Determination of Soluble Chloride in Coal Carbonization Products by W a ter-Methyl Isobutyl Ketone Extraction LEONARD GINSBURG’ and LASZLO C. PASZTOR Graham Research laboratory, Jones & laughlin Steel Corp., Pittsburgh 30, Pa.
b Water-soluble chlorides can be determined in certain coal tar products by water extraction of the chloride from methyl isobutyl ketone solution, followed by titration of the chloride by the Mohr method. Copper nitrate i s used to precipitate interferences. The technique i s rapid, convenient, sufficiently accurate for routine use, and requires approximately one fourth the time required by the existing method. Procedures are given for coal tar acid, tar acid oil, raw tar feed, and crude sodium phenolate solutions.
B
of inorganic chlorides in coal tar products interferes with subsequent purification processes by foam and emulsion formation, it is necessary to determine watersoluble chlorides in these materials. This paper is concerned with chloride determination in three coal tar products [crude tar acids (CTA), t a r acid oil (TAO), and tar feed (TF)], and in aqueous crude sodium phenolate solutions. ECAUBE THE PRESEKCE
COAL TAR PRODUCTS
The procedure now used ( I ) for chloride determination in coal tars requires refluxing the sample with water for 1 hour with intermittent agitation, followed by argentometric titration of the n a t e r layer by the N o h r (3) method. The extraction is time-consumiiig and requires extreme care to enPure complete chloride recovery. Preliminary work indicated that n l i m :in organic sample was first dissolved in mrtlij 1 isobutyl ketone (JIIBK), chloride n as quantitatively extracted by n :itw a t room temperature with manual shaking. I n addition, sulfide and other inorganic interferences such as cyanide were readily removed b y precipitation with copper nitrate or lead nitrate. The chloride-containing phase \vas sep1
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arated from the organic phase and any precipitate by filtration through qualitative filter paper.
Reagents. Methyl isobutyl ketone (MIBK). Activated carbon. washed chloride free (Norit-A neutral). Copper or lead nitrate solution, 20 grams per liter of ater. Other chemicals used were reagent grade. Procedure. T o a 125-1111. separatory funnel, a d d 25 grams of C T A or T A O sample, 25 ml. of h I I B K , and 50 ml. of distilled water. (If centrifugation is t o be used, a pear-shaped centrifuge tube, such as Corning No. 8200, is a more convenient container.) Extract t h e chloride from t h e organic phase by shaking vigorously for approvimately 10 minutes. I n the case of TF, use 125 nil. of RIIBK with 25 grams of sample and 100 ml. of water to gct a satisfactory analysis. Extract in a 500-ml. separatory funnel, then centrifuge in t n o or three stages. Alternatively, a 5-gram sample may be uscd n-ith 25 ml. of N I B K and 50 ml. of watcr. Allow the phases to settle for 10 minutes or centrifuge a t high speed for 2 minutes and filter the aqueous phase through a qualitative grade filter paper. collecting the filtrate in a graduate cylinder. Record the volume of filtrate for calculation. (The amount of chloride found in the filtrate is corrected by multiplying by the ratio of the volume of water added to the sample to the volume of filtrate obtained. This eliminates the need of recovering the last fex milliliters of filtrate, TT hith nould appreciably increase the analysis time.) Test the filtrate for the prcac.nce of sulfide b y adding 2 to 3 drops of copper solution. If a black precipitate is ohserved, add enough copper nitrate solution to precipitate all the sulfide prescnt and provide not more than 3 d r o p in excess. Filter the solution through a qualitative filtcr. Decolorize the resulting filtrate by heating to a boil n ith 2 to 3 grams of activated carbon, followed b y filtration through a qualitative grade filter. Adjust the filtrate to p H 6.5 to i . 2 n i t h nitric acid and solid sodium bicarbonate. Titrate n ith 0.10S silver nitrate. using 5% potassium dichromate as indicator ( 3 ) . If a dark coloration is formed upon
Table 1.
