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The separation of inorganic isomeric cis-trans compounds by paper chromatography and the effect of configuration on rf values
ANALYTICA
488
CHIMICA
ACTA
VOL.
19 (rS)g3)
THE SEPARATION OF INOIXGANIC ISOMERIC CIS-TRANS COMPOUNDS J3Y PAPER CHICOMATOGI~APHY AND THIS EFFECT CONI~IGURATION ON I
OF
In a study of tllc application of paper chromatography to tllc separation of stcrcoisomcricinorganiccoml~ounds, wccstahlishccl, as early as 1954, that in this way inorganic isomcric cis-lrnm compounds can bc rcsolvcd into the componentsl. In the same year, ‘L’,\Xl,\hlo*ro,NAKAIIARA AND ‘I’SUCI~IDA~ published a paper in wliich the alteration of the I\‘r; values wit11 the number of nitro groups in tllc In this study tlicy clctcrmincd the I
2. 3. 4. 5. 6.
[Co cn,(NO,),]NO, [Co cn2(N0,),]t [Co cn,Cl,]Cl CCo(Nl-I,),(NO,),INC), [Co(Nl-f,),(NW,l1 [Co en,T3r,]Br
7. 8. 9. IO. IT. 12.
[Co cn,(NCS),JCl [Cr cn,(SCN),]SCN [Co cn,(NO,)Cl]Cl [Co cn,(NCS)Cl]Cl [Co cn,(NH,)Cl]Cl, ~Pt(NH,),Py,]Cl,
Our cspcrimcnts have confirmccl that it is possible to scparatc cis-lrcrjcs isomers by paper chron~atograpliy if acetone bc ~iscd as the chief component of the solvent mixture for dcvclopment. In addition to acetone, the misture should contain water, mineral acid or potassium iodide. By combining these reagents WC have prepared seven basic solvent mixtures, by means of which the separation of cis-lrc~zs isomers has been achieved in II out of a total of 12 complcs compounds stucliccl. Only in the case of [Cr cn,(SCN),]SCN the separation could not bc achieved with a solvent mixture containing acetone. In that case, thcrcforc, a misture of ether, ethanol and water was used. The ratio of the components in the above-mentioned solvent-systems is as follows: 70 ml acctonc + 20 ml water + 10 ml I-ICl (sp.gr. 1.19). So ml acctonc + 15 ml water + 5 ml HCl (spgr. x.19). 3, Sg ml acetone $- 7.5 ml water + 7.5 ml MC1 (sp.gr. I.ig). I.
2.
* Thcao compounds wcrc sclcctccl bccnusc of their rclntivc stability nncl bccnusc they hirve been wall stuchccl. The scpnration of the cis and /mrjs isomers of tha first three compounds has already been clcscribctl in our first piipcr’. Refcrcrtccs p.
492
VOL.
19 (x9$3) 4. 5. 6. 7. 8.
CIIROMATOGRAPHY
gj 65 75 85 go
ml ml ml ml ml
acetone acetone acetone acetone ether +
OF CIS-TRANS
COMPOUNDS
489
+ + + +
5 ml HCl (sp.gr. 1.19). 30 ml water + 5 ml HNO, (sp.gr. 1.42). 5 ml water + 20 ml HBr (sp.gr. 1.38). 15 ml water + I g solid K J. 15 ml absolute ethanol + 5 ml water.
EXPERIhlENTAL All the isomcrlc compounds lnvcstigated in this paper wcrc prcparctl by mcthotls already known; composition was chcckctl by gravimctrlc analysis (l’ablc I). Cobalt was dctcrmlnctl as CoSO,, chromium us <‘rzO,, and platinum ah Pt. r\ll the scporntlonu dcscrlbctl wcrc made on Whatman NO. I pilpcr. by nsccnthng chromatographv ‘lb tcmpcraturc during the separations was do-2~~. Chromato~ral~hy was always carrxxl out with complctcly fresh solutions of the isomers in water; in tlic CRSCof more soluble salts, the conccntmtion of the solutions ranged from 0.05 tu 0 1dI.1with rcspcct to each component, while for the less siolublc salts ;L saturatctl bdution at a tcmpcraturc of abOUt 50” W;lh 1Wd. k+. IllC;LlIS of ;L llllCrO~~i~x!ttC, :llJ(Jllt 3’1 0-:’ ml of rolution was placctl 011 CXII strip as a marrow line. tlwrr
.-.----I.-.-.--_-.
