ANALYTICAL EDITION
352
is determined to some extent by the rapidity with which the acid is precipitated from solution. Rapid precipitation from the acidified bicarbonate solution yielded some very red crystals, while slow cooling of a saturated neutral bicarbonate solution gave long colorless needles. PREPARATION OF SALTSAND ANALYSES.As a rule, to form the salts, 0.01 mole of each component was dissolved by heating in the least possible amount of absolute .alcohol, after which the two solutions were poured together on a watch glass to crystallize. However, the compounds of aniline, otoluidine, m-toluidine, methylaniline, dimethylaniline, benzylamine, diethylamine, and triethylamine were prepared by adding, in equimolecular amounts, the hot liquid amine to the very finely powdered acid. Although purification was usually accomplished by recrystallization from absolute alcohol (Table I), these latter-mentioned salts were purified almost entirely by pulverizing them in cold absolute alcohol,
VoI. 6, No. 5
followed by filtration. The number of crystallizations necessary far purity in each case is indicated in the second column of Table I. The melting points, neutralization equivaIents, and nitrogen analyses were determined as described previously (1). LITERATURE CITED (1) Buehler, Currier, and Lawrence, I N D . ENG.C X E M Anal. ., Ed., 5, 277 (1933). (2) Curtius, J. prakt. Chem., (2) 76, 288 (1907). (3) Fomter and Keyworth, J . Sac. Chem. Ind., 43, 165T, 299T, 341T (1924); 46, 20T, 397T (1927). (4) International Critical Tables, Vol. VI, p , 277, McGraw-Hill Book Co., N. Y . , 1929. (5) McMaster and Wright, J . Am. Chem. Soc., 40, 686 (1921). (6) Noller and Liang, Ibid., 54, 670 (1932). (7) Pfeiffer, Ber., 47, 1580 (1914). RECEIYED June 18. 1934.
Determination of Organic Halogens FREDE. BEAMISH, University of Toronto, Toronto, Ontario, Canada
I
T HAS been reported by Jenkins, McCullough, and Booth (6)that the explosion method for organic halogen determination as outlined by Lemp and Broderson (6) produces consistently low results with ortho and para chlorinated diphenyls. Cook and Cook (3) also state that this method produces unsatisfactory results with halogenated diphenyls. Adams (1) and his co-workers have reported satisfactory results on halogenated diphenyl and diphenylbenzene compounds, using the bomb-explosion method. The present investigation was undertaken to determine whether or not the substituted halogens of these compounds and others with which the author has experienced some difficulty could be completely converted to sodium halide when subjected to the sodium peroxide-sugar explosion. It has been the author's experience that certain variations introduced into the procedure for determination of organic halogens by the explosion method produce inconsistent and low results; however, the experience gained in this laboratory through many hundreds of analyses on organic halogens prompts the statement that this method is destined to be considered as generally applicable as the Dumas method for nitrogen. Contrasted with distillation methods and the Carius method it is extremely rapid and simple of operation, besides being as accurate as any reported macromethod for organic halogen determinations. -
I
PROCEDURE The sample used should be such that the silver halide will weigh not more than 275 mg., as much larger samples are not completely oxidized. Add 12 grams or 1 scoop of sodium peroxide and 200 mg. of lactose, shake the whole thoroughly for about 45 seconds, and place in the hottest part of the Bunsen flame for about 45 seconds. This should be done behind a protective screen. Drop the bomb into cold water and wash with distilled water. Dissolve the fusion and remove %he cup in the usual manner. Add 50 cc. of 1 to 1 nitric acid slowly, and remove the gas by stirring or, if desired, boiling in the case of chlorides. Filter through a fine grade of iilter paper and wash completely. Add very slowly while stirring excess 0.1 N silver nitrate. Stir to coagulate and filter through a Goooh crucible. Wash the silver halide with 300 cc. of water, dry at 140" C. for 1 hour, cool on copper block for about 20 to 25 minutes, and weigh.
