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Gravimetric determination of molybdenum and its separation from other metals with n-benzoylphenylhydroxylamine
ANAL\iTLCA
GRAVIMETRIC
CHIMICA
DETERMINATION
SEPARATION
FROM
01;
ACTA
33
MOLYBDENUM
OTHER
METALS
AND
ITS
WITH
N-BENZOYLPHENYLHYDROSYLARIINE
,mc organic reagents have been usctl in the gravimctric dctcrminntion of molybdclrnl-3, but the scope of application of these mcthocls is limited. Srmnrl
OF BENZO’L’LI’I-IEN~‘LII~‘Dl~OSYLAMINI?:
WITII
hIOL\‘RDE:NUM(VI)
IONS
cn~oylphenyl~ryclrosylaminc formed a yellowish white precipitate with molyb2tiilm(VI) ions. The precipitate was slightly soluble in hot water at or above Xo”, conccntrntcd acicls at lower tcmpcraturcs, and in alcohol. Analjrsis of the pure .olybdenum complex indicated its composition to be MoOQ(C~~HIUOZN)~. It dccom1scd at rGg”--166”. SOLUTIONS
USED
IN ‘TM15 DETI~I~hlINATION
OF TI-IE METAL
standard solution of ammonium molybclatc was prepared to contain 3.08 mg of molybdenum per ml. Separate stanclard solutions of ferric alum, potassium chromate, upper sulphate, nickel sulphate, cobalt sulphate and sodium mctavanadatc were usccl I the study of the effect of fore,@ ions on the precipitation of niolybdcnum. A blution of benzoylphenylhydroxylamine in 95% ethyl alcohol was employed for the recipitation of molybdemim. All the chemicals employed were of AX. quality. Anal. Chim. Ada,
24 (x96x) 33-36
S. I<. SINHA,
34
J~I~TI~I~MINATION TIlE
I’I~JSCII’ITATJS
OF
ANI)
S. C. SHOME
MOLYBDDNUM~I)
WEIGHING
BY
IGNITING
AS MOLYRDENUM
TRIOXIDE
A known volume of the ammonium molybdate solution was diluted with distilled water, acidified with TO N hydrochloric acid, and the alcoholic solution of benzoylphcnylhyclroxylaminc (TO-IS ml) was slowly added with constant stirring. The yellowish white precipitate of molybdenum appeared only slowly when the acid concentration was low. As the molyhdcnum complex was moderately soluble in alcohol, the final volume of the solution shoultl not contain mdrc than so/;, of alcohol. The precipitate was stirred for about 15 min, allowed to scttlc for another 15 min, filtered and wasl~~l with 0.02 N hydrochloric acid solution. It was moistcncd with oqc or two drops of G N ammonium hydroxide solution to neutralist the free acicl prcscnt, ignited at 5oo-525” and wcighecl as molybdenum trioxide.
-_-__-_--_-____.___-___
_---.-------.--.-
__---__.-.-.-l.___.-.-
- - . ----_--_-__-_..__~_____
_.__-
30 30 30 30
0.20
O.df2
0.03 0.03 0.03 0.03
0.0770 0.0770 0.0770 0.0770
30 30 30 3”
O.‘#”
0.42 0 . .( ‘2 0.42
0.077cl 0.0770 0.0770 ..--.
so 75
0.42 0.42 0.42
80
_____. _..._.._____. _____._-_-
... ._--.._ -. - _- ..._._ ___.__._~_..
