July 15, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
were selected because preliminary experiments indicated that the maximum effect of the reducing sugars with little reduction of sucrose was attained under these conditions. The use of alphazurine G as an indicator for ceric sulfate may find application in the analytical determination of various compounds. Titrations with ceric sulfate and alphazurine G as indicator give constant results with ferrous sulfate, hydroquinoge, and potassium ferrocyanide. I n the case of potassium ferrocyanide, the results are practically unaffected by phosphoric acid, malic acid, succinic acid, and ethyl alcohol. ACKNOWLEDGMENT The writer wishes to express his sincere appreciation to John M. Nelson, Department of Chemistry, Columbia Uni-
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versity, for the kindly criticism and encouragement given during the progress of this work. It has been a true pleasure and inspiration to be under his guidance and for his friendly interest and cooperation the author is deeply grateful. LITERATURE CITED (1) Furman, N. H., and Evans, 0. M., J . Am. Chem. SOC.,51, 1128 (1929)* (2) Gentele, J. G., Chem. Zentr., 30, 504 (1859). (3) Hagedorn, H. C., and Jensen, B. N., Biochem. Z . , 135, 46 (1923). (4) Jackson, R. F., Silsbee, C. G.. and Proffitt, M. J., U. S. Bur. Standards, Sci. Paper 519 (1926). (5) Vosburgh, W. C.,J. Am. Chem. SOC.,43,226 (1921). (6) Willard, H. H., and Young, P., Ibid., 50, 1322 (1928). RECEIVED February 14, 1934.
The Mackey Oil Tester PAULH. GILLAND AUGUSTUSH. GILL, Massachusetts Institute of Technology, Cambridge, Mass.
I
NDUSTRY annually suffers large losses from spontaneous combustion, Despite the seriousness of the hazards encountered in the use of unsaturated oils, satisfactory methods of predetermining the action of such oils have not yet been developed. Ordinarily, a questionable oil is tested by exposing it to the air on fibers in a heated bath. The temperature rise within a specified time is used as an indication of the degree of hazard of the oil. I n the Mackey tester, which is used to the greatest extent, 14 grams of the oil are intimately worked into 7 grams of cotton. This material, with a thermometer in the middle, is then put into a wire gauze and the whole inserted in a combustion chamber, which is merely a water-jacketed container of specified size kept a t 100" C. in which arrangement for a continuous current of air is provided by means of tubes inserted in the cover. Any oil which shows a temperature of over 100" C. at the end of 1 hour or over 200" C. a t the end of 2 hours is arbitrarily considered as dangerous; results thus obtained seem to agree with practice. In order to study the action of the tester, samples were carefully prepared in identical manner and subjected to the test. Figure 1 shows a typical curve. Between the times of 95 and 120 minutes there is a temperature rise of 98" or 3.9" C. per minute. TABLEI. TESTS WITH CORNOIL TEMPBRATURE AT ENDOP First hour Second hour
MAXIMUM TIMETO RBACH TEMPERATURB MAXIMUM
c.
c.
c.
95 97 100 96 96 96 105 99 95 95 96 95 95 99 104 104
185 180 175 173 170 170 173 140 180 183 171 190 190 165 200 182
205 202 192 178 190 174 190 152 198 198 187 207 206 182 225 203
0
Min.
Considerable discrepancies are frequently encountered in the temperature of the samples when duplicates are tested, as is illustrated by the results of the tests on corn oil. No matter how carefully the oil is dispersed through the cotton, there is some difference between the samples. Moreover,
factors such as the depth at which the thermometer is inserted, its position in relation to the center of the wire cylinder, the condition of the cylinder itself, whether new or covered with an oily film, and the height of the water bathall cause variable results, that frequently cause the rise in temperature to vary by as much as 10 minutes. In the case of the oil in Figure 1, this would mean a temperature difference of 39" C. on the steep part of the curve. It may thus happen that a dangerous oil may be considered safe and vice versa. In m a k i n g these 230 tests, if the oil is not e x t r e m e l y inflammable, a maximum temperature is 2 reached after a quick 5 rise. If the tempera- 5 tures of the samples 170 are observed only at the suggested times 2 , 5 0 of 1 a n d 2 h o u r s , g it may well happen 2 that the m a x i m u m I3O m a y have been p a s s e d a n d a low 110 temperature would be r e c o r d e d . A 60 80 I00 120 I40 160 dangerous oil would TIME WPOSED IN MACKEY APPARATUS t h u s be p a s s e d as MINUTES safe. In order to make this test more reliable, some standard other than the arbitrary ''not over 100" in the first or over 200" C. a t the end of the second hour" should be considered. In the many tests conducted, it has been found that the time required to reach a maximum temperature gives better checks and is of much more value in determining the future action of an oil than the usual standard. The actual maximum temperature is of some value in appraising an oil, but considerable discrepancies occur in the numerical values. It is apparent that the ruling factor to be considered in judging the safety of an oil is the time required to attain the maximum temperature, and not merely the temperature at the expiration of 1 or 2 hours.
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RECEIYED March 20, 1934.
