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Analytic aspects of the chemical behaviour of 8-hydroxyquinoline (oxine)
VOL. 3 (1949)
ANAJaYTIC
ANALYTICA
ASPECTS
CHIM:CA
OF THE
561
ACTA
CHEMICAL
S-HYDROXYQUINOLINE
PJEHRVIOUR
OF
(OXINE)
l>Y
From the standpoint of analytical chemistry as well as from coordination chemistry oxinc and its dcrivativcs and their salts arc of great importance. The formation of salts of these amphiprotic organic compounds is the basis of many quantitative and qualitative analytical procedures. Osinc forms addition compounds by means of the nitrogen in its molecule. These addition compounds may be ammonium salts of acids, dinmrnines of some metal salts and adsorption compounds. Recently many diamminc and adsorption compounds with palladium(II)cya wcrc prepared, among them compounds of oxinel. Osinc also forms inner complex salts with a large number of nictals. By the introduction of acid groups into the molecule of oxinc the ability to form inner comples rings remains, but salts with inner comples anions are then formed2. The fluorcsccnce in ultraviolet light of many of the compounds of oxinc and its derivatives and their solutions in organic solvents add interest to the chemistry of these compounds. The fluorescence may be connected with the coordination of resonating forms of oxinc and its derivatives. The following investigations were undertaken to cstend our lcnowlcdge of the chemistry of oxine. I. DIFFERENTIATION
BETWEEN
FILTER
PAPERS
By the interaction of oxine and many metal ions fluorescent oxinates are formed. Therefore it is to be expected that insoluble metal compouncls may react with oxine, provided the solubility product of the oxinatc is less than that of the insoluble salt, or if the concentration of oxine is sufficiently high. From this standpoint it was thought that the small amount of metallic inorganic matter which is present in the ash of filter paper would react with osinc to give oxinates of the respective metals, some of which are fluorescent. Indeed it was found that the * On sal~bnt.ic;~l lcnvc from the University References
fi. _-jGG.
of Minnrsot:l,
Minncnpolis,
Allinn.
$32
P.
FEIGL,
G.
n. WEISIG
VOL.
3 0949)
ash of diffcrcnt kinds of paper reacts immediately with a chloroform solution of oxinc or dibrom-oxine. A water solution of 5-sulpho-oxinc or 5-sulpho-y-iodooxinc can also bc used. It was thought possible to spot the paper with a solution of oxine, since the inorganic matter is mechanically distributed through the paper or combined with cellulose in the form of water insoluble products, which can combine with of thcsc compounds is oxinc to form fluorescent compounds. The formation facilitated by the large specific surface of the solid reactants. This permits the cletcction of cxcccdingly small amounts of inorganic compounds which form
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-_
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***
EATON
. . . . . . .
. . . . , . .
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SC~ILTEICIIISR ~c11L~1c1113I~
AND AND
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“_ t -I-
-l“Ii-
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.
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----_---_ IXICISMAN
-_
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--_---.
-______
_-_
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Gcrnl:~ny.
fluorescent oxinatcs. WC found that by spotting diffcrcnt kinds of paper with a dilute chloroform solution of osinc, a fluorescent spot rcmainecl after the evaporntion of the solvent. Instead of a solution of osinc or its halogen compound in chloroform or other organic solvent a water solution of 5-sulpho-oxinc or 5-sulpho7-iodo-oxine can be used. The results obtained with different kinds or papers arc shown in Table I. From the data it can bc seen that the tests arc sensitive. Without destroying the paper, spot testing is therefore a simple, rapid and sensitive method of detecting the presence of inorganic material which forms fluorescent osinatcs. The inorganic matter in the paper which forms fluorescent compounds with osinc may bc calcium, magnesium, aluminium, etc. The direct differentiation Rcfc~rlrccsp. gG(,.