0.0770 0.0770 0.0770 0#0770
0.30 0.35
- _____ _____
-.. . _ _____ _~
--__.--_
o.oG7.5 0.1014 0. I140 “*1rss
0.0450 0.067G 0.0760 0.0770
-0.0320 -0.oog4 -0.0010 0.0000
0.01
0.1
rgo
0.1
I52
0.07G7 0.07G8 0.0773 o-0773
-0.0003
o.Go
--0.0002
rho
0.1 IGO
2.50
0.1
0.03 OS03 0.03
0. I rgG 0.1 I.58
0.0771
+o.ooo
0.0772
-I-0.0002
0.1129
0.0753
-0.0017
lfj’)
+o.ooa3 +0.0003
I
. ._~l_l---..___-l.-_-__-_I.___-.__
The cffccts of v:u-ious factors such as tcmpcrnturc of solution, rcagcnt concentration ancl acidity of the reaction mcclium on the precipitation of molybdenum wcrc studied. The results (‘l‘nblc I) indicate that the precipitation of molybdcnum(V1) is complctc when the supcrnatant liquid contains 0.03% (w/v) of the organic reagent in excess at iL temperature below 70” and the aciclity of the solution ranges from O.OI to 2.50 N l~yclrocl~loric acid. Molybclcnum(V1) was also clctcrmined (Table II) in the prescncc of chromium(VI), vanadium(V), iron(III), cobalt(ll), nickcl(II), and coppcr(IT). The metal was scparatc:d from cobalt, nickel or copper by precipitating molybclcnum(VI) ions with bcnxoyll~hcnylhyclroxylaminc (0.44 g) in the prcsencc of a sufficient amount of acid, and washing the prccipitatc with 0.2 N hydrochloric acid, followed by a 0.02 N solution of the sumc acid. In the other separations the precipitate was washed with 0.02 N hydrochloric acid only. The intcrfcrence of iron(II1) and vanadium(V) ionswasmasked by aclding disoclium cthylcncclinmine tetraacetate (1-2 g) which forms stable complexes with the two metal ions. When the vanadate was heated with EDTA, it was probably rcducecl to vanaclyl ion before the complex formationl4. Aural.
Chiut.
Ada,
24
(1961)
33-36
GIIAVIMETRY
OF
MO
WITH
N-BENZOYLPHENYLHYDROXYLAMINE
TABLE DETERMINATION
OF
MOLYDDENUM(\‘I)
Volume
_ ..-----
II
BY
of
WISIGHING
solution
=
300
AS
hlOLYBDENUM
- ---_-.-
Forrijyn
IO
ion added R
OF
TRIOXIDE
ml
.~-_----_-_-
DETI3I~MINATION
35
N lIC1 uddrd w1
MOL\‘UL)I
---
dl
d
I:‘rror I:
R
Uy
WISI(;I-IINC;
TZIE
MIlTAL
COh¶I’LlZS
DIIZISCTLY
An aliquot (ro45 ml) of the ammonium molybclate solution was diluted with distilled water, acidified with IO iV hydrochloric acid, heated to about Go” and n~olylxlcnum was prccipitatecl by adcling a solution of ixnxoylphcnylhyclrosylnmine (0.25-0.44 g) in alcohol (10-15 ml). ‘I’hc molybdenum precipitate was heated at 60” for 30 min on a water-bath, filtered on a No. 3 glass-sintcrcd crucible. w:~shccl with warm (Go”) 0.0; N hydrochloric acid and finally with ro ml of distilled water. The precipitate was dried at rIo--Ir5° for one hour and weighed. The molybdenum content was calculated on the basis that the precipitate contained 17.37~/, of the metal. Molybdenum was also prccipitatcd in the presence of other metallic ions as described before, but the precipitation ant1 washings were carried out under warm conditions to prcvcnt the contamination of the molybclcnum comples with the precipitant.
DETEIlMINhTION _-.__.__-_-
_.__--
OF nlOLYI1DIENUM(v1) Volume -._---
._- __..___lll___..
0.03Q80 0.07700 0.03080 0.03080 0.03080
o.I54(Ni+z) 0.107(C0+a) 0.051 (Cu+Z)
0.03080 0.04620 0.04620 0.03080 0.03080
o.lzq(Cu+‘J) o.384(1%+3) 0.772( I’c+:l) o.o04(V+9 o.ootl(v+G)
BY
of solution _..-_-__
WISIGIIING =
THIS I’RBCIPITATIS
300 ml -_--_.--
DIRECTLY
_..-__._____.II_.__
.___.---_
____
+ o.ooooG
2::
0.1777 0+443r 0.17613 0. I780 0.1781
0.03086
-__ -
0.07695 0.03072 0.03og 0.03og2
--0.00005 --0.00008 -~O.OOOl +0.00012
G.o
-3.0 6.0 2.0 3.0
0.1767 o.zG38 0.264r 0.1763 o. I 758
0.03068 0.0.+5&S I 0.0458G 0.0306 1
I
.o
G,O G.0 0.4 0.4 0.8
0.8
-
I
I
-0.00012
--o.o003g -0.00034 -0.0001g -0.0002
0*O3053
7
It can be seen from the results given in Table III that molybdenum(W) can be determined by weighing as MoOz(C13HloOzN)~ and this offers a simple method for the And.
