INDUSTRIAL A N D ENGINEERING CHEMISTRY
July 15, 1929
yield the desired results from the same scheme of weighting. on the other hand, there is a possibility that the scheme of the three best elongations out of five, here described, or some variation of this scheme, will be close enough to the truth to provide the basis for a standardized treatment, the urgent need for which is self-evident. T a b l e IV-Variation RELATION80 MOOS Above Below 1 5 0 pound@or more *lo0 pounds or more *I50 pounds or more *200 pounds or mOce
from Mode (Tensile a t Break) by Different Weighting Methods Method 1 5
14 9
6
4 2
NUMBER OF LABORATORIES Method B Method 3 Method 4 16
3
12 8 3 0
15 2 12
13
7
5
3
2 0
0
out upon ‘%we” rubber specimens using Schopper rings, in the course of which the author established the approximate validity of the law of accidental error as applied to 731 breaks. Those interested in the theory of probabilities will find in Fric’s paper an elegant alternative treatment of the breaking tensile data in the form of Ogive curves. By means of these, he clearly demonstrates the abnormal frequency of low values which he ascribes to flaws in the rubber. It is thus seen that the preliminary part of the present paper stands as an independent coniirmation of Fric’s observations. The present authors were, of course, primarily interested less in the ultimate reduction to most probable values than in the development of methods for weighting a small number of tests.
6 9
Addendum Since writing the above paper, the authors have noticed a study, “Essais mkcaniques du caoutchouc et probabilith,” in Chimie et kdustrie, April, 1928, by M. R. Fric. It is a pleasure to acknowledge this prior publication of experiments carried
117
Literature Cited (1) Physical Testing Committee, A. C. S. Division of Rubber Chemistry, IND.END. CHEM., 20, 1245 (1928). (2) Somerville and Cope, llzdia Rubber Worid, 79, No. 2, 64 (1928). (3) Sutcliff, “Elementary Statistical Methods,” pp. 157 and 158, McGrawHill Book Co. (4) Sutcliff, Ibid., Chap. XVI. (5) Yule, “Introduction t o Theory of Statistics,” Chap. V I I I , C. Griffin 8h co. (6) Yule, Ibid., p. 149.
Volumetric Estimation of Sulfur in Crude Petroleum‘,’ A n Adaptation of the Nikaido Method Gladys Woodwards CHEMICAL LABOR.4TORY OF THE COLLEGE OF LIBERALARTS,NORTHW~STERN UNIVSRSITY, EVANST6N, ~ L L .
LTHOUGH the lamp method ( I ) * for the determination of sulfur in petroleum light distillates is fairly rapid, there has been no rapid method, volumetric or gravimetric, for this determination in crude petroleum oils. The standard method (2) of determination as barium sulfate includes two time-consuming filtrations and weighings. A volumetric method which would avoid these would be highly desirable. Such was especially desired in the present work, where it was necessary to follow closely the change in sulfur content of the crude petroleum with each treatment. I n 1902 Nikaido (a) suggested that sulfate might be determined by titration with lead nitrate using potassium iodide as indicator. I n 50-70 per cent alcohol solution Iead iodide does not form permanently until lead sulfate is quantitatively precipitated. Thus, when the yellow color of lead iodide is permanent, the end point of the reaction is reached. Since Nikaido first suggested this method, it seems never to have been used; perhaps because the reaction must be carried out in 50-70 per cent alcohol solution, and perhaps on account of other limitations which he also mentions. However, the method may be easily applied to determine the amount of sulfuric acid present in the washings from the combustion of a sample of oil in an oxygen bomb. When the potassium iodide indicator is added to this solution, a small amount of iodine is liberated coloring the solution yellow.
