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Oxidation of some sugars with copper(III)
349
Short comrnumcattons
Summary-The coulometrtc determinatton of thtoacetamidc (TAA) with electrogenerated stlver 1s descrtbed. The tttratton 1s done m a solutton @lM m both ammoma and sodtum hydroxide, and the endpomt IS detected potenttometrrcally with a silver-silver sulphtde electrode. On repeat analyses of approx. 2-mg samples of TAA an average error of -0 4% (relative standard devtatton 0.25 %) was obtained. Important steps m the procedure mclude cleanmg the silver generating electrode m nnctc acid before each titration, purging well with nitrogen to remove oxygen, and not usmg too large a sample. Zusammenfassung-Die coulometrtsche Besttmmung von Thioacetamrd (TAA) mtt elektrtsch erzeugtem Stlber wud beschrteben. Dte Tttratton wtrd m emer Losungausgefuhrt, dte 0,l M an Ammomak und Natrmmhydroxtd tst, der Endpunkt potenttometrtsch mtt emer Stlber-Stlbersulfidelektrode ermtttelt. Bet wiederholten Analysen an Proben von etwa 2 mg TAA wurde em mtttlerer Fehler von -0,4x (relattve Standardabwetchung 0,25 %) erhalten. Wtchttge Merkmale der in Vorschrtft smd : Reuugen der Elektrode zur Sdbererxeugung Salpetersaure vor jeder Titration, gutes Spdlen mit Strkstoff, urn Sauerstoff zu entfernen, mcht zu gro8e Proben. RCsum&Gn d&it le dosage coulometrrque du thtoacetamtde (TAA) par I’argent produtt electrtquement. Le tttrage est effect& dans une solutton 0,lN en ammoniaque et en soude, et le point de fin de dosage est d&elk potenttometrtquement par une electrode argent-sulfure d’argent. Par des analyses rep&es d%chanttllons d’envrron 2 mg de TAA, on a obtenu une erreur moyenne de -0,4% (&art type relattf 0,25x). Les points importants de la technique comprennent le nettoyage de I’tlectrode productrice d’argent dans I’acide nitnque avant chaque tttrage, la bonne purge a l’azote pour thmmer I’oxyg&ne et l’emplot d’echantdlons pas trop tmportants. REFERENCES I. M. Pryszczewska, Talanta, 1965, 12,569. 2 Idem, ibid., 1966, 13, 1700. 3. D G. Bush, C. W. Zuehlke and A. E. Ballard, Anal Chem., 1959,31,1368. 4. T. J. Jacob and C. G. Nair, Talanta, 1966,13,154. 5. C. N. Retlley, Advances in AnalytlcalChemrstryandlnstrumentatron,Vol. 1, pp. 340-l. New York, 1960. 6. C. H. Ltu and S. Shen, Anal. Chem.. 1964,36, 1652.
Interscience,
Talsnra. 1966.Vol. 15.pp. 349to 352. Perganm Press Prmkd m NorthernIreland
Oxidation
of some sugars with copper(II1)
(Recewed 1 April 1967. Revised 30 August 1967. Accepted 20 October 1967) COPPER
was first reported m 1844 and its history up to 1925 has been revrewed by Votis.’ Votis,’ Malaprade’ and Malatesta’ have established beyond doubt that copper(B) may be oxidized by potassium persulphate to copper(III) which 1s stabthzed by co-ordination with a suitable anion such as periodate or tellurate. The first use of copper(III) as an oxidant in tttrimetry appears to be due to Beck, who used it for the trtrtmetric determmatron of some reducing sugars, *e6glycerol,6 ammo-acids’ and proteins.’ He also deduced the constitution of proteins from characterisuc curves obtained by dtfferential titratton of proteins with copper(II1) solutton.* The direct tttrimetric method at room temperature as recommended by Beck suffers from serious limitattons. The end-point was indicated by the appearance of a transient green colour stable for 30 sec. He used glucose as a primary standard Durmg the present work it was observed that the appearance of the transient green colour IS not a true indtcatton of the end-point. Keyworth and Stone’0 also found Beck’s method for detection of the end-pomt to be unsuitable and hence adopted
350
Short commumcatlon~
the potentlometrlc dead-stop end-pomt detectlon mct!,ud hilurcu\cr, i’,ccb L\SI mrA tl:de s ‘4 1,~alents of oxidant are requu-cd per mole of glucose, wherea \\e shn:,. m In!> ij~p~r ,n..: 25 ~1.~ I -1‘ 1. equlbalents may be needed, dependm, ‘1on the e\permiental cvndItIcn< In the present work the oxldatlon of some sugars has been l1l,:!ertahcn :nd %.. 1.~ I I c’ ‘-~a 1I 1) as an ovdant studied m dctall EXPERIMEhTAL Reagents
All reagents used acre of anal) tIcal grade. and Beth? u,cd po I,.~L:‘: F:rLu ~,TL*CLY~~\S?~_ ~oirttw~~ JenSo\sk,” copper(M) m the presence of stablhzln g lonb. and remo\ea the c\iz\s of ~0 ,u plia2c J\r i oi’mg tl-,c solution for about f hr As ue hale used the lodomctrlc mc:i:od tor L~L anaiy\ls. the c.,m+L To this end w ha\e aiiupted the folloI\\.ng prc-‘removal of unused peisulphate I&\er! Important cedure for the preparation of potassium d~telluratocupratecII1) (KJHIIC~(TcO,,),]) solrltlon Coppc’r sulphate (1 561 g), potassmm tellurlte (3 173 g), potassulm persuiphatc (4 220 g) dnd ~XZIWUI~ T;,: hydroxide (8 0 g) arc treated with ca 89 ml of Mater The order of dddltisn is not Important In about 20 mm the bolhng n:l\ttuc mixture IS shaken thoroughly and then heated on a hot-plate becomes Intensely red and the bolhng IS contmued for 15 mm more for complcLlon of the lerlcuull The mixture IS then cooled and filtered (porosity 4 smtered-glasb crucible) and the solutlcn t\ LI,~~JIJ to 100 ml. The persulphate used 1s lust sufficient to oxId;Zc the coppcr(I1) and tellllrltc to coppc, !iII, and tellurate and IS therefore completely removed durmg bodmg If an ewcss OI persc!pnate IS used The absence of persuiphJte IP, bollmg for a longer time IS necessary for Its complete decomposmun the prepared solution can be ascertamcd by acldlfymg about I ml of the soluuon R lth dilute sulphurlc acid till the red colour 1s completely discharged and copper(II1) comerted mtc, copper( adding 5 ml of 0 5Msodlum bicarbonate and 2 ml of 5 :‘, pota?smm Iodide solution, lcttmg t:and for 2 IW~ an’1 then adding a httle starch solution A blue wlour Indicates the presence of pcrsulphnte It was found that the final ConLentratlon of copper(II1). 0 03$1, IS mo!c CC 10s the >nn:c pro\ ldcd the potaswm persulphate IS added m theoretlLn1 amount or oniv m shght C‘\WSS 1%lth the dwount The d~\zrgence nnpesrs to be ofcopper taken the copper(N) solution should ha\e been 0 065\1 The tmal zoncentrat1on 01 rota>sIum due to the preclpltatwn of a copper compound durln:,G ho~l:af orptri III) I> atabii cnli In hydroxide m the prepared solution IS ctz 0 :,\i, this IS essential Luaux ic’Y0llil5 highly alkaline medli!m The solution thus obtamed 1‘1farlj b:dbte axi tl ‘2 u~wentrauon practically unaltered for several monthc The use of potassumi dlperl~,dltoLtlprate(!Il) Ed> prti’uLl b!, +,LL ~,se cl 2n lodomerric ?licLI:oti Llc.led\cr, ti,e pcrloclate m@t L( l:pcte for back-tltratmg the unconsumed ~d:um arsemtc solution with the copper(M) as o\ldant Ptepmarrotz ofcopper
PI ocedrre
To standardize the coppcr(III) sulut~on. treat 5 ml ot I: \\ltl: 5 #,1101 1’t~?.!f drr:nt:c i~ #tit :I Let the nii\turc 5tanLI tc:r i---1 ,11,1’.i,,u t!i+:r,xidiC; :I / ii,, , 1 (standardized against IO&I~C wlut1on) 0 Sic1 sulphurlc acid till the pen \uspc~~r~on d~~,~pp.us, Lc\ulrli;g I,: 2 c‘lcdr \oitrtlc 1 s11~1 ,Y acidic Add 5 ml of 0 5.11 sodium bicarbonate. and b,lck-titrate ‘hc .I 11LGd .~r~snltc yrlth ,r~:&,,l 1 ~c‘Uc ili’lc ,111)‘1 i\l:i: ‘rli!rilllili Jt_icl Iodine solution (0 Ol,V), using starch as lnJlcUtor Run d bhk IS necessary because if potassium hqdrouldc m the Inl\turc I~ rcl[ c~)~npl,l~!’ ric’ltl311,i,i .’ ,‘.c / I the Iodine added during the tltratwn w1l1 be con~unmi b) II ‘\,‘,litlon \,I c. t_\ ot b,, XL- nate I, Important masmuch as It helps mst.mt~mcouS ouldatmn ot tl\c‘ .II ~_I(~Lc ~1111 ii &I,Z and Iti j-,ecnc,: also prohibits the hberatlon of ~odmc lx coppc,(II) from the ~(,ci~cicI illt: Ia illnc ~olulll.~l For estlmatlon of sugars, add an ahquot (VX Table I) tu x: LLLC\ ($1 il ~~f~ttlll) sulutic P, hc~t :bc unwn L.~nt~; the mlvturc on a hot-plate where ncccssary for complete u\lt!atlun, and citt~riiii~:e copper(N) by the method abole The excess of Cu(III) was determlned after the c[>ppcr(lII)-,ug,ir I~I~\~uI. ‘!:.I $L.I Ltcod iui _f ,nlr, Ch) stood for 15 mm, (c) been bollcd and cooled DISCUFSION From Table I It IS clear that the .u~irg are oxicilzcd to c,!rhlln ii:~\ld~ ~-ICI \i.L\,r b\ lic’~t~nd ,~.I:I Arnbmose and \ylose, ulIo_h ,lre pLnto,c. ~cqr~i*e >U cq,u\aimt\ an excess of coppcr(III) solution sucro~ per mole; the hevoses glucose, fructose. mannosc and gal~to~~ con~unIc 21 L4u1\al;nt, requires 48. They have been estmintcd on this bn\lc The con\ll,lipl tcbn ot ‘CII col~pcr(IIl) at rooni temperature bv these sugars lndlcatcs that their owd~t~on ‘it ~~~~~III.I~~ ccr.>pcrd:tue I> mcomplere Beck’ standardized copper(lII) agamct glucose at room tenlpcrntcuc, L1\siln-~n; lii~ consamption ot S
Short communications
351
TABLE I.-STOICHIOMETRY OF OXIDATJON OF SOME SUGARS DlTELLURAToCUPRATE(I~~)
BY POTASSIUM
Equivalents of Cu(lI1) consumed per mole of sugar Sugar taken, ml
0.035M Cu(II1) taken, ml
a
b
C
24.1; 24.0 24.0; 24.0 241 24.1 24.1 24.0 24.0 24.1 241 24.1 24.0 20.1 20.0 20.0 20.0 20.1 20.1 20.0 48.1
O.OOlMGlucose
20
40
80
15 9
O*OOlMFructose
25
30
10.1
18.2
3.0
85
11.8
80
11.8
12.9
3.0
8.0
20
10.1
14.1
3.0
18.0
248
0 OOlM Mannose
25 3.0 1.0 0+048M Galactose 1.0 15 05 0 OOO!J9M Arabmose 3 0 40 2.0 1.0 O+OllM Xylose 0 OOOSMSucrose
1.0 1.0 3.0 4.0
equivalents of Cu(III) per mole of glucose. Our results in Table I indicate that the consumption of copper(IH) at room temperature- increases with standing time and hence the standardization agamst glucose cannot be recommended. Recks found that mannose stabilixed copper(II1) but our observations mdrcate that this sugar is also oxidizable and can be estimated like the others. Chemical Laboratories University of Aihzkabad Allahabad, India
s. CHANDRA K. L. YADAVA
titrimetric determination of glucose, fructosemannose, galactose, arabinose, xylose and sucrose with potassium ditelluratocuprate(III) is described. On heating, pentoses and hexoses consume 20 and 24 equivalents of copper(III) per mole respectively, and sucrose consumes 48 equivalents. Summary-The
R&.tnnt%On d&it le dosage titrimetrique des glucose, fructose mannose, galactose, arabinose, xylose et sucrose par le dttelluratocuprate(III) de potassrum. Par chauffage, les pentoses et hexoses consomment 20 et 24 CQurvalents de cuivre(III) par mole respectrvement, et le sucrose consomme 48 equivalents. ZusannnenfasstrttR-Die titrimetrische Bestimmung von Glucose, Fructose, Mannose, Galactose, Arabinose, Xylose und Sucrose mit Kahumditelluratocuprat(II1) wird beschrieben. In der H&e verbrauchen Pentosen und Hexosen 20 bxw. 24 Aquivalente Kupfer(II1) pro Mol. Sucrose 48. REFERENCES 1. M. Votis, Rec. Trav. Chim., 1925,44,425. 2. L. Malaprade, Compt. Rend., 1937,204,979. 3. L. Malatesta, Gazz. Chim Ital., 1941.71,467, 4. G. Reck, Mlkrochemie, 1950, 35, 169.
580.
Short commumcattons
352
5. Idem, ibid., 1951, 38, 152. 6. Idem, ibid., 1953, 40,258. 7. Zdem, rbld., 195 1, 38, 1, 8. Idem, ibid., 1952, 39,22; 1952,39, 147; Mlkrochrm. Acta, 1956, 977. 9. Idem, Anal. Chim. Acta, 1953,9,241. 10. D. A. Keyworth and K. G. Stone, Anal. Chem , 1955, 27, 833. 11. L. JenSovskf, Chem. Lsty, 1956,50,1103.
Tnlanta
1968. Vol.
15. pp. 352 to 356
Pcrgamon
Press. Prtntcd ID.Northern Irela.ld
Spectrophotometric titration of bismuth with EDTA (Recewed 12 ApriI 1967. Accepted 5 May 1967)
THE development of a sample and efficient method for the estrmation of phosphate m technical sugar solutron&* made it necessary to determine bismuth. The method was based on the procedure due to Vancea* for estimation of phosphate in pure solution; phosphate was precipitated quantrtatrvely by adding a known amount of bismuth at pH 4.5 and then the excess of bismuth was determined. In the past bismuth has been determined gravrmetrically,4-’ tttrrmetrrcally,8-10 and color~n~etr~cally.11-‘8 We have developed a new spectrophotometric titratron of bismuth with EDTA, usmg the non(III)salicylate complex as indicator. EXPERIMENTAL Reagents
Stock soluttons of 0 02M bismuth nitrate, aon(II1) rutrate and EDTA were made in doubly drstdled water. Salicvhc , acid solution. 0.OSM. was nrenared in 50”/, ethanol. The bismuth and iron solutions were standardized against the EDTA, th&r& and sahcycc acid respectively being used as indicators. The buffer used was prepared by mtxmg 100.0 ml of l*OM sodmm acetate and 240.0 ml of 1 OM nitric acid and diluting to 500 ml with water. Procedure
Known quantities of the standard soluttons of iron and bismuth were transferred by pipette to 25-ml standard flasks, followed by addition of 5 ml of 0.05M salicyhc acid. The pH was adjusted to 0.5 by addition of 10 ml of sodium acetate-mtric acid buffer. Increasing quantities of 0.02M EDTA were then added to the flasks, and enough ethanol to give a final concentration of 20% v/v. The solutions were diluted to the mark with water and mixed. The absorbances were then measured at
0
0.4
0.8
I2
‘2 0
2.4
2 8
3 2
3.7
42
46
SO
J
ml of EDTA
FIG. I.-Titration
curves for bismuth wrth EDTA in presence of 0 OlM sahcychc acid. Bsmuth, Ltmole: I-10; 2-20; J-30; 4-40.
Short comrnumcattons
Summary-The coulometrtc determinatton of thtoacetamidc (TAA) with electrogenerated stlver 1s descrtbed. The tttratton 1s done m a solutton @lM m both ammoma and sodtum hydroxide, and the endpomt IS detected potenttometrrcally with a silver-silver sulphtde electrode. On repeat analyses of approx. 2-mg samples of TAA an average error of -0 4% (relative standard devtatton 0.25 %) was obtained. Important steps m the procedure mclude cleanmg the silver generating electrode m nnctc acid before each titration, purging well with nitrogen to remove oxygen, and not usmg too large a sample. Zusammenfassung-Die coulometrtsche Besttmmung von Thioacetamrd (TAA) mtt elektrtsch erzeugtem Stlber wud beschrteben. Dte Tttratton wtrd m emer Losungausgefuhrt, dte 0,l M an Ammomak und Natrmmhydroxtd tst, der Endpunkt potenttometrtsch mtt emer Stlber-Stlbersulfidelektrode ermtttelt. Bet wiederholten Analysen an Proben von etwa 2 mg TAA wurde em mtttlerer Fehler von -0,4x (relattve Standardabwetchung 0,25 %) erhalten. Wtchttge Merkmale der in Vorschrtft smd : Reuugen der Elektrode zur Sdbererxeugung Salpetersaure vor jeder Titration, gutes Spdlen mit Strkstoff, urn Sauerstoff zu entfernen, mcht zu gro8e Proben. RCsum&Gn d&it le dosage coulometrrque du thtoacetamtde (TAA) par I’argent produtt electrtquement. Le tttrage est effect& dans une solutton 0,lN en ammoniaque et en soude, et le point de fin de dosage est d&elk potenttometrtquement par une electrode argent-sulfure d’argent. Par des analyses rep&es d%chanttllons d’envrron 2 mg de TAA, on a obtenu une erreur moyenne de -0,4% (&art type relattf 0,25x). Les points importants de la technique comprennent le nettoyage de I’tlectrode productrice d’argent dans I’acide nitnque avant chaque tttrage, la bonne purge a l’azote pour thmmer I’oxyg&ne et l’emplot d’echantdlons pas trop tmportants. REFERENCES I. M. Pryszczewska, Talanta, 1965, 12,569. 2 Idem, ibid., 1966, 13, 1700. 3. D G. Bush, C. W. Zuehlke and A. E. Ballard, Anal Chem., 1959,31,1368. 4. T. J. Jacob and C. G. Nair, Talanta, 1966,13,154. 5. C. N. Retlley, Advances in AnalytlcalChemrstryandlnstrumentatron,Vol. 1, pp. 340-l. New York, 1960. 6. C. H. Ltu and S. Shen, Anal. Chem.. 1964,36, 1652.
Interscience,
Talsnra. 1966.Vol. 15.pp. 349to 352. Perganm Press Prmkd m NorthernIreland
Oxidation
of some sugars with copper(II1)
(Recewed 1 April 1967. Revised 30 August 1967. Accepted 20 October 1967) COPPER
was first reported m 1844 and its history up to 1925 has been revrewed by Votis.’ Votis,’ Malaprade’ and Malatesta’ have established beyond doubt that copper(B) may be oxidized by potassium persulphate to copper(III) which 1s stabthzed by co-ordination with a suitable anion such as periodate or tellurate. The first use of copper(III) as an oxidant in tttrimetry appears to be due to Beck, who used it for the trtrtmetric determmatron of some reducing sugars, *e6glycerol,6 ammo-acids’ and proteins.’ He also deduced the constitution of proteins from characterisuc curves obtained by dtfferential titratton of proteins with copper(II1) solutton.* The direct tttrimetric method at room temperature as recommended by Beck suffers from serious limitattons. The end-point was indicated by the appearance of a transient green colour stable for 30 sec. He used glucose as a primary standard Durmg the present work it was observed that the appearance of the transient green colour IS not a true indtcatton of the end-point. Keyworth and Stone’0 also found Beck’s method for detection of the end-pomt to be unsuitable and hence adopted
350
Short commumcatlon~
the potentlometrlc dead-stop end-pomt detectlon mct!,ud hilurcu\cr, i’,ccb L\SI mrA tl:de s ‘4 1,~alents of oxidant are requu-cd per mole of glucose, wherea \\e shn:,. m In!> ij~p~r ,n..: 25 ~1.~ I -1‘ 1. equlbalents may be needed, dependm, ‘1on the e\permiental cvndItIcn< In the present work the oxldatlon of some sugars has been l1l,:!ertahcn :nd %.. 1.~ I I c’ ‘-~a 1I 1) as an ovdant studied m dctall EXPERIMEhTAL Reagents
All reagents used acre of anal) tIcal grade. and Beth? u,cd po I,.~L:‘: F:rLu ~,TL*CLY~~\S?~_ ~oirttw~~ JenSo\sk,” copper(M) m the presence of stablhzln g lonb. and remo\ea the c\iz\s of ~0 ,u plia2c J\r i oi’mg tl-,c solution for about f hr As ue hale used the lodomctrlc mc:i:od tor L~L anaiy\ls. the c.,m+L To this end w ha\e aiiupted the folloI\\.ng prc-‘removal of unused peisulphate I&\er! Important cedure for the preparation of potassium d~telluratocupratecII1) (KJHIIC~(TcO,,),]) solrltlon Coppc’r sulphate (1 561 g), potassmm tellurlte (3 173 g), potassulm persuiphatc (4 220 g) dnd ~XZIWUI~ T;,: hydroxide (8 0 g) arc treated with ca 89 ml of Mater The order of dddltisn is not Important In about 20 mm the bolhng n:l\ttuc mixture IS shaken thoroughly and then heated on a hot-plate becomes Intensely red and the bolhng IS contmued for 15 mm more for complcLlon of the lerlcuull The mixture IS then cooled and filtered (porosity 4 smtered-glasb crucible) and the solutlcn t\ LI,~~JIJ to 100 ml. The persulphate used 1s lust sufficient to oxId;Zc the coppcr(I1) and tellllrltc to coppc, !iII, and tellurate and IS therefore completely removed durmg bodmg If an ewcss OI persc!pnate