Claim.
Acta,
24
(196x)
33-36
36
S. K. SINHA,
S. C. SHOMIS
separation of molybdenum from many other metal ions. Since chromium(V1) has a tcnclency to oxidisc bcnzoylphenylhyclroxylamine, especially in presence of hot acid, molybclcnum(VI) cannot be determined in the presence of chromium(V1) by weighing the complex directly. I3eneoylphcnylhydroxylamine precipitates tungsten(W) in acid mcclium, and it is not possible to separate molybdatc from tungstatc with the reagent. ACI
One of the authors (S. K. SINII~S)is indebted to the Ministry of Scientific Cultural Affairs, Government of India, for the grant of a scholarship.
Research
and
SlIMMARY N-I3cnzoylpl~cnyll~ytlroxylttrnir~c is cmploycd as a precipitant for the determination of molybclcnum(V1). ‘l’hc prfkpitatu can IX: wci~hctl cithcr tlircctly or as molybdenum trioxide after ijinition. Molyt,clcmum can IX dctcrminccl in the prosencc of apprcciablc amounts of iron( II L), cObalt(1 I). coppcr(lI), cllroniium(V1) and vanadium(V).
I,a N-bcnzOylpl~dnyll~yclroxylaminc ost proposk COmmC rdactif pour lc dosage gravimhtriquc du inolybtl&nc(VI), Cc d(JWgc IJCut s’cffcctucr cn prhcncc dc fcr(II I), dc cobalt. dc cuivrc, tic chromc(VI) ct clc vanadium. %USAMMENFASSCJNG Zur gravimctrischcn 13cstimmung van Molybcltin(V1) rrnd Vanadium kann N-13cnzoylpl~cnyll~ydrOxylamin
Eiscn( III), ICobalt, verwenclct wcrclcn.
ncbcn
Kupfer,
Chrom(VI)
REItlSRENCES
1 I-1. 13. fAS AND S. c. SIIOMK, Proc. fudicm .%i. Corrgr., (ig60) 184. H 1). I<. RYAN AND G. 1). Lu’rwrclc, CWI. J, C/rent., 31 (1g53) g. ” Ii. w. MOSIII~~H AND J. I:. !%2lI\VARUt%l
GRAVIMETRIC
CHIMICA
DETERMINATION
SEPARATION
FROM
01;
ACTA
33
MOLYBDENUM
OTHER
METALS
AND
ITS
WITH
N-BENZOYLPHENYLHYDROSYLARIINE
,mc organic reagents have been usctl in the gravimctric dctcrminntion of molybdclrnl-3, but the scope of application of these mcthocls is limited. Srmnrl
OF BENZO’L’LI’I-IEN~‘LII~‘Dl~OSYLAMINI?:
WITII
hIOL\‘RDE:NUM(VI)
IONS
cn~oylphenyl~ryclrosylaminc formed a yellowish white precipitate with molyb2tiilm(VI) ions. The precipitate was slightly soluble in hot water at or above Xo”, conccntrntcd acicls at lower tcmpcraturcs, and in alcohol. Analjrsis of the pure .olybdenum complex indicated its composition to be MoOQ(C~~HIUOZN)~. It dccom1scd at rGg”--166”. SOLUTIONS
USED
IN ‘TM15 DETI~I~hlINATION
OF TI-IE METAL
standard solution of ammonium molybclatc was prepared to contain 3.08 mg of molybdenum per ml. Separate stanclard solutions of ferric alum, potassium chromate, upper sulphate, nickel sulphate, cobalt sulphate and sodium mctavanadatc were usccl I the study of the effect of fore,@ ions on the precipitation of niolybdcnum. A blution of benzoylphenylhydroxylamine in 95% ethyl alcohol was employed for the recipitation of molybdemim. All the chemicals employed were of AX. quality. Anal. Chim. Ada,
24 (x96x) 33-36
S. I<. SINHA,
34
J~I~TI~I~MINATION TIlE
I’I~JSCII’ITATJS
OF
ANI)
S. C. SHOME
MOLYBDDNUM~I)
WEIGHING
BY
IGNITING
AS MOLYRDENUM
TRIOXIDE
A known volume of the ammonium molybdate solution was diluted with distilled water, acidified with TO N hydrochloric acid, and the alcoholic solution of benzoylphcnylhyclroxylaminc (TO-IS ml) was slowly added with constant stirring. The yellowish white precipitate of molybdenum appeared only slowly when the acid concentration was low. As the molyhdcnum complex was moderately soluble in alcohol, the final volume of the solution shoultl not contain mdrc than so/;, of alcohol. The precipitate was stirred for about 15 min, allowed to scttlc for another 15 min, filtered and wasl~~l with 0.02 N hydrochloric acid solution. It was moistcncd with oqc or two drops of G N ammonium hydroxide solution to neutralist the free acicl prcscnt, ignited at 5oo-525” and wcighecl as molybdenum trioxide.
