Sept., 1921
T H E JOURNAL O F I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
to tensile properties, thiocarbanilide is without accelerating effect. The presence of thiocarbonilide in the pure gum stock in question leads, however, to some increase in the combined sulfur, the vulcanization coefficient at the 180min. cure being raised from 4.31 to 4.87. This k in accord with results of Kratz, Flower and Shapiro.' It is possible that the apparent increase in the vulcanization coefficient is due to the formation of acetone-insoluble products as a result of interaction between sulfur, thiocarbanilide or its decomposition products, and, possibly, caoutchouc. The thiocarbanilide is without effect on aging.
Sc41SIARY 1-In a simple rubber-sulfur inix piperidine piperidyldithiocarbamate is a comparatively powerful, and hexamethylenetetramine a weak, accelerator, 1per cent reducing the time of optimum cure to one-seventh and to two-thirds, respectively, of the time required in the absence of the accelerator. 2-These two accelerators present a notable contrast in their effects on the tensile properties of the rubber. The piperidine salt greatly enhances the tensile strength which can be developed; it leads to a snialler ultimate elongation and a lower position of the stress-strain curve (strains as ordinates) a t the optimum cure. Hexamethylenetetramine enhances the tensile strength only a little; it leads to a greater ultimate elongation and a higher position of the stress-strain curve at the optiinuni cure; it also has the effect of causing the tensile properties to change with ex-
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ceptional slowness with change in the length of the vulcanization period.
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3-The piperidine salt reduces somewhat, whereas hexathe coefficient of methylenetetramine increases vulcanization at the optimum cure. &In the absence of zinc oxide, thiocarbanilide is without accelerating effect on the vulcanization, considered with respect to tensile properties. It increases somewhat the vulcanization coefficient a t the optimum cure. 5-In a n aging test of 7 mo.' duration, pure gum vulcanizates prepared with the aid of the accelerators in question are found to age normally. ADDENDUM.Vulcanization tests which Mr. Arnold H. Smith has kindly carried out with material supplied by the authors show that the presence of zinc oxide increases the accelerating activity of piperidine pipericlyl-dithiocarhamate very greatly over that found, in the absence of zinc oxide, in the experiments recorded above. I n a mixture similar to that used above, but containing in addition 1 0 per cent of zinc oxide, the acceleration factor f o r 1 per cent of the piperidine compound is in the neighborhood of 200; 1 mins. heating a t 141" giving a n over-cure, and a good cure being obtainable by 4 mins. heating at a temperature as low as 105" ( 3 lb. steani).l It is proposed t o record more fully the data relative to these tests i n t h e Correspondence column of a succeeding issue of THIS JOIJRXAL.
LABORATORY AND PLANT A Combined Extractor, Reflux Condenser, Still and Autoclave2 By Alfred T. Shohl and Mathilde L. Koch DEPARTMENT OF
CHE1IIC.IL
HYGIDKE, SCHOOL
O F H Y G I E N B A N D PUBLIC
A good extraction apparatus to accommodate large amounts of material a t a charge, an apparatus to make absolute alcohol, and an autoclave were needed in the laboratory. Because of limited funds available a single piece of apparatus was designed to meet these needs. I n use it proved to be not only more economical, but also more efficient in several respects than any available apparatus. It is a modification of a n ordinary autoclave such as is used in sterilizing under pressure. glass tube gage which is added shows the level of the contained fluid and has a charging funnel and a draw-off spigot. The autoclave is converted into a refluxing or extraction apparatus by unscrewing the blow-oE valye and inserting the upright conpenser. The condenser is of such a type that, by changing its position, it may be'converted into a condenser for a still. The apparatus consists of six parts : (1)The main body with lid, ( 2 ) extraction trays, ( 3 ) autoclave attachment, ( 4 ) a special fitting or stuffing box, ( 5 ) a connecting tube, and (6) a condenser with stand. The main body (Fig. 1) of the apparatus consists of a riveted copper cylinder to which is soldered a seamless copper bottom. A glass tube gage connects to the body aboi-c and below through two 3-way stopcocks, A and B, and also above with a charging funnel, C, and below with a drawoff spigot, D. Thus fluid can be drawn off and fresh fluid added while the apparatus is in operation. The inner surface of the main body is heavily tinned. Connecting \vjtli 1 TH s JOERXAL. 12 (1921), 130 2 Received April 29, 1921
HEALTH, J O H X S HOPXIKSv N I V E R S I T Y , BALTINORE, &I\laRYLA.\D
the bottom entrance of the gage is a tinned tube, E, bent to reach nearly to the bottom so that the contained liquid may be syphoned off. Near the top are riveted three rightacgled strips of netal, F, 0.5 in. wide and projecting 0.5
1
LEGGED
j
ST4YD
1
P E R F O ? A T D COPP€R BASKETS
in. from the side. These are in the same horizontal plane and equidistant and are the supports for the extraction trays. The extraction trays (Fig. 2 ) contain the material to bc extracted. They may be either cylindrical or cone shaped,
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T H E J O U R N A L O F I N D G S T R I A L A NU EliiG I ATE E R IiZ'G C H E M I S T R Y
