Table 111. Application of Method to Analysis of Sediment Standard (4)
Lead, mg. Added to sorption solution containing 0 25 gram of sediment sample Found in eluate 0.0
0.01
0.5
0.52 1.02 2.51 5.02 7.52 10.01
1 0
2.5 5 0 7.5
10.0
within the whole region of concentrations used (0.5 to 10 mg. of P b per 20 ml. of mixture). The solubility of lead nitrate in the mixture applied was 1.0 mg. of lead per ml., whereas that for strontium nitrate is only 0.05 mg. per ml. Barium nitrate is even less soluble. Investigations of the influence of concentration of lead, uranium, thorium, bismuth, and thallium on column separation have shown that a quantitative separation is possible in the range of concentrations shown in Table I. From these loading esperiments it is seen that the breakthrough volume of lead decreases with increasing con-
centration. Since the elution volumes of bismuth increase with an increase of concentrations, an overlapping of the elution curves with the breakthrough volume of lead is expected when more than 10 mg. of lead and 10 mg. of bismuth are present simultaneou.ly in the sorption solution. This effect can be eliminated by employing larger columns. Analogous esperiments performed by using microgram amounts of lead and milligram quantities of the other elements showed that the lead could be recovered quantitatively in all cases, which means that this separation method can wxesqfully be applied on a micro scale. I n Table I11 are shown results of the application of this method to a standard sediment sample (4) to which known amounts of lead were added. I t is seen that lead can be recovered quantitatively with only a small error. Comparison with other procedures based on the anion exhange separation of lead, which have hitherto been developed in pure aqueous hydrochloric acid media, s h o w that the present chromatographic technique could be employed for the assay of lead in a variety of materials such as marine sediments, leaded steels, copper-base alloys, high purity metals such as uranium, optical glass, rubber products, canned food, wines, and body fluids.
Ai further application would be in the field of petroleum research for the isolation of lead prior to its quantitative determination in petroleum productsfor instance, in gasoline. Because the “light” lanthanides are coadsorbed with lead, and uranium is practically not retained on the resin, this method could also be useful for the separation of uranium from fission products, which consist to a great degree of the radioactive isotopes of the “light” rare earth elements, LITERATURE CITED
(1) Buchanan, R. F., Faris, J. P., U. S. At. Energy Comm., R e p l . RICC/173 (1960). ( 2 ) Fritz, J. S.,Iowa State Cniversity of Science and Technology, Ames, Iowa, prim te communica tion, 1964, ( 3 ) Fritz, J. S.,Greene, R. G., A N A L CHEM.,36, 1095 (1964). (4) Korkisch, J., Arrhenius, G., Zbid., 36, 850 (1964).. ( 5 ) Korkisch, J., Farag, A . , Hecht, F., Mikrochim.Acta 1958, p. 415. (6) Korkisch, J., Tera, F., AISAL.CHEM. 33, 1264 (1961). ( 7 ) Schiinfeld, T., El Garhi, M., Friedmann, C., Yeselsky, J., Mikrochz’m. Acta 1960, p. 883. RECEIVED for review February 24, 1964. Accepted -4pril 10, 1964. Research supported by the Petroleum Research Fund, administered by the American Chemical Society ( P R F grant KO.1587-A3).
Solvent Extraction of Platinum and Palladium with Derivatives of Dithiocarbamic Acid JOHN T. PYLE and WILLIAM D. JACOBS Department o f Chemistry, University o f Georgia, Athens, Ga.
b The use of selected derivatives of dithiocarbamic acid as extractable chelating agents for platinum and palladium in acidic media is described, Factors and variables affecting the analytical application of these derivatives have been investigated. Although several dithiocarbamate derivatives are unstable in an acidic medium, others were found to exhibit sufficient stability to make practical their application as complexing agents for platinum and palladium in a medium in which some base metals and other platinum group metals do not react favorably. Three such derivatives are cited. One of these derivatives, the dibenzyl, was found to be the most promising chelating agent in the presence of certain diverse ions. This derivative was made the basis of an analytical 1796
ANALYTICAL CHEMISTRY
scheme for the simultaneous separation of platinum and palladium from certain other metals. Chloroform is used as an extractant.
S
of the work by Delepine (3, 4) concerning the analytical use of sodium diethyldithiocarbamate, techniques have been developed for the use of this derivat’ive and other disubst’ituted derivabives of dithiocarbamic acid, DC-1, as analytical reagents. Callan and Henderson ( 2 ) made a systematic study of the reactions of sodium diethyl DC.l with the more common metals, and proposed a colorimetric det,ermination of small amounts of copper with this reagent. Gleu and Schwab ( 5 ) investigated the behavior of several derivatives of IICA toward the more common metal* as well ax toward IKCE THE PUBLICATIONS
noble met’als and the platinum grouli metals. Malissa and Miller ( 8 ) studied t’he reactions of metals with still other DC-4 derivatives. In this work observations were made under varied experimental conditions to determine reaction sensitivities and to ascertain t’o what extent these derivatives might serve as the basis for quant,itative separation. Welcher (13) collected a number of analytical procedures using several DC;1 derivatives. These techniques deal with qualitative and precipitation studies, as well as with extraction phenomena. Reactions involving derivatives of DC-1 have been studied mainly in alkaline, ncutral, or weakly acidic media. This palier describes the reactions of certain derivatives with platinum and palladium in a highly aridir medium. Pollard (10) used tlicxthj.1
I>CX to separate and determine micro quantities of palladium in acid solution. Yoe and Kirkland (141' have proposed a method for the simultaneous separation of platinum and palladium as diethyl D C h salts from other platinum group metals in an acid solution, using chloroform as a n extractant. I n such a medium, DCA and some of its derivatives are not very stable. According to Bode ( I ) , acidic solut'ions of sodium diethyl DCA undergo a first-order decomposition reaction a t a rate directly proportional to the hydrogen ion concentration. Various other DCA derivatives are more stable than the diethyl in acid solution ( 1 2 ) . Martens and Githens (9) have used the dibenzyl derivative as a reagent' for copper in an acidic medium because of its greater stability and selectivrty as compared to t'he diethyl derivative. I n light of this, some derivatives might exhibit sufficient stability to make practical their use as che1ati:ng reagents for platinum and palladium in a medium in which other platinum group metals and some base metals would not react favorably. Nine deri-vatives were obtained for systematic investigation. EXPERIMENTAL
form 1% aqueous solutions with two exceptions. Because of the nature of the molecule, the diphenyl and dibenzyl derivatives were not water soluble but were dissolved in water-miscible acetone and p-dioxane, respectively. Since it was deemed desirable to have the derivative miscible with the ionic phase of the solution to be encountered, such solvents as chloroform were not considered. All solutions were found to be stable for a t least three days. Longer periods of time were not investigated. OTHER REAGENTS. Standard stock solutions containing approximately 1 mg. per ml. of selected diverse ions were prepared from nitrates or chlorides of the metal, except osmium, which was prepared from potassium osmate. All other reagents were analytical grade, used without further purification. Recommended Procedure. Introduce a n aliquot of sample of 5 ml. or less, which contains a n amount of platinum and/or palladium compatible with the subsequent microanalytical scheme, a n d no foreign ions sufficient to produce extreme interference, into a 125-ml. short-stem globe separatory funnel. If platinum is t o be determined, add 1 ml. of 1 M sodium sulfite, swirl, then add 25 ml. of concentrated hydrochloric acid. The order of this addition must not be reversed. If platinum is not to be determined, omit the sulfite addition. Introduce 5 ml. of 1% solution of the derivative, and allow to stand for 30 minutes with occasional swirling. Extract with two 5-ml. portions of chloro-
form into a 25-ml. volumetric flask. Ash the sample to destroy organic matter . ASHINGTECHNIQUE. Treatment with fuming nitric acid and perchloric acid is used to destroy the organic matter. This involves first heating the chloroform extract in the 25-ml. flask to dryness in a hot water bath, followed by heating on an electric hot plate. The flask is fitted, by means of a ground glass joint, with 5-inch lengths of glass tubing with an offset U-bend to act as a baffle so that a n y bumping from superheating will not cause the sample to be expelled. After it is cooled, with the baffle still in place, the sample is treated with a 5-ml. portion of red fuming nitric acid and heated nearly to dryness on the electric hot plate. This is repeated with another 5-ml. portion of the acid. T h e sample is then treated with a 5-ml. portion of 60% perchloric acid and heated more severely to expel all oxides of nitrogen and to ensure the complete digestion of all organic matter. Just before the sample reaches dryness, it is removed from the heat, allowed to cool, and treated with a 5-ml. portion of 1JI sodium sulfite. This neutralizes the remaining perchloric acid and serves as a reducing agent for the quadrivalent platinum in the spectrophotometric scheme employed in sample analysis (6). Collecting the extract and ashing it in the same volumetric flask obviates the necessity of transferring samples. Some workers have used 30% hydrogen peroxide instead of perchloric acid following treatment with fuming nitric
Apparatus. -411 absorbance measurements were made with a Beckman Model DU spectropliotometer using matched silica cellr of 1-cm. light path. Globe separatory funnels of 125-ml. volume and stems shortened t o approximately 1 cin. were used for all extractions. Reagents. STANC~ARD PLATINUM Table I. Effect of Hydrochloric Acid Concentration on Platinum Reaction SOLUTION.About 7 grams of chloroplatinic acid hexahydrate were dis(All samples contained 113.2 pg. Pt) solved in 1 liter of distilled water with sufficient hydrochloric acid t o give a HC1, Molarity 1 .o 1.9 3.5 7.0 8.2 9.6 final concentration 1M in the acid. Derivative P t found, p g . T h e platinum content was determined Dimethyl 9.8 10.3 25.6 50.0 53.6 54.4 gravimetrically by reducing t h e platDiethyl 5.6 7.8 25.6 13.0 107.0 102.0 inum to the metal with formic acid. Dibutyl 4.6 10.9 49.5 03.5 107.2 106.0 T h e standard solutioii contained 2.83 Cyclopentamg. of platinum per ml. methylene 6.1 14.6 35.3 13.2 113.2 113.2 STANDARDPALLADIUM SOLUTION. Piperazino Did not extract About 2 grams of palladium(I1) chloride were dissolved in 1 liter of distilled 10.0 21.0 20.8 Morpholino 22.2 59.0 57.5 N-pyrrolidino 86.2 110.5 109.2 10.5 111.0 101.5 water containing sufficient hydrochloric Di- henyl 1.4 3.6 31.8 13.8 113.2 113.2 acid to give a final concentration 1JI 58.5 Digenzy 1 91.2 113.2 13.2 113.0 113.2 in the acid. The palladium content was determined gravimetrically to be 1.216 mg. per ml. by precipitation of palladium dimethylglyosimate from hoTable II. Effect of Hydrochloric Acid Concentration on Palladium Reaction mogeneous solution ( 7 ) . (All samples contained 109.8 pg. Pd) DCA DERIVATIVES.The dimethyl, the cyclopentamethylene, the piperHC1, Molarity 0.00001 0.001 0.08 1.0 4.3 8.6 azino, the morpholino, the N-pyrroliDerivative Pd found, pg dino, and the dibenzyl derivatives were obtained from Aldriclh Chemical Co., Dimethyl 108 2 109 8 109 2 107 8 109 2 109 8 Inc., Milwaukee, Wis. The dibutyl Diethyl 109 8 109 2 109 8 109 2 109 2 110 2 Dibutyl 109 6 108 3 107 3 109 4 109 2 109 5 and the diphenyl derivatives were obCyclo- entatained from K and K Laboratories, Inc., m e t iy lene 109 9 109.5 109.8 109.8 109.8 110.0 Jamaica, N. Y. The diethyl derivaPiperazino Did not extract tive was obtained from the Matheson Company, Inc., East Rutherford, N. J. MorDholino 109 5 110 5 109 5 108 .5- in9 i- -i ~n, .3~ - _ n_ All were sodium salts ejcept the dibenzyl N-p$rrolidino 109.0 109.5 10s.5 109,5 109.5 108 5 derivative which w:as a zinc salt. Diphenyl 92.5 109.0 109.5 109,5 109.9 1011.7 The reagents were used without further Dibenzyl 95.5 109.5 110.0 109.8 109 6 100.8 purification. They were dissolved to VOL. 36, NO. 9, A U G U S T 1964
1797
acid (Z&, while others have used a technique employing sulfuric acid and nitric acid followed by hydrogen peroxide to destroy organic matter (9). I n this laboratory, neither of these procedures gave completely desirable results; the former led to rather scattered data, while the latter was somewhat time-consuming and required careful heating. KO explosions or accidents occurred through the use of hot concentrated perchloric acid in the present met hod.
Table 111.
Table VI.
Effect of Diverse Ions on Simultaneous Determination Using Dibenzyldithiocarbamic Acid As Extractant
Diverse ion P t added, 56 6 pg. quantity a (mg.) Pt found, p g . Error, %’ Au( I11j, 1.25 61.7 +9.0 Fe(II1j, 1 . 0 56.8 +0.4 Co(II), 1 . 0 59.9 +5.8 Ni(II), 1 . 0 58.7 +3.7 Cr(III), 1 . 0 57.7 +1.9 Cu(II), 1 0 61 1 +8 0 RhlIII). 1 95 60 4 +6 7 IriIV). 0.42 61 2 +x 1 RU(III), 1 . 0 58.6 +3.5 Os(V1j, 1.14 58.1 +2 7 Samples contained 1 ml. of 1M sodium sulfite.
CyclopentaDimethylene phenyl Dibenzyl
Diverse ion added ( m g . ) ~ Pt Au(III), 1.25 117.0 Fe(III), 1 . 0 114.8 ColIII. 1 . 0 108.1 Ni(IIj(1 0 106 2 Cr(III), 1 0 92 5 Cu(II), 1 0 113 0 Rh(III), 1 95 35 7 IdIV). 0 42 64 3 Ru(III), 1 . 0 49.6 Os(VIj, 1.42 97.5
found, pg. 54.5 110.0’ 7 4 . 3 108.1 71.6 108.1 70 4 108 I 65 5 108 1 72 7 108 7 52 0 113 0 79 9 116 0 45.4 111.0 111.0 109.2
These samples contained 1 ml. of 1M sodium sulfite.
Table IV.
Effect of Diverse Ions on Palladium Reaction
Pd added, 121.6 pg. Derivative
CyclopentaDimethylene phenyl Dibenzyl
Diverse ion added (mg.) Au(III), 1 25 Fe(III), 1 0 Co(II), 1 0 NiIII). 1 0 Cr(III), 1 0 CulIII. 1 0 RhiIII), 1 95 Ir(IV), 0 42 Ru(IIIj, 1 0 Os(VI), 1 14 Pt(IV), 1 42
Table V.
-Pd. found, p g 119 8 97 5 124 8 123 9 120 8 123 9 121 8 123 ,? 120 8 122 9
142 152 121 120 124 140
1798
7 6 6 7
6 6 2 2 2
e
0 0
8 8 8
0
123 146 120 124 124 134
9 1 8
0 8 2
120 5 124 0 122 7 123 9 123 9 127 8 128 6 124 8 123 8 121 9 161 3
8
21 9 53 9 88.0 21 9 54 9 88 2 112 6 112 4 112 8
1
3 8 3 6
6 6 3 8
3
ANALYTICAL CHEMISTRY
25 63 98 123 123 122 24 62 101
2
3
4
5 6 7 8 FORMALITY, HCI
9
IO
Figure 1 . Effect of hydrochloric acid concentration on platinum recovery
RESULTS
Study of Variables. Preliminary investigations showed t h a t Pt(1V) did not react favorably with any of the derivatives. Pt(1V) was reduced to Pt(l1) in a manner described earlier ( 1 2 ) . Tests in each study were made on solutions which contained a fixed amount of platinum and,’or palladium and were allowed to react according to the recommended procedure except for the variable being studied. A\nalysis was completed according to the procedure. Hydrogen Ion Concentration. Studies were made on solutions of platinum and palladium separately in which the hydrogen ion concentration was varied
Table VII.
Pd, rg. Added Found 24 60 97 121 121 121 24 60 97
DIPHENYL CYCLOPENTAMETHYIERE
Simultaneous Analysis of Synthetic Samples
Pt, a . Added Found
22 56 90 22 56 90 113 113 113
+ +
Effect of Diverse Ions on Platinum Reaction
Pt added, 113.2 pg. Derivative
Pd added, 60.8 pg. Pd found, pg. Error, % 62.5 +2.7 59.6 -2.0 60.7 -0.2 60.0 -1.3 60.9 +0.2 157 8 160 93 2 53 59 3 -2 5 62.3 +2 5 -2 6 61.6
over a considerable range. Tables I and I1 show the results of these experiments. These data allowed the rejection of several derivatives from further study. Complexes with the piperazino derivative appeared to be of a polymeric nature and were unextractible with any conventional reagents, while several others failed to react completely with platinum in a highly acidic medium. hcid concentration did not appear to be a variable in the case of palladium. Only the cyclopentamethylene, the diphenyl, and the dibenzyldithiocarbamates reacted completely with platinum. Figure 1 shows the effect of hydrochloric acid concentration on platinum recovery with these three derivatives. Rate of Chelate Formation. In the case of these three derivatives it was noted that several minutes were required for complex formation. After this initial period, however, and up to 45 minutes, time has no effect on either the platinum or palladium reaction. Longer times were not investigated. Presence of Diverse Ions. The effect of certain diverse ions on the reaction between the three derivatives and platinum and palladium was examined. Although time as a variable has little effect on the formation of the complex between the derivative and platinum or palladium alone, in the presence of diverse ions, time is a factor. This indicates that there are probably competing equilibria. hbout thirty minutes
Simultaneous Analysis of Synthetic Samples
Pt, a.
Pd, rg.
ridded 22.7
Found 21.6
Added 121.6
Found 124.0
(3)
113.2 22 7
107.5 25 0
24.3 24 3
25.0 27 0
(4)
113.2
116.8
121.6
121.8
0 4
(1)
4 7 6 7 7 2
(2)
3
Diverse ions, mg. Ir, 0.42 Ru, 0 . 5 0 Os, 0 . 5 7 Same as (1) Fe, 0 50 co, 0 50 Xi, 0 50 Same as (3)
should be given to chelation in the presence of diverse ions to minimize interference, Tables 111 and IV show the results of this study. The dibenzyl derivative was found to react most favorably in the presence of diverse ions. Effect of Reagent Concentration. Observations on the dibenzyl derivative showed that extraction is complete as long as the derivative is present in a molar excess of 250 or greater. Simultaneous Extraction of Platinum and Palladium, Table V shows t h a t t h e dibenzj-1 derivative can be used successfully to extract simultaneously platinum a n d palladium. Simultaneous Separation in the Presence of Diverse Ions. Table V I
reports the results of‘ a simultaneous separation of platinurn and palladium, with dibenzyl D C h in the presence of selected diverse ions. T h e extreme interference of rhodium in t h e
simultaneous analysis may be a t tributed to the fact t h a t a reduced form of Rh(II1) is reacting with the derivative in a manner analogous to t h a t of platinum and palladium. Copper reacts in both the univalent and bivalent states with the derivative. Synthetic samples were prepared which contained several diverse ions along with varying amounts of platinum and palladium. The results of these analyses are found in Table V I I . LITERATURE CITED
(1) Bode, H., 2. Anal. Chem. 142, 414 I 1 9.54 ).
(2jCallan, T., Henderson, J. A. R., Analyst 54, 650 (1929). (3) DelBpine, M.,Compt. Rend. 146, 981 (1908): (4) DelBpine, M., Bull. SOC.Chem. 3-4, 652 (1908). (5) Gleu, K., Schwab, R., Angew. Chem. 6 2 , 320 (1950).
(6) Jacobs, W. D., ANAL. CHEM. 33, 1279 (1961). ( 7 ) Kanner, L. J., Salesin, E. D., Gordon, L., Talanta 7 , 288 (1961). ( 8 ) Malissa. H., Miller, F. F.. Mikrochim. (9) Martens, R. I.)’Githens, R. E , Sr., A N A L . C H E M . 24, 991 (1952). (10) Pollard, W. B., Analyst 6 7 , 184 (1942). (11) Pyle, J. T., Jacobs, W. D., Talanta 9, 761 (1962). (12) Sandell, E. D., “Colorimetric Determination of Traces of Metal,” 3rd ed., p. 193, Interscience, Sew York, 1959. (13) Welcher, F. J., “Organic Analytical Reagents,” Vol. 4, pp. 77-91, Van Nostrand, Sew York, 1048. (14) Yoe, J. H., Kirkland, J. J., ANAL. CHEM.26, 1335 (1964). RECEIVED for review February 28, 1964. Accepted May 1, 1964. Southeastern Regional Meeting of the American Chemical Society, Charlotte, hT. C., November 14-16, 1963. During part of this study one of the authors ( J T P ) held a Xationa Science Foundation Summer Fellowship.
Indirect Spectrophotometric Determination of Ammonia J. H. HOWELL’ and DI.
F.
BOLTZ
Department o f Chemistry, Wayne State University, Detroit,
b A rapid spectrophotometric method for
the determination of ammonia is proposed and the results of an investigation of the experimental variables are presented. Ammonia is oxidized to nitrogen by hypobromite and the differential absorbance at 330 mk of the sample relative to that of a reference standard is proportional to the ammonia concentration. The differential technique minimizes errors due to ammonia contamination of reagents and distilled water as well as the effects of reagent decomposition. Conformity to Beer’s law was observed for 1 to 42 p . p m of ammonia, the optimum concentration range being from 3 to 23 p.p.m. The absorptivity for ammonia was found to b e 0.030 cm.-’ p.p.m.-’ Concentration of ammonia in the range of 0.1 to 1.0 p.p.m. may b e (determined using 5.0-cm. silica or borosilicate absorption cells with either a hydrogen or tungsten lamp source.
T
spectrophotometric method for the determination of ammonia involves the use of Sessler’s reagent, which generally requires rigid control of reaction conditions and reagent stability l o prevent solution turbidity ( 2 ) . A sensitive method based H E MOST EXTENSIIELY USED
Mich.
on the use of a pyridine-pyrazolone reagent and the extraction of the resulting purple system with carbon tetrachloride has excellent sensitivity and specificity ( 5 ) . However, the control of p H is rather critical, the reagent is relatively unstable, the colored system does not show strict conformity to Beer’s law, and the extraction process is time-consuming. The reaction of ammonia with a phenol and hypochlorite reagent to give indophenol has also been utilized, but control of hypochlorite concentration, as well as pH, is very critical ( 1 ) . Ammonia in water has been determined recently by a colorimetric method based on the conversion of ammonia to trichloramine by treatment with hypochlorite, destruction of excess hypochlorite with nitrite, and the development of a blue color as the trichloramine reacts with a cadmium iodide-linear starch reagent (6). The high sensitivity of this method, its specificity, and its freedom from interferences are distinct advantages, but again the controi of p H is critical in order to avoid either the osidation of iodide by the nitrite under too acidic conditions or the incomplete conversion to trichloramine under more basic conditions. During a spectrophotometric study of chlorine dioxide and related species the effect of pH on the ultraviolet
spectra of hypochlorite and hypobromite solutions was investigated. On the basis of this study, hypochlorite and hypobromite have been used to oyidize ammonia, with the excess oyidant being determined by ultraviolet absorbance measurements. Because of a lack of stoichiometry and reproducibility, in spite of rigidly controlled reaction conditions, the hypochlorite oxidations were found to be inferior to those obtained with hypobromite. The osidation of ammonia by hypobromite proved to be reproducible and nearly stoichiometric. This paper reports the results of the investigation of the effect of experimental variables on the proposed method. EXPERIMENTAL
Apparatus. Absorbance measurements were made with a Cary Model 14 spectrophot~ometer and 1.000-em. silica cells, unless ot,herwise indicated. Reagents. .kmmonia-free distilled water was prepared by redistillation of distilled water from a n acidic permanganate solution in a n all-glass distillation apparatus. Reagent grade reagents were used unless otherwise specified.
Present address, Department of Chemistry. Western Michigan I-niversity, Kalamazoo, Mich. VOL. 36, NO. 9, A U G U S T 1964
1799