Determination of Chloride in Various Tar Fractions
(Results reported as milliliters of 0.10N silver nitrate) Conventional MIBK Extraction Samplea Extraction (11 CTA4 1.1,1.2, 1.2,1.3, CT.45
1.3, 1 2 1.1, 1.2,
CTh15 CTA 16 TF I1
0 5 , 0.5 0 3, 0 4 19,18
1 . 2 , 1.4 1.1
1 1 I
TFIV TA02
I
b
0 2 , 0 jC 14,16, 1 3 07, 1 0 2 3, 2 3
11, 1 2 2 3, 2 3, 2 3 ThO3 4.4) 4 5 4.4 a All samples were 25 grams. b c
End point could not be observed. End point difficult to see.
addition of the dichromate, carry a nen- sample through the analysis and conclude with a mercurimetric ( 4 ) titration. For these samples, the Erdey ( 2 ) modifications n ere necessary-i.e., titration with 0.1O.Y mercury(I1) nitrate in 30% ethyl alcohol solution adjusted to pH 2 Jvith nitric acid, using 5 ml. of 7.5% potassiuni iodate as indicator. Determine a rt,agent blank, including the activated carbon. Darkening of the qolution upon addition of potassium dichromate xvas observed only rarely and was apparently due to easily midizable materials from the sample remaining in the aqueous phase.
Results. As satisfactory standards nere not available and could not be prepared, comparison analyses !\-ere made b y t h e present method and t h e conventional ( 1 ) method (Table I). I n all cases except CTA 15 and 16, the organic phase n a s extracted a second time, and remaining chloride was determined to ascertain completeness of recovery. I n the case of N I B K extraction, all samples showed negligible chloride contents n hen eytracted a second time. K i t h the conventional eltraction, 15 to 257, of the chloride n a s found when tar feeds were extracted a second time. while a CTA and TAO VOL. 30, NO. 12, DECEMBER 1958
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Table II. Determinatibn of Chloride in Sodium Phenolate Solutions (Results reported as milliliters of 0.10N silver nitrate) Chloride M1. Added Found 0.1N 0.05N 0.05N Regular Copper soh. Sample4 Sac1 (XH&S NH,CN Calcd. proc. omitted Synthetic ... ... ... O . l O e 0.10, 0.15, 0.10 0.10, 0.10 sodium 1.00 ... ... 1.10 1.10, 1.10 1.10,1.10 phenolate* 2.00 ... . . . 2.10 2.10.2 10 2.10, 2.15. 2.10 5.00 . . . 5.10 5.10; 5 . 1 3 5.10; 5.15’ 5.00 1.00 5.10 5.10, 5.15 5.60, 5.65 5.00 ... i.oo 5.10 5.10,5.05,5.10 5 . 5 0 , 5 , 5 5 5.00 1.00 1.00 5.10 5.15, 5.10 6.05, 6.10 .
Dilute crude sodium ahenolate
. .. 0.50
1.00
I
.
...
... ...
...
... ...
7 . 3 ~ 7.3,7.3,7.3 7.8 7.8,7.8 8.3 8.3.8.3
7.9,7.9,7.8
... ...
Concentrated .. . ... . . . 2.6c 2 6, 2.6, 2 . 6 2.7, 2.7 crude so1.00 ... . . . 3.6 3.6, 3 . 6 ... dium pheno- 2.00 ... ... 4.6 4.6,4.6 ... late 3.00 ... . . . 5.6 5.6, 5 . 7 ... Samples were 25 grams except concentrated crude sodium phenolate, for which 5gram samples were used. Somewhat sharper end point obtained with synthetic samples permits use of one more significant figure. Average value.
