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Spectrophotometric and gravimetric determination of osmium and gold with thio-salicylamide
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Spectrophotometric and gravimetric determination of osmium and ~old with thiosalicylamide q'laiosalicylamide has been r e c o m m e n d e d by S h o m e et al. l"e" as a useful r e a g e n t for the d e t e r m i n a t i o n of t h a l l i u m , m e r c u r y , p a l l a d i u m , r h o d i u m , r u t h e n i u m a n d p h t t i n u m . In the p r e s e n t i n v e s t i g a t i o n , t h e r e a g e n t w a s e m p l o y e d for the gravim e t r i c ~tnd s p c c t r o p h o t o m e t r i c d e t e r m i n a t i o n of o s m i u m ( V l o r V l i l ) a n d g o l d ( i l l ) . T h e b r o w n o s m i u m c o m p l e x is p r e c i p i t a t e d q u a n t i t a t i v e l y at p H 2.5--7.0 a n d corres p o n d s to the f o r m u h t OsOz(C71-1¢,ONS)2. T h e g o l d c o m p l e x , A u ( C ~ H T O N S ) 3 C I , is y e l l o w in c o l o u r a n d is c o m p l e t e l y p r e c i p i t a t e d f r o m 2.5.--6.0 N h y d r o c h l o r i c acid s o l u t i o n . T h e t h i o s a l i c y l a m i d e c o m p l e x e s of b o t h m e t a l s a r e m o d e r a t e l y s o l u b l e in etlaanol a n d o t h e r c o m m o n o r g a n i c s o l v e n t s but h i g h l y s o l u b l e in etlaanol- isobutyl m e t h y l k e t o n e m i x t u r e . T h e r e a g e n t s o l u t i o n in i s o b u t y l m e t h y l k e t o n e , h o w e v e r , d e c o m p o s e s in h i g h l y acidic m e d i u m . Thcrclkwc, the o s m i u n a c o m p l e x is e x t r a c t e d with e t h a n o l - - i s o b u t y l m e t h y l k e t o n e m i x t u r e but the g o l d c o m p l e x w h i c h is precipitated in highly a c i d i c s o l u t i o n s is e x t r a c t e d w i t h c h l o r o f o r m . Exper#nental A p p a r a t u s . A C a r l - Z e i s s s p c c t r o p h o t o m e t c r , M o d e l P M Q !1. w i t h I-cm t l u a r t z c e i l s , was u s e d for a b s o r b a n c e m e a s u r e m e n t s . A C a m b r i d g e p H m e t e r e q u i p p e d w i t h glass a n d c a l o m e l e l e c t r o d e s w a s used for p H m e a s u r e m e n t s . S t a n d a r d otetal solutions. An o s m i u m s o l u t i o n was m a d e by t r e a t i n g p o t a s s i u m o s m a t e with 0.1 M sod ium h y d r o x i d e o r by d i s s o l v i n g o s m i c a c i d in cold distilled water. T h e s o l u t i o n was s t o r e d in the c o l d . a n d w a s s t a n d a r d i z e d by p r e c i p i t a t i n g the m e t a l as t h e s u l p h i d e , f o l l o w e d by i g n i t i o n to the m e t a l in h y d r o g e n . T h e gold s o l u t i o n was p r e p a r e d by ~tissoiving p u r e g o l d ( l l I) c h l o r i d e in d i l u t e h y d r o c h l o r i c acid. ,'tnd was s t a n d a r d i z e d by the u s u a l o x a l i c acid m e t h o d . W e a k e r w o r k i n g s o l u t i o n s of the m e t a l i o n s w e r e o b t a i n e d by a p p r o p r i a t e d i l u t i o n . Diverse ion sohttions. S o l u t i o n s o f d i v e r s e i o n s w e r e p r e p a r e d by d i s s o l v i n g k n o w n a m o u n t s o f their p u r e c o m p o u n d s in distilled w a t e r . Dilute h y d r o c h l o r i c a c i d w~ts used w h e r e r e q u i r e d . Reaoent sohttion. A I"il (w/v) s o l u t i o n of t h i o s a l i c y l a m i d e in 20",, e t h a n o l w a s u s e d for the p r e c i p i t a t i o n o f o s m i u m a n d gold. F o r s p e c t r o p h o t o m e t r i c m e a s u r e m e n t s , 0.01 M t h i o s a l i c y l a m i d e in e t h a n o l w a s used. All o t h e r c h e m i c a l s used w e r e of A . R . g r a d e . Proper'ties o f metttl c o m p l e x e s T h e o s m i u m a n d g o l d c o m p l e x e s w i t h t h i o s a l i c y l a n a i d e d c c o m p o s e at 175 ° a n d 173 ° respectively. T h e o s m i u m c o m p l e x is s t a b l e o n l y in w e a k l y a c i d i c s o l u t i o n w h e r e a s the gold c o m p l e x is s t a b l e even in s t r o n g n o n o x i d i z i n g acids. B o t h the c o r n p l e x c s are r e a d i l y d e c o m p o s e d by a l k a l i a n d fairly s o l u b l e in c o m m o n o r g a n i c solvents. T h e results of a n a l y s i s o f p u r e c o m p l e x e s w e r e as follows : O s m i u m c o m p l e x . F o u n d : 3 6 . 2 0 ' ! . Os, 5.15 "0 N . 12.08 '),, S ; r e q u i r e d for O s O 2 (C-zI-I~,ONS)2 : 36.14'~,, Os. 5 . 3 2 " , N . 12.16°,,, S. Gohi c o m p l e x dried at 105 ° . F o u n d : 24.65 ",, Au, 5.20 ",, N. 12.10 ",, S, 4.40 ",, CI ; An,:tl. Chim. Acta, 59 (1972)
307
SI i( ) R T ( ' ( ) M M U N I( " A I ' I ( ] N S
r e q u i r e d for A u ( C - r H T O N S ) 3 C I -6 H : O : 24.66",, A u . 5.25",, N . 12.00",, S. 4.45 'Y.,, CI. Gold complex dried ~tt 135 '~. F o u n d : 28.50 ",, A u . 5.95 ",', N. 13.90 ",, S, 5.10 ",, CI : r e q u i r e d for A u ( C - r H 7 O N S ) 3 C I : 28.51 ',.,, A u . 6.07 ",, N. 13.88 ';,, S a n d 5.15 ",, CI.