-_-__-_--_-____.___-___
_---.-------.--.-
__---__.-.-.-l.___.-.-
- - . ----_--_-__-_..__~_____
_.__-
30 30 30 30
0.20
O.df2
0.03 0.03 0.03 0.03
0.0770 0.0770 0.0770 0.0770
30 30 30 3”
O.‘#”
0.42 0 . .( ‘2 0.42
0.077cl 0.0770 0.0770 ..--.
so 75
0.42 0.42 0.42
80
_____. _..._.._____. _____._-_-
... ._--.._ -. - _- ..._._ ___.__._~_..
0.0770 0.0770 0.0770 0#0770
0.30 0.35
- _____ _____
-.. . _ _____ _~
--__.--_
o.oG7.5 0.1014 0. I140 “*1rss
0.0450 0.067G 0.0760 0.0770
-0.0320 -0.oog4 -0.0010 0.0000
0.01
0.1
rgo
0.1
I52
0.07G7 0.07G8 0.0773 o-0773
-0.0003
o.Go
--0.0002
rho
0.1 IGO
2.50
0.1
0.03 OS03 0.03
0. I rgG 0.1 I.58
0.0771
+o.ooo
0.0772
-I-0.0002
0.1129
0.0753
-0.0017
lfj’)
+o.ooa3 +0.0003
I
. ._~l_l---..___-l.-_-__-_I.___-.__
The cffccts of v:u-ious factors such as tcmpcrnturc of solution, rcagcnt concentration ancl acidity of the reaction mcclium on the precipitation of molybdenum wcrc studied. The results (‘l‘nblc I) indicate that the precipitation of molybdcnum(V1) is complctc when the supcrnatant liquid contains 0.03% (w/v) of the organic reagent in excess at iL temperature below 70” and the aciclity of the solution ranges from O.OI to 2.50 N l~yclrocl~loric acid. Molybclcnum(V1) was also clctcrmined (Table II) in the prescncc of chromium(VI), vanadium(V), iron(III), cobalt(ll), nickcl(II), and coppcr(IT). The metal was scparatc:d from cobalt, nickel or copper by precipitating molybclcnum(VI) ions with bcnxoyll~hcnylhyclroxylaminc (0.44 g) in the prcsencc of a sufficient amount of acid, and washing the prccipitatc with 0.2 N hydrochloric acid, followed by a 0.02 N solution of the sumc acid. In the other separations the precipitate was washed with 0.02 N hydrochloric acid only. The intcrfcrence of iron(II1) and vanadium(V) ionswasmasked by aclding disoclium cthylcncclinmine tetraacetate (1-2 g) which forms stable complexes with the two metal ions. When the vanadate was heated with EDTA, it was probably rcducecl to vanaclyl ion before the complex formationl4. Aural.
Chiut.
