1286
ANALYTICAL CHEMISTRY
(34) Ibid.. 228. 401 (1949). Ibid.: 229: 51 (1949).
(75) Marin. Y., and Duval, C., Anal. Chim. Acta, 4, 393 (1950). (76) hIamrow, W ~and , Rluthmann, F., Z . anorg. Chem., 13, 209 (1897). (77) JIerritt. L.L., and Walker, J. K., ISD. Eac,. CHEM., ai^.\^.. ED., 16, 387 (1944). (78) Moeller, T., and Fritz, S . D., ASAL. CHEW,20, 1055 (1948). (79) Morandat, J., and Duval, C.. Anal. Chini. Acta, 4, 498 (1950). 180) Muller. I\-..Ber.. 35. 1587 (1902). (81) Sieuaenburg, C. J. Van, and Hoek. T Van der, Mzkrochemie, 18, 175 (1935). (82) I’anchout, S.,and Duval, C., Anal. Chim. Acta, 5, 170 (1951). (83) Parks, W.G., and Prebluda, H. S., J . An. Chem. SOC.,57, 1676 (1935). (84) Pauling, L., Ibid., 55, 1895, 3052 (1933). (85) Pavelka, F., and Zucchelli, A., Mikrochemie, 31, 69 (1943). (86) Peltier, S., diplame d’btudes supbrieures, Paris, June 11, 1947. (87) Peltier, S.,and Duval, C., Anal. Chim. Acta, 1, 346 (1947). (88) Ibid., p. 351. (89) Ibid., pp 355, 348, 362. (90) Ibid., p. 408. (91) Ibid., 2, 211 (1948). (92) Peltier, S.,and Duval, C., C o m p t . rend., 226, 1727 (1948). (93) Pirtea, T. I., 2. anal. Chem., 118, 26 (1939). (94) Rammelsberg, C., Pogg. Ann., 44, 577 (1838); Ber., 1, 70 (1868). (95) Rby, H. N., J . Indian Chem. SOC.,17, 586 (1940). (96) Robinson, P. L., and Scott, W. E., 2. anal. Chem., 88, 417 11932). (97) Rogers. L. B., and Caley, E. R., IND. ENG.CHEM.,A N ~ LED., . 15, 209 (1943). (98) Solodovnikov, P. P., Trans. Kirov. I m t . Chem. Tech. Kazun, NO.8, 57-60 (1940). (99) Soule, B. A., J . Am. C h m . Soc., 47, 981 (1925). (100) Spacu, G., and Dick, J., 2. anal. Chem., 78, 241 (1929). (101) Spacu, G., and Dima, L., Ibid., 120, 317 (1940). (102) Spacu, G., and Macarovici, C. G., Ihid., 102, 350 (1935). (103) Spacu, G., and Spacu, P., Ibid., 96, 30 (1934). CHEM.,21, 986 (104) Spakowski, A. E., and Freiser, H., .%N.~L. (1949). (105) dtachtchenko, J., and Duval, C., A M I . Chim. Acta, in press
Duval, C.’, A&. Chim.Acta, 2, 92 (1948). Ibid., p, 432. Ibid., 3, 163 (1949). Ibid., p. 335. Ibid., p. 338. Ibid., 4, 55 (1950). Ibid., p. 160. Ibid., p. 190. Duval, C., Chim. anal., 31, 177 (1949). Duval, C., Compt. rend., 224, 1824 (1947). Ihid., 226, 1276 (1948). Ibid., 227, 679 (1948). Duval, C., Conference held at Centre de Perfectionnement technique, Nov. 22, 1945; Chim. anal., 31, 173, 204 (1949). Duval, C., Conference held a t Ier CongrBs International de Microchimie, Graz, July 6, 1950; Mikrochemie. 36, 425-65 11951) \ - - - - I
Ibid., 35, 242 (1950).
Duval, C., Troisihe Rapport de la Cornmissiori des ieactifs nouveaux, Paris, Librairie Istra, 1948. Duval, C., and Dat Xuong, Ng., Anal. Chim. Acta, 5, 180 (195 1).
Ibid., in press (article on mercury). Duval, T., and Duval, C., Anal. Chim. Acta, 2, 103 (1948). lhid., p. 207.
