January 15, 1931
INDUSTRIAL AND ENGINEERING CHEMISTRY
Summary of Recommendations for Routine Electrical Ash Determinations in Sugar Cane Products
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procedure, with only one conductivity determination, based on actual comparisons of chemical ash and specific conductance of the various products. These should include not only the materials studied by the writers, but should be extended to the several types of juices. When samples are received from many different sources, such as in regulatory and similar work, the choice of the proper method will depend on the type of product analyzed. For granulated and other refined sugars of low ash content, the simple C-ratio method outlined in this paper is sufficiently accurate. For raw cane sugars and soft sugars the simple conductometric formula with two conductivity determinations should be used, the factor being 0.001757 for raw sugars (7), and 0.001695 for soft sugars. The same method, with the factor 0.01757, will also suffice for sirups and molasses known to have been produced without char treatment (8), but otherwise it is safest to resort to the general conductometric formula based on three conductivity determinations, one on the solution itself, one with the addition of phosphoric acid, and one with the addition of potassium hydroxide
EQUIPMENT-For routine conductivity measurements it is advisable to use a self-contained instrument with as little outside wiring as possible, to prevent current leaks and other inconveniences. If it is operated by a battery this should also be enclosed in the instrument case. With this type a telephone receiver is necessary as a null indicator. I n a noisy factory laboratory the telephone is practically useless, and if alternating line current is available or can be provided, it is better to use an instrument to be connected to the a. c. line with a galvanometer as null indicator. The only other outside connection should be with the conductivity cell. The instrument should be calibrated in terms of specific conductance a t 20" C.; this necessitates a compensator for variations in the cell constant. For cane products it is not advisable to have the scale calibrated directly in ash percentage, on account of the variations in the C-ratio, but an additional blank scale might be provided which could be calibrated by the individual worker for the C-ratio most frequently used. The instrument should also be provided (4). with a compensating device for variations in temperature. Acknowledgment Since the temperature coefficient itself varies to some extent as has been shown by the writers, especially when conducThe writers are indebted to various sugar refining comtivity determinations are made also in the presence of acid panies in the New York district for the samples used in and alkali, it is safest to keep the temperature of the solu- this investigation. tion as close as possible to the standard of 20" C. This is Literature Cited most readily accomplished by the use of the Lange type of cell provided with a water jacket, as employed by the writers. (1) Lundbn, 2. Ver. deul. Zuckerind., 76, 763 (1925). This cell has the further advantage for routine work that the (2) Nees, IND. END.CHEM.,19, 225 (1927). solution which has been tested can be run out rapidly and (3) Sattler and Zerban, F a d s about Sugar, 28, 686, 713 (1928). the next solution be filled in without delay. Dipping cells (4) Sattler and Zerban, IND.ENG.CHEM.,Anal. Ed., 8, 38 (1931). may also be used if preferred, but they are not as convenient (5) Zerban and Mull, Facts about SUEQY,21, 278 (1926). ( 6 ) Zerban and Sattler, I b z d . , 21, 1158 (1926). as the Lange type of cell. (7) Zerban and Sattler, I b i d . , 22, 990 (1927). METRoD--For the control work of individual factories it (8) Zerban and Sattler, IND.ENG.CHEM.,Anal Ed., 2, 32 (1930). is desirable and quite possible to use the ordinary C-ratio (9) Zerban and Sattler, Zbid., 2, 322 (1930).
The Plastometer'~z A New Instrument for Measuring Plastic Properties of Coal Joseph D. Davis U. S. BUREAUOF MINES,4800 FORBES ST.,PITTSBURGH, PA.
B
ETWEEN certain limiting temperatures, depending on its rank and to some extent on its origin, a coking coal assumes a semi-fused or plastic state. Destructive distillation of the coal substance and of those constituents which fuse, begins as soon as or before fusion sets in and is greatly accelerated by rising temperature; the mass may assume a more or less plastic state before solidifying as coke. As the temperature rises to the limit of the plastic range (or state), most of the volatile matter is driven off and the mass sets into coke. Plasticity develops, however, only when a favorable heating rate, such as that prevailing in industrial coking practice, is chosen. Audibert (2) has shown, for example, that it is possible to choose a heating rate SO slow that the fusible matter is decomposed before it has actually fused. I n such a case the coal does not become plastic and coke is not formed. On the other hand, heating may be so rapid that, although fusion does take place, decompo1 Received September 19, 1930. Presented before the Division of Gas and Fuel Chemistry at the 80th Meeting of the American Chemical Society. Cincinnati, Ohio, September 8 to 12, 1930. (Xot 2 Printed by permission of the Director, U. S. Bureau of Mines. subject to copyright.)
