Determination of Potassium Perchlorate in the Presence of Chloride Ion by Ion Exchange and Nonaqueous Titration E. W. ALBAUGH,' J. E. BUHLERT, and R. M. PEARSON2 Aeroiet-General Corp., Sacramenfo, Calif.
b A method for the determination of perchlorate ion in the presence of aluminum chloride and hydrochloric acid i s described. The procedure is based on conversion of the salts to their acids b y cation exchange. The generated perchloric acid is titrated in the presence of residual hydrochloric acid using nonaqueous sodium acetate solution.
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satisfactory methods for the determination of perchlorate ion involve the reduction of the perchlorate ion to chloride ion with subsrquent titration of the resulting chloride ion. The relative merits of these methods have been reviewed by Kura, Kober, and Berl (S), Crump and Johnson ( I ) , and S a b a r and Raniachandran HE M05T
( 4 )*
When these methods are applied t o materials that contain chloride, such as mixtures of aluminum chloride and potassium perchlorate, it is necessary to apply a correction. Normally, this is done by titrating a separate sample with silver nitrate. If the amount of chloride is comparatively large, the error in the final calculation can be very significant. To overcome this difficulty, a method has been developed which consists of converting the mixture of perchlorates and chlorides t o the acids. The perchloric acid is then titrated nonaqueously with sodium acetate solution ( 2 ) . EXPERIMENTAL
Apparatus. TITRATOR. For these analyses a Precision-Dow Recordomatic titrator equipped with a calomel-glass electrode system was used. IONEXCHANGE COLUMNS.The ion exchange columns utilized were similar t o those described by Seim, Morris, and Frew (6). For samples with 30 to 55% potassium perchlorate the column used had a IO-cm. length, a 2-em. inside diameter and s resin bed 7 cm. high. Present address, Koppers Co., Inc., Pittsburgh, Pa. Present address, Department of Chemistry, University of California, Davis, Calif.
For samples containing 670 potassium perchlorate a column 41 em. long with a n inside diameter of 2 em. and a resin bed 34 em. high was utilized. Reagents. RESIN. Dowex 50 X 8, 50- to 100-mesh ion exchange resin in t h e hydrogen form was used in all determinations. After each determination the resin was regenerated by passage of 6 N hydrochloric acid until potassium was no longer detected in the effluent and was then washed with distilled water until the p H reached t h a t of the wash water. PREPARATIOX OF o.lAr 80DIUlzI ACETATE SOLUTION.Dissolve 13.6 grams of C2H30&a 3H20 in 1 liter of 9 to 1 glacial acetic acid-acetic anhydride mixture. Standardize the solution by titration n-ith standard 0.1N perchloric acid in glacial acetic acid. STAXDARD 0.liV PERCHLORIC ACID IS GLACIAL ACETICACID. Nix 8.5 ml. of 72Yc perchloric acid with 200 ml. of glacial acetic acid, add 20 ml. of acetic anhydride, and dilute to 1 liter with glacial acetic acid. Standardize the perchloric acid by titration against potassium acid phthalate. Weigh approximately 0.5 pram of potassium acid into a 150-ml. beaker. Bdd 60 ml. of glacial acetic acid and then heat for a few minutes to effect solution. Cool and then titrate with perchloric acid to a potentiometric endpoint. PROCEDURE FOR MIXTURES OF POTASSIVM PERCHLORATE AND ALUhXINU&f CHLORIDE.Pipet an aliquot of the solution containing 1 to 2 meq. of potassium perchlorate into the fluid reservoir of the ion exchange column and place a 300-ml. Berzelius beaker under the outlet of the column to collect effluent. Adjust the stopcock so that a flow rate
Table 1.
through the column of 4 ml. per minute is obtained. When the fluid reservoir is empty, rinse it with two 10-ml. portions of water. Remove the reservoir and rinse the neck of the column with water, adjust the fluid level, rinse the column again, and adjust the fluid level to '/a inch above the resin bed. Replace the fluid reservoir and pass 150 ml. of distilled water through the column a t a flow rate of 4 ml. per minute. Remove the beaker containing the effluent, cover with a watch glass, and place it on a hot plate. Boil the solution a t a very slow rate until a volume of 6 to 7 ml. is reached. Watch the sample closely during the final stages of evaporation so that the volume does not become too small, Remove the sample from the hot plate, cool, and slowly add 100 ml. of a 3 t o 1 mixture of acetic anhydride and glacial acetic acid. This operation must be done in a hood as the reaction is violent when the dehydration mixture is added too rapidly. Allow the sample to cool; then titrate on the PrecisionDow Recordomatic titrator (or equivalent) with 0 . 1 s sodium acetate solution. RESULTS AND DISCUSSION
Three mixtures containing 45,70, and 9461, aluminum chloride and 55, 30, and 6% potassium perchlorate, respectively, were analyzed. These samples were prepared from solutions of aluminum chloride and potassium perchlorate. The results are shown in Table I. The HC1 could not be completely removed during the evaporation, therefore a nonaqueous differential tech-
Potassium Perchlorate Analysis
Sample A Sample B Taken Found Taken Found (yoKC104) (% KC1O4) (% KC104) (% KC104) 54.77
Mean Std. dev. Range Mean error
54.48 54.44 54.23 54.23 54.20 54.16 54.29 1 0 . 14 0.32 -0 . 4 8
30.43
30.30 30.22 30.19 30.17 29.95 30.17 10.13 0.35 -0.26
Sample C Taken Found (% KC104) ( % Kclos) 6.09
6.12 6.12 6.04 6.02 6.08 10.05 0.10
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VOL. 35, NO. 2, FEBRUARY 1963