Grat'imetric determinaticm o f osmium and gold Procedure. D i l u t e t h e o s m i u n a s o l u t i o n to a b o u t 150 ml, a d j u s t its a c i d i t y to p H 4 . 0 - 6 . 0 w i t h 10",, s o d i u m a c e t a t e s o l u t i o n a n d p r e c i p i t a t e the m e t a l in t h e c o l d by a d d i n g 8 - 1 2 t i m e s the t h e o r e t i c a l a m o u n t o f t h i o s a l i c y l a m i d e s o l u t i o n . A l l o w t h e p r e c i p i t a t e to s t a n d o n a h o t w a t e r b a t h for a b o u t I h. F i l t e r o n a N o . 4 s i n t e r e d g l a s s c r u c i b l e , w a s h w i t h h o t w a t e r , d r y a t 110--120 '~ for 2 h a n d w e i g h as O s O 2 ( C v H 6 O N S ) 2 . F o r t h e d e t e r m i n a t i o n o f g o l d . d i l u t e the m e t a l s o l u t i o n to 150 ml a n d a d j u s t its a c i d i t y to 3--4 :~/ in h y d r o c h l o r i c acid. W a r m t h e s o l u t i o n to 6 0 - 7 0 °, a d d 4---5 t i m e s t h e t h e o r e t i c a l a m o u n t of the r e a g e n t s o l u t i o n a n d a l l o w t h e p r e c i p i t a t e f o r m e d to s t a n d o n a h o t wztter b a t h for 1 h. F i l t e r o n a N o . 4 s i n t e r e d g l a s s c r u c i b l e , w a s h w i t h h o t !0",, h y d r o c h l o r i c a c i d , d r y at 135" a n d w e i g h a s A U ( C T [ - 1 7 O N S ) 3 C I . O s m i u m w a s d e t e r m i n e d in t h e r a n g e 7.5-.-30 m g a n d g o l d in t h e r a n g e 4.85-29.1 nag; in all c a s e s , the e r r o r w a s less t h a n 0.25'!,,. El.'fect of acidity. T h e o s m i u m c o m p l e x b e g i n s to c o a g u l a t e a b o v e pFi 2.0, t h e o p t i m u m p H r a n g e for q u a n t i t a t i v e p r e c i p i t a t i o n b e i n g 2.5--7.0. G o l d is c o m p l e t e l y p r e c i p i t a t e d w h e n t h e a c i d i t y o f t h e s o l u t i o n is m a i n t a i n e d at 2.5--6.0 M in h y d r o c h l o r i c acid : at l o w e r acidities, t h e p r e c i p i t a t e b e c o m e s s l i m y a n d d o e s n o t c o a g u l a t e . El.l'ect o.fdicerxe ions. O s m i u n a o r g o l d w a s d e t e r n l i n e d w i t h t h i o s a l i c y l a m i d e in t h e p r e s e n c e o f k n o w n a m o u n t s o f C o , Ni, M n , Zn, Ti, AI, In, C d , C r (as t h e i r sulphates), u r a n y i a c e t a t e , z i r c o n y l c h l o r i d e o r a m m o n i u m m o l y b d a t e . C y a n i d e , r u t h e n i um and rhodium interfered with the determination of osmium. Rhodium and ruthenium did not interferewith the determination ofgold when the latter was precipitated from 6 M hydrochloric acid solution. Palladium, platinum, copper, nitric acid and other oxidizing agents, however, interfered with the determination of gold. The results are r e c o r d e d in T a b l e I. It w o u l d b e p o s s i b l e to s e p a r a t e o s m i u m f r o m p a l l a d i u m , p l a t i n u m , r h o d i u m , F A BLI'~ ! ;I!I~AI,~ArI()N ( W ()SMIIJM A N I ) ( i ( ) l . I ) I.R()M IMVliRSF, I()NS
Gold = 9 . 7 0 mg
O,wnito~z = 9 . 5 0 m q
rrorei~.ln l o t 1
Au.]Otoul
l"orei~lta ion
,4tl.Iotmd
Fort'i#ltl itm
0.'," fOtoul
t:orei~ln iotl
Os.lbund
tdded (m~.l)
(re.q)
added (rag)
(re.q)
added (re.q)
(m~.l)
udded (re.q)
On.q)
~o 2. (200) 'qi 2 . ( 2 0 0 ) Vln z " ( 3 0 0 ) ~n 2 ~ (400) Yd" ~ (500) Fi ' + (40) M 3+ ( 2 0 0 ) In "~' ( 2 0 0 ) ~ a "a ' ( 1 0 0 )
9.70 9.67 9.72 9.72 9.70 9.70 9.72 9.72 9.70
Z r "~' (4f~)) U ~'~ ( 1 5 0 ) Mo"' (30) "Fh "t" ( 2 0 0 ) lr a ~ ( 2 0 ) R u "~+ ( 1 3 . 0 ) R h 3+ ( 5 . 5 6 ) R h 3~ ( 1 1 . 1 2 )
9.67 9.72 9.72 9.70 9.70 9.72 9.70 9.72
F e 3 ~ (20)" Co 2 " (50)" N i 2 ~ (40)" Zn 2 ~ (80)" M n z ~ (25)" G;.| 3q" ( 4 0 ) " In 3~ (40) u TI 3~ (20)" AI "~ ~ (20)"
9.49 9.52 9.46 9.52 9.50 9.49 9.49 9.50 9.49
M o " * (80) W"' (30) U ~'~ ( 4 0 ) "Fh "*~ (80)" V "~' ( 4 0 ) C u z* (30) t' "Fi "~ (30)" I r " ~ (10)
9.52 9.52 9.49 9.52 9.52 9.49 9.49 9.52
" in presence
oftartrate,
h In presence of EDTA.
" In presence
of fluoride.
