INDUSTRIAL AND ENGINEERING CHEMISTRY
646
on its side, and the formation of a lather is observed. This procedure is continued until a lather is formed which covers the entire surface of the liquid and lasts for 1 minute. If the test requires more than 7 ml. of soap solution, an aliquot portion is diluted to 50 ml. with distilled water so that the final end point will be less than 7 ml.
Calculation of Results
TABLE IV. OPERATOR’S TOLERANCE Present as CaCOa Cs. Mg P.p.m. 21.7 54.2 108.4
The calcium content of the sample as p. p. m. of calcium carbonate is obtained from the formula [Ml. of soap (titrated)
- 0.20 ml.]
X
Effect of Ions I n order to determine whether other ions usually found in industrial water interfere with the test, various amounts of silicate, sulfate, bicarbonate, and iron were added to different samples; they did not noticeably affect the accuracy of the method, as shown in Table 111. Since ammonium chloride is added in the determination, chloride can also be regarded as noninterfering.
Industrial and Synthetic Waters A series of synthetic samples was analyzed by several different operators (Table IV). The maximum error was small and on a par with the standard soap method. A list of industrial waters that have been analyzed is given in Table V, showing that good accuracy can be expected from this method.
Conclusions This method gives accurate results for calcium in the presence of magnesium, and is as easily executed as the standard soap method. It is not affected by normal concentrations of ions found in industrial waters. The difference between a total hardness determination by the usual Clark method and by the method described reveals the approximate hardness due to magnesium. It is therefore possible to determine distribution of hardness in terms of calcium and magnesium
P.p.m. 86.7 54.2 0
Ca as CaCOa Found by Operator B C D
A P.p.m. 21 51 106
P,p.m. 24 54 105
P,p.m. 20 53 106
P.p.m. 23 50 106
OF INDUSTRIAL WATERS TABLE V. ANALYSIS
Test
1000 X 1.14 = p. p. m. of Ca as CaCOa No. of ml. of sample
Vol. 14, No. 8
KO.
Source
1
Feed Raw Raw Raw Well City Test well Well Test well Well City Well Well Well Well
2 3 4 5
6
7 8 9 10 11
12 13
14 15
Gravimetric Ca as Mg as CaCOa CaCOs P. p . m . 19.7 35.8 46.9 56.7 171.4 268 156.5 26.1 372.2 370 81.7 472 183.6 322.6 497
Dilution Factor
Ca Found as CaCOa
Total Hardness by Soap
1 1
18 35 46 53 168 256 158 26 360 380 SO 465 184 320 485
29 50 73 64 196 480 220 46 570 555 122 730 270 460 730
P . p . m.
...
... ...
...
29.4 202 76 17.2 195 176.4 41.7 242.4 83.3 141 245
1 1 2 5 2 1 5 5 1 5 2 5 5
by this new modified method. Its application t o boiler waters will be the subject of a later paper.
Acknowledgment The authors are indebted to C. A. Koll, chief chemist, for his suggestions and to W. H. & L. D. Betz for making this investigation possible.
Literature Cited (1) American Public Health Association, “Standard Methods of Water Analysis”, 8 t h ed., p. 59, 1936. (2) Breaseale, E. L., and Greene, R. A., J. Am. Water W o r k s Assoc., 30, 1040 (1938). (3) Clark, T., Chem. Gaz., 5 , 100 (1847). (4) Durovdier, R., Ann. fals.,27, 273 (1934). (5) Froboese, V., 2. anorg. allgem. Chem., 89, 370 (1914). (6) Kellog, Chemist-Analyst, 29, 4 (1940). (7) Langelier, W. F., J . Am. Water Works Assoc., 32, 279 (1940). PRBSENTED before the Division of Water, Sewage, and Sanitation Chemistry CHEMICAL SOCIETY, Memphis, Tenn. a t the 103rd Meeting of the AMERICAX
Colorimetric Determination of Phenothiazine with Palladous Chloride LYLE G. OVERHOLSER
C
AND
JOHN H. YOE, University of Virginia, Charlottesville, Va.
