Simple Evaporation Tests for Mineral Oils J. J. SHANK, T h e Wayne Laboratories, Waynesboro, Pa.
D
URING the course of some work undertaken a t this laboratory for the purpose of assisting clients to obtain information relative to various desirable properties of petroleum oils for use in a manufacturing process, the necessity of making comparative determinations of the volatility of different oil samples became apparent. It has been found useful t o impregnate certain varieties of crushed rock granules with oil when these granules are to be used as a surfacing on asphalt felt roofing. This treatment is given in order to eliminate t o some extent certain conditions which arise when the surfacing is applied to the felt, among which are blistering and staining of the granules. The volatility tests now in use do not give results which indicate what may be expected when mineral oils are exposed to evaporation (and oxidation) under such conditions. It is felt that under such conditions there is an accelerated evaporation and oxidation which is entirely different from the volatilization observed when conducting a test under A. S. T. M. designation D 6-30 (1). Since the result desired was to be an expression of the rate of volatilization and oxidation for a given sample when spread out upon a relatively large and uneven surface, and it was desired to compare various samples of oil to obtain a sample which was most constant under such conditions, it was felt that a method could be devised which would give this information with more certainty than the procedure outlined under D 6-30. The following method has been found very satisfactory when used for comparing the changes obtained with various petroleum oils when subjected to the conditions of the test. The procedure is designed t o simulate as closely as possible actual exposure conditions on the roof in regards to area and surface exposed. The results obtained agree very closely, and it has been found possible to reproduce them a t will. METHOD The method requires the use of a shallow porcelain dish having a diameter of 70 mm., a depth of 10 to 12 mm., and a capacity of 45 ml. The porcelain dish supplied by the Arthur H. Thomas Company, Philadelphia, Pa., Catalog S o . 4484, Size 1 , meets the requirements and was the dish used in these experiments. In addition, there will be required a quantity of ordinary lead shot, Size 6. This lead shot is carefully dried and stored in a desiccator until used. Place 44 grams of lead shot (* 1 shot) in the porcelain dish and weigh the dish and shot accurately. Add from a weighing bottle fitted with a dropping pipet 0.3 gram of the oil to be bested. This should preferably be done while the dish is on the balance pan, since this will eliminate the necessity of weighing the oil and the weighing bottle. This amount of shot and oil has been worked out so that there is a sufficient quantity of shot to present a large oil surface to the oven atmosphere when a 0.3-gram sample is used. Place the dish and its contents in an ordinary electric drying oven which has been brought t o a temperature of 60" C. Allow 15 minutes for the dish and contents t o attain the temperature of the oven, and then heat the sample for 5 hours maintaining the temperature constant a t 60" C. Remove, cool in the desiccator, and weigh rapidly when cold. Calculate the loss in weight as volatile matter a t 60" C. under test conditions as outlined. The lead shot serves to break up the sample of oil and present a large area for a given volume in the form of a film.
No comparison has been made between this method and the standard A. S. T. M. method of test, D 6-30. It is quite possible that there will be little if any agreement. It is felt, however, that the method as outlined is a good indication of the relative volatility of the various petroleum oils which we are called upon to test. This is more particularly true since, under the conditions of use, the oil will be spread over a large surface, thus presenting a large area for evaporation. Comparisons with samples of oil of equivalent weight but tested without the addition of lead shot show that the results are higher when the shot is used. This was expected, since it was felt that the addition of lead shot would in a sense produce an accelerated volatilization. The increase was practically proportional when the results on various samples were compared by both methods. A small amount of additional work seems to indicate that so long as the size of the sample is kept reasonably small there is little or no difference in results, whether they are determined on catch weights or on exactly 0.3-gram samples. The main point seems to be that only enough oil should be taken so that it is evenly distributed over the shot without covering it completely, thus insuring a large surface for evaporation. RESULTS The following figures of actual tests performed in duplicate are indicative of the results obtained by this method: L O S E WITH
OIL
SAMPLE 1
LOSS SAMPLE WITH 2
%
%
0.12 0.12 0.26 0.20 0.23 0.22 0.49 0.48 0.57 0.60 0.22 0.18 0.12 0.14 0.25 0.25 0.12 0.14 0.09 0.09 10 0.09 0.12 11 0.06 0.06 12 0.12 0.18 13 0.37 0.41 14 0.27 0.31 15 NOTE., Catdchweights of approximately 0.3 gram were used in these determinations.
The possibility of oxidation of oil has not been overlooked, but no work has been done on this feature. LITERATURE CITED (1) Am. SOC.Testing Materials, Standards, p. 638, D 6-30 (1930). RECEIVED February 29 1932. Resubmitted May 21, 1932
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