Ibid., p. 223. Duval, R., and Duval, C., Ibid., 5, 71 (1951). Ibid., p. 84. (60) (61) (62) (63)
Duval, C., and Morette, A,, Compt. rend.. 230. 545 11950): Anal. Chim.Acta.. 4. 490 (1950). ’ Feigl, F., Ber., 56,2083’(1923). Friedrich, K., Metallurgie, 6, 175 (1909). Garrido, J., Anales f6s. 8 q u h . (Madrid),43, 1195 (1947). Gentry, C. H. R., and Sherrington, L. G., Analyst, 70, 419
(1945). (64) Girard, J., Chim. ana2. 4, 382 (1899). (65) Hecht, F., and Donau, J., “Anorganische Mikrogewichtsanalyse,” p. 205, Vienna, Librairie Springer, 1940. (66) Herrrnann-Gurfinkel, M.. Bull. SOC. chim. Belg., 48, 94 (1939). (67) Jamieson, G. S., and Wrenshall, R., J . I n d . Eng. Chem., 6 , 203 (1914). (68) Jilek, A., and Rysanek, A., Collection Czechoslov. Chem. Commum., 10, 518 (1938). (69) Jolibois. P.. and L e f h e . H.. Comat. rend.. 176. 1317 (1923). . . (70j Kolthoff, I.’ M., and Bendix,’ G. H., IND.ENG.’CHEY., ANAL. ED., 11, 94 (1939). (71) Kolthoff, I. M.,and Meene, G. H. P. van der, 2. anal. Chem., 72, 337 (1927). (72) Krustinsons, J., Ibid., 125, 98 (1943). (73) Kumins, A., ANAL.CHEM.,19, 376 (1947). (74) Marin, Y., dipl6me d’btudes supbrieures, Paris: Nov. 28, 1949.
(article on zirconium).
.
(106) Vanino, L., and Guyot, O., Arch. Phann., 264, 98 (1926). (107) Vejdilek, Z., and Vorisek, J., Chem. Obzor, 20, 138 (1945). (108) Voter, R. C., Banks, C. V.,and Diehl, H., BNAL.CHEM.,20, 459 (1948). (109) Wenger, P. E., Cimerman, C., and Corbaz, A., Mikrochim. Acta, 2, 314 (1938). (110) Willard, H. H., and Hall, D., J . A m . Chem. SOC.,44, 2219 (1922). (111) Woy, R., Chem. Ztg., 21,441 (1897).
RECEIVED December 13, 1950,
Phenyl Mercuric or Ethyl Mercuric Compounds Direct Determination of Several Compounds in Dilute Aqueous Solution V. L. MILLER, DOROTHY POLLEY,
T
HE
AND C.
J. GOULD, Western Washington Experiment Station, PuyalIup, Wash.
diphenylthiocarbazone (dithizone) procedures €or analysis of small amounts of metals are well known ( 2 , 5 ) , but the use of the dithizone procedure for analysis of intact metallo-organic compounds has not been previously reported. FVebb el al. (10) prepared and made elemental analyses of several compounds resulting from the reaction of dithizone with organic mercurials. Earlier, Steiger ( 7 ) reported that diphenyl mercury or copper acetylide rubhed with a crystal of dithizone gave a yellow or red color. However, in his methods of analysis of tetraethyllead or nickel carbonyl, the metallo-organic compound was first decomposed (8). Similarly, organic mercurials have been analyzed following decomposition (6, 9). The method here recorded may be used to determine several ethyl mercuric or phenyl mercuric cornpounds directly in the presence of many metal ions, including the mercury ions. Qualitative differentiation between phenyl and ethyl mercuric compounds is possible.
REAGENTS
D u Pont C.P. reagent hydrochloric acid is used without further purification. All water and chloroform are redistilled from glass (6). Reagent 1. Concentrated hydrochloric acid is diluted to 3.5 S. To this is added 1 ml. of dithizone-extracted 207, hydroxylamine hydrochloride for each 17 ml. of the acid. Reagent 2. Concentrated hydrochloric acid is diluted to 3 S. Reagent 3. A solution of sodium acetate is adjusted to p H 4.5 with glacial acetic acid, diluted t o normal concentration with respect to sodium acetate, and rigorously purified by dithizone extraction. Reagent 4. Eastman Kodak white label dithizone is dissolved in chloroform at the rate of 1 mg. per ml. This solution is kept refrigerated and diluted as needed. Reagent 5. Standard phenyl mercuric compounds. One hundred and fifty milligrams of C.P. phenyl mercuric acetate (Berk) are dissolved in 3 to 5 ml. of glacial acetic acid and diluted volumetrically to 250 ml. The strength may be checked by titrating with 0.005 h’ thiocyanate by the Volhard procedure.