OSSIDERABLE interest has been manifested in the use of phenothiazine as a n insecticide and in the determination of small amounts found in spray residues. Eddy and D e Eds ( 2 ) determined small amounts of phenothiazine colorimetrically by oxidizing a n alcoholic solution t o a highly colored red compound with bromine water. Recently, Cupples ( I ) reported additional information concerning this reaction. The authors have observed that phenothiazine reacts with a number of inorganic ions. Most of these ions are oxidizing agents and the red or green colored solutions formed are due to an oxidation of phenothiazine. Palladous chloride reacts with phenothiazine, yielding a dark blue colored solution or precipitate which is not a n oxidation product but a complex having the formula Pd(CI2H&S)2C12. A procedure for the colorimetric determination of small
amounts of phenothiazine based on this reaction, methods for the preparation of the complex, and a description of its properties are presented in this paper.
Reagents A compound obtained ffom the Eastman PHENOTHIAZINE. Kodak Co. (P1456) was purified by recrystallization from ethyl alcohol. The purified compound melted a t 182” C. An acetone solution containing 0.05 mg. per ml. was used. (An ethyl alcohol solution of the same concentration may be used.) The solution slowly acquires a pink color; for this reason a fresh solution should be prepared at least once a Fveek. SODIUM ACETATE-HYDROCHLORIC ACID BUFFER. Fifty milliliters of 1 M sodium acetate were added to 50 ml. of 1 M hydrochloric acid and the solution was diluted to 250 ml. with water. This buffer has a pH of 2.6 which increases Bo 2.9 upon dilution of 5 ml. to 25 ml. with water. PALLADOCS CHLORIDE.A standard palladous chloride solution containing 1 mg. of palladium per ml. in 1 M hydrochloric
ANALYTICAL EDITION
August 15, 1942
mll FIGURE1. REL.4TIVE ABSORPTIONOF PALLADOES CHLORIDEPHEXOTHIAZINE COMPOUND I. Ethyl acetate medium 11. Buffer medium
acid was diluted with water to give a solution containing 0.03 mg. of palladium per ml.
Procedure Transfer 5.0 ml. of the sodium acetatehydrochloric acid buffer to a 28-ml. volumetric flask and, after adding 1.0 ml. of the palladous chloride solution, add the amount of acetone required to give a constant amount in the standards and unknowns. Limit the acetone concentration t o 20 per cent and preferably less. Add sufficient water t o brin the solution to within several milliliters of the mark, add the fesired volume of phenothiazine solution, make up to the mark with water, and mix well. The unknowns are prepared in the same manner, adding the desired volume of an acetone solution containing the sample to be determined. Color comparison should be made immediately and may be performed with 50-ml. Nessler tubes or other suitable cylinders. The increments of phenothiazine used in preparing the standards are as follows: 0 t o 40 micrograms, 2.5 micrograms; 45 to 100 micrograms, 5 micrograms, These values also correspond to the sensitivity at the respective concentrations. Best results are obtained usin 40 micrograms or less. Amounts of phenothiazine in excess o f 100 micrograms may be determined, but difficulty in the color matching frequently arises due to decreased stability .of the colored solutions at these higher concentrations.
Discussion A blue to purple solution is formed, depending upon the amount of phenothiazine added to the buffered solution containing palladous chloride. The colored complex is completely removed if the solution is extracted with ethyl acetate. In the process the color of the complex changes, resulting in a red ethyl acetate solution. This suggests the possibility of performing the color comparison in this medium. The red color abserved in the ethyl acetate, however, is less stable than the blue color formed in the buffered solution and consequently less suitable for colorimetric purposes. It might, however, have some application for the qualitative detection of phenothiazine where interfering colors are present. The stability of the blue solutions, while more satisfactory than that in ethyl acetate, is not so great as might be desired f o r colorimetry, but by preparing the standards and unknowns a t as nearly the same time as possible and comparing the color immediately, satisfactory comparisons are obtainable. This is especially true when determining small amounts .of phenothiazine where the stability of the colored solution is greatest. Attempts to stabilize the colored solutions by the addition of gelatin, gum ghatti, and gum damar were unsuccessful.
