INDUSTRIAL
AND
ENGINEERING CHEMISTRY
ANALYTICAL E D I T I O N PUBLISHED
BY
THE
AMERICAN
CHEMICAL
SOCIETY
HARRISON
E.
HOWE,
EDITOR
Organic Halogen Compounds in Mineral Oils Detection, Determination, and Identification RI. S . AGRUSS, GEORGE W. AYERS, JR., AND HANS SCHINDLER The Pure Oil Company, Chicago, I11
nitrate solution. In order to obtain a sharp end point, it is essential that the solution be vie\ved through bright yellow glass during the titration with silver nitrate solution. A blank determination must be carried out, in which 0.500 gram of the c. P. sodium bicarbonate, dissolved in exactly the same volume of wat,er used in the beaker during the test, is titrated under the same conditions as when the sample was used. The halogen content is calculated in the usual manner after the quantity of silver njtrate solution used in the blank is subtracted from that used for the sample. If the particular halogen present-bromine, chlorine, or iodineis unknown, a second sample is burned in the bomb and the contents are examined by the usual qualitative procedure.
D””“
i G the past fifteen years, and particularly during the past five years, addition of organic halogen compounds to various types of mineral oils has become a practice in the petroleum industry. These mixtures include a wide range of products, such as fireproof cleaning solvents, cutting oils, break-in oils, and special lubricants. I n almost every case the halogen compound used in the mixture is a chlorine compound. Methods for the detection, determination, and identification of the organic halogen compound or compounds present in mineral oils are therefore necessary in the examination of such products. Methods are included in the present paper for (1) the determination of total halogen (such as chlorine) in a n oil, (2) the determination of the type of halogen compound presenti. e., whether the chlorine is or is not attached directly t o an (3) the possible identification of the aromatic ring-and halogen compound present.
Typical results by the above procedure are shown in Table I. TABLE I. DETERMINATION OF To9XL HALOGEN IN LUBRICATING OIL Halogen Compound Added
Determination of Total Halogen A number of well-known methods have been advanced for the determination of halogen in organic compounds or in mineral oils, but these consume too much time t o be used in ordinary laboratory operations. The following method, in which the hydrogen chloride formed during combustion of the mineral oil in a Parr oxygen bomb is absorbed by sodium bicarbonate solution (in the bomb), which is in turn titrated with standard silver nitrate solution b y either the Mohr or Volhard procedure, is rapid and accurate and has given excellent results over a period of several years.
Ha 1ogen Calculated Found
70
%
n-Heptyl bromide
0.045
0.044
n-Amyl chloride Triphenylmethyl chloride
0,333 0. Old 0.143 0.069 0,690 0.028
Ethylene dichloride Benzyl chloride o-Dichlorobenzene
0.450
0.280 0 479 0.048
0.466
0.324 0.014 0.140 0.067 0 695 0 029 0.294 0 470 0.050
Determination of Type of Halogen Compoiind Present Procedures given in the literature and well-known qual? a-
PROCEDURE. About 20 ml. of distilled water, in which is dissolved 0.500 gram of c. P. sodium bicarbonate, are placed in a Parr oxygen bomb of 400-ml. capacity. From 0.6 to 0.8 gram of the oil to be tested is placed in the weighed oil cup and the weight of the charge is determined to the nearest milligram. The cup is then placed in the bomb, which is previously arranged so that the iron firing wire (10 cm.) touches the oil sample when the cup is placed in position. The bomb is tightly closed and oxygen a t 30 atmospheres is admitted, after which the ignition is carried out in the usual manner in a container of cold water. After ignition the bomb is allowed to cool (10 minutes) and the pressure is released a t a uniform rate such that the operation requires not less than 1 minute. The bomb is opened and the inside is examined for traces of unburned oil and sooty deposit. If either is found, the determination is discarded. If complete combustion has taken place, the interior of the bomb, including the oil cup, is rinsed with a line jet of distilled water into a 400-ml. beaker. The washings usually do not exceed 350 ml. To the beaker is added 1 ml. of 2.5 per cent potassium chromate indicator solution and the halogen content is determined by titration with 0.05 N silver