extent in this laboratory. However, all results reported in this article and many others have been obtained without potassium nitrate, and it may be concluded that potassium nitrate is not a necessary constituent of the explosion mixture. Table I is included to indicate the range of amlicabilitv and accuracy of the method. TABLEI. TYPICALRESULTSOBTAINED IX SOMECOMPOUNDS ANALYZED~
-
SVBSTANCE
.A
HALOGEN Calculated Obtained
%
%
a
m-Chloronitrobenzene
22.50
2,5-Dichloronitrobenzene
36.88
1,2,4-Dichloroaniline
43.7s
Hexachlorobenzene
74.71
m-Nitrobenzalohloride
34.43
m-Bromobenzoic acid
39.77
p-Chloroacetanilide
20.92
9,lO-Dibromoanthracene
47.58
Chloroacetophenone
22.95
6-Chlorocoumarin
19.64
5,7-Dibromo-8-hydroxyquinoline
52.77
Trichlorobutyrio acid
55.57
Propylene bromide
79.17
Iodopropionic acid
63.47
Chloroacetamide
37.92
Triphenylohloromethane
12.73
Compounds were purified where necessary.
'
22.45 22.45 36.96 36.86 43.75 43.76 74.56 74.71 34.43 34.43 39.64 39.74 20.94 21.02 47.53 47.47 22.96 23.00 19.58 19.73 52.72 52.71 55.46 55.46 79.20 79.29 63.46 63.49 37.96 37.95 12.79 12.75
DISCUSSIOX DETERMINATION OF HALOGENATED DIPHENYLS.A sample of the 0- and p-chlorodiphenyl taken from the original stock was obtained from Jenkins, McCullough, and Booth (5). The results obtained on halogenated diphenyls and a substituted diphenylbenzene, together with those obtained by Huntress and reported by Jenkins, McCullough, and Booth ( 5 ) , appear in Table 11, and indicate that by means of the procedure here employed consistent and accurate results Potassium nitrate has been reported by Elek and Hill (4,can be obtained on halogenated diphenyls. The sample of Lemp and Broderson (6), and others as a necessary con- the substituted diphenylbenzene was provided by Roger stituent of the explosion mixture and has been used to some Adams, University of Illinois.
September 15, 1934
I N D U S T R I A L A N D E N G 1.N E E R I N G C H E M I S T R Y
353
TABLE11. RESULTSOBTAIXEDON HALOGENATED DIPHENYLSbe used for the first filtration. Too rapid filtering requires HALOGEN HUNTRESS'^ HALOGEN much wash water to eliminate the last traces of sodium SUBSTANCE CALCULATED RESULTS FOUND halide. S o appreciable opalescence should appear in the % % % wash water after filtering through the Gooch crucible. Coo-Chlorodiphenyl 18.81 18.81 18.78 18.79 18.76 agulation is aided somewhat by addition of alcohol to the 18.75 18.74 silver nitrate solution. Stirring the solution is sufficient to 18.72 coagulate the silver halide and boiling is not necessary. p-Chlorodiphenyl 18.81 18.79 18.86 18.90 18.86
p-Bromodiphenyl
34.30
... ...
4,4-Dibromodiphenyl sulfone
42.63
...
C~aHzBrrCHs)e(OH)z (a brominated iiphenylbenzene) a
18.85 18.74 18.80 18.75 34.34 34.37 42.65 42.69
...
48.30
48.18 48.21
Carius method used.
EFFECTOF OVERHEATING BOMBCUP. I n the procedure outlined by Lemp and Broderson (6) ignition is effected in the hottest part of the Bunsen flame, the heating being continued until the cup is red for a t least one-fourth of its length. With certain organic bromine compounds when the stainless steel cup is used low results are obtained by so heating unless a suitable reducing reagent is employed. This was not observed when the nickel cup described by the author (2) was used, even though heating was continued until the gasket melted and flowed down the walls of the bomb. The comparative results obtained using nickel and steel cups are illustrated in Table 111. The explosion usually takes place about 20 to 35 seconds after the flame is applied to the bomb, so that further heating is unnecessary and rapidly depletes the life of the cup. TABLE111. EFFECTO F OVERHEATINQNICKELd N D STEEL CUPS SUBSTANCE Bromooamphor
TIMEOF HEATING Min.
-HALOGENCaloulated
Steel CUP
Nickel CUP
%
%
%
0.5-0.75 1
34.59
...
34.50 34.48 34.41
34.58 34.55 34.57
3
...