BEHAVIOUR OF 8-HYDROXYQUINOLINE
VOL. 3 (I9491
563
between these elements is impossible for the fluorescence of their oxinates is nearly the same*. Titanium oxide, sometimes used as a filler, as well as iron which may be present as an impurity, cannot be detected, since their oxinates show no fluorescence. The inorganic matter in the paper may be converted to oxinates by exposure to the vapour of oxine. This can be clone at ordinary tcmpcraturc by placing the paper over a crucible which contains some osine. After a few minutes, a weak fluorcscencc which incrcascs with further exposure to the osine is then observed in the ultraviolet light. It is striking that even the 10~ vapour prcssurc of oxinc at ordinary temperature is sufficient to form oxinatcs**. The action of oxinc vapour can hardly bc explained by assuming a transformation of the inorganic matter into stoichiomctric osinates without a solvent. It is more probable that the osinc (vapour or its solution) reacts with metal on the surface without forming a new phase, i.c., it is chemically adsorbed’ * *. II. A FLUORIDE TEST BASED ON THE QUENCHING OF METAL OX7NATES When aluminium oxinate is treated with a solution containing fluoride ions, the fluoresccncc disappears. This is due to the reaction of aluminium oxinate with the fluoride ion to form aluminium fluoride or the hcxafluoaluminatc ion. The fluorescence of calcium or magnesium oxinate is destroyed similarly. This is used as the basis for a test for fluorides. The test can be carried out using quantitative paper impregnated with aluminium oxinate. This is done by dipping a piece of the paper in a chloroform solution of aluminium oxinatc. After drying, the fluorescent paper is exposed to hydrogen fluoride vapour. In ultraviolct light the surface which came in contact with hydrogen fluoride does not fluoresce. A simpler procedure is based on the method of differentiating papers, described in I. The test may also be made by exposing qualitative filter paper to the vapour of hydrogen fluoride and spotting with a chloroform solution of osinc. In ultraviolet light the area coming in contact with hydrogen fluoride remains dark while the other part of the paper is fluorescent. The latter is the better method. To cheek the sensitivity of the test, we have used spot test techniques. Into a 1.5 ml porcelain crucible, 3 drops of 6-N sulphuric acid and I drop of a sodium fluoride solution are placed and covered with a piccc of qualitative filter paper sufficiently larger in diameter than the crucible, so that the areas exposed and l However by exposing the fluorcsccnt spst to ncctic acid vclpour, the oxinatcs of calcium nnc~;nagncsium clccomposc. Only the fluorcsccncc of aluminium oxinatc persists. J?crhups by the incorporation of ZL suitable mctnllic compound in certain parts of the paper or in the ink and the clcvclopmcnt of the fluoresccncc by treatment with oxinc vnpour or possibly its solution in an organic solvent can bc usccl for the preparation and tcstipg of bank, security, note, etc., paper. l ** This assumption was proved with oxinc and other compouncls which form inner complcxcs by F. 1~EIcL AND I-1. W. %OCHER, pnpcr in prcpnmtion.
Rc/cYc?2ccs
fi.
5GG.
F.
564
FEIGL,
G. B.
HEISIG
VOL.
3 (1949)
unexposed to hydrogen fluoride can be compared easily. The crucible covered with the i>aper is hcatccl to so-Go” for 5 minutes, the paper spotted with a chloroform solution of oxinc (0.5 mg/ml) and observed in the ultraviolet light. The limit of identification of 0.05 of fluorine corresponds to a concentration limit of I: Io”. The sensitivity of the fluorine test is somewhat lowered by the presence of boric acid probably due to the formation of fluoboric acid. The sessitivity in the prcscncc of 50 y of boric acid is 0.5 y fluorine.
III.
A TEST
FOJZ
CYANIDE
IONS
l3ASED
FROM
ON
COPPI:R
‘I-ME (11)
FORMATION
OF
ALUMINIUM
OXINATE
OSINATC
Although the following new test for a cyanide is not more scnsitivc, or sclcctivc, than other icsts found in the litcraturc, it is intcrcsting from the standpoint of the vcrsatilily of oxinc as a reagent. The test is based on the fact that coppcr(II)oxinatc reacts immcdiatcly with hydrogen cyanide, forming coppcr(I)cyaniclc and oxinc. The osinc which forms is convcrtcrt to the fluorescent aluminium oxinatc. The method of carrying out the test was essentially that used in the fluoride test just dcscribccl. rlY~c reagent paper was prcparecl by impregnating quantitative filter paper with a chloroformic solution of copper(II)osinate (0.x m&ml) which has no fuorcscencc. hftcr csposurc to vnpour which might contain hydrocyanic ncicl, the pnpcr was spotted with aluminium chloriclc (I mg/ml) and csamined in ultraviolet light for the fluorcsccnce of the aluminiunl osinatc formed. The limit of idcntilication is 2.5 y nncl the concentration limit is I :2. I&.
1V.
QUENCJIING
OF
TIJJ’: J3Y
PLUORESCJ’:NC@ NON-FLUORESCENT
OF
ALUMINIUM METAL
OSINATJ?