tive organic texts are very indefinite with respect t o expximental details for the determination of the type of halogen compound present. Potassium and sodium hydroxide solutions, both aqueous and alcoholic, have long been suggested as reagents for this purpose. It has been found that 1 N alcoholic potassium hydroxide solution when boiled 5 7 mutes with the sample does not react with halogen attached t o an aromatic ring except in the case of iodine where a positive group such as a carboxyl or aldehyde group is in the ortho position. Practically all other organic halogen compounds are attacked by the alcoholic potassium hydroxide solution. PROCEDURE. From 0.1 to 0.2 gram of the halogen compound or 8 cc. of mineral oil containing a halogen conipound is placed in a 15-cm. (&inch) test tube with 8 cc. of 1 N alcoholic potassium hydroxide solution (prepared from special potassium hydroxide containing not more than 0.002 per cent chlorine and 95
69
70
Vol. 13, No. 2
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE 11. REACTIVITY OF ORGANIC HALOGEK COMPOUNDS (With 1 N alcoholic potassium hydroxide and saturated silver nitrate solutions) Positive Reaction with 1 N Alcoholic KOH Ne ative reaction with Negative Reaction Positive reaction with alcoholic AgNOs a?coholic AgNOa with 1 N Alcoholic KOH Isopropyl bromide Acetylene tetrachloride Chlorobenzene n-Butyl chloride Trichloroethylene Trichlorobenzene Isobutyl bromide Tetrachloroethane o-Dichlorobenzene n-Butyl bromide Pentachloroethane a-Chloronaphthalene n-Amyl chloride Tetrachloroethylene p-Chlorodiphenyl n-Amyl bromide p-Bromoaniline Chlorohydroquinone Isoamyl bromide Bromobenzene Isoamyl chloride rr-BromonaDhthalene n-Heptyl bromide p-Dibrornobenzene Tetrachloronaphthalene Triphenyl methyl chloride Benzyl chloride Benzyl bromide p-Dichlorobenzene Iodobenzene Hexachloroethane p-Phenylphenacyl bromide Chloroacetal Dichloropentane Chlorocyclohexane Nitrobenzyl bromide utadiene ' tetrabromide Trichloroacetic acid Carbon tetrachloride Iodoform Ethylene dibromide Ethylidene bromide o-Iodobenzoic acid Slightly positive reaction with alcoholic AgNOs Propylene dichloride Chlorex B-Phenoxy-O'-chloroethyl ether hlonochloroacetic acid Methvlene chloride Chloroform, Ethylene dichloride l,l,Z-Tribrornoethane
B
per cent ethyl alcohol). The teat tube is placed in a steam bath for exactly 5 minutes; then 5 cc. of distilled water are added and the contents are filtered through Whatman No. 42 filter paper. The filtrate is acidified with dilute nitric acid; if turbid it is filtered through sufficient a t e r paper to give a clear solution. To this solution is added 0.5 cc. of 0.05 N silver nitrate solution and it is examined for turbidity due to silver halide. Blank tests on the reagents are carried out in the same manner. Any excess of turbidity over that given by a blank test on the reagents used indicates the presence of organic halogen not attached to an aromatic ring (except with a few iodine compounds as stated above). The results obtained m-ith a number of organic halogen compounds are shown in Table 11. For purposes of comparison, results obtained by heating the halogen compound with a saturated solution of silver nitrate in absolute alcohol are also included. The sensitivity of the test for the determination of organic halogen compounds in mineral oil is shown in Table 111. In case the two types of organic halogen compounds are present in the same sample of mineral oil, the halogen not attached to an aromatic ring may usually be removed from the oil b y continued refluxing with 1 N alcoholic potassium hydroxide until the halogen content of the mineral oil decreases to a constant value, this latter value indicating the amount of halogen attached directly to an aromatic ring.
