~r and SE~- GVPTA: Complexometric Determination of Palladium 18i

References 1 MAJV~nAR, A. K., and J. G. S1~1r GretA: Z. analy~. Chem. 161, 100 (1958).

2 MA,IlnVID~m, A, K., and J. G. SEI~ GVPT~: Z. analy~. Chem. 161, 104 (1958).

Prof. Dr, A. K. MAJUMDAI~, Jada~llr University, College of Arts and Science, Calcutta-32 (lzldia)

Jadavpur University, Ca]cu?~ta-32 (India)

a-Picolinie Acid and Quinaldinic Acid in the Separation and r Determination of Palladium

By A. K. MAJUIVlDAR and J. G. SEN GUPT&

(Eingegangen am 7. November 1957)

Palladium can be determined in presence of a large number of ions after separating it by precipitation with ~-picolinic acid or quinaldinic acid, dissolving the precipitate in potassium nickel cyanide and titrating the liberated nickel with disodimn salt of ethylenediamine t~tra acetic acid (EDT&) in ammoniacal medium, using a solid mixture of murexide and sodium chloride as the indicator. The method has been applied to both micro and macro quantities of palladittm and the accuracy o-btahled is highly satisfactory.

Although there are several volumetric methods for the determination of palladium in solution, yet no satisfactory volumetric method applied to palladium precipitate is found in the literature except those due to ~ I A : r t ~ ) ~ and co-workers% 1~ who have dissolved the palladium preci- pitate in an excess of cyanide solution and back-titrated the excess cyanide by silver nitrate solution.

The previous volumetric metJaods which have been developed ,by various workers for the determination of palladium from solution are usually oxidimetric-~, 1~, acidimetric~, complexometric and sometimes based on direct t i tration with potassium iodide ~,~.

In complexometrie titrations, an excess of EDTA is added to the palladium solution and the excess is back-titrated with manganous sulphate v, zinc nitrate s, or bismuth nitrate~ solution. ]~'l_dscm~• 3 has determAned palladium on a micro scale (from 0.293 mg to 2.93 mg) by demasking the nickel cyanide complex and ti trating ~he liberated nickel ~4ttl disodium salt of ethylenediamine tetraacetic acid.

FI~ASCHKAS method with suitable modification has been extended to the determination of palladium in palladium precipitates containing organic ligands and the results thus obtained tbr the micro and the m~cro amounts of paltadinm are highly accurate.

182 A. I~. MAJU~])~ and J . G. SEN GUPTA:

E x p e r i m e n t a l

Reagents

Standard Palladium Solution: The palladium solution was prepared by dissolving 1 g of palladous chloride of Johnson and ~ a t t h e y in 500 ml of water, containing 5 ml of p. a. concentrated hydrochloric acid. This solution was stand~rdised by the usual palladium dimethylglyoxime method l~

A 1% (w/v) solution of c~-picolinic acid (neutralised with sodium carbonate) and a 2% (w/v) solution of quinaldinic acid were used as the precipitants.

Standard Nickel Solution~ Solution of nickel (containing approx. 1 mg/ml) was prepared by dissolving p. a. nickel sulphate (cobalt free) in water and the amount of nickel present in solution was determined by precipitation with dimethyl- glyoxime 14 followed by drying at 110 ~ C.

Standard EDTA (disodium salt) Solution: 5.5 g of disodium salt of ethylene- diamine tetraacetic acid were dissolved iu water and diluted to 1 litre. For the standardisation of this solution, 10 ml of the nickel solution were diluted to 50 ml with water and mixed with 5 ml of ammonium hydroxide solution (1 : 1) and 0.2 g of the indicator (0.1 g of murexide mixed with 20 g of finely ground pure sodium chloride). This solution was then t i trated with the EDTA solution till its colour changed from yellow to deep purple.

Potassium Nickel Cyanide, K~Ni(CN)4: This compound was prepared according to the method of FLASOm~X and HUDITZ 4.

For measurement of the volume of tile palladium solution and for subsequent ti tratious a micro burette was used.

Procedure

Palladium was precipitated from solution by ~-picolinic acid (sodium salt) or qninaldinic acid 11 and the precipitate obtained in each ease was filtered and washed, according to the methods of M ~ J U ~ D ~ and SE~ Gue~Al~ n. In the case of palla- dium picoHnate, the precipitate was transferred into a beaker by washing with hot water and then dissolved by he~ting with an equivalent amount of K~Ni(CN)4.

