July 15, 1930
IXDVSTRIAL A N D EiYGI-X-EERISG CHEMISTRY
tilling out the trichloromethane, and it was naturally absolute alcohol, the water distilling out with the first trichloromethane, this behwing similarly to benzene in the well-known commercial absolute alcohol process. Results with chlorobenzene were conclusively negative. Thus, operating with reflux ratio 1 O O : l they found successive densities (grams per cc., 20” C.) 1.1052, 1.1056, 1.1061, 1.1070, 1.1067, 1.1066, l.lOG9, 1.1070, 1.1070; the first few lower densities being obviously due to an impurity, for practically all the chlorobenzene was still in the retort. They then distilled out all the chlorobenzene with reflux ratio 2 :1 dividing into three successive fractions, which gave densities 1.1070, 1.1069, and 1.1070. The density of chlorobenzene is calculated as 1.1025, assuming the atomic weight of chlorine to be 35. It is generally accepted that isotopes give compounds with the same vapor pressure, but with different rates of evaporation, and Peoples and Kewsome should accordingly have used irreversible distillations in their column. While they would expect no difficulty in designing an irreversible column even t o fill tank cars with isotopes of 99 per cent purity, it was necessary to abandon the project. Such a column would consume tremendous quantities of energy compared with a rerersible column. Other mixtures such as ethyl ether-acetone-ethyl alcoholwater and ethyl ether-methanol-ethyl alcohol-water hare been successfully handled in the 20-foot column, but further description is perhaps unnecessary. Such a column is suggested for use in hospitals for making pure ether for anesthesia, such ether being distilled on the dag i t is to be used. The 20-foot column, even with reflux ratio 9:1, was unable to make anhydrous ether, and it was thought that if acetone were added to wet ether in the retort this acetone would reflux in the lower part of the column, washing all water back into the retort. However, ether purified this way was still wet, as shown by the classical test with anhydrous copper sulfate. A distillation curve is given for Oronite petroleum ether, made by the Standard Oil Company of California. (Figure 6) Also, a sample of ‘[normal pentane” (true b. p. 36’ C.) from the Sharples Solvents Company showed the presence of a slightly lower boiling fraction, possibly isopentane (b. p. 28” C.), which we imperfectly fractionated. However, a strongsmelling hydrocarbon boiling a t 48-49’ C., with a specific gravity of 0.690 a t 27’/4’ C., and giving a constant boiling
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mixture with methyl alcohol a t 40” C. was easily isolated. This hydrocarbon constitutes about 3 per cent of the Sharples “pentane,” and accounts for most of its odor. Actually the “pentane” fractionation was carried out in the presence of methanol, so that the controlling boiling points were actually 24.5”, 31 ”, and 40’ ( 2 . 4 . e., the constant-boiling mixtures with methyl alcohol. Undoubtedly fairly pure isopentane could hare been isolated by a second distillation, as with mixed fractions of the methyl-ethyl alcohol mixtures, the isopentane being only around 5 or 10 per cent of the original mixture. “Xormal hexane” from the Viking Gasoline C‘orporation had a gradual boiling range of about 6 degrees so that a small amount of end fractions only was removed. It would be interesting to carry on such distillations Tvith a similar column 100 feet or more long. Acknowledgment
The authors are indebted to IT. J . Cumniings for much of the glass-bloTving. For suggestions they are also greatly indebted to Professor Rlerle Randall and Frank Healy. of this university, and to D. S. RIcKittrick, of the Standard Oil Company of California. Literature Cited Cooper and Fasce, ISD. E s c . CHGhr., 20, 420 (1928). Davis, 11.I. T . Thesis, 1923. Drane, J . S O L .Chem. Ind., 43, 329T (1924). Encyclopedia Britannica, “Liquid Gases,” (1911). Hausbrand, “Principles and Practice of Industrial Distillation,” translated by Tripp, Table 11,p . 185, Wiley, 1926. Hill and Ferris, IND.ENG.CHEM.,19, 379 (1927). Hurter, J . SOC.Chem. Ind., 4, 639 (1885); 6, 707 (1887); l a , 227, 989 (1893). Kent’s Mechanical Engineers’ Handbook, p. 638, Wiley, 1923. Landolt-Bornstein, Tabellen, p. 734 (1927). Leslie and Geniesse, IND.ENG.CHEM.,18, 590 (1926). Marks, Mechanical Engineering Handbook, p. 317, hIcGrdw-I-lill,
1924. Marshall and Sutberland, IND.ENG.CHEX.,19, 735 (1927). hfarshall and Sutherland, Ihid., 20, 1379 (1928). Perkin, J . SOL.Chem. Ind., 40, 118T (1920). Peters, J . IND.ESG. CHEM.,14, 476 (1922). Peters and Baker, Ihid., 18, 69 (1926). Raschig, German Patents 286,122 and 292,622. Rosanoff and Easley, Jr., J . A m . Chem. Soc.. 31, 953 (1909). Walker, Lewis, and McSdams, “Principles of Chemical Engineering,” p . 705, McGram-Hill, 1927.