...
34.52 34.49 34.89 34.84 67.81 17.51
Bromodiphenyl"
0.5-0.75 34.30 2 ... 2 67.76 2,4-Dinitrochlorobenzene 0.5-0.75 17.51 2 a This sample of bromodiphenyl was not purified. Dibromobenaene
...
... 34.81 33.91 67.56
...
17.53
*..
Overheating either steel or nickel cups containing the chlorinated organic compounds did not appear to affect the result. When heating was continued for only 35 to 45 seconds, using either the nickel or steel cups, reducing reagents were in no case found necessary with either bromine or chlorine compounds. EFFECT OF DELAYEDEXPLOSION. In most cases the effect of delay in exploding becomes important only after an interval of some hours and seems to affect only volatile compounds. With two compounds low results were obtained after a delay of 15 to 20 minutes. The amount of loss is illustrated in Table IV and, in some cases a t least, does not appear to be due to leakage during the interval of rest. DETERMINATION OF BLANKS. A great deal of the difficulty experienced in obtaining consistently accurate results may be traced to incorrect blanks. The crucible must be carefully prepared. A suitable method is to macerate a thin layer of asbestos with a fine stream of water, continuing until the filtered water shows no trace 'of suspended asbestos. The asbestos is then tapped down with the stirring rod. A fine grade of filter paper similar to Whatman's No. 32 must
TABLEIV. EFFECTOF TIME INTERVAL BETWEEN SHAKING MIXTUREAND EXPLOSION Immediate explosion
After 15 to 20 minutes
Over 15 hours
%
%
%
%
p-Dichlorobenzene
48.20
47.69
48.25
rn-Dichlorobenzene
48.29 48.39 50.91 50.89 28.16 28.00 89.00 89.13 67.66 67.76
47.92 48.04 50.94 50.94 28.02 28.11 88.67 89.21
47.77 47.45 47.71 46.78 49.64
50.91
SUBSTANCE
Bromobenzene Chlorotoluene Chloroform Dibromobenzene
...
...
Calculated
48.25
27.55
28.02
69.55
89.11
67.64
67.76
DETERMINATION OF HALOGENIN COMPOUNDS WHICH SUBLIME. The author has experienced some difficulty with compounds which sublime. For instance, with dibromoanthracene it was observed that the yellow compound remained on the cover of the cup and the results were often inconsistent and low. This was overcome by covering with a layer of sodium peroxide about 1 cm. deep after mixing the explosion mixture. The results obtained are given in Table I. INFLUENCE OF MELTINGPOINT.An intimate mixture of compound and explosion mixture apparently becomes essential only in the case of those substances with high melting points. Organic halogenated compounds with low melting points-i. e., up to about 90" C.-do not require a fine state of division. Liquids were weighed out in a glass bulb or tube. A thin glass rod sealed to the neck serves as a handle in filling, and should be broken off before placing the tube in the bomb cup. It is essential that the wall of the bulb be extremely thin. SUMMARY
.
The determination of substituted halogens in diphenyl and diphenylbenzene compounds by means of the sodium peroxide-sugar explosion has been accomplished. Continued heating of the steel cup after the explosion produces low halogen results with some bromine compounds, while overheating the nickel cup does not affect results. Addition of supplementary oxidizing substances to the sodium peroxide-sugar explosion mixture is not necessary. The results obtained on chloroform indicate that the method is adapted to volatile liquids, although results may be low if the explosion is delayed. ACKNOWLEDGMENT The author is indebted to J. Russell for checking results of analysis. LITERATURECITED (1) Adams, R., J . Am. Chem. SOC.,53, 343, 2203 (1931). (2) Beamish, F. E., IND. ENG.CHEM.,Anal. Ed., 5, 348 (1933). (3) Cook, W. A., and Cook, K. H., Ibid., 5, 186 (1933). (4) Elek, A., and Hill, D. W., J. Am. Chem. Soc., 55, 2550 (1933). ( 5 ) Jenkins, McCullough, and Booth, IND. ENG.CHEM.,22,32 (1930). (6) Lemp and Broderson, J. Am. Chem. Soc., 39, 2069 (1917). RECEIVED April 23, 1934:
