A Modification of the Bed-ICullmann Melting Point Block Electrically Heated Glass Melting Point Apparatus F. W. BERGSTROM, Chemical Laboratory of Stanford University, Calif.
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The eo per block, FGHI, together with the Tamp used for the illumination of the melting point specimen and its housing, ABCDE, is shown in Figure 1. The block itself is 5 em. in diameter by 7 em. in length (the dimensions in Figure 1 are given in inches) and it is pierced by a hole, I J , parallel to the bottom and intersecting the vertical axis. A small hoIe, G, is drilled along the axis of the block to enter I J , while a second hole, KP, is 30mm drilled from above to intersect I J at, the center. The angle + which 50mrir; this hole makes with the vertical is 45-50'! and the angle e between the intersecting pIanes determined by GI-PK and. GP-PJ is 45-55". If $C is No,it is difficult to observe the specimen i n t h e capillary because of reflections from the surface of the glass. The thermometer is placed in H , which is drilled A s l i g h t l y b e l o w the bottom of PJ so that the m e l t i n g p o i n t specimen in the capillary will be approximately on a level with t h e c e n t e r of t h e thermometer. A little glass wool or copper p o w d e r is placed in T the bottom of H to l e s s e n the danger of FIGURE 2 breaking the thermometer. The bottom of the capillary is illuminated thrc 1 the slanting hole, KP, by means of the ele C lamp, B, which is surrounded by a housing 9 made of brass tubing 0.8 mm. (0.03 inch) in ti ness. The open end of C , which fits snugly ag: t the melting point block, should be ground conca Y to the same radius of curvature. The holes, 4 and K , are covered with small mica windows ,1 in place by means of Monel metal or stainless frames (see L) with a radius of curvature equ 0 that of the block. (The author is indebted tc e demrtment mechanician, Mr. Grebmeier, for e deiign of these window frames, and for the ai 11 construction of the block.) The window, K , ing the slanting hole, K P , is 12 mm. (0.5 i 1 wide, instead of the 10 mm. (0.375 inch) shorn n Figure 1 at L. Small mica windows, such as are described, show less tendency than larger ones to split in use. Four small metal washers, FF, held on the top of the block by set screws, serve to support the block in a ring of 5-cm. (2-inch) internal diameter (it may be necessary to cut away a portion of the ring to accommodate C). An alternate support is afforded by four set screws (with large heads) around the side of the block near the top. Heat is supplied by a Bunsen burner shielded from drafts by a thin brass or steel cylinder or pipe, but the portion of the block below I can be wound with asbestos-covered Wichrome wire and heated electrically in the manner described by Monsch (6).
0 AVOID the use of liquid baths for the determination of. melting points, Thiele (7) constructed a copper block, which proved to be satisfactory only in the modified form described by Berl and Kullmann (1; of. 3, b, 6, 8). This block is of considerable value when one is concerned with substances of high melting point, but it suffers from the disadvantage that the capillary is observed against an illuminated background, so that the contents appear almost black and it is very hard to observe color changes or sweating prior to melting. It is felt that these difficulties have been overcome in the present modification, since the capillary is illuminated by light directed from above at a n angle, the contents appearing therefore as in the customary liquid bath. An electrically heated glass melting point apparatus designed for use with a n ordinary 250' or 360" thermometer
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without stem correction is also described.
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OPEN t 3"Ex+.
FIGURE 1 340
ANALYTICAL EDITION
JULY 15, 1937
341
It is recommended that the block be heated rapidly to a temperature 10’ or 15” below the melting point of the specimen, and then at a rate gradually diminishing to 1’ or 1.5”a minute within 3” to 5” of the melting point. If the block is heated too rapidly, the thermometer lags, and the observed melting point is low. The results, with proper operation, are as reliable as those obtained with a liquid bath. For observation of the capillary and its contents (through window I), it is best to use one eye only, the other being kept open and directed against a dark background to avoid strain. One or two cheap magnifying glasses are placed in front of I and a square of metal (painted black) or black paper is placed behind window I , unless the substance in the capillary is dark colored or gives a dark-colored melt, in which case a dully illuminated white asbestos or transite board background is generally more satisfactory.
