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Adsorption indicators - v
44
ANALYTICA
ADSORPTION
CHIMICA
VOL.
ACTA
INDICATORS
-
9
(1953)
V
bY G.
MANNELLI
AND
RI. L.
ROSS1
Many authors have turned their attention to adsorption indicators liable to be used in an acid medium. I
$?I~;
SO,Na References
p.
48.
N-~~;;;~OCH~
wxv
ADSORPTION INDICATORS V
9 @953)
45
This substance, really, acts very well either in an acid medium or in a strongly alkaline medium. The solution of the indicator is of an intense vioIet colour which assumes a blue-green colour when, by degrees, the silver halide is formed inside the liquid itself. This blue-green colour turns sharply to an apple-green colour at the equivalent point.
100
90
c
I
;I , . , , 400
450
WO
550
(
,
,
MK) 650 ~CW “P
Following KOLTHOI;F’S hypothesis, we have executed, analogously to MEHROTRA, a test to demonstrate the perfect stability of the colouring absorbed by the silver salt. After having precipitated the silver iodide, this has been washed three times for decantation with distilled water, and N HNO, or N NH,OH has been added. Even with energetic shaking the liquid remained colourless and we only noticed a slight variation of the colour of the precipitate, which in acid medium is sharply green, while in the presence of ammonia it assumes a green colour showing a slight tendency to blue. Although we cannot consider Blue sulphonc acid B as a neutralization indicator, nevertheless it presents some change of colour according to the pu of the solution. flefevences p. 48.
46
G. MANNELLI,
hf. L. ROSS1
VOL.
9
(1953)
It assumes a perfect blue colour till pH 3, between pH 3 and pH 4 it becomes violet-blue, while it is of an intense violet between pH 4 and PH IO. For PEI greater than II the colouring firstly becomes lilac and then red. Although the solution assumes a different colour according to the variation of PH, the colour which we obtain at the equivalent point is nearly the same colouring is applc-green colour. Working in an alkaline medium a blue-violet initially observecl, which WC also observe in a neutral medium. When the alkalinity of the solution containing I- ions is not produced by ammonium hydroxide it is necessary to rcmovc it in order to avoid the prccipitation of the silver oxide. In such a case the indicator which wo propose is very good because it permits, on the one hand, the regulation of the prr value of the solution and, on the other hand, the argentomctric titration. The salty charge which forms in the solution does not interfere with the good dcvelopmcnt of the next dctcrmination and the colour change occurs at the end point. Under such circumstances, after the addition of the indicator, it is sufficient to add nitric acid to the solution until the red or lilac colour changes to a sharp blue and afterwards the usual argentometric titration can be carried out. We have noticed that the rate of addition of the solution of silver nitrate is very important and we have obtained the best results with a rate of 45-50 drops a minute. For a larger number of drops the consumption of the titrating solution is lower than that which WC should have obtained. It is important that the titration be performed in one action, that is, without stopping it from beginning to end. Blue sulphonc acid B may be eventually used as a neutralization indicator between pri II and 12. We have determined the spectrophotomctric curves in this rnngc; they show a characteristic isosbestic point at 520 rnp (see Fig.).
Reagents
eqbloyed
Blue sulphonc acid B twice recrystallized and its 0.1% solution in water. Silver nitrate from silver Iooo”/oo Potassium iodide of Pfizer Co. twice rccrystallizcd. The solutions prepared at the desired concentrations have been standardized according to the usual methods. Purified sodium chloride has been used as primary standard.
References
p.
48.
9
VOL*
ADSORPTION
(1953)
HNO, N/IO added ml
INDICATORS
V
tiz found -~.-.
difference --_ -___
o-1593 0.1593 0.1593 O-1593 0.1593
0.1586 0.1586 0.1586 0.1578 0.1588
7‘KO’i 7’LO’1 7.ro” x.5.10-3 5.x04
o-1593 0.1593 0.1593 o-1593
o. 1587 O.I58G 0.1580 0.~583
6.x0-’ 7. to+ x.3.10-3 x.10-3
N/IOO ,* IS s, ‘I I,
0.1593 O-1593 0.1593 0.1593 0.1593 0.1593
0.x591 0.1588 0.158G 0.1589 0.1588 0.1588
N/r00 ‘, ,, ,, ,, $8 3, ,, ,t
0.1593 0.1593 oar593 o-*593 0.1593 o*r593 0 .I!593 o-r593 0.1593
0.x592 0.1593 O.I592 0.15go 0.1592 0.1593 0.1593 0.1593
I*IO"1 0.00
0.15go
3-10~
0.1593 o.r.593 0.1593 o-r593 o*r593 0*x593
0.15g2
x*104
0.1593
0.00
0.1590 0.1592
3.10~' 0.00 L.I04
o.rggr
2*x04
present
KI __-_
N/r00 ,, #,
I
2 IO
I5
3,
20
,.