V O L U M E 2 3 , NO. 9, S E P T E M B E R 1 9 5 1
The investigation was begun to find a method of analysis that could be used to determine the stability of organic mercurial fungicides in the presence of soil and plant material. The method may be used to determine approximately 1 to 150 micrograms of phenyl mercuric or ethyl mercuric compounds in dilute aqueous solution in the presence of many metal ions, including inorganic mercury. Several other organic mercurial fungicides do not interfere. The usual wet combustion or hydrolysis of this type of mercury compounds is avoided. This is the first report of a method of analysis for intact organic mercury compounds using the dithizone reagent. It may lead to development of direct procedures for other organic mercury compounds, which are used as fungicides, bactericides, and medicinals.
Weighed amounts of other phenyl mercuric compounds, including the phthalate and salicylate, are dissolved in approximately 0.02 AT sodium hydroxide. Phenyl mercuric borate is dissolved in water. Reagent 6. Standard ethyl mercuric compounds. Fifty milligrams of ethyl mercuric phosphate are dissolved by long shaking in about 300 ml. of water and diluted to 500 ml. This solution is discarded when a precipitate is formed. Ethyl mercuric chloride and ethyl mercuric p-toluene sulfonanilide (supplied by G. F. Miles, E. I. du Pont de Semours 8i Co.) are dissolved a t the rate of 50 mg. per 500 ml. of 0.02 ,Ir sodium hydroxide by long shaking.
1287
photometric density of z micrograms of phenyl mercuric acetate and L2is the photometric density of I micrograms of ethyl mercuric phosphate. Several other ethyl mercuric compounds can be calculated from the percentage of ethyl mercury. The same principle applies to phenyl mercuric compounds. DISCUSSION
Preliminary Fork indicated that, of the common metal ions, copper would be the most likely to interfere in the analysis of phenyl or ethyl mercuric compounds by the above procedure (Table I). T o determine the best concentration of acid to use to prevent interference of copper, a series of experiments was conducted with several acid concentrations (Table 11). The number of extractions was varied. From the results of this trial, and as Klein (3) has reported that inorganic mercury may be partially extracted from 2 iV acid solutions, two extractions using 3 AV hydrochloric acid were selected. Although better results were obtained with three extractions, the slight improvement in accuracy did not seem to justify the extra step for ordinary work. Large amounts of mercuric compounds (approximately 1000 micrograms of mercury) in 20 ml. of water will cause discoloration of the dithizone in the separatory funnel containing Reagent 1. However, the 3 ’V acid in the second separatory funnel extracts the inorganic mercury from the chloroform solution of dithizone. The error caused by this dilution of Reagent 1 and contaminating mercury caused a positive error of not greater than 2% in the final result. Table I.
Effect of Copper Ion on Accuracy of Analytical Procedure
PROCEDURE
Eighteen milliliters of Reagent 1, 20 ml. of Reagent 2, and 5 ml. of Reagent 3 are placed in three small separatory funnels from dispensing burets. To the funnel containing Reagent 3 are added 15 to 20 ml. of rvater. Exactly 11 ml. of diluted dithizone solution containing approximately 10 micrograms per ml. are added to the funnel containing Reagent 1. Between 50 and 100 micrograms of one of the ethyl or phenyl mercuric compounds listed above, in 0.5 to 20 ml. of water or very dilute acid or alkali, are accurately measured into the first separatory funnel and the funnel is shaken vigorously for 1 minute. When the layers have separated, the chloroform is drained into the funnel containing Reagent 2. The shaking is repeated, and after separation the chloroform layer is transferred !o the separatory funnel containing Reagent 3. Following shakmg and separation, the percentage transmittance is determined in an Evelyn photoelectric colorimeter, using filter 620, with the macro model set for a 6-ml. volume with chloroform giving 100% transmittance. The green color of the unreacted dithizone is determined rather than the yellow of the organic mercury dithizonate. The values for unknown samples are determined by comparison with a standard curve. Although the method is designed to be used in the range of 50 to 150 micrograms of several ethyl or phenyl mercuric compounds, by using 8 ml. of dithizone solution containing 3 micrograms per ml., 1 microgram can be determined by the above procedure. Percentage transmittance is determined immediately. However, theee dithizonates seemed stable to ordinary laboratory light for 3 hours. The color stability may have been improved by the plesence of acetic acid in the buffer, as suggested by Klein (3) for other dithizonates. PREPARATIOS OF STANDARD CURVE
Known amount& of the compound to be tested are carried through the procedure described and the results are recorded on semilog graph paper. The curve follows Beer’s law. Ethyl mercuric compounds are not generally available in pure form. However, the amount of ethyl mercuric phosphate can be determined from the phenyl mercuric acetate curve with less than 2T0error from the formula L1 - 5oo = Lp, in which L, is the
CzHaHg,
Y
Original
Recovered
65 65 65
65 68 69
CaHsHg,
Recovered
74 74 74
75 79 83
-
50 100 200
Effect of Strength of Acid and Number of Extractions on Interference of Copper
Acid Normality 3.0 3.0 3.0 2.5 2.5 2.0 2.0
50 100 200
Y
Original
Table 11.
