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INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 9, NO. 12
(2) Cannon, Me R., and Fenske, M. R., Oil Gas J., 33, No. 47, 52 (1935); 34, No. 47, 45 (1936). (3) Everett, H. A., and Stewart, F. C., Penna. State Coll. Eng. Expt. Sta. Ser., Bull. 44 (1935). (4) Hersh, R. E., Fisher, E. K., and Fenske, M. R., IND.ENQ.CHEM., 27, 1441 (1935). (5) Mougey, H. C., paper before Subcommittee I on Corrosion Test for Lubricating Oils, Am. Soc. Testing Materials, Committee D-2, June 28, 1937, on “Tests to Determine the Corrosive Properties of Oils as Related to Bearing Metals.” (6) Rescorla, A. R., Carnahan, F. L,, and Fenske, M. R., Ibid., 9, 505 (1937). (7) Rescorla, A. R., Fry, E. M., and Carnahan, F. L., IND. ENQ. CHEM.,Anal. Ed., 8, 242 (1936). (8) Rogers, T . H., and Shoemaker, B. H., Ibid., 6, 419 (1934).
The authors are very grateful for the technical assistance of
E. K. Fisher, R. H. McCormick, and G. E. Woods in obtaining the data and for the cooperation of H. A. Everett and his associates in the Department of Mechanical Engineering in furnishing test data and oil samples in connection with their investigations on lubricants under service conditions. The work was part of the research program of the Pennsylvmia Grade Crude Oil Association, and is published with its permission and that of the School of Chemistry and Physics of The Pennsylvania State College.
Literature Cited (1) Am. Soo. Testing Materials, Report Committee D-2, Standards on Petroleum Products and Lubricants, p. 61, September, 1936.
RBCEIVED August 12, 1937.
Determination of the Saponification Value of Asphalts and Asphaltic Oils Use of an Improved Titration Flask J. E. FRATIS AND D. H. CONDIT Standard Oil Company of California, San Francisco, Calif.
ethyl alcohol and add 25 cc. of 0.05 N potassium hydroxide in 50 per cent aqueous alcohol. Reflux for 1 hour and transfer while hot to the s ecial titration flask, rinsing the saponifying flask with 10 cc. ofthe 50 er cent benzene-alcohol. (In order t o reduce absorption of carfon dioxide the sample should not be exposed t o the air more than necessary before and after refluxing.) Add 25 cc. of neutral 0.1 M barium chloride solution and 3 cc. of 0.5 per cent phenol-
A simple and rapid method for determining the saponification value of asphalts and asphaltic oils, based upon standard metho d s and the use of a special titration flask,
is described. Data are presented to demonstrate the accuracy and usefulness of the method.
T
H E natural characteristics of asphalts have always been an obstacle to the accurate determinrition of their saponification value. Despite the fact that numerous investigators have contributed to the literature concerned with this subject, the most widely recognized methods fail to give sufficiently rapid and accurate results for control work. Recent investigations in this laboratory have included a study of the saponifiable constituents of asphalt. Among other data to be obtained from a large number of samples was the saponification value. The modified method presented below includes the usual refinements used in conventional methods: (1) the use of benzene-alcohol solutions to give contact during saponification and to prevent hydrolysis (I, 4 ) ; (2) addition of barium or sodium chloride to give a clear aqueous layer ( I , 2) ; and (3) the use of dilute reagents to increase accuracy. A further refinement which the authors have found extremely helpful in obtaining a sharp end point has been the use of a special titration flask (3). The flask is a 250-cc. glassstoppered Erlenmeyer with a horizontal tube approximately 5 mm. in diameter sealed so as to reach one-third around the flask near its bottom (Figure 1). By tilting the flask, the side tube can be filled with the aqueous layer alone, thereby affording a close observation of the end point.
.