IN
CI?J_OROBORM
OSINATJSS
It is well known that many oxinatcs arc soluble in chloroform and other organic solvents. In the cast of solicl fluorescent oxinntcs the chloroform solution is also fluorcsccnl. The solutions of the non-fluorescent solid osinntcs are likewise not fluorescent. An analytical USC)of osinc is to cstract oxinatcs formed under suitable conditions with chloroform and Co note the colour and fluorescence of the chloroform solution. Therefore the bchnviour of misturcs of fluorescent and nonfluorcsccnt osinntcs is of analytical intcrcst. WC have stuclicd the influence of some non-fluorescent oxinates on the fluorescent aluminium oxinate. Equimolar chloroform solutions of osinatcs of cerium, chromium, thorium, iron(III), thallium(TII), qucnchcd the fluorcsccncc of a chloroformic solution aluminium osinate, whereas l&nut11 osinntc. did not. In view of these results it is important that care bc usecl before drawing conclusions from a fluorescence esamination of a chloroform solution of osines. Rc/c~c?tccs
fi.
566.
VOL.
3 (1949)
BEHAVIOUR
V. BEHAVIOUR
OF FRESHLY
OF
PREPARED
8-HYDROXYQUINOLINE OXINATE
WITH
3-N
s% HYDROCHLORIC
ACID
With few exceptions all metal oxinates arc precipitated in alkaline, neutral or buffered acid solution. The pEr range for the analytical precipitation of osinatcs lies bctwcen 2.7 and 14.6 314.These values give no indication about Chc masirnum pEr (minimum concentration of hydrogen ion) at which no precipitation occurs nGF the plr at which the precipitated osinc dissolves completely. From these values one would cspect that an osinatc would dissolve immcdintely when an acid was added whose prr ~vas much less than the minimum values given for the . precipitation of the osinntc. However it is known that ageing often decreases the solubility of prccipitatcs in acidsan cffcct which is often considered as being due of the establishment of a false equilibrium. Since such an cffcct is not uncommon among inner complex salts, WC have tested the behaviour of freshly precipitated and dried oxinates of many metals with 3-N hydrochloric acid. The pfr is so much 1ower than the lowest piI permitted for the complctc precipitation, that in all cases immediate solution can be cspcctcd. This was true of the osinatcs of antimony(III), bismuth, cadmium, ccrium(III), cl~romiun~(III), cobalt(II), copper( indium(III), lead, magnesium, zinc, lanthanum, zirconium, and nickel, but was not true for the osinates of aluminium, gallium, and iron(lI1). ‘I’llis phenomenon is unmistakable. The osinntes of the first group arc sol~~blc in 11~ hcid cvcn though the precipitate has been dried at the temperature given in the literature for obtaining an anhydrous product. The suspension of the members of the second group, freshly precipitated or dried, arc stable for some time and slowly clissolvc in the acid. Since thcrc is no cliffcrencc in the behaviour of the freshly precipitated or dried product, the resistance to acids can not be due to the ageing of the precipitate. It may be due to the fact that the members of the second group arc anhydrous when they are precipitated or lose their water of hydration readily, while the members of the first group are hydrated, and even the anhydrous products obtained by drying become hydrated and dissolve in the hydrochloric acid.
One
of us, G. 13. H., wishes to espress
AGRICULTURE tamento tical
da
OF PJR,\zII. for permission Producao
and
to the
to
the
in the laboratories
University
of Minnesota
MINISTRY
01:
of the Deparfor the sabba-
leave.
As a result of lhe I. A fluorcsccncc nium in paper. The esnniining the spot Rcfevences 37
Mineral
his appreciation
to work
p. 566.
study of the clwnical bchaviour of some mctallo-osinatcs it. 15 shown tht : test can be used to dctcct the prcscnrc of calcium, mogncsium :~ritl alum~test is made by spotting the pnpcr or its ash with ;I solution of osinc ;~ntl in the ultraviolet Ilght.
566
F. FEIGL,
G. B.
VOL.
HEISIG
3 (1949)
2. A test for a fluoride can be based on the inability of a qualitative filter paper which has been cxposcd to hyclrogcn fluoride to form fluorcsccnt oxinatc by spotting ~7th oxinc. 3. A test for a cyanidc can be based on the liberation of oxinc from coppcr(II)oxinntc and the dctcction of the oxinc by the formation of fluorescent aluminium oxinatc. 4. Some non-fluorescent oxinatcs arc able to quench the fluoresccncc of aluminium oxinatc dissolvccl in chloroform. 5. The oxinatcs of aluminium, gallium, ant1 iron(II1) have ELrcmnrlcablc rcsistancc to the action of 3 N hydrochloric acid, whcrcas all other oxinatcs dissolve immcdiirtcly. An cxplanation for this bchaviour is proposed.