“stoppers” made by wrapping slightly moistened asbestos paper (2.5 cm. or 1inch, in width) several times around B. The terminals of the heating element are tied to two small glass rings at the ends of B, and are brought through the asbestos stoppers to the outside. The melting point tube is fastened to the thermometer by means of fine copper wire or asbestos string. The thermometer passes through a cork stopper closing the top of tube B, the cork having a small V-groove cut on the side parallel to the axis. Heat regulation is provided by a rheostat (capacity 6 amperes) or by a bank of lamps. The rate of heating near the melting point should not exceed 1 ” a minute. The melting point apparatus just described may be made with a Dewar seal at the top, as in the heater described by Franklin
Glass Melting Point Apparatus
(1) Berl and Kullmann, Ber., 60B,814 (1927). ENQ.CHEM.,Anal. Ed., 8, 74 (1936). (2) Dowzard and Russo, IND. (3) Eastman Kodak Co., “Synthetic Organic Chemicals,” Vol. X, No. 2, p. 4, April, 1937. (4) Franklin, “Nitrogen System of Compounds,” American Chemical Society Monograph, p. 321, New York, Reinhold Publishing Corp., 1935. (b) Friedel, Biochem. Z., 209, 65 (1929). (6) Monsch, Hela. Chim. Acta, 13, 509 (1930). (7) Thiele, 2. angew. Chem., 15, 780 (1902). (8) Walsh, IND. ENG.CHEM.,Anal. Ed., 6, 468 (1934).
The electrically heated glass melting point apparatus shown in Figure 2 is a modification of that described by Dowzard and Russo ( 2 ) . The heating element of Nichrome wire (No. 24, 1.63 ohms per foot) is wound on a long Pyrex tube, B, whose dimensions vary with the thermometers available. The spacing of the windings is uniformly 1.5 or 2.0 cm. To provide some insulation, an outer tube, A , is placed around B, being held in place by two asbestos
(4). Literature Cited
RECEIVED April 30, 1937.
Quantitative Determination of Oil in Fish Flesh MAURICE E. STANSBY AND JAMES M. LEMON U. S. Bureau of Fisheries, Technological Laboratory, College Park, Md.
Fish oils, being unusually susceptible to oxidation and polymerization, are difficult to extract quantitatively from fish flesh except after drying the flesh in a vacuum desiccator for a period of a week or more. A method is described in which the drying and oil-extraction processes are combined by extracting the fish with acetone. The crude oil thus obtained is purified by treatment with ethyl ether. A rapid semi-
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RDINARY methods of determining oil in flesh products such as meat are not entirely satisfactory for fish, because of the tendency of fish oil to decompose very readily when heated with the flesh. Such decomposition prevents a complete extraction of the oil from the fish. I n the methods ordinarily used for such products the substance is first dried thoroughly, in order to prevent the extraction of water soluble material and to ensure a complete recovery of the oil. The dried material is then extracted for about 16 hours in a continuous extractor, using ethyl ether or petroleum ether, more frequently the former. The solvent is then removed by evaporation and the oil is dried and weighed. I n fish flesh, the greatest decomposition of the oil usually occurs during the drying process; in order to minimize these changes, it is customary to employ a vacuum desiccator for this step, drying the fish over sulfuric acid. Since fish contains large quantities of gluelike substances, it has a tendency to dry to a hornlike mass, enclosing moisture which is very difficult to remove. By mixing the fish flesh with sand or cotton, this difficulty is lessened, and a fairly thorough dry-
quantitative method is also described in which the oil is extracted by agitating the moist fish flesh with anhydrous sodium sulfate and ethyl ether. Data are presented to show that the widely quoted value of 7.1 per cent for the oil content of the common mackerel is in error, a value of 12 to 15 per cent being closer to the average oil content of this species.
ing is attained in from 10 days to 2 weeks. This procedure may result in a loss of oil either during the mixing of the flesh with the sand or during the subsequent transfer of the dried material to the extraction apparatus. Moreover, such a lengthy procedure is undesirable and in endeavoring to avoid it, the following methods were developed. The first method described is a rapid semiquantitative one. The second method is believed to give a t least as great precision as any existing method and with a considerable saving in time. This method, in conformance with general usage, assumes that the oil content of a substance is equivalent to the content of substances extracted by ethyl ether from the dried material.
Semiquantitative Method A brief description by Sebelin (4) has been given of a method, devised by Bull, for determining the oil content of fish. This method consists of mixing a weighed portion of finely ground fish with anhydrous sodium sulfate and then shaking with a measured quantity of benzene. An aliquot