_____--
[~‘~(NI-I,)~(NO,),]I\JO, [C~J(NII,),(NO,),JI [
_---
__-
co :
34
co:
2,7 8 9110
co. CO:
Cr. Co: Co: co:
3.8 7 II,12
1%:
_-_-
_--_
--
17 GG
20.97 ’ 7.03 1-I 07 17.H2
19.52
15.15 X9.87 r9.00 19.35
15.01 19.91 l9*l3 19.48
42.51
4r.2G
2 I .o.)
21.09
17.14 13.80 17,77
16
15.18 19.76 18go
87
I.#.01
GZ.rjO
Complex cohlt compounds wcrc clctcctccl by immersing tlrictl strips iii a rN solution of aminonium sulphidc; [Cr cn,(SCN),)SCN was tlctcctctl by lmrncrslny tlr~ctl strips in a 2.V solution of ferric chloritlc, whllc [I’t(Nl-I&Py,]CI, was tlctcctccl by immcrslng clrictl strips III n .#A’ solution of sodium Iormatc and hating to I 10~. The RI.* vducs obt;rinctl and other cxpcririicntnl data arc p\*cn III ‘I’al~lc 11.
RESULTS
From Table II and the photographs of the chromatograms obtained (Fig. I), it can be seen that the RF values in all the cases investigated arc considerably higher for the cis form than the RI: values for the tvnns form. This regularity is even more clearly illustrated by Fig. 2. From Table II it can also be seen that the RF valueshave no connection with the solubility of isomeric pairs, as the regularity in the A’F values exists regardless of whether one isomer is more or less soluble than the other. In short, it can be concluded that of the isomcric compounds belonging to the group of electrolytes with complex cations, the cis isomers have higher RF values than the ivans forms, when a solvent mixture with acetone as chief component is used for chromatographic development. References 9. 4ga
G. STEFANOVId,
490
. . . . . ..-
.I
_
5
.,....
_
_..
.
T. JANJI6
,.
.I
..-
._..
VOL.
*
__
.
. .
19 (1958)
e
1:1g. I. A11figiircs, cxccpt X0. \’ which is ;Lthagram, arc photographs of the chromatograms obtained. The first chromatogram rcprcvcnts pure C~S, the second a mixture of CIS and frarrs and the thwd pure Iraw isonicr.
As already mentioned, on using solvents not containing acetone successful separation was achieved in only one instance, viz. the isomcric forms of [Cr en,(SCN),]SCN. It is therefore not yet possible to say whether this regularity is of broader significance, i.e. whether the cis forms have higher RF values than the tram forms, regardless of the composition of the solvent mixture used. If it were confirmed in the case of other complex compounds, this regularity, which might be due to the structure of cellulose b&ides other factors, could be applied to the determination of configuration. The proposed method is simpler than the other chemical and physical methods for the determination of configuration, and it also has the advantage that only small quantities of the isomers to bc investigated are required. References
9. 49a
19 (rgjj8)
VOL.
CHHO~MATOGRAPHY
TABLE
-
3.
solvntl
CompcwJ
No.
fCOWH,),(N0,),7NO,
[Co
_.-_-*
22
w7.
-I_--_-
I
._ ___-___-___._ [Co en,(NCS),jCl
0 46
0.85
0.62
0.73
0.62
0.66
0.45
-----.
- _.-.-
0.gG
0.07
3
tram
(23O) _----_-,-__-o.ogGr (SW -_~-o.or4r (22”) -_..._.-
-. -I---_.-
-------.-
g.