Identification of Halogen Compound Present Mineral oils containing halogen compounds may be distilled in uucuo, the halogen compounds usually being concentrated in one or more of the fractions obtained. Upon examining the results obtained by the methods mentioned above and the physical constants of the fractions, the halogen compound present usually is readily identified and a derivative may be prepared if desired. This examination of the fractions is time-consuming and may be replaced in many instances by a simple procedure by which the halogen compound may be extracted from the mineral oil as a thiuronium salt and identified by means of the corresponding thiuronium picrate. One hundred grams of mineral oil and 50 cc. of PROCEDURE. c. P. benzene are refluxed for 2 hours with 10 cc. of 95 per cent ethyl alcohol containing 1 gram of thiourea. The alcohol layer is separated and the oil extracted with 25 cc. of hot 95 per cent alcohol, after which the two alcohol solutions are combined and evaporated to dryness on a steam bath. The resulting thiuronium salt is washed with cold hexane to remove traces of oil, then dissolved in 10 cc. of 95 per cent alcohol, and 1 gram of picric acid is added. The mixture is heated on the steam bath until complete solution is attained, then allowed t o cool slowly. The thiuronium picrate is filtered off, washed with 5 cc. of cold 95 per cent alcohol, then repeatedly recrystallized from 95 per cent alcohol until the melting point becomes constant. Usually two recrystallizations are sufficient. Table IV shows the melting points of the thiuronium picrates obtained by this procedure from several portions of lubricating oil to which had been added the compounds listed. TABLEIV. MELTIXGPOINTS OF THIURONIUM PICRATES DERIVED FROM HALOGEN COMPOUNDS IN LUBRICATING OIL Halogen Compound Added to Lubricating 0 1 1 (1%in Each Case)
Melting Point of Thiuronium Picrate Found (picrate derived from halogen comLiterature pound in oil) value ( I )
c.
c.
n-Amyl chloride n-Heptyl bromide Triphenylmethyl chloride Ethylene dichloride Benzyl chloride
Since no value for the melting point of s-triphenylmethyl thiuronium picrate was available in the literature, this compound was prepared by refluxing triphenylmethylchloride with thiourea in alcoholic solution, followed by addition of picric acid and recrystallization from alcohol. The melting point was 172" C. and analysis of the compound indicated 5.4 per cent of sulfur (theoretical, 5.85 per cent).
Lit erature Cited (1) Levy, W. J., and Campbell, Neil, J. Chem. SOC.,1939, 1442. before the Division of Petroleum Chemistry a t the 100th Meeting of the American Chemical Society, Detroit, Mich.
PmsENrm
Note on Determination of Silica in Calcined Alumina J. E. EDWARDS
OF TESTFOR HALOGEN IN TABLE 111. SENSITIVITY LUBRICATING OIL
(Where halogen is not attached t o a n aromatic ring) Compound Minimum Halogen Minimum Halogen Compound Present Detected by Test Detected by Test Present
% n-Amyl chloride n-Heptyl bromide Benzyl chloride Chloroform Carbon tetrachloride Tri henylmethyl choride
0.002 0.002 0.001 0.005 0,005
0.001
% Hexachloroethane Trichloroethylene Pentachloroethane Ethylene dichloride Monochloroacetio aoid Trichloroacetic acid Chlorex
0.005 0.004 0.004 0.004 0.002 0.003 0.003
154, Hillcroft Crescent, Oxhey, Watford, Herts, England
T
HE determination of traces of silica in calcined alumina required for the manufacture of aluminum presents a number of difficulties. The author has found t h a t silica may be determined in calcined alumina colorimetrically as silicomolybdate in acid solution and that this method is quicker and more accurate than the gravimetric method. It may also be adapted t o many estimations of small amounts of silica or silicon.