Ancd. Chim. Acta, 5 9 ( 1 9 7 2 )
308
S|
I()RT
('()M
M IJN I('A'I'i()NS
or r u t h e n i t m l by p r i o r r e d u c t i o n o f O s ( V i o r VIII) w i t h s t d p h u r d i o x i d e t o O s ( I V ) ~tnd p r e c i p i t a t i n g the foreign m e t a l with t h i o s a l i c y h t m i d e by the e a r l i e r p r o c e d u r e s 2. O s m i u m ( I V ) w h i c h w o u l d r e m a i n in the filtrate, c o u l d b e o x i d i z e d to o s m i c acid w i t h c o n c e n t r a t e d nitric acid a n d distilled. T h e o s n l i u m c o n t e n t of the distillate c o u l d t h e n be d e t e r m i n e d w i t h t h i o s a l i c y h m a i d e as d e s c r i b e d a b o v e .
Sl~e(.trophotomelric determit~ation rJ/'osmiton ctJtd .qold T h e o s m i u m - t h i o s a l i c y l a m i d e c o m p l e x was Cltmntitatively e x t r u c t e d with isobutyl m e t h y l k e t o n e e t h a n o l m i x t u r e at pl-! 4.5--6.0. T h e b r o w n e x t r a c t s h o w e d m a x i m a l a b s o r b a n c e at 385 n m a n d o b e y e d Beer's l a w o v e r the r a n g e 3.0-15.4 itg Os m l - ~. "l'hc g o l d c o m p l e x was c o m p l e t e l y extr~ictcd in c h l o r o f o r m f r o m 2.0--4.0 1~'! h y d r o c h l o r i c acid s o l u t i o n . T h e o r a n g e - y e l l o w e x t r a c t s h o w e d an a b s o r p t i o n pe~ik at 460 nrn a n d o b e y e d Beer's law o v e r t h e r a n g e 2.78-16.68 ltg A u m l IJrocedure.for osmittm. Phlce t h e o s m i u m sol u t i o n in a 100-ml s e p a r a t i n g f u n n e l a n d ~td.iust its .'lcidity to pl-I 4.5--6.0 w i t h 5'"i, s o d i u m a c e t a t e a n d I M h y d r o c h l o r i c acid. Mix t h o r o u g h l y w i t h u k n o w n a m o u n t o f the t h i o s a l i c y l a m i d e s o l u t i o n a n d place o v e r a hot w a t e r b a t h for I 0 rain. C o o l a n d a d d 0.5 g of solid p o t a s s i u m c h l o r i d e . A d d 10 ml of e t h a n o l a n d extr~lct w i t h 5-ml p o r t i o n s o f i s o b u t y l m e t h y l k e t o n e . Collect the e x t r a c t s in a 50-ml v o l u m e t r i c Ilask tuld d i l u t e to the m a r k with i s o b u t y l m e t h y l k e t o n e . M e a s u r e t h e a b s o r b u n c e o f the c o m p l e x ~lt 385 n m a g a i n s t a r e a g e n t blank s o l u t i o n . Proc'edto'e.f'orqohi. I n t r o d u c e the gold s o l u t i o n i n t o a 100-hal separ~lting funnel. A d j u s t the a c i d i t y to 2 M with d i l u t e h y d r o c h l o r i c ~lcid, zldd a k n o w n a m o u n t o f the t h i o s a l i c y l a m i d e s o l u t i o n ~md s h a k e well. A l l o w the m i x t u r e to s t a n d for 10-15 rain. E x t r a c t the y e l l o w p r e c i p i t a t e with f o u r 5-ml p o r t i o n s o f c h l o r o f o r m . D i l u t e the c o m bined e x t r a c t s to 25 ml w i t h c h l o r o f o r m a n d m e a s u r e the a h s o r h a n c e ut 460 n m against a reagent blank solution. T h e n b s o r b a n c e c u r v e s o f t h e soltttions of the ~lbovc m e t a l c o m p l e x e s a r e sho.wn in Fig. I. 0'6
o'~ ~ ~
I ,~
O'5
0'1
340
~
i
380
420
460
WAVELENGTH (nm)
500
540 i.
Fig. I. A b s o r b n n c e curves of m e t a l -thios~dicylnnlide complexes, ((-.~I ( ) s m i u n l -thiosalicylanaide c o m p l e × in i s o b u t y l methyl k e t o n e -eth~nol mixture. I ( ) s ] -= 7.70 Itg n l l t . ( 0 ' ) ( ; o l d - t h i o s u l i c v h l m i d e ct~nlplex in
clah~roform. IAt(I = 1~.52t~g ml " Anal. Chim. Ac'ta. 59 (1972)
SI4()RT COMMU
309
N I('ATI()NS
E{'lbct o.['ptl. T h e pH o f time o s m i u m s o l u t i o n w a s a d j u s t e d w i t h 5 " , sodiunm a c e t a t e s o l u t i o n a n d d i l u t e h y d r o c h l o r i c acid. T h e p H v a l u e s o f the a q u e o u s layers w e r e m e a s u r e d after time e x t r a c t i o n o f t h e o s m i u m - - t h i o s a l i c y l a m i d e c o m p l e x . It w a s o b s e r v e d t h a t 100 ",, e x t r a c t i o n o f t h e osmiunm c o m p l e x c o u l d be m a d e at p H 4.5-6.0. B e l o w p H 3.50, time r e a g e n t w a s p a r t l y o x i d i z e d a n d a n o m a l o u s r e s u l t s w e r e o b t a i n e d . Gold -thiosalicylamide complex was quantitatively extracted with chloroform f r o m 2.0-4.0 .~,I h y d r o c h l o r i c a c i d s o l u t i o n . El.]'ect q f d i r e r s e ions. O s m i u m a n d g o l d c o u l d s e p a r a t e l y be d e t e r m i n e d in p r e s e n c e o f a p p r e c i a b l e a m o u n t s o f d i v e r s e iotas by f o l l o w i n g t h e a b o v e p r o c e d u r e s . 1)/ T h e t o l e r a n c e l i m i t s (i.e. c o n c e n t r a t i o n s c a u s i n g a n e r r o r less t h a n ___2/,,) are recorded in T a b l e I1, E D T A , t a r t r a t e , f l u o r i d e a n d p h o s p h a t e c o u l d be t o l e r a t e d in a m o u n t s u p to 20 m g b u t c y a n i d e i n t e r f e r e d , as d i d p l a t i n u m , r h o d i u m a n d r u t l a c n i u m . "I'A BI.I'~ I!FFF('T
11
f)F I)IVI-R~i*.*IONS IN I'~IF SIq!I*I'I:,I)iqI(YI'()MI"I'I~.I(" D I ! T I - R M I N : A T I ( ) N ( ) I : ( ) ~ M I ( T M A N D ( ; ( ) I
O s m i u m ( I X7. I lag) I)irerxe ion
,,Imtnlt:t tolerated
(;old Direrse ion
(llq) M n'
/)it'er.s(, ion
(tUl)
I()0(1"
T h "~ '
N i~ '
1 5 0 ( 1"
V '~ '
('o z '
2( )0( )"
Z =1: ' I : c "~ '
/Imotlllt
I)il'('l'N( ~
/| IHOllll!
tolerated
if m
toler.ted
(,,)
(It.q) M n-" '
5000
"l'i ~ '
(. ' o a .
