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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.
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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.