A
Received March 29, 1929. This paper contains results of an investigation carried out as part of project No. 17 of the American Petroleurn Institute research program. Financial assistance in this work has been received from a research fund donated by the Universal Oil Products Company. This fund is being administered by the American Petroleum Institute with the cooperation of the Central Petroleum Committee of the National Research Council. Frank C. Whitmore is director of project No. 17. a Research Fellow, American Petroleum Institute. * Italic numbers in parenthesis refer to literature cited a t end of article. 1
9
This is caused by the ferric salts present in the washings. The solution cannot be titrated when it is colored, as the end point is obscured. The color is easily removed by boiling with a trace of aluminum powder. After concentration to a volume of about 50 cc., alcohol is added to produce the 50-70 per Gent alcohol solution necessary, The end point is very definite, but it may vary a few drops according to the individual. It becomes more accurate as the eye becomes accustomed to the intensity of the yellow, color desired. The end point is not easy to distinguish, however, in yellow light, and therefore the titration must be carried out in daylight or in a room lighted by blue bulbs. The method is accurate to two drops of lead nitrate solution. This means that, when 0.20 gram of sulfuric acid is present in the solution to be titrated, the error in the end point does not exceed 0.4 per cent; when 0.03 gram is present, the error does not exceed 3.0 per cent. There is, therefore, a smaller percentage of error as the amount of sulfuric acid increases. But there is a limit to this, for as the amount becomes greater another error enters in. When a larger amount of lead nitrate solution is required to react with this larger amount of sulfuric acid, the alcohol solution becomes more dilute and the value of the lead nitrate solution changes slightly. However, for as much as 0.30 gram of sulfuric acid the titration is sufficiently accurate. Table I contains results of analyses on oil samples of varying composition using both the present method and the standard method ( 2 ) . It will be seen that the greatest error occurs in cases where a very small sample of low sulfur content was used. With the crude oils, however, where the amount of sulfuric acid formed was from 0.1 to 0.25 gram, the deviation between the methods did not exceed 1.8 per cent, which is no greater than the error the barium sulfate determination allows between check determinations.
ANALYTICAL EDITION
118 Table I-Comparison
of Lead S u l f a t e a n d B a r i u m S u l f a t e Methods SAMPLE USED H2S0, SULFUR PbSO4 FORMED PbSO4 METHOD Grams
Heavy oil residue 1.4500 Panuco crude oil 1 2910 Heavy oilresidue 1:5634 Upton-Crane crude oil 1.5932 Inalewood crude oil 1.2838 Silks ael with adsorbsd sulfur compounds 1.3130 Distillate, b. p. 195230’ C. 0,6340 Distillate, b. p. 155170’ C. 1.2500 Light oil 0.7633
Gram 0.2497 0.2089 0.1306 0,1087 0.0888
1
Per cent
2.23 2.28
2.30
I
Procedure
1
1 Per-0cent .9
Enough oil is burned in the oxygen bomb to produce approximately 0.03 t o 0.25 gram of sulfuric acid. The bomb
-
Note-A Parr oxygen bomb of illium alloy with a capacity of 375 cc. was used. The oxygen pressure was 35 atm. In exploding the sample the procedure of the A. S. T. M. Method D129-27 (2) was followed except that a larger sample was used.
ilff
5.68
I
fl.1 -1.8 -0.9 1.7
0,0321
0,800
0.831
-3.7
0.0151
0.780
0.820
-4.9
0.0129 0,0117
0.338
0.335 0.507
+0.9
0.499
POTASSIUM IODIDE-Dissolve 50 grams of potassium iodide in water and make up to 50 cc.
Bas04
1 Per5.63cent ;%
DEVIA-
AS:
VoI. 1, No. 3
-1.6
Solutions Three solutions are necessary-an approximately 0.2 N aqueous solution of lead nitrate; a standardized, approximately 0.1 N solution of sulfuric acid to be used in standardizing the lead nitrate; a strong, almost saturated solution of potassium iodide t o be used as indicator. LEADNITRATE-Dissohe about 33 grams of lead nitrate in water and make up to 1 liter. Standardize by titration against the standard sulfuric acid as follows: Take about 20 cc. of the sulfuric acid and add water to a volume of 50 cc. Add 100 cc. of 95 per cent alcohol. The alcohol and water may be measured from a graduated cylinder. Add about 0.2 cc. of potassium iodide indicator. It is most convenient to measure this by drops and to take the same number of drops each time. Run in the lead nitrate until a permanent yellow color is produced. The following calculation gives the sulfur value of 1 cc. of the lead nitrate solution: Cc. H&O* X normality &So4 X 0.016032 = grams sulfur per cc. CC.Pb(N0a)s SULFURIC ACID-An approximately 0.1 N solution of sulfuric acid should be used. This may be conveniently made by diluting 3 cc. of the conrentrated acid (sp. gr. 1.84) to 1 liter and standardizing by any of the usual methods.