sample indicated negligible chloride on second extraction. I n general, a g r e e ment of results obtained by the two procedures appears to be satisfactory. The present work indicates a usable range of approximately 1 t o at least 16 mg. of chloride per 25 grams of sample. The average analysis time using the MIBK procedure was approximately 20 minutes; the conventional method (1) requires 1.5 t o 2 hours. CRUDE SODIUM PHENOLATE SOLUTIONS
Crude sodium phenolate solutions are aqueous solutions containing dissolved and suspended coal t a r products, inorganic chlorides, sulfides, cyanides, etc., in addition to sodium phenolate. l I I B K extraction used in conjunction with copper precipitation in acidic solution serves to eliminate interferences with chloride determination. Copper Nitrate-Nitric Acid Reagent. Dissolve 1 gram of copper nitrate and 50 ml. of nitric acid (sp. gr. 1.42) in distilled water and dilute t o 1 liter. All other reagents are as used for coal tar products. Procedure. DILUTECRUDE SoDIUM PHENOLATE. T o a 125-ml. pearshaped centrifuge tube or separatory funnel, add 25 grams of sample and 25 ml. of copper nitrate-nitric acid solution. If t h e resulting solution is not acid t o p H paper, use a higher concentration of nitric acid in t h e reagent solution. T h e p H must be
2040
ANALYTICAL CHEMISTRY
below 3 . Add 40 t o 50 ml. of M I B K and shake the container vigorously for 3 t o 4 minutes. Centrifuge for 2 minutes a t high speed or allow the mixture t o settle in a separatory funnel for 5 minutes. Filter the aqueous phase through a qualitative filter, collecting the filtrate in a graduated cylinder. Withdraw 10 ml. of the filtrate and test for copper with hydrogen sulfide solution. If copper is shown t o be present, take 25 ml. of the remaining filtrate and neutralize with solid sodium bicarbonate. Add 2 grams of activated carbon, heat to boiling, filter through a qualitative filter, and adjust the p H to 6.5 to 7 mith solid bicarbonate and nitric acid. If the sample does not contain any ammonium ion, add only solid bicarbonate until no more effervescence occurs. Titrate with 0.10N silver nitrate, using 2 ml. of 5% dichromate solution as indicator (3). Multiply the silver nitrate titer by 2 to calculate total chloride. Where higher accuracy is required, wash the filter with 25 ml. of distilled water and collect the filtrate and washings in a 100-ml. volumetric flask. Withdraw suitable aliquots for the copper test and titration. If extraordinarily large amounts of sulfide are present, the copper lvill be entirely consumed. I n this case, it is most convenient to analyze a new sample, using a more concentrated copper nitrate solution. A large excess of copper is to be avoided. CONCENTRATEDCRUDE SODIUM PHENOLATE. Use a 5-gram sample, 75 ml. of copper nitrate-nitric acid
solution, and 20 to 25 ml. of MIBK. Proceed as above, but titrate a 40-ml. aliquot of filtrate. Results. The results obtained with this procedure are reported in Table 11. A synthetic sodium phenolate solution was prepared using a small amount of low-chloride tar. To this and t o t h e crude sodium phenolate solutions were added t h e indicated amounts of chloride, sulfide, and cyanide. For comparison, several of these solutions were analyzed by t h e recommended procedure, but omitting the copper precipitation. The results indicate that chloride recovery by this method is quantitative and that precipitation with copper serves as a satisfactory means of eliminating inorganic interferences. CONCLUSIONS
The procedure using cold extraction with water-methyl isobutyl ketone mixture is satisfactory for determination of water-soluble chloride in coal tar products and crude sodium phenolate solutions. Precipitation with copper can be used to eliminate inorganic interferences such as sulfide. The determination is rapid, convenient and sufficiently accurate for routine use. Although only certain coal tar materials are considered in the present paper, the method would appear to offer a satisfactory approach to the determination of water-soluble chlorides in a wide range of organic materials and residues. LITERATURE CITED
Barrett Division, Allied Chemical & Dve Cora. Tentative Method B-26-T. 25,’1957. rdey, L., Bgnyai, E., Magyar Tudomhnuos Akad., VIZ Oszt., Kozl. 3, 525 (1953). (3) Kolthoff, I. M., Sandell, E. B., “Textbook of Quantitative Inorganic Analysis,” 3rd ed., p. 542, Macmillan, New York, 1952. (4)Ibid., p. 548.
(1)
(2pk.
RECEIVEDfor review January 27, 1958. Accepted July 16, 1958.
Correction I n the article on “Determination of Fluoride Ion by Turbidimetric Titration” [JJ7. W.Brandt and A. A. Duswalt, Jr., ANAL. CHEM. 30, 1122 (1958)], the authors of reference 4 should have been given as Elving, P. J., Horton, C. A,, and Ji7illard,H. H.