-
-__-_-_ 0.0159
o*7i
--
.-_--en,(NCS)Cl]Cl
-_.
[Co cn,(NEI,)Cl]CI,
z.
[Pt( NH,),l?y,]Cf,
0.60
. - ___-_-“.--_--
10
0.17
0.87
0.G.g --.I--_.-
48
I---_
2
2
Rf 1.0 O.Q-
-
O-57 ---_
0.50
O.fi
0
-
00
_--
.__--
More soluldc than cis isomer
_.._.-
aiJo1:t 0.0303 (JO”) -
--
15 less soluble ~__.____
--.._
o.r85 (18”)
___..-drr awrgnnisctrerr Chewre (Kobalt, --
* The values for solubiltty arc taken from Tcil I3 (x930) ; I3and V Abt. 3 (xz)I~) and Band
III Abt. I (1912) : most of them Ilave been racalcuIn gram-molob gcr lltcr of water.
in1 :1:
latcd in order to cxprcss solublltty
iLbout o.oyG
---.-
CIS isowcr -
GMULIIV’Y Ifuotdhrch
_-
0.88
___-
irLto1rt o.or96 (zoo) (ISO)
---_
__
(16.!?)
0 109
0 G3
____-I__-_-_.-___-_
1 _.. - - ^______.__ I
-_--.-
I I. -_--
1..^1_ ..__^_-.. 4
3
---.. .__-_--
0.79
0.06G8 O\‘Cl-
-_ ._---_----__---~--Spurrngly soluble
-- -----
20
.-.--.-_- “. --. I___-_--
... __I.---..--
[Co en,(NO,)CI](‘I
-_------. 10. [Co
I
H
((8”) 0.06G3 (16 $1
o ‘3
(20
__-_._-_I___-_. -_ ____._-_ __ -__._ 8. [Cr cn,(SCN),~SCN
_-
dolIt
0.013 (23O) (ZOO) --_.__._-____,--_^0.0900 0.0198
_.. _--.- ---.-
- .-^ I _- __
4
_-_
abo11 t 0.132
o 42
-..._ _I_ _C_..--_-___ 6 0 74
-rn moiesjl water*
E&s
0.73
i__._-___-___ 0.52
24
-- .-.- _--_--_----_-_ G I____ --
fratlf
-
22
-___ --_-.---__-.-en&i&I -..--
Sdubdtty
__.. ___._______---
__7
-----[Co cn,l3r,JBr
C‘f
3
5
CC0 ~n@O,),lf
6.
-
_--_-__II-_
___--__-~-.-_
------w---5. [Co
--
__.__..._~.__
cn#JO,),]NO,
-_4.
---7
-_
K* values
3
__--
491
--._.. _.-
dW~~~$imi
5
COMPOUNDS
II
Tsmr ot
?W.llUIC 1v0.
_-.--....--.-_ z. [CO(NH,)~(NO,),]I 3.
OF CIS-TRANS
-
_.
f
^._
Rf r 1.0
-0.9
s._.
0.S
0.70.6 O.J0.4 0.30.2 0.1 -
0.0 J
-mm
___(
- 0.8 - 087
_a_
me_
.-_
-.
_s_
_
A
B
L
J C
D
L
E
J _
F Fig.
Cis isomer - - - -:
A. P=WW,W,lCh
D. [Co cn,(NO,)CI]Cl c. [Co en,C1,]C1 D. [Co en,(NO,),]I For clarity, the chromatograms References p. 492
G
~
I
J
- ok5 - 025 ” 0.4 - 0.3 -0.2 -0.1 ‘Ox]
2.
trans Isomer
I. [Co cn,JNO,)JNO, E. CWNW.W%hlN% F. [Co cn,(NH,)Cl]Cl, .I. ICo(NW,(NQ),lf I<.. [Co cn,(NCS)ClJCI G. [Co en,Br,]Br L. [Co en,(NCS)JCl H. [CT en,(SCN&jSCN are arranged in the order of increasing RF values for lrans isomers.