Cut+ Added, I
Added No. of (CzHsHg)rPOA, Extractions Y 87.5 87.5 75.0 87.5 87.5 75.0 75.0
cu++ Added, Y
100 100 100 100
100 70 70
Error from Cut
+
%
+ 2 + 5
+I1 + 8 1-8 + 5
+ 7
The method was developed to determine the stability of mercurial fungicide solutions in the presence of aoil. Therefore, possible interference from traces of most metallic ions and the decomposition products of the fungicides must be eliminated. Various ions were added singly a t the first step in the procedure and carried through the extraction process. In the presence of 50 to 80 micrograms of phenyl mercuric acetate, 1000 micrograms of manganese, iron, cobalt, nickel, zinc, silver, cadmium, tin (ous), mercury (ic), lead, or bismuth did not interfere. The noble metals and thallium were not tested, but the\- are not likely to be contaminants in ordinary work. If much copper is present, it gives an off-color to the dithizone solution. Mercury (ous) interferes to a less extent than copper. Although mercurous ions are reported to be a decomposition product of the organic mercurials ( I ) , the low solubility of most of its compounds precludes interference from this source except in rare cases. When mercurous nitrate was added to the first separatory funnel and then allov ed to stand, the interference from mercury (ous) could
ANALYTICAL CHEMISTRY
1288 Table 111. Effect of Standing Time on Mercury (ous) Interference in Ethyl Mercury Determination CpHaHg. Original 68 74 74 84 84 84
Table IV.
y
Hg + Added, y 100 200 200 200 300 500
Found 68 86 76 86 86 87
Time Elapse, Minutes 0 0 20 20 40 85
Comparison of Sensitivity of Method and of Interference of Cu + +
(Using carbon tetrachloride and chloroform as solvent for dithizone) Ethyl % Transmittance % Error Mercuric In In 100 y C u + + , 50 y C u + + , Chloride, y CHCh CClr CHCls CClr 75 23 48 ... ... 105 73 62 +5 +28 Phenyl Mercuric Acetate, y 60 90
25 68
29 54
+7
...
compounds to fungicide solutions which have been in contact with soil or plant material. Ethyl and phenyl mercuric compounds can be identified qualitatively by their relative stability in Reagent 1. The solution of the ethyl or phenyl mercuric compound is mixed with Reagent 1 without the addition of dithizone. Decomposition of phenyl mercuric compounds is appreciable in an hour, while ethyl mercuric compounds appear to be stable for several hours (Table VI). Webb et al. (IO)reported that the absorption spectra of ethyl mercury and mercury bisdithizonates are similar but not identical. This has been confirmed Jvith a chloroform solution of the dithizonates, using a Beckman Model D U spectrophotometer. Measurements were made in increments of 5 mp. It was found that the maximum and minimum absorption in chloroform of the reaction product of dithizone with phenyl mercuric acetate, ethyl mercuric phosphate, and salicyl-( yhydroxymercuri-p-methoxypropy1)-amide-o-acetic acid (obtained under the trade name Salyrgan) were identical. The minimum absorption of these compounds was 15 mp less than that of mercuric bisdithizonate.
+30
...