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nique had to be used. Conversion of the aqueous system to a nonaqueous one was first carried out by the addition of a 1 to 1 mixture of acetic anhydride-acetic acid. The solution was then heated to boiling, cooled, and titrated. This method produced a sharp break at the equivalence point but gave low results. Elimination of heating after addition of the acetic anhydride produced results which Tvere close to theoretical; however, residual water caused the break in the titration curve to be too obscure for precise results. Changing the ratio of acetic anhydride to acetic acid from 1 to 1 to 3 to 1 in the dehydration mixture caused a higher temperature from the heat of reaction resulting in adequate removal of water without additional heating. Also, the break a t the equivalence
point, was sharpened adequately without producing conditions which would lead to a loss of perchloric acid. While the results on Samples A and B in Table I are somewhat lower than theoretical, they are sufficiently precise and accurate for control purposes. The elapsed time on the method is 3 hours; hovr-ever, most of this time does not require the attention of an analyst. While samples are washing through the ion exchange columns and during most of the evaporation, the operation can be left completely unattended. The critical part of the procedure is the final stage of evaporation. If too large a volume remains, not all of the water will be removed by the acetic anhydride and the end point will not be distinct; if the evaporation is carried too far, perchloric acid
will be lost. However, after completing a few samples, the analyst has no trouble in judging the proper place to discontinue the evaporation. I n general, the method is straight forward and lends itself very well t o routine operations. LITERATURE CITED
(1) Crunip, N. L., Johnson, N. C., ANAL. CHEX.27, 1007 (1955). (2) Fritz, J. S., “Acid-Base Titrations In Nonaaueous Solvents.” The G. Fredrick Smith‘Chemical Co., Columbus, Ohio. (3) Kurz, E., Kober, G., Berl, M., ANAL. CHEM. 30, 1983-6 (1958). (4) Nabar, C. M., Ramachandran, C. R., Ibid., 31, 263-5 (1959). ( 5 ) Seim, H. H., Morris, R. J., Frew, D. W., Ibid., 29,443-6 (1957). RECEIVED for review September 4, 1962. Accepted December 12, 1962.
Spectrophotometric Determination of Prima ry, Secondary, and Tertiary Fatty Amines in Aqueous Solution RONALD M. SILVERSTEIN Betz laboratories, Inc., Philadelphia, Pa.
b Conditions are established for the spectrophotometric analyses of aqueous solutions of fatty amines in the parts per million concentration range. A method is developed whereby primary, secondary, and tertiary amines may b e differentiated. These amines react with methyl orange a t pH 3 to 4 to form a yellow complex soluble in an organic liquid. The color intensity is a direct measure of total amine concentration. In the presence of salicylaldehyde, primary amines do not react with methyl orange. In the presence of acetic anhydride, only the tertiary amine reacts with methyl orange. Analyses of aqueous mixtures of octadecylamine, dioctadecylamine, and trioctadecylamine in the 0- to 2-p.p.m. range show an accuracy to 0.1 p.p.m. The analysis is nonspecific and may b e applied to various amines.
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methods for the spectrophotometric determination of amines have been described. Critchfield and Johnson ( 2 ) determined primary amines in the presence of secondary amines by first complexing the primary amine with copper and then determining the copper in this complex. Hershenson and Hume ( 5 ) ARIOUS
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ANALYTICAL CHEMISTRY
produced a yellow color in alcohol by reacting cupric chloride with the amine. Munter (12) used copper plus ;izurol B dye t o form a color in his lake method. The reaction of primary or secondary amines with l-fluoro-2,4-dinitrobenzene (8) mas found to be a n effective way t o determine these amines. 1Iilun (9) reported on the effectiveness of determining primary amines via the formation of a Schiff’s base. In conjunction with Kelson (11), X l u n also developed a technique of determining primary and secondary amines in the presence of each other. Pearce (13) showed that the reaction of amines with sulfonphthalein offers an excellent method for determining amines. Many other approaches have also been advanced. Sass et al. (14) determined tertiary and quaternary amines in the presence of one another. Many analyses involved the titration of amine with acid (3, 6, 7). Others depended upon preliminary reactions before titration (1, 4, 10). This paper deals with the quantitative identification of primary, secondary, and tertiary fatty amines in the presence of each other. The analytical method can be effectively applied t o aqueous solutions having a total amine concentration of from 0 t o 2 1J.p.m. .Iqueous mixtures of the three amines are analyzed by
separate analyses of three portions of the solution. One solution is thoroughly mixed with an appropriate dye and a water-immiscible liquid at an adjusted pH. The resulting color formed in the immiscible liquid is a measure of the total amine present. The same technique is applied to the second portion of the solution, except that a small quantity of salicylaldehyde is added. The resulting color is a measure of the secondary and tertiary amine present. The tertiary amine is determined using the same technique, except that acetic anhydride is substituted for salicylaldehyde. EXPERIMENTAL
Apparatus. ,111 routine measurements were made with a Beckman Model D U spectrophotometer using 1-cm. matched silica cells. Reagents. Acid Buffer. Dissolve 125 grams of potassium chloride and 70 grams of sodium acetate trihydrate in 500 ml. of distilled water. Add 300 ml. of glacial acetic acid and bring t o 1 liter with distilled water. Salicylaldehyde Solution. Dilute 5 ml. of redistilled salicylaldehyde (start with a 100-ml. batch, discard a 10-ml. forerun, and collect 70 ml. in a brown glass bottle) to 1 liter with ethylene dichloride. This solution is stable for approximately one month.