G.
492
STE:r;ASOVI&
T.
JAJIt:
VOL.
19 (1958)
It has been cvtabllshctl that of all the illcJrganlC ivomcrlc crs-lru7ls compounds that have been scparntctl by paper chromatography up to the present, the cts ivomcrs have higher Rr: values than the trms formu 011 the bask of thrs rcgiilarlty, a new method hav been suggcstcd for the rlctermlnation of the conflguration of inorganic lvomeric czs-Ircors compounds.
1 GJ. ST~~NOVI& AND ‘1‘. JANJI~, Anal. Cirirrr. Acfu, I I (1954) 5.50. 2 Y. YAMAMOTO, A. NAKAIIAIU AND I<. ‘J’SUCHIVA, J. CJICW. SW. Japm, 232.
PttrcCJrctn.
licccivctl
A
SYSTEMATIC
STUDY
OF
INSOLUBLE
Sect..
75 (1954)
March 3rr1, I g58
SUBSTANCES.
I
bY
Scvcral papers I,2 have been published from this laboratory dealing with the systcmatic detection of insoluble substances in qualitative analysis. A number of substances which become difficultly soluble on heating was reported and included in the scheme of dctcction. In view of tllc marked cffcct of heating on the solubility of some substances a systematic investigation of those substances which arc likely to become less soluble on heating has been undcrtakcn. The result of this investigation has shown that the effect of heating on the solubility of substances is far more general and pronounced than is generally supposccl and the list of substances which are callccl ‘insoluble’ has to be cnlargcd very considerably. &cause the problem was investigated from the analytical point of view, the approximate method for measuring the insolubility of substances was based on the procedure used in separating the insoluble residue from the soluble portion in qualitative analysis. This enabled us not only to gain some idea as to how these substances would behave in analysis, but also to compare their bchaviour with those substances which have already been included in the list of insoluble substances. The standard procedure which has been recommended in the more comprehensive scheme’ of clualitative analysis for References
fi. 495
488
CHIMICA
ACTA
VOL.
19 (rS)g3)
THE SEPARATION OF INOIXGANIC ISOMERIC CIS-TRANS COMPOUNDS J3Y PAPER CHICOMATOGI~APHY AND THIS EFFECT CONI~IGURATION ON I
OF
In a study of tllc application of paper chromatography to tllc separation of stcrcoisomcricinorganiccoml~ounds, wccstahlishccl, as early as 1954, that in this way inorganic isomcric cis-lrnm compounds can bc rcsolvcd into the componentsl. In the same year, ‘L’,\Xl,\hlo*ro,NAKAIIARA AND ‘I’SUCI~IDA~ published a paper in wliich the alteration of the I\‘r; values wit11 the number of nitro groups in tllc In this study tlicy clctcrmincd the I
2. 3. 4. 5. 6.
[Co cn,(NO,),]NO, [Co cn2(N0,),]t [Co cn,Cl,]Cl CCo(Nl-I,),(NO,),INC), [Co(Nl-f,),(NW,l1 [Co en,T3r,]Br
7. 8. 9. IO. IT. 12.
[Co cn,(NCS),JCl [Cr cn,(SCN),]SCN [Co cn,(NO,)Cl]Cl [Co cn,(NCS)Cl]Cl [Co cn,(NH,)Cl]Cl, ~Pt(NH,),Py,]Cl,
Our cspcrimcnts have confirmccl that it is possible to scparatc cis-lrcrjcs isomers by paper chron~atograpliy if acetone bc ~iscd as the chief component of the solvent mixture for dcvclopment. In addition to acetone, the misture should contain water, mineral acid or potassium iodide. By combining these reagents WC have prepared seven basic solvent mixtures, by means of which the separation of cis-lrc~zs isomers has been achieved in II out of a total of 12 complcs compounds stucliccl. Only in the case of [Cr cn,(SCN),]SCN the separation could not bc achieved with a solvent mixture containing acetone. In that case, thcrcforc, a misture of ether, ethanol and water was used. The ratio of the components in the above-mentioned solvent-systems is as follows: 70 ml acctonc + 20 ml water + 10 ml I-ICl (sp.gr. 1.19). So ml acctonc + 15 ml water + 5 ml HCl (spgr. x.19). 3, Sg ml acetone $- 7.5 ml water + 7.5 ml MC1 (sp.gr. I.ig). I.