HNO,
N N/x00
;
,,
IO
#.
15 H,PO,
I.
~V/ro X0 20
30 50 70 90 NH,O_H 5 IO
15 20
25 30 35 40 N/IO I 2 5 IO
=5 20
Refevcnces
2.104
5.10-a 7.104 4.104
~-IO-~ 5010~
N
I
NaOH
47
p.
48.
0.1593
I.104
3.10~ x.104 o*oo o*oo oaoo
48
G. BiANNELLI,
M.
L. ROSS1
VOL.
9
(1953)
SUMMARY Blue sulphonc acid I3 has been proposed as an adsorption fit to be employccl in strongly alkalmc media.
indicator
for I--ions
cst prop04 Lc blcu sulfonc acrdc 13, nouvcl indicateur d’adsorption, titrations argcntom&riques dcs ions I-. Cet indicateur cst particuli&emcnt sant cn solut~nsr8s alcalincs.
pour les intcircs-
% USRRIMENITASSUNG Ein ncucr Adsorptionmdiltator, Blnu Sulphonsiture B, wurde fur argentomctrische Titricrungcn bcschrlcbcn. DIG grossc Nirtzlichkcit des Indikators liegt darin class cr such fur schr allcalm~schc Liisungen benutzt wcrden lcann. REFERENCES J. M. KOL’TIIOIT AND (I907) 1X. C.
L. H. VON
BERK,
Z.
Amzl.
Chru.,
70 (1927)
369;
iDid., 71
235.
MEIIROTRA, AmZ. Chtr~z. Acln, 2 (1948) 3G; L. M. KUL'BERG AND P. J. DURANT, 13ULANZIlIZ C./l., 44 (1950) 1057G; A. J. BERRY (1933) G13; R. BERG AND E. BEKER,Z. Anal. Clrenr., 119 (1940) 8x;L. AND G. PIAZZA, A7tn. Chrn. npphcatn. 22 (1932) 631. R. LANG AND J. MESSINGTZR, Bev., B63 (1930) rl)rg. Am. C/ram. npplicnhz, 40 (1950) 163, 1G6, 175. 1;;.FAJANS AND 13. \vOLPl:, %. mror~. Clri~., 137 (1924) 221. R. C. MIXI~OTRA, Aural. Chzru. ffctn, 3 (1949) 78. Received
April
AND I. N. Analysl, 55 BELLADEN
znd,
1953
ANALYTICA
ADSORPTION
CHIMICA
VOL.
ACTA
INDICATORS
-
9
(1953)
V
bY G.
MANNELLI
AND
RI. L.
ROSS1
Many authors have turned their attention to adsorption indicators liable to be used in an acid medium. I
$?I~;
SO,Na References
p.
48.
N-~~;;;~OCH~
wxv
ADSORPTION INDICATORS V
9 @953)
45
This substance, really, acts very well either in an acid medium or in a strongly alkaline medium. The solution of the indicator is of an intense vioIet colour which assumes a blue-green colour when, by degrees, the silver halide is formed inside the liquid itself. This blue-green colour turns sharply to an apple-green colour at the equivalent point.
100
90
c
I
;I , . , , 400
450
WO
550
(
,
,
MK) 650 ~CW “P
Following KOLTHOI;F’S hypothesis, we have executed, analogously to MEHROTRA, a test to demonstrate the perfect stability of the colouring absorbed by the silver salt. After having precipitated the silver iodide, this has been washed three times for decantation with distilled water, and N HNO, or N NH,OH has been added. Even with energetic shaking the liquid remained colourless and we only noticed a slight variation of the colour of the precipitate, which in acid medium is sharply green, while in the presence of ammonia it assumes a green colour showing a slight tendency to blue. Although we cannot consider Blue sulphonc acid B as a neutralization indicator, nevertheless it presents some change of colour according to the pu of the solution. flefevences p. 48.
46
G. MANNELLI,
hf. L. ROSS1
VOL.
9
(1953)
It assumes a perfect blue colour till pH 3, between pH 3 and pH 4 it becomes violet-blue, while it is of an intense violet between pH 4 and PH IO. For PEI greater than II the colouring firstly becomes lilac and then red. Although the solution assumes a different colour according to the variation of PH, the colour which we obtain at the equivalent point is nearly the same colouring is applc-green colour. Working in an alkaline medium a blue-violet initially observecl, which WC also observe in a neutral medium. When the alkalinity of the solution containing I- ions is not produced by ammonium hydroxide it is necessary to rcmovc it in order to avoid the prccipitation of the silver oxide. In such a case the indicator which wo propose is very good because it permits, on the one hand, the regulation of the prr value of the solution and, on the other hand, the argentomctric titration. The salty charge which forms in the solution does not interfere with the good dcvelopmcnt of the next dctcrmination and the colour change occurs at the end point. Under such circumstances, after the addition of the indicator, it is sufficient to add nitric acid to the solution until the red or lilac colour changes to a sharp blue and afterwards the usual argentometric titration can be carried out. We have noticed that the rate of addition of the solution of silver nitrate is very important and we have obtained the best results with a rate of 45-50 drops a minute. For a larger number of drops the consumption of the titrating solution is lower than that which WC should have obtained. It is important that the titration be performed in one action, that is, without stopping it from beginning to end. Blue sulphonc acid B may be eventually used as a neutralization indicator between pri II and 12. We have determined the spectrophotomctric curves in this rnngc; they show a characteristic isosbestic point at 520 rnp (see Fig.).