is washed out into a beaker keeping the volume of the solution as small as possible. The indicator is then added, the same amount being used as in the standardization of the lead nitrate solution. A small amount of powdered aluminum is then added (about 0.01 gram is enough ordinarily), and the solution is boiled down to a volume slightly less than 50 cc. If the solution still remains yellow, not enough aluminum has been added. A 300-cc. Erlenmeyer flask is marked to show when a volume of 50 cc. is reached. The solution is transferred to this flask and cooled by holding the flask under running cold water. The beaker is rinsed out into this flask with a small amount of water, enough t o make up to 50 cc., and the rinsing finished with the 95 per cent alcohol to be used in making the solution up to a 50-70 per cent alcohol solution. To do this, 100 cc. are measured out and added to the 50 cc. of aqueous solution in the flask, as much as desired being used to complete the rinsing of the beaker. The solution should be colorless. The presence of metallic iron or aluminum in the flask does not interfere. The lead nitrate is then run in until a permanent yellow color is produced. The calculation of the percentage of sulfur in the sample is as follows: Cc. Pb(NO& X sulfur value of 1 cc. X 100 = per cent sulfur Grams sample Literature Cited (I) Am. Soc. Testing Materials, Tentative Standards, 1927, p. 433, Method DDO-26”. (2) Ibid., Standards, 1927, Pt.11, p. 419, Method D129-27. (3) Nikaido, J . Am. Chem. SOC.,24, 774 (1902).
Rapid Method for Determination of Phenols‘
.
J. A. Shaw THEKOPPERSCOMPANY, MELLONINSTITUTE OF INDUSTRIAL RESEARCH, UNIVERSITY OF PITTSBURGH, PITTSBURGH, PA.
HE following method has been used in these laboratories in developing the gas recirculation process for the recovery of phenols from ammonia liquor. The development of this method has enabled one man to run a very greatly increased number of tests and as a consequence has facilitated research work upon phenol removal. The words “phenol” and “phenols” are used in the generic sense in this article and refer not only to CaH60Hbut also t o homologous and related compounds.
T
Apparatus One steam chamber (Figure 1) Two Pyrex test tubes, 8 X 1inch (20.3 X 2.5 cm.) Three test tubes, 4 X ’/zinch (10.2 X 1.2 cm.) One Liebig condenser, 10 inch (25.4 cm.) One set of graduated cylinders, 25, 50, 100, and 250 ml. Two No. 5 rubber stoppers, two holes, for 8 X 1 inch test tubes One rubber stopper for condenser inlet Presented before the Division of Water, 1 Received March 19, 1929. Sewage, and Sanitation Chemistry a t the 77th Meeting of the American Chemical Society, Columbus, Ohio, April 29 to May 3, 1929.
TWO 10-h~ MOIX pipets Two 300-ml. bottles with stoppers for standard solutions One 500-ml. bottle with stopper for standard solution Necessary glass and rubber tubing and iron stands Water and compressed air connections
Description of Steam Chamber One of the main advantages of this method of determining phenols is the short time required. Since it involves a distillation, it is necessary that the sample shall be very small or the rate of heat input high. There are various objections to using a high-temperature source of heat, one of which is the danger of charring the organic matter in the sample. It was therefore decided to employ a form of steam distillation. With a small sample, such as 10 ml., only R very small amount of either evaporation or condensation is allowable. The present system using a steam chamber was therefore adopted. The flow of hot vapor is easily and delicately controlled by the setting of the air valve. The temperature is kept almost exactly a t the boiling point by inclosing the
.