2.
* Thcao compounds wcrc sclcctccl bccnusc of their rclntivc stability nncl bccnusc they hirve been wall stuchccl. The scpnration of the cis and /mrjs isomers of tha first three compounds has already been clcscribctl in our first piipcr’. Refcrcrtccs p.
492
VOL.
19 (x9$3) 4. 5. 6. 7. 8.
CIIROMATOGRAPHY
gj 65 75 85 go
ml ml ml ml ml
acetone acetone acetone acetone ether +
OF CIS-TRANS
COMPOUNDS
489
+ + + +
5 ml HCl (sp.gr. 1.19). 30 ml water + 5 ml HNO, (sp.gr. 1.42). 5 ml water + 20 ml HBr (sp.gr. 1.38). 15 ml water + I g solid K J. 15 ml absolute ethanol + 5 ml water.
EXPERIhlENTAL All the isomcrlc compounds lnvcstigated in this paper wcrc prcparctl by mcthotls already known; composition was chcckctl by gravimctrlc analysis (l’ablc I). Cobalt was dctcrmlnctl as CoSO,, chromium us <‘rzO,, and platinum ah Pt. r\ll the scporntlonu dcscrlbctl wcrc made on Whatman NO. I pilpcr. by nsccnthng chromatographv ‘lb tcmpcraturc during the separations was do-2~~. Chromato~ral~hy was always carrxxl out with complctcly fresh solutions of the isomers in water; in tlic CRSCof more soluble salts, the conccntmtion of the solutions ranged from 0.05 tu 0 1dI.1with rcspcct to each component, while for the less siolublc salts ;L saturatctl bdution at a tcmpcraturc of abOUt 50” W;lh 1Wd. k+. IllC;LlIS of ;L llllCrO~~i~x!ttC, :llJ(Jllt 3’1 0-:’ ml of rolution was placctl 011 CXII strip as a marrow line. tlwrr
.-.----I.-.-.--_-.
_____--
[~‘~(NI-I,)~(NO,),]I\JO, [C~J(NII,),(NO,),JI [
_---
__-
co :
34
co:
2,7 8 9110
co. CO:
Cr. Co: Co: co:
3.8 7 II,12
1%:
_-_-
_--_
--
17 GG
20.97 ’ 7.03 1-I 07 17.H2
19.52
15.15 X9.87 r9.00 19.35
15.01 19.91 l9*l3 19.48
42.51
4r.2G
2 I .o.)
21.09
17.14 13.80 17,77
16
15.18 19.76 18go
87
I.#.01
GZ.rjO
Complex cohlt compounds wcrc clctcctccl by immersing tlrictl strips iii a rN solution of aminonium sulphidc; [Cr cn,(SCN),)SCN was tlctcctctl by lmrncrslny tlr~ctl strips in a 2.V solution of ferric chloritlc, whllc [I’t(Nl-I&Py,]CI, was tlctcctccl by immcrslng clrictl strips III n .#A’ solution of sodium Iormatc and hating to I 10~. The RI.* vducs obt;rinctl and other cxpcririicntnl data arc p\*cn III ‘I’al~lc 11.
RESULTS
From Table II and the photographs of the chromatograms obtained (Fig. I), it can be seen that the RF values in all the cases investigated arc considerably higher for the cis form than the RI: values for the tvnns form. This regularity is even more clearly illustrated by Fig. 2. From Table II it can also be seen that the RF valueshave no connection with the solubility of isomeric pairs, as the regularity in the A’F values exists regardless of whether one isomer is more or less soluble than the other. In short, it can be concluded that of the isomcric compounds belonging to the group of electrolytes with complex cations, the cis isomers have higher RF values than the ivans forms, when a solvent mixture with acetone as chief component is used for chromatographic development. References 9. 4ga
G. STEFANOVId,
490
. . . . . ..-
.I
_
5
.,....