Reagents
eqbloyed
Blue sulphonc acid B twice recrystallized and its 0.1% solution in water. Silver nitrate from silver Iooo”/oo Potassium iodide of Pfizer Co. twice rccrystallizcd. The solutions prepared at the desired concentrations have been standardized according to the usual methods. Purified sodium chloride has been used as primary standard.
References
p.
48.
9
VOL*
ADSORPTION
(1953)
HNO, N/IO added ml
INDICATORS
V
tiz found -~.-.
difference --_ -___
o-1593 0.1593 0.1593 O-1593 0.1593
0.1586 0.1586 0.1586 0.1578 0.1588
7‘KO’i 7’LO’1 7.ro” x.5.10-3 5.x04
o-1593 0.1593 0.1593 o-1593
o. 1587 O.I58G 0.1580 0.~583
6.x0-’ 7. to+ x.3.10-3 x.10-3
N/IOO ,* IS s, ‘I I,
0.1593 O-1593 0.1593 0.1593 0.1593 0.1593
0.x591 0.1588 0.158G 0.1589 0.1588 0.1588
N/r00 ‘, ,, ,, ,, $8 3, ,, ,t
0.1593 0.1593 oar593 o-*593 0.1593 o*r593 0 .I!593 o-r593 0.1593
0.x592 0.1593 O.I592 0.15go 0.1592 0.1593 0.1593 0.1593
I*IO"1 0.00
0.15go
3-10~
0.1593 o.r.593 0.1593 o-r593 o*r593 0*x593
0.15g2
x*104
0.1593
0.00
0.1590 0.1592
3.10~' 0.00 L.I04
o.rggr
2*x04
present
KI __-_
N/r00 ,, #,
I
2 IO
I5
3,
20
,.
HNO,
N N/x00
;
,,
IO
#.
15 H,PO,
I.
~V/ro X0 20
30 50 70 90 NH,O_H 5 IO
15 20
25 30 35 40 N/IO I 2 5 IO
=5 20
Refevcnces
2.104
5.10-a 7.104 4.104
~-IO-~ 5010~
N
I
NaOH
47
p.
48.
0.1593
I.104
3.10~ x.104 o*oo o*oo oaoo
48
G. BiANNELLI,
M.
L. ROSS1
VOL.
9
(1953)
SUMMARY Blue sulphonc acid I3 has been proposed as an adsorption fit to be employccl in strongly alkalmc media.
indicator
for I--ions
cst prop04 Lc blcu sulfonc acrdc 13, nouvcl indicateur d’adsorption, titrations argcntom&riques dcs ions I-. Cet indicateur cst particuli&emcnt sant cn solut~nsr8s alcalincs.
pour les intcircs-
% USRRIMENITASSUNG Ein ncucr Adsorptionmdiltator, Blnu Sulphonsiture B, wurde fur argentomctrische Titricrungcn bcschrlcbcn. DIG grossc Nirtzlichkcit des Indikators liegt darin class cr such fur schr allcalm~schc Liisungen benutzt wcrden lcann. REFERENCES J. M. KOL’TIIOIT AND (I907) 1X. C.
L. H. VON
BERK,
Z.
Amzl.
Chru.,
70 (1927)
369;
iDid., 71
235.
MEIIROTRA, AmZ. Chtr~z. Acln, 2 (1948) 3G; L. M. KUL'BERG AND P. J. DURANT, 13ULANZIlIZ C./l., 44 (1950) 1057G; A. J. BERRY (1933) G13; R. BERG AND E. BEKER,Z. Anal. Clrenr., 119 (1940) 8x;L. AND G. PIAZZA, A7tn. Chrn. npphcatn. 22 (1932) 631. R. LANG AND J. MESSINGTZR, Bev., B63 (1930) rl)rg. Am. C/ram. npplicnhz, 40 (1950) 163, 1G6, 175. 1;;.FAJANS AND 13. \vOLPl:, %. mror~. Clri~., 137 (1924) 221. R. C. MIXI~OTRA, Aural. Chzru. ffctn, 3 (1949) 78. Received
April
AND I. N. Analysl, 55 BELLADEN
znd,
1953