Rapid Method of Qualitative Color Comparison for Opaque Solids‘ John J. Shank and Joseph S. Martin THEWAYSELABORATORIES, 17 E. MAINST.,WAYSESBORO, PA.
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H I S laboratory has had several calls to compare the colors of preparations of gravel made from a local schistose rock. I n the finished product, which is about 40 mesh, the difference in color is so little that it is not perceptible to the naked eye. The modern spectrophotometer in one of its forms would undoubtedly be the most satisfactory and the most expensive means of attaining the desired results. However, it was desired to have a rapid qualitative method of determining variations in color of these gravels which would be suitable for use in the hands of the non-technical operator in an industrial plant. Another requisite was that the e q u i p ment be simple and non-expensive and also of such construction that i t would withstand the handling to which such material would be subjected in the course of the day’s work. 1 Received February 24, 1930.
Owing to the difficulty of noting small differences in color when vie\\-ing specimens of gravel in the natural state, i t was decided to make all comparisons on specimens which had been ground to a fineness that would permit placing the POTYders into glass cells or other containers so that a solid color would result. I t was found that the colors of the powders were more easily compared when viewed through a glass cell. Based upon this principle, an instrument has been constructed which is very convenient for repeated use. The construction can be seen by a glance a t the sketch. A thin metal partition divides the box longitudinally so that the standard povder on one side presents a sharp dividing line with the test powder on the opposite side. It is readily cleaned; being Constructed mostly of metal, it is sturdy; the standard powder is sealed when desired, so that it is not
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A.Yd LY T I C AL EDI TI0.V
3.14
disturbed by repeated testing, arid it is therefore possible to use the same standard for a large series of tests. The only caution to be observed in preparing the sainple\ for examination is to be certain that a representative saniplti is powdered and that all of the material is passed through thc. sieve. An agate mortar is recommended for the grinding and a sieve of a t least 80 mesh should be used. Failure to pas> any portion of coarse material through the sieve or the loss of dust particles usually materially changes the color of the test powder. The sketch illustrates the construction of the comparator and the method and precautions necessary in using it should be self-explanatory, While this method is crude and only of qualitative value, it can be used to advantage in the industrial plant for the rapid checking of products in which the perception of small color differences is somewhat difficult.
Apparatus for the Determination of Ignition Temperature of Powder Substances’ Paul W. E d w a r d s a n d Roger W. H a r r i s o n CHEMICAL
EKGIKEERING DIVISION, BUREAUOF
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HE ignition temperature of solids has been defined in a number of ways and methods have been devised to determine some of these temperatures in accordance with the definitions. I n some cases it appears that the tempcratures obtained b y the methods described and taken as ignition temperatures do not fulfil the requirements of the definitions. Some of the definitions of ignition temperature of solid combustibles found in the literature are as follow: (1) That temperature a t which substances take fire SPontaneously in air ( 4 ) . (2) Temperature of ignition in oxygen is defined as that temperature t o which fuel must be raised for its ignition t o take place without the aid of external agents of inflammation (6).
(3)
The temperature of the glow point of the fuel ( I ) . (4) The temperature zone a t which rapid self-heating begins ( 2 ) . ( 5 ) s prom a practical as u,ell as a theoretical point of view, it is sufficient to know a t what temperature, under standard conditions, different coals begin to react with oxygen so rapidly that the ultimate appearance of flame is assured (7).” (6) The temperature a t which the material, in contact with air of the same temperature, suffers such accelerated oxidation as results in a marked increase in temperature and formation of products of combustion (5).
C H E M I S T R Y A N D SOILS, W A S H I K G T O N ,
D. C.
substances as coal takes place a t normal atmospheric teinperatures. Apparatus
The apparatus used to make ignition-temperature determinations (Figure 1) consists of a multiple-unit electric crucible furnace in which is placed a Pyrex glass J-tube having a k i i m . bore. The lower end of the tube is flared funnel shape and is approximately mm. in diameter. The opposite end of the tube is passed through the cover of the furnace. Alundum cement is used to attach the tube to the cover. The end of t,he tube projecting through the cover is attackled to a calibrated manometer or flowmeter with rubber or glass tubing and the flowmeter is connected to a vacuum line. A platinum-platinum rhodium thermocouple in conjunction with a potentiometer or high-resistance millivoltmeter is used to make the temperature determinations. d rheostat is placet1 in series with the electrical circuit of the furnace. -4ir is admitted to the furnace through an opening around the cover plate.
The following definition is proposed by the authors: The ignition temperature of a solid combustible may be defined as that temperature at which the exothermic reaction predoininates to the extent that the reaction becomes rapidly accelerated and the ultimate appearance of glow or flame is assured without further addition of heat from external sources. The oxidation must accelerate rapidly for, as Wheeler has cited ( 7 ) , self-heating of such Received April 22, 1930.
Figure 1-Ignition
Temperature Apparatus for Dusts in Static Condition