_
_..
.
T. JANJI6
,.
.I
..-
._..
VOL.
*
__
.
. .
19 (1958)
e
1:1g. I. A11figiircs, cxccpt X0. \’ which is ;Lthagram, arc photographs of the chromatograms obtained. The first chromatogram rcprcvcnts pure C~S, the second a mixture of CIS and frarrs and the thwd pure Iraw isonicr.
As already mentioned, on using solvents not containing acetone successful separation was achieved in only one instance, viz. the isomcric forms of [Cr en,(SCN),]SCN. It is therefore not yet possible to say whether this regularity is of broader significance, i.e. whether the cis forms have higher RF values than the tram forms, regardless of the composition of the solvent mixture used. If it were confirmed in the case of other complex compounds, this regularity, which might be due to the structure of cellulose b&ides other factors, could be applied to the determination of configuration. The proposed method is simpler than the other chemical and physical methods for the determination of configuration, and it also has the advantage that only small quantities of the isomers to bc investigated are required. References
9. 49a
19 (rgjj8)
VOL.
CHHO~MATOGRAPHY
TABLE
-
3.
solvntl
CompcwJ
No.
fCOWH,),(N0,),7NO,
[Co
_.-_-*
22
w7.
-I_--_-
I
._ ___-___-___._ [Co en,(NCS),jCl
0 46
0.85
0.62
0.73
0.62
0.66
0.45
-----.
- _.-.-
0.gG
0.07
3
tram
(23O) _----_-,-__-o.ogGr (SW -_~-o.or4r (22”) -_..._.-
-. -I---_.-
-------.-
g.
-
-__-_-_ 0.0159
o*7i
--
.-_--en,(NCS)Cl]Cl
-_.
[Co cn,(NEI,)Cl]CI,
z.
[Pt( NH,),l?y,]Cf,
0.60
. - ___-_-“.--_--
10
0.17
0.87
0.G.g --.I--_.-
48
I---_
2
2
Rf 1.0 O.Q-
-
O-57 ---_
0.50
O.fi
0
-
00
_--
.__--
More soluldc than cis isomer
_.._.-
aiJo1:t 0.0303 (JO”) -
--
15 less soluble ~__.____
--.._
o.r85 (18”)
___..-drr awrgnnisctrerr Chewre (Kobalt, --
* The values for solubiltty arc taken from Tcil I3 (x930) ; I3and V Abt. 3 (xz)I~) and Band
III Abt. I (1912) : most of them Ilave been racalcuIn gram-molob gcr lltcr of water.
in1 :1:
latcd in order to cxprcss solublltty
iLbout o.oyG
---.-
CIS isowcr -
GMULIIV’Y Ifuotdhrch
_-
0.88
___-
irLto1rt o.or96 (zoo) (ISO)
---_
__
(16.!?)
0 109
0 G3
____-I__-_-_.-___-_
1 _.. - - ^______.__ I
-_--.-
I I. -_--
1..^1_ ..__^_-.. 4
3
---.. .__-_--
0.79
0.06G8 O\‘Cl-
-_ ._---_----__---~--Spurrngly soluble
-- -----
20
.-.--.-_- “. --. I___-_--
... __I.---..--
[Co en,(NO,)CI](‘I
-_------. 10. [Co
I
H
((8”) 0.06G3 (16 $1
o ‘3
(20
__-_._-_I___-_. -_ ____._-_ __ -__._ 8. [Cr cn,(SCN),~SCN
_-
dolIt
0.013 (23O) (ZOO) --_.__._-____,--_^0.0900 0.0198
_.. _--.- ---.-
- .-^ I _- __
4
_-_
abo11 t 0.132
o 42
-..._ _I_ _C_..--_-___ 6 0 74
-rn moiesjl water*
E&s
0.73
i__._-___-___ 0.52
24
-- .-.- _--_--_----_-_ G I____ --
fratlf
-
22
-___ --_-.---__-.-en&i&I -..--
Sdubdtty
__.. ___._______---
__7
-----[Co cn,l3r,JBr
C‘f
3
5
CC0 ~n@O,),lf
6.