and are made of wire mesh or of tinned metal perforated with numerous small holes, The size of the holes depends on the nature of the material to be extracted. Three strips of metal converge from the upper edge to the center, and a t the union there is a knob which serves both as a handle to pick u p the tray and as a spreader to distribute the extracting fluid as it drops from the condenser. The lid of the apparatus is of cast brass. This lid is seated on the cast brass i-ing which forms the top of the main body by means of a ground joint. It is held in place by six toggle bolts with wing nuts. There are two threaded holes through the lid. The central hole carries the autoclave attachment. The other is provided f o r a thermometcr. The autoclave attachment (Fig. 3 ) consists of a blox-off valve, G, which screws into hole 0, and also, attached by right-angle side arms to the central tube carrying the blow-off valve, a safety valve, H, and a pressure gage, I. A special fitting or stuffing box (Fig. 4 ) , with ground joint, of the same size and thread as the blowoff valve, can be screxyed in place of the blow-off valve when the apparatus is used as an extractor, still, or reflux condenser. The ground joint, J, of Fig. 4 is tapered and is female. Into this nut fits a connecting tube. This connecting tube (Fig. 5 ) is of brass, lined with block tin. I t has a ground male taper joint, K, at one end and a ground female taper joint, L, at the other, so that below it connects with the main body of the apparatus and above with the condenser. The condenser (Fig. 6 ) is a block-tin, coiled pipe surrounded by a copper cylinder wa;ter jacket. One end of the pipe, M, extends a short distance below the condenser, while the other end, N, extends ab0T-e the condenser in a rough semicircle. Both ends are tapered male ends. The
Vol. 13, No. 9
water jacket fits into a stand made of two bands of strap iron held together by and resting on three legs. The heating is accomplished by gas or by a n electric hot plate. When the stand supporting the condenser is placed upon the lid of the main body, the legs of the stand interlock their feet with three of the wing nut clamps and thus hold the condenser in position. By inserting tube (Fig. 5 ) , that is, fitting K into J and L into M, the apparatus is in position to be used as an extractor or as a reflux condenser. When the condenser stand rests beside the apparatus with the upper end of the congensing tube N fitted into the tapering joint J, the apparatus is in position to be used as a still. When the blow-off valve G is screwed into hole 0, the apparatus is ready f o r use as a n autoclave. The apparatus is most satisfactory for the extraction of material either in the dry, powdered state or in the fresh, moist state, with the different f a t solvents or with water. Without removing o r disturbing the material, the solvent can be drawn off and fresh solvent added for reextraction. Then without cooling the extract can be concentrated and the solvent recol-ered by distillation. Absolute alcohol can be made from ordinary alcohol by refluxing the alcohol over lime, and the absolute alcohol can then be distilled without exposure to the air. Extraction or distillation can be conducted under either positive or negative pressure. The advantages of this apparatus are that it is easily set u p and readily transported; it is easy to clean, and, above all, simple to operate. Its greatest value is that it allows a combination of procedures such as refluxing and distilling, or extracting and distilling, in a single piece of apparatus.
Radiation Effects in Thermometry By Clark S. Robinson] DEPARTMENT OF CHEMICALENGINEERIKG, MASSACHUSETTS IKSTITUTEOF TECHNOLOGY, CAMBRIDGE, MASSACHUSETTS
A thermometer, pyrometer, or other temperature measuring device, when inserted in a gas f o r the purpose of measuring its temperature, does not, except under unusual conditions, recorcl the true gas temperature, and the deviation may, in cases of high temperature, amount t o several hundred degrees, and a t ordinary temperatures it may be as much as ten or more degrees. It has long been known that heat is transmitted by radiation in a similar manner to light, and that it can be reflected, refracted, and absorbed. That different substances have different radiating as well as different absorbing powers has also been known, and as early as 1814 Dr. William Charles Wells performed many interesting experiments on these phenomena. However, while the effects of radiation on thermometer and pyrometer measurements of gas temperatures have been well known by physicists, it has not been common knowledge that thermometer o r pyrometer measurements are subject to such deviatiorls. Thousands of tests on furnaces, boilers, and the like have been made by engineers, in which gas temperature have been measured by the usual means, and furnace efficiencies calculated, when the temperatures thus measured may have been f a r from the fact, It is the purpose of this article to explain how true gas temperatures may be calculated, and to give the results of some experiments made by Xr. Goodman Mottelson in connection with his thesis on this subject a t the Massachusetts Institute of Technology during the past year. IReceived June 24 1921. An Essay on De$', London, 1914.
THE CALCULATION OF TRUE GAS TEMPERATURES A thermometer or other temperature measuring instrument, \Then introduced into a gas, tends to approach the temperature of the gas. I n order to do this it must receive heat, if the gas is a t a higher temperature, o r it must lose heat, if the gas is a t a lower temperature. This flow of heat to o r from the thermometer occurs in two ways, by conduction and convection between the gas and the thermometer, and by radiation between the t.hermometer and the surroundings, usually the walls of the chamber o r flue. Imagine, for instance, a tube in a fire-tube boiler, through which hot furiiace gases are passing, giving u p p a r t of their heat t o the cooler walls of the tube. A pyrometer inserted in the tube, if a t the gas temperature, would radiate heat to the cooler tube, which would lower the thermometer temperature. Heat would then flow into it from the gas, and when equilibrium was reached the pyrometer would be a t a temperature sufficiently below gas temperature, yet sufficiently above tube temperature, so that its loss of heat by radiation to the tube would just compensate f o r the heat gained by conduction from the gas. On the other hand, a thermometer inserted in the a i r between the tubes of a steam coil heater for air, where the heating tubes are hotter than the air, would indicate a temperature hetween that of the air and that of the hot surfaces, the thermometer reading too high where in t h e former case it would read too low. The rate of flow of heat by conduction from the gas t o the thermometer can be expressed by the equation
