AN A L Y TICAL EDI TI 012'
274
tillate were diluted to 15 ml., they matched 30 p. p. m. standard upon bromination. Then
:$
The ether, after having been thoroughly washed with both dilute caustic and acid, may be saved if desired and used for subsequent work. I n addition to making possible the rapid analysis of waters containing relatively low concentrations of phenols, this preliminary treatment renders the previously published method satisfactory for determining phenols in ammonia liquors dephenolized by immiscible solvents. For some reason not well understood by the writer, the bromine method as previously published failed to give good results on liquors dephenolized in this manner. It is the writer's opinion that this difficulty arose from the relatively large amount of thiosulfate which is usually formed when handling sulfide-bearing liquors in contact with air.
= 7 . 5 ~p.. m. phenol
Discussion
By the procedure as outlined, solutions containing 1 p. p. m. of phenols or even less can be analyzed in 1 hour, and the error shDuld be distinctly less than 10 per cent. The following results are some that were obtained on synthetic solutions : In sample P. P. m. 25 0 5 0 1 0
PHENOL
VOl. 3, No. 3
Found P. p . m. 25.1
Literature Cited
4.80
(I) Shaw, J A,, IND END.C H B M .Anal. , Ed., 1, 118 (1929).
1.00
Determination of Organic Halogen b y Liquid Ammonia-Sodium Process* Thomas H. Vaughn and J. A. Nieuwland DEPARTMENT OF CHEMISTRY,
UNIVERSITY OR
NOTRED A M E 8 NOTREDAXE, IND.
The liquid ammonia process for the determination HILE investigating tions, using tetrachloroethylof organic halogen has been modified SO as to dispense the action of soluene as an example: with all special apparatus, to increase the accuracy, tions of sodium in c1 and to reduce the time required for a complete deliquid ammonia on organic \ termination. By the modified method determinations haloids, it occurred to the c=c +4NaNHz+ are extremely BimpIe, very accurate, and require in authors that since halogens \Cl c1/ most cases only 20 to 40 minutes for completion. were apparently q u a n t i t a The modified method has been applied to the de2 " tively removed from all types termination of organic fluorine and gives excellent of organic compounds, this \ /", + 4NaCI results. * /c=c\ method of treatment might be used as a basis for halogen 2" 2" determination. Such proved to be the case. NHz \ I", On looking up the literature, it was found that Chablay + HN=C=C=NH + 2NHa (1) had employed this reaction for the determination of organic /c=c\ chlorine, bromine, and iodine; and that Dains and co-workers 2" NHz (2, 8) had used the method and investigated the possibility HN=C=C=NH + 2NaNHz +2NaCN 2NHs of error caused by cyanides produced during the decomposiSimilar equations can be written for all observed cases of tion. According to the method described by Chablay, the sub- cyanide formation. stance is placed in a special reaction tube which is cooled I n the procedure to be described, the original Chablay in a bath of solid carbon dioxide and acetone. Ammonia method has been modified in such a manner as to increase is condensed in the tube and metallic sodium added. After the rapidity and accuracy of analysis of insoluble materials completion of the reaction, the ammonia is distilled off and and to do away with all special apparatus. the halogen precipitated as silver halide. This method, while Modified Procedure very rapid for compounds soluble in liquid ammonia, requires an hour or more for the decomposition of insoluble substances. Fifty milliliters of liquid ammoniaare run into a 400-~1. With insoluble compounds, moreover, low results are usually beaker and 0:1to 0.4 gram of the halogeno-organic iaterial obtained added. If solution does not take place upon stirring, ether, D a h s and Brewster (9) investigated the action of sodium monobutylamine, dimethyl acetal, or other organic solvent in liquid ammonia on organic compounds and examined the inert towards sodium in liquid ammonia is slowly added until products of reaction for cyanide. They found that cyanides the material is dissolved. One gram of freshly cut metallic were Produced from haloen compounds in Only a few cases* sodium is then added in small pieces and the covered beaker It is interesting to note that in all of these cases two or more allowed to stand until the reactionis complete(usually 30 halogens were attached to a single carbon atom. I n view of seconds to 2 minutes). At this point the solution should this fact, and since it is known that one of the principal prod- have a persistent blue colorof uniform depth. ~i~~grams of ucts of the reaction of sodium in liquid ammonia on organic ammoniumnitrate dissolved in few of liquid haloids is an amine, the production of cyanide in these special ammoniaare now added to the excess sodium. The cases can probably be by the following set Of reac- covered beaker is placed in a water bath at room temperature, and the solution allowed to evaporate to dryness (hood). The 1 Received March 13, 1931.
+
.