Table V.
be greatly decreased with ethyl mercuric compounds (Table 111). This may be due to complex formation (4). Carbon tetrachloride is used in many dithizone procedures. However, in the determination of ethyl or phenyl mercuric compounds, the sensitivity was less and the interference of copper was greater when a carbon tetrachloride solution of dithizone was used in the above procedure (Table IV). As no previous record of the dithizone method of analysis of organic mercury compounds has been found, several other organic mercurials were tested using the procedure outlined above. Although pyridyl mercuric acetate (a commercial product supplied by hfallinekrodt Chemical Works), p-aminophenyl mercuric acetate, and o-chloromercuripheno1 gave a similar yellow color reaction with neutral dithizone solutions in chloroform, they are retained in the aqueous acid in this determination. Procedure for analysis for these compounds was not perfected. The reaction takes place a t p H values above 2.5 and below 8.7. Below p H 2.0, the color formation was inhibited. The p H of 4.5 was selected because the acetate buffer is relatively resistant to small amounts of acid a t that pH, and there is less tendency for acid solutions to extract small amounts of metals from glass containers. The alkaline p H range is not recommended, because erratic results are sometimes obtained. Numerous compounds may be used in dithizone procedures for elimination of interfering elements. The materials tested in this investigation for the effect on the interference of copper included potassium thiocyanate, sodium bromide, sodium thiosulfate, and sodium cyanide a t approximate p H values of 4.5, 6.5, and 8.5. None was effective in markedly reducing copper interference. Sodium cyanide a t any p H depressed color formation. The other reagents had essentially no effect on the color formed, except sodium bromide and sodium thiosulfate a t p H 4.5. Two grams of sodium bromide a t p H 4.5 in the third separatory funnel made little difference with phenyl mercuric acetate. However, with ethyl mercuric phosphate, color formation was depressed approximately one fourth. The color was decreased approximately one third in the case of phenyl mercuric acetate by 1 gram of sodium thiosulfate a t p H 4.5, whereas no color was formed with ethyl mercuric phosphate under those conditions. I n the alkaline range, unexplainable off-colors occasionally appeared. The accuracy of the method is approximately within 2%. Table V gives the recovery of known amounts of phenyl mercuric
Original, 64 79 58 27 6
Table VI.
Recovery of Added Phenyl Mercuric Acetate y
Found, y 124 110 104 58 36
Error, 0 +1
y
+1
+1 0
Decomposition of Ethyl and Phenyl Mercuric Compounds in 3 N Hydrochloric Acid
Original Mercuric Compound, y Phenyl 90 90 90 90 90
Added, 60 30 45 30 30
Time Elapse, RIinutes
Found, y
Loss, %
20 40 80 140 255
81 77 76 64 47
10 14 16 29 48
ACKNOWLEDGMENT
Acknowledgment is made to M. F. Adams, Washington State College, Institute of Technology, for aid in determination of the absorption spectra. LITERATURE CITED
(1) Anon, “Phenyl Mercuries," Chicago, Ill., Metalorganics, Inc. (2) Fischer, H., Passer, M., and Leopoldi, G., Mikrochemie vet. Mikrochim. Acta, 30, 307 (1943). (3) Klein, A. K., J . Assoc. Ofic. A ~ TChemists . 33, 594 (1950). (4) Partington, J. R., “Textbook of Inorganic Chemistry,” 3rd ed., London, Macmillan Co., 1930. (5) Sandell, E. B., “Colorimetric Determination of Trace Metals,” S e w York, Interscience Publishers, 1944. (6) Shiraeff, D. A., Am. Dyestuf Reptr., 33, 310 (1944). (7) Steiger, B., Mikrochemie, 22, 216 (1937). (8) Steiger, B., Petroleum Z.,33, No. 27 (1937); Chem. Zentr., 108, 3114 (1937). (9) Stonestreet, G. O., and Wright, G. F., Can. J . Research, 18B,246 (1940). (10) Webb, J. L. A,, Bhatia, I. S., Corwin, A. H., and Sharp, A. G., J . Am. Chem. SOC.,72, 91 (1950). RECEIVEDDecember 18, 1950. Presented a t the Northwest Regional Meeting, AMERICAXCHEMICALSOCIETY,Seattle, Wash., June 8 and 9, 1951. Scientific Paper 981, Washington Agricultural Experiment Stations, Institute of Aaricultural Sciences, The State College of Washington, Pullman.