Ada,
24
(1961)
33-36
GIIAVIMETRY
OF
MO
WITH
N-BENZOYLPHENYLHYDROXYLAMINE
TABLE DETERMINATION
OF
MOLYDDENUM(\‘I)
Volume
_ ..-----
II
BY
of
WISIGHING
solution
=
300
AS
hlOLYBDENUM
- ---_-.-
Forrijyn
IO
ion added R
OF
TRIOXIDE
ml
.~-_----_-_-
DETI3I~MINATION
35
N lIC1 uddrd w1
MOL\‘UL)I
---
dl
d
I:‘rror I:
R
Uy
WISI(;I-IINC;
TZIE
MIlTAL
COh¶I’LlZS
DIIZISCTLY
An aliquot (ro45 ml) of the ammonium molybclate solution was diluted with distilled water, acidified with IO iV hydrochloric acid, heated to about Go” and n~olylxlcnum was prccipitatecl by adcling a solution of ixnxoylphcnylhyclrosylnmine (0.25-0.44 g) in alcohol (10-15 ml). ‘I’hc molybdenum precipitate was heated at 60” for 30 min on a water-bath, filtered on a No. 3 glass-sintcrcd crucible. w:~shccl with warm (Go”) 0.0; N hydrochloric acid and finally with ro ml of distilled water. The precipitate was dried at rIo--Ir5° for one hour and weighed. The molybdenum content was calculated on the basis that the precipitate contained 17.37~/, of the metal. Molybdenum was also prccipitatcd in the presence of other metallic ions as described before, but the precipitation ant1 washings were carried out under warm conditions to prcvcnt the contamination of the molybclcnum comples with the precipitant.
DETEIlMINhTION _-.__.__-_-
_.__--
OF nlOLYI1DIENUM(v1) Volume -._---
._- __..___lll___..
0.03Q80 0.07700 0.03080 0.03080 0.03080
o.I54(Ni+z) 0.107(C0+a) 0.051 (Cu+Z)
0.03080 0.04620 0.04620 0.03080 0.03080
o.lzq(Cu+‘J) o.384(1%+3) 0.772( I’c+:l) o.o04(V+9 o.ootl(v+G)
BY
of solution _..-_-__
WISIGIIING =
THIS I’RBCIPITATIS
300 ml -_--_.--
DIRECTLY
_..-__._____.II_.__
.___.---_
____
+ o.ooooG
2::
0.1777 0+443r 0.17613 0. I780 0.1781
0.03086
-__ -
0.07695 0.03072 0.03og 0.03og2
--0.00005 --0.00008 -~O.OOOl +0.00012
G.o
-3.0 6.0 2.0 3.0
0.1767 o.zG38 0.264r 0.1763 o. I 758
0.03068 0.0.+5&S I 0.0458G 0.0306 1
I
.o
G,O G.0 0.4 0.4 0.8
0.8
-
I
I
-0.00012
--o.o003g -0.00034 -0.0001g -0.0002
0*O3053
7
It can be seen from the results given in Table III that molybdenum(W) can be determined by weighing as MoOz(C13HloOzN)~ and this offers a simple method for the And.
Claim.
Acta,
24
(196x)
33-36
36
S. K. SINHA,
S. C. SHOMIS
separation of molybdenum from many other metal ions. Since chromium(V1) has a tcnclency to oxidisc bcnzoylphenylhyclroxylamine, especially in presence of hot acid, molybclcnum(VI) cannot be determined in the presence of chromium(V1) by weighing the complex directly. I3eneoylphcnylhydroxylamine precipitates tungsten(W) in acid mcclium, and it is not possible to separate molybdatc from tungstatc with the reagent. ACI
One of the authors (S. K. SINII~S)is indebted to the Ministry of Scientific Cultural Affairs, Government of India, for the grant of a scholarship.
Research
and
SlIMMARY N-I3cnzoylpl~cnyll~ytlroxylttrnir~c is cmploycd as a precipitant for the determination of molybclcnum(V1). ‘l’hc prfkpitatu can IX: wci~hctl cithcr tlircctly or as molybdenum trioxide after ijinition. Molyt,clcmum can IX dctcrminccl in the prosencc of apprcciablc amounts of iron( II L), cObalt(1 I). coppcr(lI), cllroniium(V1) and vanadium(V).
I,a N-bcnzOylpl~dnyll~yclroxylaminc ost proposk COmmC rdactif pour lc dosage gravimhtriquc du inolybtl&nc(VI), Cc d(JWgc IJCut s’cffcctucr cn prhcncc dc fcr(II I), dc cobalt. dc cuivrc, tic chromc(VI) ct clc vanadium. %USAMMENFASSCJNG Zur gravimctrischcn 13cstimmung van Molybcltin(V1) rrnd Vanadium kann N-13cnzoylpl~cnyll~ydrOxylamin
Eiscn( III), ICobalt, verwenclct wcrclcn.
ncbcn
Kupfer,
Chrom(VI)
REItlSRENCES
1 I-1. 13. f