons, I n c , 1922 adding either hot or cold water until it was exactly the same "Laboratoriumsbuch fur Braunkohlenteerindustrie as the temperature of the calorimeter proper. When no 4 Physik Z , 9, 671 (1908) increase or decrease in the temperature of the calorimeter 6 Pelvoleurn, 14, 12 (1918) J
I'
September, 1927
IXDUSTRIAL A N D ENGINEERING CHEMISTRY
was observed for 5 minutes the wax was added as rapidly as possible through the tube. The temperature of the wax had been noted a t this time. Readings were taken on both the calorimeter and bath temperatures a t intervals of 50 seconds. The bath temperature was adjusted so that a t all times it was exactly the same as the calorimeter temperature. The air current used for stirring was sufficient to mix the water thoroughly, so that there was very little lag when it was desired to make a quick change in the temperature of the bath by the addition of cold or hot water. Bfter sufficient experience had been gained in the operation of the apparatus, it was possible so to gage the rate a t which cold water should be added that the temperature of the bath was well within 0.2" C. of the calorimeter temperature. As the wax dissolved the temperature of the eontents of the calorimeter dropped. When no further drop in the temperature took place over an interval of 200 seconds the solution was considered to be a t equilibrium. The calorimeter vessel was then opened immediately and the contents were examined to make sure that the wax had dissolved completely. The heat of solution is calculated from the drop in temperature and the specific heat of the oil. Correction is made for the water equivalent of the calorimeter and the change in temperature which the wax itself undergoes.
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these averages gave the average wattage over the period. The input in calories was calculated from the formula: Time in seconds X watts = calories 4.182
The water equivalent is 323 + 5.48 = 58.9 calories per degree. C a l c u l a t i o n s for O n e D e t e r m i n a t i o n
-.
of-
Temperature of water: Final Initial
50.74 45.26
Increase Time of heating, 450 seconds Average volts, 14.34 Average amperes, 1.63 Average watts, 23.37
450 4oo
5.48
:,2d3' -._--
= 2515 calories input 5,48 = 2192 calories absorbed by water 323 calories absorbed b y calorimeter over 5.48' C. range
A number of determinations made in this way gave the values: 59.05, 56.31, 54.38, 61.08, 58.94; average, 57.95. The value 58 calories per degree was used as the water equivalent in all the heat of solution determinations.
C a l c u l a t i o n s for O n e D e t e r m i n a t i o n Gas oil: 400 grams; specific heat, 0.386 Wax: 20 grams; melting point, 125O F. (51.7O C . ) ; specific heat, 0.6
TEMPERATURES
c. 28.3
Room Oil in calorimeter: Initial Final
30,48 26.95
Drop Q'ax: Initial Final
3.53 28 30 26 95
1 35 Cakiries 545.0 16.2 204.7
Drop H e a t given up by oil: 400 X 0.386 X 3.53 = Heat given up by wax: 20 X 0.6 X 1.35 = Water equivalent of calorimeter: 58 X 3.53 =
-_
Total heat absorbed when 20 grams of wax dissolved
766.9
.Vole-The value for the specific heat of solid paraffin wax was taken as 0 . 6 . This value was obtained by averaging the few values given in the Landolt-BGrnstein "Tabellen" and was considered t o be close enough in these determinations, since the temperature changes in the wax involved a relatively small amount of heat.
The heat of solution is therefore 765.9 per gram.
+ 20
=
38.3 calories
D e t e r m i n a t i o n of W a t e r Equivalent F i g u r e 1-Adiabatic
Four hundred grams of water were put into the inner vessel and heated by means of the heating coil to a temperature approximating the final temperatures obtained in the heat of solution experiments. The temperature of the water bath was adjusted t o that of the calorimeter and the stirring was cont,inued until there was no change in the calorimeter temperature over a period of 200 seconds. The current in the heating coil was then turned on and a stop watch was started simultaneously. Readings of the voltage and amperage on the coil, as well as the calorimeter and bath temperatures, were taken a t 50-second intervals. The bath temperature was adjusted to that of the calorimeter by running hot water into it. The heating was continued over a temperature range corresponding t o the drop in temperature in the heat of solution determinations. When the desired temperature was reached the current was shut off and the stirring was continued until no further rise in temperature was observed. The voltage and amperage were averaged over the time that the current was on and the product of
Calorimeter
Specific H e a t s of the Solvent Oils
The specific heats of the oils used were determined in the same may that the water equivalent was determined. H e a t of S o l u t i o n of 1 2 5 O F. (51.7" C.) M . P. P a r a f f i n Wax SPECIFIC HShT O F T E M P E R A T U R E H E A TO F S O L ~ T I O N EXPT. OIL OIL Initial Final Room C. C. O C. Cal./g. B.l.u./lb. 1 Presseddistillate 0 . 4 3 8 50.27 48.15 23.3 40.6 73.2 2 Presseddistillate 0 . 4 3 8 51.80 47.33 26.0 39.6 71.0 3 Pressed distillate 0 . 4 3 8 51.08 46.65 25.6 39.0 70.2 4 Presseddistillate 0 . 4 3 8 49.79 45.16 25.6 42.2 75.9 5 Gas Oil 0.386 35 30 31.10 26 1 41.6 74.9 0.386 30.48 28.3 38.3 68.9 6 Gas 011 7 Gas Oil 0 386 31.28 25.0 40.7 73.2 72.5 Average 4 0 . 3
The Universal Oil Products Company announces that'the British American Oil Refineries, Limited, will install immediately a 1000-barrel Dubbs Cracking Unit a t their refinery a t Toronto.