sition is accelerated to such an extent that plasticity cannot be measured and a frothy coke results. The instrument to be described was designed in connection with the Bureau of Mines Survey of the Gas- and Coke-Making Properties of American Coals, for heating rates within the range of those prevailing in industrial practice under these conditions. Coke is invariably produced, provided that the coal is suitable for coke-making. Previous Methods for Studying Plastic State of Coal
The method devised by Foxwell (3) and modified by Layng and Hathorne (4), and that of Agde and von Lyncker (1) will serve as examples of experimental methods previously used for study of the plastic state of coal. Layng and Hathorne carbonize a standard column of sized coal at a suitable rate in an electric tube furnace while passing nitrogen through it. Sufficient nitrogen for the test is confined in a bottle connected to the tube containing the coal. This is caused to flow by water displacement a t constant head, so that resistance to its passage develops when the coal fuses. A manometer connected to the nitrogen
ANALYTICAL EDITION
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Vol. 3, No. 1
at constant speed by a 1/4-horsepower motor
I
Figure 1-The
Plastometer
Figure 2-Diagram
ness, is provided with screw caps. A tubular shaft
truding end of the shaft is fitted with a circular brass disc whose rim carries a scale similar to that of a torsion viscometer head. A pulley is also fixed to the end of the shaft and a chain is attached to its face. The other end of the chain is fixed to a spiral tension spring; as long as the rabble arms within the retort encounter no resistance in the rotating retort, the shaft does not turn and the spring is under no tension. Method of Making Test Eight grams of the 20- to 40-mesh coal sample3 to be tested are charged into the retort and the heads are screwed in place, a thick paste of graphite and oil being used to prevent the threads from “freezing” on subsequent heating. The charged retort is now placed in the furnace, the drive chain is attached, and a thermocouple is inserted in the hollow shaft. The temperature .is given continuously by a recording milli-
of Plastometer
bottle serves to indicate the amount of resistance and the rate a t which it develops. This is plotted against the temperature (or time) and defines the plastic range of the coal. Agde and von Lyncker carbonine a small sample of coal packed in a vertical tube furnace at a constant heating rate. A weighed needle, which is free to move vertically, rests on the coal. When the coal fuses the needle begins to sink and the rate of sinking is noted on a vertical scale provided for the purpose. The more plastic the coal the more rapid is the rate of sinking. When the charge sets into coke the needle comes to rest. Although the Layng-Hathorne method with most coals serves to define approximately the limits of the plastic range, it does not give a direct measure of the plasticity of the charge within this range. The Agde-von Lyncker method, on the other hand, gives a figure which corresponds with the ease with which the charge yields to a needle. It is in effect a penetrometer, and the result obtained is not necessarily a measure of plasticity. I n addition, it defines the limits of the plastic range with more or less precision. I n the hands of the writer this method proved difficult to carry out,. yielding results difficult of close reproduction. Without discussing the relative merits of these methods it is perhaps sufficient to observe that, when properly carried out, both will yield specific information of considerable value to one studying the coking process. Of course great care must be employed in interpretation of such results. The specific information sought by the plastometer is the plasticity of the charge within the plastic range, together with close definition of the temperature limits.
:I t is recognized that the selection of a size fraction of coal is not rep. resentative of the entire coal, and it is hoped t o modify the apparatus so that a strictly representative sample in which the fine coal is not rejected may be used.