5()00
R h "~ '
500
M o r' '
20IX)
N i a,
4( )00
'l'h ~ '
5000
3( )()()"
\ V ~' '
1500
Zn a,
3000
V ~ '
15()()"
"IT s '
6 ( ) O I'
C'd a '
5000
t !~' '
C r "~ '
I (100"
( " tt a ,
5(10 ~
/% I "~ '
5000
A I "~ "
120()"
INI : '
100
I O(X)
1500"
A u* '
100
C ; a "~ " I n "~ '
I n "~ '
I ( )00"
Ir~ '
I O0
C'r'* '
5000
TI '~ '
SO0"
'
" In presence
of fluoride,
! 000"
ltg)
500
Ga*
'
,,Imottlll tolerated
(2()8.~
I)
F c "~ f' I n p r e s e n c e
oftartrate.
" In presence
1000
1 5 0 'l
6000
I 0(X)
'
o f F, D T A .
5 ( ) 0 'l
a In presence
of phosphate.
E[.'l'ect o f reuqent concentration and nature o f the complex. It w a s f o u n d t h a t osmiunm(Vl) was completely extracted when the reagent concentration was eight t i m e s time m o l a r c o n c e n t r a t i o n o f the m e t a l ion. F o r o s m i u m ( V i i i ) , t h e r e a g e n t c o n c e n t r a t i o n r e q u i r e d for c o m p l e t e e x t r a c t i o n w a s 10 t i m e s t h a t o f t h e m e t a l ion. T h e results o f t h e m o l e - r a t i o m e t h o d 3 for t h e s t u d y o f t h e n a t u r e of o s m i u m c o m p l e x were inconclusive. The empirical formula of the gold(lli)--thiosalicylamide complex was determ i n e d by t h e m o l e - r a t i o m e t h o d 3, w h i c h i n d i c a t e d t h e f o r m a t i o n o f a 1 : 4 c o m p l e x ; t h i s w a s s u p p o r t e d b y t h e s l o p e - r a t i o m e t h o d "~. T h e d i s s o c i a t i o n c o n s t a n t o f t h i s c o m p l e x in c h l o r o f o r m w a s d e t e r m i n e d f r o m t h e m o l e - r a t i o c u r v e 4 to be 1 . 5 7 6 . 1 0 -22 M o l a r tthsorptit,ity, setTsitil,it),, precision trod accuracy. T h e s e d a t a for the m e t a l c o m p l e x e s are g i v e n in T a b l e III. Discussion A n a l y t i c a l r e a g e n t s for t h e p r e c i p i t a t i o n o f o s m i u m a n d g o l d in d i r e c t w e i g h i n g Anal. Chim. Acta, 59 (1972)
3 10 'I'A t 3 L F
SHORT
( :OMM U N I ( 'A'I'I()NS
Ill
.q,|(II.AR AIIS()IC, l r I ' I V I ' I ' Y , S I ! N S I ' I ' I V I ' I ' Y , IJRI:,f'INI(IN A N D
('Oral;h,.\"
( )slnium.lhiosldicylamide
A('('iJRA('Y
Al olco" ~d~.s'o~'plirit)'
.~ensit it'il v (Itq c m 2")
I~el~tt ire .~l a n d a r d ch'victlitm ( " , . )
R e h t t i r e me~tp~ e r r o r ('",',)
66. Icl. 102
0,1)287
0.63
0.24
I O.Ot"v I 0 ~
0.0196
1).61
0.25
( h~ld
thit~s~tl icyl;tnlide
f o r m s are f e w in n u m b e r . T h i o s a l i c y l a m i d e is a n e x c e l l e n t g r a v i m e t r i c reagent for b o t h the m~ztals, s i n c e it is h i g h l y s o l u b l e in h o t w a t e r a n d easily forms w a t e r i n s o l u b l e c o m p l e x e s o f d e f i n i t e c o m p o s i t i o n w h i c h c a n be freed from e x c e s s reagent by w a s h i n g . B o t h g o l d a n d o s m i u n a can be s e p a r a t e d f r o m a l m o s t all t h e b a s e m e t a l s with t h i o s a l i c y h m a i d e as precipitant. T h e metal c o m p l e x e s are easily e x t r a c t a b l e in o r g a n i c s o l v e n t s and are well s u i t e d tbr the s p e c t r o p h o t o m e t r i c d e t e r m i n a t i o n o f tl'~.lce maaotmts o f the l'nc~t~|ls. K. S u r M. M a z u m d a r S. C. S h o m e
D e p a r t m e n t oj " C'hentistrv, Presidency C'olle,qe, Calcutta- 12 ( lttdia) I 2 3 4
S. C. SII()MF. ANI) M. MAZtJ~ll)AP,, Atlt:l. ( ' / t i m . /Ictct, 46 11969) 1 5 5 : 5 6 (1971) 149. K. ,NUR AND S. C . SllOMI', /ht¢tl. C / t i m , ~Icier, 48 (1969) 145; 57 (1972) 21)1. A. S. MI-YF.I~, ANI, G . I I. A Y g l ' s , ,I. / l i t t e r . ( ' I t e m . S¢Jc., 79 1 1 9 5 7 ) 4 9 . A. E. HAItvl.,",' ANI) D. !_,. IMIANNIN(;, .I. / | m e r . Cheryl. S o t . , 72 ( 1 9 5 0 ) 4 4 8 8 .