Rl%UMl? hprbs unc ttuclc sur Its propriGt& chimiqucs dc quclqucs m0tallo-oxinntes, on pcut conclurc clue : I. Unc r&action tic fluorcsccncc pcut @trc cmploy&c pour vGrificr In prOscncc dc calcium, clc m;~gnGsium ct cl’nluminium clans clu papict. L’cssai cst cffcctu6 cn touchant Ic papicr ou scs ccndrcs xvcc unc solution d’oxinc, ct en cxaminant la tnchc nux rayons ultraviolets. 2. Unc r&&ion dcs fluorurcs pcut @Lrc bas6c sur l’inhibition clc fluorcscencc par acljonction d’oxinc sur filtrc qunlitatif, cxposG B l’acidc fluorhydriquc. 3. Rcclrcrchc clcs cynnurcs, ils pcuvcnt libbrcr l’oxinc clc l’oxinatc dc cuivrc (II) ct on contdlc l’oxinc par sn drrction dc fluorcsccncc avcc I’aluminium. 4. Quclqucs oxinntcs non-fluorcsccnts pcuvcnt cmp0clicr la fluorcsccncc dc l’oxinntc cl’;duminium cm solution clans lc cl~loroforn~c. 5. Lcs oxinntcs cl’:rluminium, rlc g:dlium ot tic fcr (III) sont trbs stables clans l’acitlc chlorhyclriquc 3N, contraircmcnt aux autrcs oxinatcs; on cn donnc unc explication. %USAMMENFASSUNG Als Ergcbnis von Stuclicn iibcr cIns chcmischc Vcrhnltcn von Mctalloxinatcn wurdc gcfunclcn : x. Ein I;Il~orcsccllztlnchwcis zur I+ststcllung von Calcium, Mngncsium uncl Aluminium, clcr dnrnuf bcruht, Papicr oclcr dcsscn Aschc mit cincr LGsung von Oxin nnzutiipfcln uncl tlcn *J’iipfclflcclc im U.V. Licht zu bctrachtcn. 2. Ein Nnchwcis ftir Fluor, clcr clnrauf bcruht, class qualitativcs Filtcrpapicr, dns dcr Einwirkung von Fluorwnsscrstoff nusgcsctzt wurclc, clic Eihiglccit vcrlicrt, bcim Antiipfcln mit Oxin fluorescicrcndc Oxinatc zu bildcn. 3. Ein Nnchwcis von Cyanid. clcr auf Frcilcgung von Oxin aus Kupfcroxinat uncl Nachwcis clcs Oxins clurch I3ilclung von Alunliniurnoxin~~i bcruht. ‘1. Einigc nicht fluorcscicrcnclc Oxinatc Eschcn clic Fluorcsccnz von in Chloroform gcl6stcm Aluminiumoxinat aw. 5. IXc Oxinatc von Aluminium, Gallium uncl Eiscn zcigcn cinc bcmcrkcnswcrtc Rcsistcnz gcgcn 3 N Si~lzsiiurc, wiiln-cncl nllc nntlcrcn Mctalloxinatc sofort gcliist wcrdcn. Einc ErklYrung ftir dicscs Vcrhaltcn wircl vorgcschlagcn. REFERENCES l I?. Fmcr, AND C. 13. ~II%ISIG, pnpcrs in prcpnration. n F. ~IXGI., c/rCi)liSfYy O/ sl)ECifiC, ,Sclcclivc and Scusilivc Rcnclions (1949), p. x87-189, Acadcmic Press Inc., New Yorlc. 3 I. KOLTI~OFIF AND E. SANDIZLL, Tcsfbook of qzrnntifcztive i7~07,nn~rzc amlysis (1943) p. 80, MncMlllnn Co., New York. 4 J. FLAGG, Orgmic Rca~c~rts used i?t Graviwrctvic rmrt Volzorrelvic A?zaiysis (1948) p. 184-9, Intcrscicncc Publishers, Inc. New Yorlc.