Description of Plastometer Figure 1 is a photograph of the plastometer and Figure 2 shows a vertical section through the instrument. The plastometer consists of a steel retort 5 inches (127 mm.) in length by l’/s inches (22 mm.) in diameter, mounted on a tubular axle through the center of a 2-inch (51-mm.) tube furnace 12 inches (305 mm.) in length, and arranged for rotation
TEMPERATURE,
Figure 3-Resistance
OC
Developed in Heat1ng:Coal in1Plastometer
January 15, 1931
INDUSTRIAL A N D ENGINEERING CHEMISTRY
voltmeter. The motor is now started and the furnace is rapidly heated (7" C. per minute) to approximately 375" C., below which point no tension of the coil spring develops. From 375' C. through the plastic range (480" to 500" C.) the heating rate is maintained constant ( * 0.2") at 3.4"C. per minute. A note of the scale reading is made a t 1-minute intervals during the plastic range and a t the end of the experiment the readings, reduced to pound-inches of torque, are plotted against the temperature. Tension develops at 400"to 460" C. depending on the coal, and drops sharply at temperatures ranging from 450" to 480" C. The plastic range is defined by these limiting temperatures for each coal. Behavior of Different Kinds of Coal under Test
By the manner of development of tension on the plastometer head several kinds of coking coals have been distinguished : (1) Coals that fuse at a low temperature, have a wide plastic range, and become very plastic at intermediate temperatures. These coals fuse together well and should produce well-fused coke-i. e., the Powellton coal of Figure 3. (2) Gas coals containing splint that have a short plastic range and exhibit little or no plasticity, as the Elkhorn coal. (3) Semi-bituminous coals having a high fusing temperature, very little plasticity, and a short plastic range
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which gives an exceedingly high plastic tension, as shown by the Pocahontas coal of Figure 3. (4) High oxygen, weakly coking coals of which the limiting temperatures of the plastic range are just distinguishable by the plastometer. Hocking coal represents this type. Practical Value of Plastometer
Only a few coals have been tested by this method and no broad generalization can be made as to indication of coke quality. However, with coals so far tested it may be observed that: (1) Class 1 coals produce a fine-grained coke which does not fracture badly when exposed to high coking temperatures; (2) class 2 coals have large cells and when coked without admixed low-volatile coals give a more fractured high-temperature coke than class 1 or class 3 coals; (3) class 3 coals produce strong fine-grained coke but one which does not shrink appreciably after setting and which offers resistance to pushing from ovens. Literature Cited (1) Agde, G.,and von Lyncker, L. V., Brennstoff-Chem., 10, 86-7 (1929). (2) Audibert, E.,Rev. i n d . mindralc, 1916, 115-36. (3) Foxwell, G.E.,J . SOC.Chem. I n d . , 40, 193-201T. 220T (1921). (4) Layng, T.E., and Hathorne, W. S., IND. ENG.CHEM.,17, 165 (1925). See also Layng, T. E., and Coffman, A. W., Ibid., 19, 924 (19271,and 20, 165 (1928).
Determination of Alkalinity of Reclaimed Rubber' Henry F. Palmer and George W. Miller XYLOSRUBBERCOMPANY, AKRON,OHIO
A new method is given for determining the relative end point of the usual indialkalinity of reclaimed rubber. The extraction of the cators is m a s k e d . The paper is to present a alkaline material is based on a digestion of the sample m e t h o d developed and demethod for determinin a mixture of ethanol, benzene, and water. The scribed below overcomes these ing the relative alkalinity of method is compared with the previous method described difficulties since a relatively reclaimed rubber which, in by the authors in 1928. The experimental figures given higher percentage of alkaline the authors' opinion, has cershow that the new method gives results which are dematerial is removed and a tain advantages over other pendable, and approximately four times as accurate as m o r e efficient t i t r a t i o n m e t h o d s in use at presthe previous method. The higher degree of accuracy method is applied. ent. is due to the elimination of much of the personal error, I n general other methods Method of Titration the extraction of a larger percentage of alkaline macurrent for determining alkaterial, and a more accurate titration end point. linity consist of a digestion in Inasmuch as the color of water of various sizes of samthe solution often causes the ples for times varying from 3 to 48 hours. I n the discussion of end point of usual indicators such as methyl red to be very an article by Shepard, Palmer, and Miller (2) in 1928, the indistinct, an application has been made of the iodine-starch relative control method then in use by the authors was de- end point. The procedure after the sample is prepared for scribed. This method has recently been referred to by titration is as follows: Stafford (3) in an article on the testing of reclaimed rubber. To the solution 0.1 N HC1 is added from a buret until the Briefly this method consists in digesting a 25-gram sample solution is distinctly acid. This point may be most definitely in water for 3 hours, after which the sample is squeezed and determined by using litmus paper. Approximately 5 cc. thoroughly washed during squeezing. The sample is further each of 3 per cent KIO, solution and of 1 N KI solution are digested, and the liquor titrated with normal acid using then added. The mixture is allowed to stand 3 minutes methyl red as the indicator. A disadvantage of this method and the same volume of 0.1 N Na2SzO3as 0.1 N HC1 is added. is that it involves a personal factor in the Squeezing of the The mixture is allowed to stand for 15 minutes after which sample after digestion. Another disadvantage of the method 5 cc. of fresh starch solution are added. Titration is then and other unpublished methods known to the authors, is made with 0.1 N iodine solution until the appearance of the that a relatively small quantity of the total alkali is ex- usual iodine-starch blue color. This color may of course be tracted which naturally means that errors in the method black due to the brown color of the solution. will magnify the differences in alkalinity. Further, the soluThe particular advantage of this method of titration is tion to be titrated is often brown enough in color so that the that the end point can always be distinguished and even the darkest solutions can be diluted so that the end point is 1 Received September 20, 1930. Presented before the Division of visible. I n cases of reclaim of low alkalinity the solutions Rubber Chemistry at the 80th Meeting of the American Chemical Society, are less deeply colored and the end point may often be deCincinnati, Ohio, September 8 to 12, 1930.
T
HE purpose of this