(Received 2nd November A n a l . C h i m . A c t a , 59 (1972)
1971)
306
ra
:|tiLt
I':l~cvicr Puh]ishillg ¢~'ompany. Alnslcrdaln Printed in The Netherlands
Spectrophotometric and gravimetric determination of osmium and ~old with thiosalicylamide q'laiosalicylamide has been r e c o m m e n d e d by S h o m e et al. l"e" as a useful r e a g e n t for the d e t e r m i n a t i o n of t h a l l i u m , m e r c u r y , p a l l a d i u m , r h o d i u m , r u t h e n i u m a n d p h t t i n u m . In the p r e s e n t i n v e s t i g a t i o n , t h e r e a g e n t w a s e m p l o y e d for the gravim e t r i c ~tnd s p c c t r o p h o t o m e t r i c d e t e r m i n a t i o n of o s m i u m ( V l o r V l i l ) a n d g o l d ( i l l ) . T h e b r o w n o s m i u m c o m p l e x is p r e c i p i t a t e d q u a n t i t a t i v e l y at p H 2.5--7.0 a n d corres p o n d s to the f o r m u h t OsOz(C71-1¢,ONS)2. T h e g o l d c o m p l e x , A u ( C ~ H T O N S ) 3 C I , is y e l l o w in c o l o u r a n d is c o m p l e t e l y p r e c i p i t a t e d f r o m 2.5.--6.0 N h y d r o c h l o r i c acid s o l u t i o n . T h e t h i o s a l i c y l a m i d e c o m p l e x e s of b o t h m e t a l s a r e m o d e r a t e l y s o l u b l e in etlaanol a n d o t h e r c o m m o n o r g a n i c s o l v e n t s but h i g h l y s o l u b l e in etlaanol- isobutyl m e t h y l k e t o n e m i x t u r e . T h e r e a g e n t s o l u t i o n in i s o b u t y l m e t h y l k e t o n e , h o w e v e r , d e c o m p o s e s in h i g h l y acidic m e d i u m . Thcrclkwc, the o s m i u n a c o m p l e x is e x t r a c t e d with e t h a n o l - - i s o b u t y l m e t h y l k e t o n e m i x t u r e but the g o l d c o m p l e x w h i c h is precipitated in highly a c i d i c s o l u t i o n s is e x t r a c t e d w i t h c h l o r o f o r m . Exper#nental A p p a r a t u s . A C a r l - Z e i s s s p c c t r o p h o t o m e t c r , M o d e l P M Q !1. w i t h I-cm t l u a r t z c e i l s , was u s e d for a b s o r b a n c e m e a s u r e m e n t s . A C a m b r i d g e p H m e t e r e q u i p p e d w i t h glass a n d c a l o m e l e l e c t r o d e s w a s used for p H m e a s u r e m e n t s . S t a n d a r d otetal solutions. An o s m i u m s o l u t i o n was m a d e by t r e a t i n g p o t a s s i u m o s m a t e with 0.1 M sod ium h y d r o x i d e o r by d i s s o l v i n g o s m i c a c i d in cold distilled water. T h e s o l u t i o n was s t o r e d in the c o l d . a n d w a s s t a n d a r d i z e d by p r e c i p i t a t i n g the m e t a l as t h e s u l p h i d e , f o l l o w e d by i g n i t i o n to the m e t a l in h y d r o g e n . T h e gold s o l u t i o n was p r e p a r e d by ~tissoiving p u r e g o l d ( l l I) c h l o r i d e in d i l u t e h y d r o c h l o r i c acid. ,'tnd was s t a n d a r d i z e d by the u s u a l o x a l i c acid m e t h o d . W e a k e r w o r k i n g s o l u t i o n s of the m e t a l i o n s w e r e o b t a i n e d by a p p r o p r i a t e d i l u t i o n . Diverse ion sohttions. S o l u t i o n s o f d i v e r s e i o n s w e r e p r e p a r e d by d i s s o l v i n g k n o w n a m o u n t s o f their p u r e c o m p o u n d s in distilled w a t e r . Dilute h y d r o c h l o r i c a c i d w~ts used w h e r e r e q u i r e d . Reaoent sohttion. A I"il (w/v) s o l u t i o n of t h i o s a l i c y l a m i d e in 20",, e t h a n o l w a s u s e d for the p r e c i p i t a t i o n o f o s m i u m a n d gold. F o r s p e c t r o p h o t o m e t r i c m e a s u r e m e n t s , 0.01 M t h i o s a l i c y l a m i d e in e t h a n o l w a s used. All o t h e r c h e m i c a l s used w e r e of A . R . g r a d e . Proper'ties o f metttl c o m p l e x e s T h e o s m i u m a n d g o l d c o m p l e x e s w i t h t h i o s a l i c y l a n a i d e d c c o m p o s e at 175 ° a n d 173 ° respectively. T h e o s m i u m c o m p l e x is s t a b l e o n l y in w e a k l y a c i d i c s o l u t i o n w h e r e a s the gold c o m p l e x is s t a b l e even in s t r o n g n o n o x i d i z i n g acids. B o t h the c o r n p l e x c s are r e a d i l y d e c o m p o s e d by a l k a l i a n d fairly s o l u b l e in c o m m o n o r g a n i c solvents. T h e results of a n a l y s i s o f p u r e c o m p l e x e s w e r e as follows : O s m i u m c o m p l e x . F o u n d : 3 6 . 2 0 ' ! . Os, 5.15 "0 N . 12.08 '),, S ; r e q u i r e d for O s O 2 (C-zI-I~,ONS)2 : 36.14'~,, Os. 5 . 3 2 " , N . 12.16°,,, S. Gohi c o m p l e x dried at 105 ° . F o u n d : 24.65 ",, Au, 5.20 ",, N. 12.10 ",, S, 4.40 ",, CI ; An,:tl. Chim. Acta, 59 (1972)
307
SI i( ) R T ( ' ( ) M M U N I( " A I ' I ( ] N S
r e q u i r e d for A u ( C - r H T O N S ) 3 C I -6 H : O : 24.66",, A u . 5.25",, N . 12.00",, S. 4.45 'Y.,, CI. Gold complex dried ~tt 135 '~. F o u n d : 28.50 ",, A u . 5.95 ",', N. 13.90 ",, S, 5.10 ",, CI : r e q u i r e d for A u ( C - r H 7 O N S ) 3 C I : 28.51 ',.,, A u . 6.07 ",, N. 13.88 ';,, S a n d 5.15 ",, CI.