Analytical Method Accurately weigh a 10-gram sample into a 250-cc. alkali-resistant Erlenmeyer flask. Dissolve the sample in 50 cc. of a mixture of 50 per cent benzene and 50 per cent of 95 per cent neutral
FIQURBI 1. TITRATION FLASK
DECEMBER 15, 1937
ANALYTICAL EDITION
TABLEI. SAPONIFICATION VALUES Petroleum Asphalts
Saponification Value
Natural Asphalts
Mg./gram
Arkansas California Mexico Russia Texas Venezuela (Quire Quire) Venezuela (Lake) West Virginia Wyoming
0.68 0.50-3.25 1.05-1.30 0.99 0.46 5.70 1.04 0.56 0.36
Saponificstion Value Mdoram
Bermudez (Lake) 6.20 Bermudez (fluxed) 11.30 Road Oils 0,.75-2.75 C aIif ornia 0.40 Midcontinent 1.04 Oklahoma 0.42 Pennsylvania
TABLE11. ACCURACY Asphalt
Operator 1 1.56-1.56 3.12-3.08 0.81-0.83 0.14-0.17
A B C
D
Operator 2 1.58-1.56 3.06-3.09 0.79-0.83 0.13-0.17
Operator 3 1.54-1.55 3.07-3.05 0.81-0.84 0.15-0.16
TABLE111. COMPARISON OF RESULTS Asphalt California (A) California (B) Bermudez
Saponification Value Indicator Glass electrode method method 1.56 1.73 3.08 3.38 11.30 11.27
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The last trace of pink in the side tube should be taken as the end point. A blank should always be run on the reagents and solvents to determine the amount of caustic lost during the rocess. This blank usual1 amounts to 3 or 4 m of caustic a n i is fairly constant. DupGcate determinations stodd be made where greater accuracy is desired. When determining the saponification value of asphalts having an unusually high value (Bermudez, Table I) a smaller sample is used. While there might be some question regarding the limit of accuracy of the method, the authors have obtained a sufficient number of check results to indicate an experimental error of 0.05 mg. of potassium hydroxide per gram.
Analytical Results Table I lists the saponification values for a series of representative paving grade asphalts. Table I1 illustrates the accuracy obtained by different operators using the method. The accuracy of the method was also checked by electrometric titration using a glass electrode. Table I11 is a comparison of the results obtained by the two methods.
Literature Cited
phthalein. Titrate immediately against 0.05 N aqueous hydrochloric acid. Add the acid ra idly without shaking the flask until the indicator be ins to fafe in the water layer. As the end point is approacheif shake the flask after each addition of acid and tilt so that the side tube is downward. Touch the corner of the tube t o a hot plate for a moment. This breaks any emulsion and cleans the walls of the tube, permitting observation of the aqueous layer.
(1) Abraham, H.,“Asphalts and Allied Substances,” 3rd ed., p. 752, New York, D. Van Nostrand Co., 1930. (2) Coburn, IND. ENQ.CHE~M., Anal. Ed., 2, 181 (1930). (3) Davidsohn, A,, Fettchem. Umschau., 42,9-10 (1935). (4) Marcusson, J., Burchartz, H., and Wilke, P., “Die naturlichen und kiinstlichen Asphalte,” p. 90, Leipzig, Wilhelm Engelmann, 1931. RE~CZIVZD June 28, 1937.
Arsenious Oxide in the Standardization of Solutions of Potassium Permanganate HARRY A. BRIGHT National Bureau of Standards, Washington, D. C.
Values obtained in the standardization of 0.1 N potassium permanganate solutions by National Bureau of Standards’ arsenious oxide No. 83, using potassium iodide or potassium iodate as a catalyst (Lang’s procedure), have been compared to those obtained with sodium oxalate by the method of Fowler and Bright. The normalities found agreed to within one part in 3000, which demonstrates the suitability of arsenious oxide as a direct primary standard in permanganimetry.
checked the accuracy of the procedure by means of iodine (through permanganate-iodide and thiosulfate), though this is not stated clearly. Kolthoff, Laitinen, and Lingane (2) compared the normality of 0.5 N potassium permanganate determined by Lang’s procedure with that found by direct potentiometric titration of potassium iodide with permanganate in very dilute acid solution. The factors obtained by the two methods agreed within 0.03 per cent. Recently the author has made a careful comparison of Lang’s procedure with the sodium oxalate procedure of Fowler and Bright (1) to determine whether the former is sufficiently accurate to permit the use of the National Bureau of Standards’ standard sample No. 83 of arsenious oxide (now issued as an iodometric standard) as a fundamental standard in permanganimetry. The experimental details, in brief, were as follows:
T IS WELL known that the direct titration of trivalent arsenic with permanganate in dilute acid solutions is unsatisfactory because the reaction does not proceed according to stoichiometric relations. Lang (3) has stated that a very small amount of potassium iodate or iodide acts as a catalyst to complete the reduction of manganese to the divalent state. His data show satisfactory precision, and he apparently
Weight burets were used, and all weights were corrected to the vacuum standard. National Bureau of Standards’ sodium oxalate No. 40c (purity taken as 99.95 per cent) and arsenious oxide No. 8 3 (purit taken as 99.98 per cent) were used. Both materials were &ed for 1 hour at 105” C. immediately before use. In the potentiometric titration the usual bright platinum-calomel electrode arrangement was used. Standardization with sodium oxalate was done as described by Fowler and Bright.
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