Table I Table 2

Pd taken

mg

EDTA (disodium salt) soln. consumed

ml

Pd found Pd taken

mg rag

0.931 1.86 2.79 4.655 7.45

13.1 16.375

0.6 1.2 1.8 3.0 4.8 8.4

10.4

0.93 0.931 1.865 1.86 2.79 2.79 4.65 4.655 7.44 7.45

13.02 9.31 16.12 11.17

13.965

EDTA (disodium salt) soln. consumed

ml

Pd found

mg

0.6 1.2 1.8 3.0

4 . 8 6.0 7.2 9.05

0.93 1.865 2.79 4.65 7.44 9.3

11.16 14.03

Slight excess of K2Ni(CN)a, however, had no harmful effect. When the precipitate was completely dissolved, the solution was cooled and to it were added 5 ml of ammonium hydroxide solution (1:1) and 0.2 g of indicator and titrated for the liberated nickel with EDTA (disodinm salt) solution until the colour changed from yellow to purple. The palladium quinMdinate precipitate, however, required boiling

Complexometrie Determination of Palladium 183

for some time with a slight excess of K~Ni(CN)t solution for dissolution and then addition of 5 ml of ammonium hydroxide solution (1 : 1) and 1--3 g of ammonium chloride before it was ready for titration. The addition of ammonium chloride was necessary to prevent the precipitation of nickel qninaldinate. Use of a large excess of I~2~Ni(CN)a should be avoided as otherwise its yellow colour would obscure the colour change at the end-point. The results due to palladium picolinate are given in Table 1 and those due to palladium quinaldinate in Table 2.

1 ml of 0.01t5 ~[ EDTA (disodium salt) solution __~ 1.55 mg Pd

Summary P a l l a d i u m has been d e t e r m i n e d f r o m p a l l a d i u m - p i c o l i n a t e or pa l la-

d i u m - q u i n a l d i n a t e p r e c i p i t a t e b y d i sso lv ing i t in p o t a s s i u m n icke l cyan ide

a n d t h e n t i t r a t i n g t h e d i sp l aced n icke l b y d i s o d i u m sal t of e t h y l e n e d i a m i n e

t e t r a a c e t i e acid, us ing a sol id m i x t u r e of m u r e x i d e a n d s o d i u m chlor ide

as t h e ind ica to r . T h e m e t h o d is v e r y a c c u r a t e a n d can be app l i ed to t h e

d e t e r m i n a t i o n o f 0.93 m g to 16 m g of pa l l ad ium.

Refe rences

1 AT~:I~soN, I~. H. : Analyst 79, 368 (1954) ; cf. Z. anMyt. Chem. 145, 300 (1955).-- Bv~IEn, F., and F. PI~o: An. Real Soc. espafi. Fisica Qulm., Ser. B, 47, 261

{1951); cf. Z. anMyt. Chem. 188, 213 (1953). - - 3 FnASCKKA, H. : Mikrochim. Acta (Wien) 1958, 226; cf. Z. analyt. Chem. 148, 218 (1954). - - a FLASCKKA, H., and F. ttVDITZ: Z. analyt. Chem. 187, 104 (1952/53). - - ~ GArgDE, M.: Bull. Soc. chim. Belgique 45, 9 (1936). - - 6 Km~s~ING, R.: Liebigs Ann. Chem. 87, 25 (1853). - -

KINNVN]~, J., and B. MERIK~NTO: Chemist-Analyst 44, 11 (1955); cf. Z. anal:ft. Chem. 148, 283 (1955/56). - - s MAeNEvI~, W. iK., and 0. H. K]CIEGE: AnMyt. Chemistry 27, 535 (1955); cf. Z. anMyt. Chem. 14:9, 292 (1956). - - 9 MAJ~lgDAtr A. K., and M. M, CtIAK~A~TTY: Z. analyt. Chem. 156, 103 (1957). - - 10 M~JuM~ D/m, A. K., and J. G. SEN GvPTA: Z. analyt. Chem. 161, 100 (1958). - - 11 MAJVM- DAR, A. K., and J. G. SEN GUPTA: Z. anMyt. Chem. 161, 104 (1.958). - - 1~ ~ 5 v M . ])AR, A. K., and J. G. S~,~ GUPTA: Z. analyt. Chem. 161, 179 (1958). - - 18 SYRO- ]~OMSK~J, V. S., and S. M. GU]~EL'B~_lVK: Z. anal. Chim. 4, 146, 203 (1949). [Russisch]. - - ~ VOGEl, A. I. : A Text Book of Quantitative Inorganic Analysis. London: Longmans, Green and Co. 1953.

Prof. Dr. A. K. !~AJVMDAR, Jadavpur University, College of Arts and Science, Calcutta-32 (India)