Received
l?ebruary
Ist, xg4g
ANAJaYTIC
ANALYTICA
ASPECTS
CHIM:CA
OF THE
561
ACTA
CHEMICAL
S-HYDROXYQUINOLINE
PJEHRVIOUR
OF
(OXINE)
l>Y
From the standpoint of analytical chemistry as well as from coordination chemistry oxinc and its dcrivativcs and their salts arc of great importance. The formation of salts of these amphiprotic organic compounds is the basis of many quantitative and qualitative analytical procedures. Osinc forms addition compounds by means of the nitrogen in its molecule. These addition compounds may be ammonium salts of acids, dinmrnines of some metal salts and adsorption compounds. Recently many diamminc and adsorption compounds with palladium(II)cya wcrc prepared, among them compounds of oxinel. Osinc also forms inner complex salts with a large number of nictals. By the introduction of acid groups into the molecule of oxinc the ability to form inner comples rings remains, but salts with inner comples anions are then formed2. The fluorcsccnce in ultraviolet light of many of the compounds of oxinc and its derivatives and their solutions in organic solvents add interest to the chemistry of these compounds. The fluorescence may be connected with the coordination of resonating forms of oxinc and its derivatives. The following investigations were undertaken to cstend our lcnowlcdge of the chemistry of oxine. I. DIFFERENTIATION
BETWEEN
FILTER
PAPERS
By the interaction of oxine and many metal ions fluorescent oxinates are formed. Therefore it is to be expected that insoluble metal compouncls may react with oxine, provided the solubility product of the oxinatc is less than that of the insoluble salt, or if the concentration of oxine is sufficiently high. From this standpoint it was thought that the small amount of metallic inorganic matter which is present in the ash of filter paper would react with osinc to give oxinates of the respective metals, some of which are fluorescent. Indeed it was found that the * On sal~bnt.ic;~l lcnvc from the University References
fi. _-jGG.
of Minnrsot:l,
Minncnpolis,
Allinn.
$32
P.
FEIGL,
G.
n. WEISIG
VOL.
3 0949)
ash of diffcrcnt kinds of paper reacts immediately with a chloroform solution of oxinc or dibrom-oxine. A water solution of 5-sulpho-oxinc or 5-sulpho-y-iodooxinc can also bc used. It was thought possible to spot the paper with a solution of oxine, since the inorganic matter is mechanically distributed through the paper or combined with cellulose in the form of water insoluble products, which can combine with of thcsc compounds is oxinc to form fluorescent compounds. The formation facilitated by the large specific surface of the solid reactants. This permits the cletcction of cxcccdingly small amounts of inorganic compounds which form
-_-_-
l:zzlcr : QLKII. ,. ,. ~u;\nt. 0 ,, 0 crs
.&
Gogf . . . Gr;)’ . . . Grg’ . * . 589 J-3luc*’ #II) 1
58tJ3 No L-c .
. . Onion Skin . Ihawing . . Trmxng . . . ToilcL. . . .
. . . . . .
. . . . . . .
l%A.ographic
.
,
News J>rinL J3ond . . .
-_
**
***
EATON
. . . . . . .
. . . . , . .
* . . . .
. . . . . . . .
.
.
.
.
.
.
.
. . . . . . .
. . . . . . .
. . . . . . .
. . . . . . .
. . . . . . .
* . . . . . .
. . . . . , .
.
l
. . . . ,
.
SC~ILTEICIIISR ~c11L~1c1113I~
AND AND
-:
__
no a\11 I
I
.,
noL igniLc(l “”
“_ t -I-
-l“Ii-
I “_ _-----__“~_-Co., hIC. T-IoIly Springs, 1%. SCII~~LL, New York. .
.
.
.
.
----_---_ IXICISMAN
-_
_”
Scrrti~t,
_”
--..”
--_---.
-______
_-_
_
Gcrnl:~ny.
fluorescent oxinatcs. WC found that by spotting diffcrcnt kinds of paper with a dilute chloroform solution of osinc, a fluorescent spot rcmainecl after the evaporntion of the solvent. Instead of a solution of osinc or its halogen compound in chloroform or other organic solvent a water solution of 5-sulpho-oxinc or 5-sulpho7-iodo-oxine can be used. The results obtained with different kinds or papers arc shown in Table I. From the data it can bc seen that the tests arc sensitive. Without destroying the paper, spot testing is therefore a simple, rapid and sensitive method of detecting the presence of inorganic material which forms fluorescent osinatcs. The inorganic matter in the paper which forms fluorescent compounds with osinc may bc calcium, magnesium, aluminium, etc. The direct differentiation Rcfc~rlrccsp. gG(,.