Grat'imetric determinaticm o f osmium and gold Procedure. D i l u t e t h e o s m i u n a s o l u t i o n to a b o u t 150 ml, a d j u s t its a c i d i t y to p H 4 . 0 - 6 . 0 w i t h 10",, s o d i u m a c e t a t e s o l u t i o n a n d p r e c i p i t a t e the m e t a l in t h e c o l d by a d d i n g 8 - 1 2 t i m e s the t h e o r e t i c a l a m o u n t o f t h i o s a l i c y l a m i d e s o l u t i o n . A l l o w t h e p r e c i p i t a t e to s t a n d o n a h o t w a t e r b a t h for a b o u t I h. F i l t e r o n a N o . 4 s i n t e r e d g l a s s c r u c i b l e , w a s h w i t h h o t w a t e r , d r y a t 110--120 '~ for 2 h a n d w e i g h as O s O 2 ( C v H 6 O N S ) 2 . F o r t h e d e t e r m i n a t i o n o f g o l d . d i l u t e the m e t a l s o l u t i o n to 150 ml a n d a d j u s t its a c i d i t y to 3--4 :~/ in h y d r o c h l o r i c acid. W a r m t h e s o l u t i o n to 6 0 - 7 0 °, a d d 4---5 t i m e s t h e t h e o r e t i c a l a m o u n t of the r e a g e n t s o l u t i o n a n d a l l o w t h e p r e c i p i t a t e f o r m e d to s t a n d o n a h o t wztter b a t h for 1 h. F i l t e r o n a N o . 4 s i n t e r e d g l a s s c r u c i b l e , w a s h w i t h h o t !0",, h y d r o c h l o r i c a c i d , d r y at 135" a n d w e i g h a s A U ( C T [ - 1 7 O N S ) 3 C I . O s m i u m w a s d e t e r m i n e d in t h e r a n g e 7.5-.-30 m g a n d g o l d in t h e r a n g e 4.85-29.1 nag; in all c a s e s , the e r r o r w a s less t h a n 0.25'!,,. El.'fect of acidity. T h e o s m i u m c o m p l e x b e g i n s to c o a g u l a t e a b o v e pFi 2.0, t h e o p t i m u m p H r a n g e for q u a n t i t a t i v e p r e c i p i t a t i o n b e i n g 2.5--7.0. G o l d is c o m p l e t e l y p r e c i p i t a t e d w h e n t h e a c i d i t y o f t h e s o l u t i o n is m a i n t a i n e d at 2.5--6.0 M in h y d r o c h l o r i c acid : at l o w e r acidities, t h e p r e c i p i t a t e b e c o m e s s l i m y a n d d o e s n o t c o a g u l a t e . El.l'ect o.fdicerxe ions. O s m i u n a o r g o l d w a s d e t e r n l i n e d w i t h t h i o s a l i c y l a m i d e in t h e p r e s e n c e o f k n o w n a m o u n t s o f C o , Ni, M n , Zn, Ti, AI, In, C d , C r (as t h e i r sulphates), u r a n y i a c e t a t e , z i r c o n y l c h l o r i d e o r a m m o n i u m m o l y b d a t e . C y a n i d e , r u t h e n i um and rhodium interfered with the determination of osmium. Rhodium and ruthenium did not interferewith the determination ofgold when the latter was precipitated from 6 M hydrochloric acid solution. Palladium, platinum, copper, nitric acid and other oxidizing agents, however, interfered with the determination of gold. The results are r e c o r d e d in T a b l e I. It w o u l d b e p o s s i b l e to s e p a r a t e o s m i u m f r o m p a l l a d i u m , p l a t i n u m , r h o d i u m , F A BLI'~ ! ;I!I~AI,~ArI()N ( W ()SMIIJM A N I ) ( i ( ) l . I ) I.R()M IMVliRSF, I()NS
Gold = 9 . 7 0 mg
O,wnito~z = 9 . 5 0 m q
rrorei~.ln l o t 1
Au.]Otoul
l"orei~lta ion
,4tl.Iotmd
Fort'i#ltl itm
0.'," fOtoul
t:orei~ln iotl
Os.lbund
tdded (m~.l)
(re.q)
added (rag)
(re.q)
added (re.q)
(m~.l)
udded (re.q)
On.q)
~o 2. (200) 'qi 2 . ( 2 0 0 ) Vln z " ( 3 0 0 ) ~n 2 ~ (400) Yd" ~ (500) Fi ' + (40) M 3+ ( 2 0 0 ) In "~' ( 2 0 0 ) ~ a "a ' ( 1 0 0 )
9.70 9.67 9.72 9.72 9.70 9.70 9.72 9.72 9.70
Z r "~' (4f~)) U ~'~ ( 1 5 0 ) Mo"' (30) "Fh "t" ( 2 0 0 ) lr a ~ ( 2 0 ) R u "~+ ( 1 3 . 0 ) R h 3+ ( 5 . 5 6 ) R h 3~ ( 1 1 . 1 2 )
9.67 9.72 9.72 9.70 9.70 9.72 9.70 9.72
F e 3 ~ (20)" Co 2 " (50)" N i 2 ~ (40)" Zn 2 ~ (80)" M n z ~ (25)" G;.| 3q" ( 4 0 ) " In 3~ (40) u TI 3~ (20)" AI "~ ~ (20)"
9.49 9.52 9.46 9.52 9.50 9.49 9.49 9.50 9.49
M o " * (80) W"' (30) U ~'~ ( 4 0 ) "Fh "*~ (80)" V "~' ( 4 0 ) C u z* (30) t' "Fi "~ (30)" I r " ~ (10)
9.52 9.52 9.49 9.52 9.52 9.49 9.49 9.52
" in presence
oftartrate,
h In presence of EDTA.
" In presence
of fluoride.