I
INDUSTRIAL AND ENGINEERING CHEMIXTRY
July 1.5, 1931
solids are taken up in water, diluted to 150 ml., filtered if necessary, acidified with nitric acid, and treated with an excess of silver nitrate solution. The solution is boiled to coagulate the silver halide, filtered, and washed with water containing a few drops of nitric acid and then with acetone. The precipitate is dried a t 135" C. for 15 minutes, and weighed. The use of organic solvents reduces the time of reaction of insoluble substances remarkably and does away with low results by facilitating complete decomposition. With hexachloroethane, for example, the time of reaction was reduced from 90 to 2 minutes and the error was decreased from 0.42 to 0.07 per cent. When the ammonia solutions are allowed to evaporate as recommended by Chablay, and the excess sodium destroyed by the addition of water, tars result in many cases. The addition of ammonium nitrate in liquid ammonia before evaporation obviates this. When solids are being analyzed, the beaker containing the material should be cooled by placing in a shallow dish containing a layer of about 0.5 cm. of liquid ammonia, before the solvent ammonia is added. This avoids the violent spattering caused by the rapid vaporization of the ammonia on contact with the bottom of the beaker. Volatile liquids can be weighed in thin-walled glass bulbs which are then broken under liquid ammonia in a beaker. After decomposition, evaporation, and addition of water, the solution can be decanted from the glass fragments and analyzed in the usual manner. I n some cases organic solids are produced during the decomposition. These must either be filtered off or put in solution by the addition of aldehyde-free acetone or other suitable solvent before precipitation of the halide. In an attempt to speed up the determination, volumetric methods were tried. The Fajans method, using sodium eosin as an indicator, was found to give satisfactory results, since the titrations can be made in acid solutions. All volumetric determinations reported were made by this method. The Volhard method also gives excellent results. The modified methQd was tried on a micro scale and gave good results. Samples containing 16 mg. of 3,5-dibromo-2aminobenzoic acid were decomposed, taken up in water, and titrated by the Fajans method with 0.01 N silver nitrate solution. Bromine calculated was 57.15 per cent; bromine found, 57.39 per cent; difference, 0.24 per cent. Results of analyses of chloro, bromo, and iodo compounds are given in Tables I, 11, and 111,respectively. All percentages given are the average of a t least two determinations. Table I-Analyses COMPOUND Trichloroacetic acid Chloral hydrate Hexachloroethane Chlorobenzene 9- ichlorobenzene &:chlorobenzene 2,4,5-Trichloroacetanilide Chlorophenylpyrazolone 1-Chloro-2-methylanthraquinone
275
this class of compounds, it must be assumed that any silver cyanide precipitated was decomposed by the action of dilute nitric acid during the coagulation of the silver chloride, or that in the presence of an organic solvent cyanide formation is inhibited. Table 111-Analyses COMPOUND n-Butyl iodide Methylene iodide Phenyl iodide Tetraiodophthalic anhydridea a Volumetric determination
of Iodo Compounds IODINE IODINE PRESENT FOUND DIFFERENCE % % % 68.98 68.86 0.12 94 77 94.84 0.07 62.23 62.23 0.00 77.91 77.08 0.83
The agreement between duplicate analyses of the same sample of various halides is shown in Table IV. Table IV-Agreement of Analyses COMPOUND SAMPLE I SAMPLE I1 DIFPERENCB
% 9-Dichlorobenzene 48.17 18.25 Chlorophenylpyrazolone Methylene iodide 94.77 1,3-Dimethyl-5-bromofluorobenzene 9 . 3 3 2-Fluoroanthraquinone 9.13
%
%
48.28 18.13 94.61 9.27 9.27
0.11 0 12
0 14 0.06 0 14
Analysis of Fluoro Compounds
There seems to be, so far as we know, no completely satisfactory method available for the determination of organic fluorine. It has been found that sodium in liquid ammonia reacts quantitatively with fluoro organic compounds to form sodium fluoride and this reaction has been applied to the determination of organic fluorine. The material containing fluorine is decomposed by the modified procedure given above. The decomposition products are taken up in hot water to which 5 grams of ammonium nitrate have been added, and the fluorine ion precipitated by the addition of an excess of hot calcium nitrate solution. The precipitate is digested for 30 minutes, cooled, filtered on a Gooch crucible, washed with water and acetone, dried a t 180' C., and weighed. The volume of wash water used is measured and the weight of precipitate corrected for the solubility of calcium fluoride. Cyanides cannot interfere in the determination of fluorine, since calcium cyanide is soluble. Results of analyses for fluorine are given in Table V. These results are, like those in Tables I, 11, and 111, the average of a t least two determinations, Table V-Analyses
of Fluoro Compounds FLUORINE FLUORINE PRESENT FOUND DIFFERENCE
COMPOUND % % % CHLORINE CHLORINE PRESENT FOUND DIFFERENCE Fluorobenzene 19.79 19.78 0 01 9-Fluoronitrobenzene 13.47 1 3 . 2 8 0 .19 9% % % 1,3-Dimethyl-5-bromofluorobenzene 9 . 3 6 9.30 0.06 65.11 65 19 0 08 o-Chlorophenylfluoroform 31.58 31.36 0.22 64.33 64.21 0.12 2-Fluoroanthraquinone 9.06 9.20 0.14 89.86 89.91 0.05 35.56 35.56 0.00 48.28 48.23 0.05 Fluorine and bromine were both determined on the same 74.73 74.80 0.07 44.62 44.55 0.07 sample in the case of 1,3-dimethyl-5-bromofluoro benzene. 18.23 18.19 0.04 The fluoride mas first precipitated and the bromide determined 15.25 15.20 0 05
of Chloro Compounds
in the filtrate.
Table 11-Analyses COMPOUND
of Bromo Compounds BROMINE BROMINE PRESENT FOUND DIPFERENCE
Ethyl bromide5 3,5-Dibromobenzoic acid Styrene dibromidea Dibromoisatin 1,3-Dimethyl-5-bromofluorobenzene a Volumetric determination.
%
%
%
73 37 57.15 60.56 62.46 39.37
73.46 57.00 59.95 52.55 39 42
0.09 0.15 0.61 0.09 0.05
In Table I analyses of three compounds which contain three halogens to a single carbon atom are given. Inasmuch as Dains and Brewster (2) reported cyanide production from
Acknowledgment The writers are indebted to Roger Adams of the University of Illinois, and to the Jackson Laboratory, E. I. du Pont de Nemours and Co., for a number of the compounds on which this method was tested. Literature Cited (1) Chablay, Ann. chzm., [91 1, 610 (1914). (2) Dains and Brewster, J. A m . Chem. SOC.,42, 1573-9 (1920). (3) Dains, Vaughan, and Janney, I b i d , 40, 936 (1918); see also Clifford, I b i d , 41, 1051 (1919)
