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Vol. 13, No. 1
INDUSTRIAL A N D ENGINEERING CHEMISTRY
sufficiently. If copious nitrogen peroxide fumes are still visible in the flask when the sample is nearly to dryness, as will often be the case when fish meals or oily substances are present, another 15 ml. of nitric acid should be added and the slow digestion continued. Care should be taken to avoid burning or charring the sample. All the perchloric acid should be added at one time. Precautions of Kahane (5) are: (1) Oxidize as much as possible with nitric acid before adding the perchloric acid because it is the easily oxidized material that reacts vigorously with perchloric acid, and (2) always add a n excess of perchloric acid and never boil the solutions too rapidly.
Acknowledgment The author wishes to thank James Maddox, student, for his technical assistance.
Literature Cited (1) Assoc. Official Agr. Chem., J . Assoc. Oficial Agr. Chem., 22, 78-80 (1939). (2) Bolin, D. W., J . A ~ TResearch, . 48, 657-63 (1934). (3) Davidson. Jehiel, J . Assoc. Official AQT.Chem.. 14, 551 (1931). Gerritz, H. W., IND.ENQ.CHEM.,Anal. Ed., 7, 167-8 (1935). (5) Kahane, E., 2.anal. Chen., 111, 14-17 (1937). (6) Kahane, E., and Brand, D., Bull. SOC. china. biol., 16, 710-19 (1934). (7) Richards, M. B., Analyst, 55, 554-60 (1930). (8) Smith, G. F., “Perchloric Acid”, G. F. Smith Chemical Co., 1931.
(4
(9) Smith, J. B., and Dessyck, E. J., J. Assoc. Oficial A g r . Chem., 22, 673 (1939). (10) Wilgus, H. S., Jr., Norris, L. C., and Heuser, G. F., Science, 84, 252-3 (1936). SCIENTIFIC PAPBR474, College of Agriculture and Agricultural Experiment Station, State College of Washington.
Boron Determination in Volatile Organic Compounds Using the Parr Oxygen Bomb WINTHROP M. BURKE, Standard Oil Company of California, Richmond, Calif.
A
REVIEW of the literature regarding the methods for the
determination of boron in organic compounds reveals the fact that some of the methods are either lacking in accuracy or are long and cumbersome. I n foods and fertilizers boron is usually present as boric acid or borax, which are less volatile than the aliphatic boron compounds, and the organic matter may be destroyed by ashing in the presence of a n alkaline substance. This method (2) obviously cannot be applied to organic compounds which volatilize before decomposing or oxidizing. Several attempts have been made to analyze for boron when fluorine is present. Bowlus and Nieuwland (S) analyzed boron fluoride for boron with an average error of about 6 per cent, using the Carius method of decomposition. Pflaum and Wenzke (6)used the Parr fusion bomb with a n oxidizing mixture of sodium peroxide, sugar, and potassium chlorate. The high concentration of alkali caused difficulties in the determination of fluorine, which were overcome by adding ammonium chloride. Then in preparation for the boron determination, more strong sodium hydroxide was used to remove the ammonium ion. Snider, Kuck, and Johnson (6) used the Parr fusion bomb for the determination of boron in boronic acids. They obtained good results, but the fusion bomb has the limitations of a maximum sample of about 0.3 gram and the introduction of larger amounts of reagents; these limitations are not necessary in decomposing aliphatic boron compounds by the oxygen bomb method described below. The digestion with hydrogen peroxide and the subsequent evaporation and fusion with sodium hydroxide are timeconsuming, and still involve the use of large amounts of rea gents.
Improved Oxygen Bomb Method An accurately weighed sample of approximately 1 gram is used in the Parr oxygen bomb according to A. S. T. M. Method D-129-39 ( I ) , with the addition of about 1 gram of sodium carbonate to the water in the bomb. Volatile substances should be weighed in a gelatin capsule. After the oxidation, the alkaline solution containing the boron in the form of sodium borate is evaporated t o about 25-ml. volume, transferred t o a 500-ml. Erlenmeyer flask, and then acidified with 3 N hydrochloric acid
using methyl red indicator and 3- to 5-ml. excess of acid. The solution is boiled for about 20 minutes under R reflux condenser to liberate carbon dioxide, cooled, and brought t o neutrality with carbonate-free sodium hydroxide. Then 0.1 N hydrochloric acid is added until the sample is just pink t o methyl red, and the solution is finally titrated with 0.1 N sodium hydroxide in the presence of mannitol, using phenolphthalein as an indicator. Results are calculated thus: ml. of 0.1 N NaOH required X 0.001082 X 100 % boron = weight of sample According to Hillebrand and Lundell (4) the boric oxide titer of sodium hydroxide is not accurate when calculated directly from the sodium hydroxide content; hence the 0.1 N sodium hydroxide was standardized using pure dry boric oxide. A blank test was run on the reagents used, determining the differences between the methyl red and phenolphthalein TABLE
Weight of Sample
Titration
Gram6
M1.
1.0270 1.0861 1.1719 1.0280
38.04 40.69 43.49 38.29
I. RESULTS OF ANALYSIS
Blank Net Titration Boron M1. Ml. % Amyl Borate (B. P. 122-123O C., 3 Mm. Hg Pressure). NaOH (0.1001 N ) , 1 M1. = 0.001083 Gram of Boron 1.09 1.09 1.09 1.09
3.90 3.91 3.95 3.92 3.92 3.97
36.95 39.60 42.40 37.20
Average Theoretical Amyl Borate (Eastman Practical). NaOH (0,1020N ) , M1 1. Gram of Boron 1.0060 1.0221 1.0230
36.90 37.50 37.40
1.09 0.80 0.80
35.81 36.70 36.60
Average Theoretical
=
0.001103 3.93 3.96 3.95 3.95 3.97
n-Butyl Borate (Eastman White Label). NaOH (0.0994 N ) , 1 M1. = 0.001076 Gram of Boron 1.2103 1.0321 1.0214 1.0815
53.33 45.90 45.38 48.20
1.05 1.05 1.05 1.05
52.30 44.85 44.33 47.15
Average Theoretical
4.65 4.68 4.67 4.69 4.67 4.70
January 15, 1941
ANALYTICAL EDITION
end points. The accuracy obtained was about one part in 100 of the percentage of boron found. Using this procedure the analyses presented in Table I were performed.
Summary The Parr oxygen bomb is satisfactory for t’he combustion of organic boron compounds in preparation for the determination of boron. It provides a means for decomposing organic boron compounds without the use of large amounts of reagents, and gives equal or greater accuracy than some methods heretofore proposed.
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Literature Cited (1) Am. SOC. Testing Materials, “Standards on Petroleum Producta and Lubricants” (Sept., 1939). (2) Assoc. Official Agr. Chem., Official and Tentative AMethods of Analysis, 4th ed., p. 436 (1935). (3) Bowlus, H., and Nieuwland, J. A., J. Am. Chem. SOC.,53, 3835 (1931).
(4) Hillebrand, W. F., and Lundell, G. E. F., “Applied Inorganic Analysis”, p. 612, New York, John Wiley & Sons, 1929. (5) Pflaum, D., and Wenrke, H., IND. ENQ.CHEY.,Anal. Ed., 4, 392 (1932). (6) Snider, H. R., Kuck, J. A., and Johnson, J. R., J . Am. Chem. Soc.. 60, 105 (1938).
Oxidation of Lubricating Oils Apparatus and Analytical Methods M. R. FENSKE, C. E. STEVENSON, R. A. RUSK, N. D. LAWSON, M. R. CANNON, AND E. F. KOCH The Pennsylvania State College, State College, Penna.
A n apparatus and procedure are described which permit determination of the rate of lubricating oil oxidation. Studies are usually made over the range 130’ to 180” C. using oxygen in a circulatory system. Methods have been developed for the determination of substantially all the volatile and nonvolatile end products of the reaction. Ninety to 100 per cent of the oxygen absorbed by various oils has been accounted for in the products determined. The chief product is water, which accounts for 40 to 60 per cent of the reacting oxygen. Soluble saponifiable materials represent another considerable portion, while carbon dioxide, carbon monoxide, volatile acids, fixed acids, and precipitable products account for the remainder. The analysis of insoluble materials produced by laboratory and engine oxidation indicates these to be relatively highly oxygenated materials (14 to 24 per cent oxygen) produced by polymerization or condensation of the oxidized oil. Molecular weights and elementary analyses suggest certain empirical formulas for the insoluble bodies. The oxidation of several commercial light oils shows that rates of oxidation vary widely and that induction-type oxidation curves may be common. In general, these results show the widely different oxidation characteristics existing in oils, and that much of the oxidation mechanism remains to be understood before corrective measures are generally applicable.
M
ODERN developments in the refining of lubricating oils for internal combustion engines have produced many changes in the methods of their preparation. b7ithin the past few years the stability of such oils toward deterioration in use with the formation of harmful products has become a problem of considerable importance. This may be attributed to several circumstances. Variations in engine design intended for more economical operation have reduced oil consumption, and consequently the amount of make-up oil which must be added between drain periods. At the same time manufacturers have tended to recommend longer mileages between drains, which also has prolonged the period of exposure of the oil to deterioration. During the past ten years in automobile engines the horsepower per cubic inch of displacement has increased 30 per
cent, the average compression ratio 26 per cent, the average brake mean effective pressure a t maximum horsepower 13 per cent, and the brake horsepower 25 per cent. I n general, such increases lead to increased engine block and crank case temperatures. Along with these more severe conditions have come the introduction of certain bearing alloys more susceptible to corrosion than the conventional babbitt bearings, and the use of decreased clearances, which necessitate that the lubricant shall not produce deposits that will cause the pistons or valves to stick within their operating passages. It has been shown many times (5,l.Z)that the major effects of oil deterioration are those due to oxidation of the lubricant. Most studies of oil deterioration have involved one or another of numerous arbitrary and relatively simple oxidation tests. I n some of these [Michie (Z),Sligh ( I @ , Indiana (14), etc.] a standard quantity of oil is subjected to air or oxygen (sometimes under pressure) a t a set temperature, with or without catalysts, and such values as acid number, sludge, tar formation, oxygen absorption, viscosity change, etc., are measured as an index of the degree of deterioration. Many attempts have been made to correlate such laboratory tests with engine tests on various oils, but failure to do so is signally evident. A logical approach to an understanding of the mechanism of oil failure in service is to study oils while oxidizing under controlled conditions, and to determine the extent and kinetics of the oxidation reaction and, in so far as possible, the amount and nature of all the products. Such studies on insulating oils have been made by Balsbaugh (4). However, relatively few workers have conducted extensive oxygen absorption tests, and it is particularly unfortunate that some who have made such tests have failed to describe adequately the oils with which they worked. I n other cases no attempt was made to indicate the nature of the materials produced by such oxidation. One of the aims of this work was to secure such an understanding of the oxidation reaction that it would be possible to write equations which would indicate the quantities of all the oxygenated end products. This does not imply that the structure and chemical nature of all these materials need to be known, but only that i t should be possible to classify them, to determine quantitatively the classes present, and to calculate the complete oxygen balance from a knowledge of the oxygen content of each of these classes. The apparatus used in this investigation is an elaboration of a simpler type used by Dornte (8). Means were provided for circulating oxygen, or oxygen-containing gas mixtures, through a quantity of oil maintained a t a constant tempera-