BEHAVIOUR OF 8-HYDROXYQUINOLINE
VOL. 3 (I9491
563
between these elements is impossible for the fluorescence of their oxinates is nearly the same*. Titanium oxide, sometimes used as a filler, as well as iron which may be present as an impurity, cannot be detected, since their oxinates show no fluorescence. The inorganic matter in the paper may be converted to oxinates by exposure to the vapour of oxine. This can be clone at ordinary tcmpcraturc by placing the paper over a crucible which contains some osine. After a few minutes, a weak fluorcscencc which incrcascs with further exposure to the osine is then observed in the ultraviolet light. It is striking that even the 10~ vapour prcssurc of oxinc at ordinary temperature is sufficient to form oxinatcs**. The action of oxinc vapour can hardly bc explained by assuming a transformation of the inorganic matter into stoichiomctric osinates without a solvent. It is more probable that the osinc (vapour or its solution) reacts with metal on the surface without forming a new phase, i.c., it is chemically adsorbed’ * *. II. A FLUORIDE TEST BASED ON THE QUENCHING OF METAL OX7NATES When aluminium oxinate is treated with a solution containing fluoride ions, the fluoresccncc disappears. This is due to the reaction of aluminium oxinate with the fluoride ion to form aluminium fluoride or the hcxafluoaluminatc ion. The fluorescence of calcium or magnesium oxinate is destroyed similarly. This is used as the basis for a test for fluorides. The test can be carried out using quantitative paper impregnated with aluminium oxinate. This is done by dipping a piece of the paper in a chloroform solution of aluminium oxinatc. After drying, the fluorescent paper is exposed to hydrogen fluoride vapour. In ultraviolct light the surface which came in contact with hydrogen fluoride does not fluoresce. A simpler procedure is based on the method of differentiating papers, described in I. The test may also be made by exposing qualitative filter paper to the vapour of hydrogen fluoride and spotting with a chloroform solution of osinc. In ultraviolet light the area coming in contact with hydrogen fluoride remains dark while the other part of the paper is fluorescent. The latter is the better method. To cheek the sensitivity of the test, we have used spot test techniques. Into a 1.5 ml porcelain crucible, 3 drops of 6-N sulphuric acid and I drop of a sodium fluoride solution are placed and covered with a piccc of qualitative filter paper sufficiently larger in diameter than the crucible, so that the areas exposed and l However by exposing the fluorcsccnt spst to ncctic acid vclpour, the oxinatcs of calcium nnc~;nagncsium clccomposc. Only the fluorcsccncc of aluminium oxinatc persists. J?crhups by the incorporation of ZL suitable mctnllic compound in certain parts of the paper or in the ink and the clcvclopmcnt of the fluoresccncc by treatment with oxinc vnpour or possibly its solution in an organic solvent can bc usccl for the preparation and tcstipg of bank, security, note, etc., paper. l ** This assumption was proved with oxinc and other compouncls which form inner complcxcs by F. 1~EIcL AND I-1. W. %OCHER, pnpcr in prcpnmtion.
Rc/cYc?2ccs
fi.
5GG.
F.
564
FEIGL,
G. B.
HEISIG
VOL.
3 (1949)
unexposed to hydrogen fluoride can be compared easily. The crucible covered with the i>aper is hcatccl to so-Go” for 5 minutes, the paper spotted with a chloroform solution of oxinc (0.5 mg/ml) and observed in the ultraviolet light. The limit of identification of 0.05 of fluorine corresponds to a concentration limit of I: Io”. The sensitivity of the fluorine test is somewhat lowered by the presence of boric acid probably due to the formation of fluoboric acid. The sessitivity in the prcscncc of 50 y of boric acid is 0.5 y fluorine.
III.
A TEST
FOJZ
CYANIDE
IONS
l3ASED
FROM
ON
COPPI:R
‘I-ME (11)
FORMATION
OF
ALUMINIUM
OXINATE
OSINATC
Although the following new test for a cyanide is not more scnsitivc, or sclcctivc, than other icsts found in the litcraturc, it is intcrcsting from the standpoint of the vcrsatilily of oxinc as a reagent. The test is based on the fact that coppcr(II)oxinatc reacts immcdiatcly with hydrogen cyanide, forming coppcr(I)cyaniclc and oxinc. The osinc which forms is convcrtcrt to the fluorescent aluminium oxinatc. The method of carrying out the test was essentially that used in the fluoride test just dcscribccl. rlY~c reagent paper was prcparecl by impregnating quantitative filter paper with a chloroformic solution of copper(II)osinate (0.x m&ml) which has no fuorcscencc. hftcr csposurc to vnpour which might contain hydrocyanic ncicl, the pnpcr was spotted with aluminium chloriclc (I mg/ml) and csamined in ultraviolet light for the fluorcsccnce of the aluminiunl osinatc formed. The limit of idcntilication is 2.5 y nncl the concentration limit is I :2. I&.