642
The acetone concentration should be controlled closely because the intensity of the color formed is dependent upon it. h constant amount should be used as determined by the volume of the unknown that is to be employed. Where possible, a constant volume of 1 or 2 ml. of acetone is recommended and in no instance should it exceed 5 ml. A marked decrease in the sensitivity results a t higher acetone concentrations. When the sample containing phenothiazine must be prepared for analysis with ethyl alcohol as a solvent, the method is applicable if an alcoholic solution of phenothiazine is used for the preparation of the standards. The methods using acetone or ethyl alcohol are similar. A constant amount of ethyl alcohol must be used in the standards and unknowns and should not exceed 20 per cent. The use of buffered solutions is recommended because small amounts of acids or salts alter the color intensity considerably in unbuffered solutions. Using the designated buffer concentration, the limits of acids or salts that may be present without error are: 0.05 ml. of 1 M hydrochloric acid and 0.2 ml. of 1 1M sodium chloride. The stability of the colored solutions formed is increased by the presence of the buffer. The reverse procedure-i. e., addition of palladous chloride to phenothiazinemay be employed but the colored solutions formed are less stable and less reproducible. Phenothiazine may also be used for the detection of palladium but is less satisfactory than other reagents previously employed (3).
Preparation and Properties of Complex The complex must be precipitated from acetone-water or alcohol-water mixtures in order to obtain a pure product. Otherwise, a compound contaminated with phenothiazine results, owing to the low solubility of the latter in aqueous medium. Transfer 5 ml. of the palladous chloride solution ( 5 mg. of palladium) to a beaker, dilute with water to 100 ml., and add 80 ml. of acetone (or alcohol). Add 10 ml. of a filtered acetone solution containing 40 mg. of phenothiazine. After the suspension has stood for several hours, filter through a sintered-glass crucible and dry at 120" for 2 hours. The product obtained is a bluish-black solid, insoluble in water, sodium acetatehydrochloric acid buffer, and carbon tetrachloride; sparingly soluble in ethyl alcohol; moderately soluble in ether and ethyl acetate; and readily soluble in acetone and dioxane (deep purple colored solutions). The complex is destroyed by concentrated acids and bases. The complex has the composition Pd(ClzHgNS)zC12 as found by analysis. Calculated for Cz4HlsN2SzPdCI,: C, 50.07; H , 3.14; Pd, 18.52; C1, 12.31. Found: C, 50.40; H , 3.47; Pd, 18.30; C1, 12.2. Relative absorption data for the colored solution formed in the presence of the sodium acetate-hydrochloric acid buffer and the red solutions obtained by extracting with ethyl acetate are plotted in Figure 1. These measurements were made with a Beckman spectrophotometer, Model D. Although the solutions are not sufficiently stable to permit extensive use of transmittancy measurements, a limited application such as this is possible. Curve I1 was obtained for a solution prepared according to the procedure given for the colorimetric determination using 1 ml. of phenothiazine. Curve I represents the values obtained after extraction with ethyl acetate. The general character of the two curves is similar but the maximum shifts to a shorter wave length upon extraction.
Literature Cited (1) Cupples, H. L., IND.ENG.CHEM.,ANAL.ED.,14, 53 (1942). (2) Eddy, C. W., and De Eds, Floyd, Food Research, 2, 305 (1937). (3) Overholser, L. G., and Y o e , J. H., J . Am. Chem. SOC.,63, 3224 (1941).
