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INDUSTRIAL AND ENGINEERING CHEMISTRY
while the extracted aromatic oils of high viscosity could be substituted for paraffinic-type oils removable by distillation or solvent treatment, thereby to improve the homogeneity of asphalts, as might be desirable in certain applications. The differences found in content and character of fractions in three SC-6 road oils (Table XIII), illustrates the wide variety of such products available. The highly paraffinic Mid-Continent road oil derives its viscosity mainly from highly viscous resin and oil fractions instead of a normal content of hexaneinsolubles. For this reason i t would be slow to set upon the road and would form a brown-colored bituminous mat likely t o “bleed”. The asphaltic-type road oil, while having a very high content of insolubles, has always rated highly in service performance. The analysis of a n oil formed by mild cracking of a paraffinic Mid-Continent stock is shown in column 2, Table XIII. This oil is low in hard resin and high in wax content. The high hexane-insoluble and wax content and low content of hard resins indicate that after a period of exposure this road oil would become nonhomogeneous and deterioration of the road mat would result for this reason.
Vol. 16, No. 5
A
Controlled-Atmosphere Induction Melting Furnace for the Laboratory F. S. BOERICKE AND W. M. BANGERT Pacific Experiment Station, Bureau of Miner, Berkeley, Calif.
SUMMARY
The procedure of analysis has been found adequate for accurate classification of asphalts from widely differing sources according t o the content and character of their five main fractions. The method is suitable for products varying in consistency from road oils to highly blown products. While only a few trials have been made on cracked asphalts, the treatment is thought also to be applicable in the separation of their fractions, except for some products produced by high level cracking which, although resinous, are largely insoluble in hexane. Other petroleum products which contain some or all of the fractions found in residua may also be subjected to analysis, such as extracts and precipitates from lubricating stocks and lubricating oils which have been in heavy-duty service. ACKNOWLEDGMENT
The authors wish to express their appreciation t o John W. Poole for many helpful suggestions and to Janet M. Lemley for assistance in the laboratory determinations. LITERATURE CITED
(1) Abrahama, Herbert, “Asphalts and Allied Substances”, 4th ed., p. 993, New York, D. Van Nostrand Co., 1938. (2) Ibid.,p. 1007. (3) American Association of State Highway 05cials, Washington, D. C., “Standard Specifications for Highway Materials and Methods of Sampling and Testing”, Part 11, 4th ed., p. 113, 1942. (4) Betts, R. L.,and Wirsig, H. D., IND.ENG.CHEM.,ANAL.ED., 15,478 (1943). (5) Cannon, M.R., and Fenske, M. R., Ibid., 10, 297 (1938). Asphalt P a d w (6) Grant, F. R., and Hoiberg, A. J., Proc. ASSOC. Technologists, 12,87 (1940). (7) Hoiberg, A. J., IND. ENG.CHEM.,ANAL.ED., 14,323 (1942). (8) Hoiberg, A. J., Hougen, 0. A., and Zapata, Jos., Univ. of Wis. Eng. Expt. Sta., Bull. 86 (1939). (9) Holde, D., “Untersuchung der Kohlenwaaserstoffole und Fette”, p. 45, Berlin, Julius Springer, 1913. (10)- Holmes, A.. and Raphael, A. L., Proc. Assoc. Asphalt Paoing Technologists, 8, 105 (Jan. 1937). (11) Horne, J. W., and Holliman, W. C., Bur. Mines Tech. Paper 583 (1938). (12) Kalichevsky, V. A,, “Modern Methods of Refining Lubricating Oils”, 1st ed. p. 60, New York, Reinhold Publishing Corp., 1938. (13) Knowles, E. C.,and Levin, Harry, IND.ENQ.CHEM.,ANAL. ED., 13, 314 (1941). (14) Marcusson, Julius, 2.angew. Chem., 29,I, 21 (1916). (15) Pfleiffer, J. Ph., and Van Doormaal, P. M., J . Inst. Petroleum Tech., 22, 414 (1936). (16) “U.O.P. Laboratory Test Methods for Petroleum and Ita Products”, 2nd ed., p. A-21.Chirago, Universal Oil Producta Co., 1943.
THE
most common controlled-atmosphere (or vacuum) furnace for melting small metal samples by induction has been described frequently and is supplied as standard equipment by the Ajax Electrothermic Corporatim. Its construction entails the use of silica tubing which is fragile, expensive, and difficult to work without special glass-blowing equipment. The disadvantages in the use of silica have led to the development in this laboratory of a less delicate piece of equipment which serves the same purpose and can be ronstructed in a few hours in a well-equipped shop. lmportant construction features are shown in the dia rammatic drawing. I n essence, the heating unit is merely encfosed by a gas-tight shell so that the entire assembly, including the furnare coil, can be evacuated or flushed with inert gas. The water-cooled heating coil, A , is connected with the converter cables a t P and Q and with water lines at N and 0. It is the standard coil supplied with the 3 kv.-amp. furnace assembly. The Alundum thimble, C, contains the melting crucible, D, and is surrounded with Norconite, B , or other suitable insulating powder. A layer of sheet mica, rolled into a cylinder, separates this powder from the cooling coil, and prevents its lateral escape. The assembly, E, above the melting crucible, serves to diminish the upward radiation from the molten charge, while permitting a clear view of the charge through sight tube G. This whole unit is surrounded by the chamber formed by fiber plates, I and J, and leucite (or metal) cylinder, K . Rubber gaskets in the grooves of the top and bottom plate and a t the water-cooled electrical connections render the entire assembly gas-tight when compressed by the six vertical bolts, L,M , etc., and the brass nuts and washers of the cooling tubes. The gas input and exit tubes, H and F , are sealed with DeKhotinsky cement to the top plate, as is also G. The temperature of the molten charge may be determined either by a n optical pyrometer, sighted through a cemented window a t G, or by a thermocouple, within a gas-tight protection tube, inserted into the charge through G and oemented a t the top. Insulation is unnecessary outside the water-cooled coil and the bolts are far enough from the inductiod currents to remain cool, despite crucible tcniperatures of 1 5 O f i O C. or above. The crucible and contents cool rapidly when the current is interrupted and may be replaced in a few minutes by removal of the top plate and the radiation shields. P U B L I S Hby ~ Dpermission of the Director, Bureau of Mines, U..S. Department of the Interior (not copyrighted)