1V.
QUENCJIING
OF
TIJJ’: J3Y
PLUORESCJ’:NC@ NON-FLUORESCENT
OF
ALUMINIUM METAL
OSINATJ?
IN
CI?J_OROBORM
OSINATJSS
It is well known that many oxinatcs arc soluble in chloroform and other organic solvents. In the cast of solicl fluorescent oxinntcs the chloroform solution is also fluorcsccnl. The solutions of the non-fluorescent solid osinntcs are likewise not fluorescent. An analytical USC)of osinc is to cstract oxinatcs formed under suitable conditions with chloroform and Co note the colour and fluorescence of the chloroform solution. Therefore the bchnviour of misturcs of fluorescent and nonfluorcsccnt osinntcs is of analytical intcrcst. WC have stuclicd the influence of some non-fluorescent oxinates on the fluorescent aluminium oxinate. Equimolar chloroform solutions of osinatcs of cerium, chromium, thorium, iron(III), thallium(TII), qucnchcd the fluorcsccncc of a chloroformic solution aluminium osinate, whereas l&nut11 osinntc. did not. In view of these results it is important that care bc usecl before drawing conclusions from a fluorescence esamination of a chloroform solution of osines. Rc/c~c?tccs
fi.
566.
VOL.
3 (1949)
BEHAVIOUR
V. BEHAVIOUR
OF FRESHLY
OF
PREPARED
8-HYDROXYQUINOLINE OXINATE
WITH
3-N
s% HYDROCHLORIC
ACID
With few exceptions all metal oxinates arc precipitated in alkaline, neutral or buffered acid solution. The pEr range for the analytical precipitation of osinatcs lies bctwcen 2.7 and 14.6 314.These values give no indication about Chc masirnum pEr (minimum concentration of hydrogen ion) at which no precipitation occurs nGF the plr at which the precipitated osinc dissolves completely. From these values one would cspect that an osinatc would dissolve immcdintely when an acid was added whose prr ~vas much less than the minimum values given for the . precipitation of the osinntc. However it is known that ageing often decreases the solubility of prccipitatcs in acidsan cffcct which is often considered as being due of the establishment of a false equilibrium. Since such an cffcct is not uncommon among inner complex salts, WC have tested the behaviour of freshly precipitated and dried oxinates of many metals with 3-N hydrochloric acid. The pfr is so much 1ower than the lowest piI permitted for the complctc precipitation, that in all cases immediate solution can be cspcctcd. This was true of the osinatcs of antimony(III), bismuth, cadmium, ccrium(III), cl~romiun~(III), cobalt(II), copper( indium(III), lead, magnesium, zinc, lanthanum, zirconium, and nickel, but was not true for the osinates of aluminium, gallium, and iron(lI1). ‘I’llis phenomenon is unmistakable. The osinntes of the first group arc sol~~blc in 11~ hcid cvcn though the precipitate has been dried at the temperature given in the literature for obtaining an anhydrous product. The suspension of the members of the second group, freshly precipitated or dried, arc stable for some time and slowly clissolvc in the acid. Since thcrc is no cliffcrencc in the behaviour of the freshly precipitated or dried product, the resistance to acids can not be due to the ageing of the precipitate. It may be due to the fact that the members of the second group arc anhydrous when they are precipitated or lose their water of hydration readily, while the members of the first group are hydrated, and even the anhydrous products obtained by drying become hydrated and dissolve in the hydrochloric acid.
One
of us, G. 13. H., wishes to espress
AGRICULTURE tamento tical
da
OF PJR,\zII. for permission Producao
and
to the
to
the
in the laboratories
University
of Minnesota
MINISTRY
01:
of the Deparfor the sabba-
leave.
As a result of lhe I. A fluorcsccncc nium in paper. The esnniining the spot Rcfevences 37
Mineral
his appreciation
to work
p. 566.
study of the clwnical bchaviour of some mctallo-osinatcs it. 15 shown tht : test can be used to dctcct the prcscnrc of calcium, mogncsium :~ritl alum~test is made by spotting the pnpcr or its ash with ;I solution of osinc ;~ntl in the ultraviolet Ilght.
566
F. FEIGL,
G. B.
VOL.