Ancd. Chim. Acta, 5 9 ( 1 9 7 2 )
308
S|
I()RT
('()M
M IJN I('A'I'i()NS
or r u t h e n i t m l by p r i o r r e d u c t i o n o f O s ( V i o r VIII) w i t h s t d p h u r d i o x i d e t o O s ( I V ) ~tnd p r e c i p i t a t i n g the foreign m e t a l with t h i o s a l i c y h t m i d e by the e a r l i e r p r o c e d u r e s 2. O s m i u m ( I V ) w h i c h w o u l d r e m a i n in the filtrate, c o u l d b e o x i d i z e d to o s m i c acid w i t h c o n c e n t r a t e d nitric acid a n d distilled. T h e o s n l i u m c o n t e n t of the distillate c o u l d t h e n be d e t e r m i n e d w i t h t h i o s a l i c y h m a i d e as d e s c r i b e d a b o v e .
Sl~e(.trophotomelric determit~ation rJ/'osmiton ctJtd .qold T h e o s m i u m - t h i o s a l i c y l a m i d e c o m p l e x was Cltmntitatively e x t r u c t e d with isobutyl m e t h y l k e t o n e e t h a n o l m i x t u r e at pl-! 4.5--6.0. T h e b r o w n e x t r a c t s h o w e d m a x i m a l a b s o r b a n c e at 385 n m a n d o b e y e d Beer's l a w o v e r the r a n g e 3.0-15.4 itg Os m l - ~. "l'hc g o l d c o m p l e x was c o m p l e t e l y extr~ictcd in c h l o r o f o r m f r o m 2.0--4.0 1~'! h y d r o c h l o r i c acid s o l u t i o n . T h e o r a n g e - y e l l o w e x t r a c t s h o w e d an a b s o r p t i o n pe~ik at 460 nrn a n d o b e y e d Beer's law o v e r t h e r a n g e 2.78-16.68 ltg A u m l IJrocedure.for osmittm. Phlce t h e o s m i u m sol u t i o n in a 100-ml s e p a r a t i n g f u n n e l a n d ~td.iust its .'lcidity to pl-I 4.5--6.0 w i t h 5'"i, s o d i u m a c e t a t e a n d I M h y d r o c h l o r i c acid. Mix t h o r o u g h l y w i t h u k n o w n a m o u n t o f the t h i o s a l i c y l a m i d e s o l u t i o n a n d place o v e r a hot w a t e r b a t h for I 0 rain. C o o l a n d a d d 0.5 g of solid p o t a s s i u m c h l o r i d e . A d d 10 ml of e t h a n o l a n d extr~lct w i t h 5-ml p o r t i o n s o f i s o b u t y l m e t h y l k e t o n e . Collect the e x t r a c t s in a 50-ml v o l u m e t r i c Ilask tuld d i l u t e to the m a r k with i s o b u t y l m e t h y l k e t o n e . M e a s u r e t h e a b s o r b u n c e o f the c o m p l e x ~lt 385 n m a g a i n s t a r e a g e n t blank s o l u t i o n . Proc'edto'e.f'orqohi. I n t r o d u c e the gold s o l u t i o n i n t o a 100-hal separ~lting funnel. A d j u s t the a c i d i t y to 2 M with d i l u t e h y d r o c h l o r i c ~lcid, zldd a k n o w n a m o u n t o f the t h i o s a l i c y l a m i d e s o l u t i o n ~md s h a k e well. A l l o w the m i x t u r e to s t a n d for 10-15 rain. E x t r a c t the y e l l o w p r e c i p i t a t e with f o u r 5-ml p o r t i o n s o f c h l o r o f o r m . D i l u t e the c o m bined e x t r a c t s to 25 ml w i t h c h l o r o f o r m a n d m e a s u r e the a h s o r h a n c e ut 460 n m against a reagent blank solution. T h e n b s o r b a n c e c u r v e s o f t h e soltttions of the ~lbovc m e t a l c o m p l e x e s a r e sho.wn in Fig. I. 0'6
o'~ ~ ~
I ,~
O'5
0'1
340
~
i
380
420
460
WAVELENGTH (nm)
500
540 i.
Fig. I. A b s o r b n n c e curves of m e t a l -thios~dicylnnlide complexes, ((-.~I ( ) s m i u n l -thiosalicylanaide c o m p l e × in i s o b u t y l methyl k e t o n e -eth~nol mixture. I ( ) s ] -= 7.70 Itg n l l t . ( 0 ' ) ( ; o l d - t h i o s u l i c v h l m i d e ct~nlplex in
clah~roform. IAt(I = 1~.52t~g ml " Anal. Chim. Ac'ta. 59 (1972)
SI4()RT COMMU
309
N I('ATI()NS
E{'lbct o.['ptl. T h e pH o f time o s m i u m s o l u t i o n w a s a d j u s t e d w i t h 5 " , sodiunm a c e t a t e s o l u t i o n a n d d i l u t e h y d r o c h l o r i c acid. T h e p H v a l u e s o f the a q u e o u s layers w e r e m e a s u r e d after time e x t r a c t i o n o f t h e o s m i u m - - t h i o s a l i c y l a m i d e c o m p l e x . It w a s o b s e r v e d t h a t 100 ",, e x t r a c t i o n o f t h e osmiunm c o m p l e x c o u l d be m a d e at p H 4.5-6.0. B e l o w p H 3.50, time r e a g e n t w a s p a r t l y o x i d i z e d a n d a n o m a l o u s r e s u l t s w e r e o b t a i n e d . Gold -thiosalicylamide complex was quantitatively extracted with chloroform f r o m 2.0-4.0 .~,I h y d r o c h l o r i c a c i d s o l u t i o n . El.]'ect q f d i r e r s e ions. O s m i u m a n d g o l d c o u l d s e p a r a t e l y be d e t e r m i n e d in p r e s e n c e o f a p p r e c i a b l e a m o u n t s o f d i v e r s e iotas by f o l l o w i n g t h e a b o v e p r o c e d u r e s . 1)/ T h e t o l e r a n c e l i m i t s (i.e. c o n c e n t r a t i o n s c a u s i n g a n e r r o r less t h a n ___2/,,) are recorded in T a b l e I1, E D T A , t a r t r a t e , f l u o r i d e a n d p h o s p h a t e c o u l d be t o l e r a t e d in a m o u n t s u p to 20 m g b u t c y a n i d e i n t e r f e r e d , as d i d p l a t i n u m , r h o d i u m a n d r u t l a c n i u m . "I'A BI.I'~ I!FFF('T
11
f)F I)IVI-R~i*.*IONS IN I'~IF SIq!I*I'I:,I)iqI(YI'()MI"I'I~.I(" D I ! T I - R M I N : A T I ( ) N ( ) I : ( ) ~ M I ( T M A N D ( ; ( ) I
O s m i u m ( I X7. I lag) I)irerxe ion
,,Imtnlt:t tolerated
(;old Direrse ion
(llq) M n'
/)it'er.s(, ion
(tUl)
I()0(1"
T h "~ '
N i~ '
1 5 0 ( 1"
V '~ '
('o z '
2( )0( )"
Z =1: ' I : c "~ '
/Imotlllt
I)il'('l'N( ~
/| IHOllll!
tolerated
if m
toler.ted
(,,)
(It.q) M n-" '
5000
"l'i ~ '
(. ' o a .