-
_--_-__II-_
___--__-~-.-_
------w---5. [Co
--
__.__..._~.__
cn#JO,),]NO,
-_4.
---7
-_
K* values
3
__--
491
--._.. _.-
dW~~~$imi
5
COMPOUNDS
II
Tsmr ot
?W.llUIC 1v0.
_-.--....--.-_ z. [CO(NH,)~(NO,),]I 3.
OF CIS-TRANS
-
_.
f
^._
Rf r 1.0
-0.9
s._.
0.S
0.70.6 O.J0.4 0.30.2 0.1 -
0.0 J
-mm
___(
- 0.8 - 087
_a_
me_
.-_
-.
_s_
_
A
B
L
J C
D
L
E
J _
F Fig.
Cis isomer - - - -:
A. P=WW,W,lCh
D. [Co cn,(NO,)CI]Cl c. [Co en,C1,]C1 D. [Co en,(NO,),]I For clarity, the chromatograms References p. 492
G
~
I
J
- ok5 - 025 ” 0.4 - 0.3 -0.2 -0.1 ‘Ox]
2.
trans Isomer
I. [Co cn,JNO,)JNO, E. CWNW.W%hlN% F. [Co cn,(NH,)Cl]Cl, .I. ICo(NW,(NQ),lf I<.. [Co cn,(NCS)ClJCI G. [Co en,Br,]Br L. [Co en,(NCS)JCl H. [CT en,(SCN&jSCN are arranged in the order of increasing RF values for lrans isomers.
G.
492
STE:r;ASOVI&
T.
JAJIt:
VOL.
19 (1958)
It has been cvtabllshctl that of all the illcJrganlC ivomcrlc crs-lru7ls compounds that have been scparntctl by paper chromatography up to the present, the cts ivomcrs have higher Rr: values than the trms formu 011 the bask of thrs rcgiilarlty, a new method hav been suggcstcd for the rlctermlnation of the conflguration of inorganic lvomeric czs-Ircors compounds.
1 GJ. ST~~NOVI& AND ‘1‘. JANJI~, Anal. Cirirrr. Acfu, I I (1954) 5.50. 2 Y. YAMAMOTO, A. NAKAIIAIU AND I<. ‘J’SUCHIVA, J. CJICW. SW. Japm, 232.
PttrcCJrctn.
licccivctl
A
SYSTEMATIC
STUDY
OF
INSOLUBLE
Sect..
75 (1954)
March 3rr1, I g58
SUBSTANCES.
I
bY
Scvcral papers I,2 have been published from this laboratory dealing with the systcmatic detection of insoluble substances in qualitative analysis. A number of substances which become difficultly soluble on heating was reported and included in the scheme of dctcction. In view of tllc marked cffcct of heating on the solubility of some substances a systematic investigation of those substances which arc likely to become less soluble on heating has been undcrtakcn. The result of this investigation has shown that the effect of heating on the solubility of substances is far more general and pronounced than is generally supposccl and the list of substances which are callccl ‘insoluble’ has to be cnlargcd very considerably. &cause the problem was investigated from the analytical point of view, the approximate method for measuring the insolubility of substances was based on the procedure used in separating the insoluble residue from the soluble portion in qualitative analysis. This enabled us not only to gain some idea as to how these substances would behave in analysis, but also to compare their bchaviour with those substances which have already been included in the list of insoluble substances. The standard procedure which has been recommended in the more comprehensive scheme’ of clualitative analysis for References
fi. 495