HEISIG
3 (1949)
2. A test for a fluoride can be based on the inability of a qualitative filter paper which has been cxposcd to hyclrogcn fluoride to form fluorcsccnt oxinatc by spotting ~7th oxinc. 3. A test for a cyanidc can be based on the liberation of oxinc from coppcr(II)oxinntc and the dctcction of the oxinc by the formation of fluorescent aluminium oxinatc. 4. Some non-fluorescent oxinatcs arc able to quench the fluoresccncc of aluminium oxinatc dissolvccl in chloroform. 5. The oxinatcs of aluminium, gallium, ant1 iron(II1) have ELrcmnrlcablc rcsistancc to the action of 3 N hydrochloric acid, whcrcas all other oxinatcs dissolve immcdiirtcly. An cxplanation for this bchaviour is proposed.
Rl%UMl? hprbs unc ttuclc sur Its propriGt& chimiqucs dc quclqucs m0tallo-oxinntes, on pcut conclurc clue : I. Unc r&action tic fluorcsccncc pcut @trc cmploy&c pour vGrificr In prOscncc dc calcium, clc m;~gnGsium ct cl’nluminium clans clu papict. L’cssai cst cffcctu6 cn touchant Ic papicr ou scs ccndrcs xvcc unc solution d’oxinc, ct en cxaminant la tnchc nux rayons ultraviolets. 2. Unc r&&ion dcs fluorurcs pcut @Lrc bas6c sur l’inhibition clc fluorcscencc par acljonction d’oxinc sur filtrc qunlitatif, cxposG B l’acidc fluorhydriquc. 3. Rcclrcrchc clcs cynnurcs, ils pcuvcnt libbrcr l’oxinc clc l’oxinatc dc cuivrc (II) ct on contdlc l’oxinc par sn drrction dc fluorcsccncc avcc I’aluminium. 4. Quclqucs oxinntcs non-fluorcsccnts pcuvcnt cmp0clicr la fluorcsccncc dc l’oxinntc cl’;duminium cm solution clans lc cl~loroforn~c. 5. Lcs oxinntcs cl’:rluminium, rlc g:dlium ot tic fcr (III) sont trbs stables clans l’acitlc chlorhyclriquc 3N, contraircmcnt aux autrcs oxinatcs; on cn donnc unc explication. %USAMMENFASSUNG Als Ergcbnis von Stuclicn iibcr cIns chcmischc Vcrhnltcn von Mctalloxinatcn wurdc gcfunclcn : x. Ein I;Il~orcsccllztlnchwcis zur I+ststcllung von Calcium, Mngncsium uncl Aluminium, clcr dnrnuf bcruht, Papicr oclcr dcsscn Aschc mit cincr LGsung von Oxin nnzutiipfcln uncl tlcn *J’iipfclflcclc im U.V. Licht zu bctrachtcn. 2. Ein Nnchwcis ftir Fluor, clcr clnrauf bcruht, class qualitativcs Filtcrpapicr, dns dcr Einwirkung von Fluorwnsscrstoff nusgcsctzt wurclc, clic Eihiglccit vcrlicrt, bcim Antiipfcln mit Oxin fluorescicrcndc Oxinatc zu bildcn. 3. Ein Nnchwcis von Cyanid. clcr auf Frcilcgung von Oxin aus Kupfcroxinat uncl Nachwcis clcs Oxins clurch I3ilclung von Alunliniurnoxin~~i bcruht. ‘1. Einigc nicht fluorcscicrcnclc Oxinatc Eschcn clic Fluorcsccnz von in Chloroform gcl6stcm Aluminiumoxinat aw. 5. IXc Oxinatc von Aluminium, Gallium uncl Eiscn zcigcn cinc bcmcrkcnswcrtc Rcsistcnz gcgcn 3 N Si~lzsiiurc, wiiln-cncl nllc nntlcrcn Mctalloxinatc sofort gcliist wcrdcn. Einc ErklYrung ftir dicscs Vcrhaltcn wircl vorgcschlagcn. REFERENCES l I?. Fmcr, AND C. 13. ~II%ISIG, pnpcrs in prcpnration. n F. ~IXGI., c/rCi)liSfYy O/ sl)ECifiC, ,Sclcclivc and Scusilivc Rcnclions (1949), p. x87-189, Acadcmic Press Inc., New Yorlc. 3 I. KOLTI~OFIF AND E. SANDIZLL, Tcsfbook of qzrnntifcztive i7~07,nn~rzc amlysis (1943) p. 80, MncMlllnn Co., New York. 4 J. FLAGG, Orgmic Rca~c~rts used i?t Graviwrctvic rmrt Volzorrelvic A?zaiysis (1948) p. 184-9, Intcrscicncc Publishers, Inc. New Yorlc.
Received
l?ebruary
Ist, xg4g