5()00
R h "~ '
500
M o r' '
20IX)
N i a,
4( )00
'l'h ~ '
5000
3( )()()"
\ V ~' '
1500
Zn a,
3000
V ~ '
15()()"
"IT s '
6 ( ) O I'
C'd a '
5000
t !~' '
C r "~ '
I (100"
( " tt a ,
5(10 ~
/% I "~ '
5000
A I "~ "
120()"
INI : '
100
I O(X)
1500"
A u* '
100
C ; a "~ " I n "~ '
I n "~ '
I ( )00"
Ir~ '
I O0
C'r'* '
5000
TI '~ '
SO0"
'
" In presence
of fluoride,
! 000"
ltg)
500
Ga*
'
,,Imottlll tolerated
(2()8.~
I)
F c "~ f' I n p r e s e n c e
oftartrate.
" In presence
1000
1 5 0 'l
6000
I 0(X)
'
o f F, D T A .
5 ( ) 0 'l
a In presence
of phosphate.
E[.'l'ect o f reuqent concentration and nature o f the complex. It w a s f o u n d t h a t osmiunm(Vl) was completely extracted when the reagent concentration was eight t i m e s time m o l a r c o n c e n t r a t i o n o f the m e t a l ion. F o r o s m i u m ( V i i i ) , t h e r e a g e n t c o n c e n t r a t i o n r e q u i r e d for c o m p l e t e e x t r a c t i o n w a s 10 t i m e s t h a t o f t h e m e t a l ion. T h e results o f t h e m o l e - r a t i o m e t h o d 3 for t h e s t u d y o f t h e n a t u r e of o s m i u m c o m p l e x were inconclusive. The empirical formula of the gold(lli)--thiosalicylamide complex was determ i n e d by t h e m o l e - r a t i o m e t h o d 3, w h i c h i n d i c a t e d t h e f o r m a t i o n o f a 1 : 4 c o m p l e x ; t h i s w a s s u p p o r t e d b y t h e s l o p e - r a t i o m e t h o d "~. T h e d i s s o c i a t i o n c o n s t a n t o f t h i s c o m p l e x in c h l o r o f o r m w a s d e t e r m i n e d f r o m t h e m o l e - r a t i o c u r v e 4 to be 1 . 5 7 6 . 1 0 -22 M o l a r tthsorptit,ity, setTsitil,it),, precision trod accuracy. T h e s e d a t a for the m e t a l c o m p l e x e s are g i v e n in T a b l e III. Discussion A n a l y t i c a l r e a g e n t s for t h e p r e c i p i t a t i o n o f o s m i u m a n d g o l d in d i r e c t w e i g h i n g Anal. Chim. Acta, 59 (1972)
3 10 'I'A t 3 L F
SHORT
( :OMM U N I ( 'A'I'I()NS
Ill
.q,|(II.AR AIIS()IC, l r I ' I V I ' I ' Y , S I ! N S I ' I ' I V I ' I ' Y , IJRI:,f'INI(IN A N D
('Oral;h,.\"
( )slnium.lhiosldicylamide
A('('iJRA('Y
Al olco" ~d~.s'o~'plirit)'
.~ensit it'il v (Itq c m 2")
I~el~tt ire .~l a n d a r d ch'victlitm ( " , . )
R e h t t i r e me~tp~ e r r o r ('",',)
66. Icl. 102
0,1)287
0.63
0.24
I O.Ot"v I 0 ~
0.0196
1).61
0.25
( h~ld
thit~s~tl icyl;tnlide
f o r m s are f e w in n u m b e r . T h i o s a l i c y l a m i d e is a n e x c e l l e n t g r a v i m e t r i c reagent for b o t h the m~ztals, s i n c e it is h i g h l y s o l u b l e in h o t w a t e r a n d easily forms w a t e r i n s o l u b l e c o m p l e x e s o f d e f i n i t e c o m p o s i t i o n w h i c h c a n be freed from e x c e s s reagent by w a s h i n g . B o t h g o l d a n d o s m i u n a can be s e p a r a t e d f r o m a l m o s t all t h e b a s e m e t a l s with t h i o s a l i c y h m a i d e as precipitant. T h e metal c o m p l e x e s are easily e x t r a c t a b l e in o r g a n i c s o l v e n t s and are well s u i t e d tbr the s p e c t r o p h o t o m e t r i c d e t e r m i n a t i o n o f tl'~.lce maaotmts o f the l'nc~t~|ls. K. S u r M. M a z u m d a r S. C. S h o m e
D e p a r t m e n t oj " C'hentistrv, Presidency C'olle,qe, Calcutta- 12 ( lttdia) I 2 3 4
S. C. SII()MF. ANI) M. MAZtJ~ll)AP,, Atlt:l. ( ' / t i m . /Ictct, 46 11969) 1 5 5 : 5 6 (1971) 149. K. ,NUR AND S. C . SllOMI', /ht¢tl. C / t i m , ~Icier, 48 (1969) 145; 57 (1972) 21)1. A. S. MI-YF.I~, ANI, G . I I. A Y g l ' s , ,I. / l i t t e r . ( ' I t e m . S¢Jc., 79 1 1 9 5 7 ) 4 9 . A. E. HAItvl.,",' ANI) D. !_,. IMIANNIN(;, .I. / | m e r . Cheryl. S o t . , 72 ( 1 9 5 0 ) 4 4 8 8 .
(Received 2nd November A n a l . C h i m . A c t a , 59 (1972)
1971)