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INDUSTRIAL AND ENGINEERING CHEMISTRY
I n order to utilize this method for determining elementary sulfur present in gasoline, the following procedure is suggested: Two hundred cubic centimeters of the gasoline to be tested are vacuum-distilled till about 50 per cent comes over. The sulfur determination is then made on the residue and the result obtained is calculated as milligrams of sulfur per 100 cc. of gasoline. Birch and Norris (3) stated that a copper-corroding substance is obtained when a petroleum distillate containing a mercaptan is treated with sulfuric acid. They found that this substance, dialkyltrisulfide, on reduction with zinc and hydrochloric acid, yields a mercaptan and hydrogen sulfide. Therefore, in order to analyze an acid-treated distillate for free sulfur, the quantity of hydrogen sulfide which will be formed by reduction of such substances must be deducted from the total amount of hydrogen sulfide. This can readily be accomplished by treating a sample of the distillate to be analyzed for free sulfur with mercury for the purpose of removing the free sulfur. The sample thus treated is then analyzed by the above described method for the corrosive trisulfide, and the amount of hydrogen sulfide obtained is then subtracted from the total hydrogen sulfide.
VOL. 8 , NO. 6
All the experimental data, with the exception of the results contained in Tables I and 11,were obtained in the laboratories of the Houdry Process Corporation a t Paulsboro, N. J. The writer expresses his appreciation for the permission to publish these results, and, especially, feels indebted to W. F. Faragher for his suggestion that peroxides must be the inhibitors which affect the corrosive action of sulfur on copper.
Literature Cited (1) Am. SOC.Testing Materials, D 130-30, Part 11, p. 488, 1930. (2) Antropoff, J . prakt. Chem., 77, 273 (1908). 21, 1087 (1929). (3) Birch and Norris, IND.ENQ.CHEM., (4) Birch and Norris, J. Chem. SOC.,127, 898 (1925). (5) British Standards, Standard Methods, 18 (1929). (6) Brooks, B. T., IND.ENQ.CHEM.,18, 128 (1926). (7) Cloez, Ann. Chena. Phys., 47, 819 (1858). (8) Cossa, Ber., 1, 117 (1868). (9) Faragher, Morrell, and Comay, IND.ENQ. CHEM.,20, 527 (1928). (10) Garner, J . Inst. Petroleum Tech., 17, 451 (1931). (11) Hoffert and Claxton, Second Report of National Benzole
Association.
(12) Kiemstedt, Petroleum Z.,28, No. 28, 1 (1932). (13) Kingzett, J. Chem. SOC.,12, 511 (1874). (14) Ormandy and Craven, J. Imt. Petroleum Tech.., 9,133 (1923). RECIPIYED
December 13, 1935
Metal Extractor for Laboratory Use J. M. LEMON, F. P. GRIFFITHS, AND M. E. STANSBY Technological Laboratory, U. S. Bureau of Fisheries, College Park, Md.
I
N T H E course of chemical and biochemical studies and analyses, it is frequently necessary to extract various quantities of such materials as wheat germ, casein, or protein meals. The usual glass apparatus found in laboratories is rather difficult to set up so as to form a continuous extractor. Soxhlet and other extractors are not ordinarily of sufficient size to permit use of large samples. McCay (2) and Bryant (1) have described apparatus which work well for relatively large amounts of material (20 to 50 pounds). As no simple and inexpensive apparatus for the continuous extraction of from 1to 5 pounds of material was found listed in various scientific catalogs, the extractor illustrated in Figure 1 was designed for use in this laboratory. Two are
now in use and have proved to be efficient and to require very little attention. A is a 20-quart cream-setting can, 9 inches in diameter and 20 inches high, supplied with a cover which fits closely over the top and 2 inches down the side. The condenser, B, consists of a 15-foot spiral of soft-copper tubing 0.25 inch in outside diameter and is soldered inside this cover, a proximately even with the bottom edge of the lid. In bending tiis ty e of tubing, it is necessary to fill it with some material which wilp revent its collapsing. in this instance, the tubing may first be slEd with fine dry Band and the ends tightly stopped. After the bending is completed, the sand is easily removed by lightly tapping the tubing and revolving the coil at the same time. The container for the material, C, is made by removing the bottom of a £ ether can. A co per siphon tube, D, is soldered through the cap of the can anzbent so that the top of the siphon loop is about two-thirds up the side of the container. The end of the siphon extends about 2 inches below the side of the can. The extractor is supported by an ordinary iron Iaboratory tripod, the legs of which have h e n cut to a length of 7 inches. The tripod is kept in place by three U-strips of tin soldered to the can.
A wire gauze is placed in the bottom of container C and over this is laid a layer of cotton; C is then filled with the material to be extracted and placed inside the large can, A . About one and one-half tunes as much solvent is added as is necessary for the operation of the siphon. After setting the Iid in pIace and starting a good flow of water through the coil, the can is set on a three-heat, 600-watt electric heater. When using alcohol or acetone the heater is turned on high, but with ether i t is advisable to use medium or low heat. The cost of materials for constructing this apparatus, not including the heater, is less than three dollars. FIGURE 1. EXTRACTION APPARATUS A. Cream-setting can B. Cover with oopper coil C . Inside container for material D. Siphon tube The apparatus assembled for use is shown on the right.
Literature Cited (1) Bryant, L. R., IND.ENQ.CHEM.,And. Ed., 1, 139 (1929). (2) MoCay, C. M., Ibid., 5, 219 (1933). RECEIVED
June 3, 1938.
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