IS used The absence of persuiphJte IP, bollmg for a longer time IS necessary for Its complete decomposmun the prepared solution can be ascertamcd by acldlfymg about I ml of the soluuon R lth dilute sulphurlc acid till the red colour 1s completely discharged and copper(II1) comerted mtc, copper( adding 5 ml of 0 5Msodlum bicarbonate and 2 ml of 5 :‘, pota?smm Iodide solution, lcttmg t:and for 2 IW~ an’1 then adding a httle starch solution A blue wlour Indicates the presence of pcrsulphnte It was found that the final ConLentratlon of copper(II1). 0 03$1, IS mo!c CC 10s the >nn:c pro\ ldcd the potaswm persulphate IS added m theoretlLn1 amount or oniv m shght C‘\WSS 1%lth the dwount The d~\zrgence nnpesrs to be ofcopper taken the copper(N) solution should ha\e been 0 065\1 The tmal zoncentrat1on 01 rota>sIum due to the preclpltatwn of a copper compound durln:,G ho~l:af orptri III) I> atabii cnli In hydroxide m the prepared solution IS ctz 0 :,\i, this IS essential Luaux ic’Y0llil5 highly alkaline medli!m The solution thus obtamed 1‘1farlj b:dbte axi tl ‘2 u~wentrauon practically unaltered for several monthc The use of potassumi dlperl~,dltoLtlprate(!Il) Ed> prti’uLl b!, +,LL ~,se cl 2n lodomerric ?licLI:oti Llc.led\cr, ti,e pcrloclate m@t L( l:pcte for back-tltratmg the unconsumed ~d:um arsemtc solution with the copper(M) as o\ldant Ptepmarrotz ofcopper
PI ocedrre
To standardize the coppcr(III) sulut~on. treat 5 ml ot I: \\ltl: 5 #,1101 1’t~?.!f drr:nt:c i~ #tit :I Let the nii\turc 5tanLI tc:r i---1 ,11,1’.i,,u t!i+:r,xidiC; :I / ii,, , 1 (standardized against IO&I~C wlut1on) 0 Sic1 sulphurlc acid till the pen \uspc~~r~on d~~,~pp.us, Lc\ulrli;g I,: 2 c‘lcdr \oitrtlc 1 s11~1 ,Y acidic Add 5 ml of 0 5.11 sodium bicarbonate. and b,lck-titrate ‘hc .I 11LGd .~r~snltc yrlth ,r~:&,,l 1 ~c‘Uc ili’lc ,111)‘1 i\l:i: ‘rli!rilllili Jt_icl Iodine solution (0 Ol,V), using starch as lnJlcUtor Run d bhk IS necessary because if potassium hqdrouldc m the Inl\turc I~ rcl[ c~)~npl,l~!’ ric’ltl311,i,i .’ ,‘.c / I the Iodine added during the tltratwn w1l1 be con~unmi b) II ‘\,‘,litlon \,I c. t_\ ot b,, XL- nate I, Important masmuch as It helps mst.mt~mcouS ouldatmn ot tl\c‘ .II ~_I(~Lc ~1111 ii &I,Z and Iti j-,ecnc,: also prohibits the hberatlon of ~odmc lx coppc,(II) from the ~(,ci~cicI illt: Ia illnc ~olulll.~l For estlmatlon of sugars, add an ahquot (VX Table I) tu x: LLLC\ ($1 il ~~f~ttlll) sulutic P, hc~t :bc unwn L.~nt~; the mlvturc on a hot-plate where ncccssary for complete u\lt!atlun, and citt~riiii~:e copper(N) by the method abole The excess of Cu(III) was determlned after the c[>ppcr(lII)-,ug,ir I~I~\~uI. ‘!:.I $L.I Ltcod iui _f ,nlr, Ch) stood for 15 mm, (c) been bollcd and cooled DISCUFSION From Table I It IS clear that the .u~irg are oxicilzcd to c,!rhlln ii:~\ld~ ~-ICI \i.L\,r b\ lic’~t~nd ,~.I:I Arnbmose and \ylose, ulIo_h ,lre pLnto,c. ~cqr~i*e >U cq,u\aimt\ an excess of coppcr(III) solution sucro~ per mole; the hevoses glucose, fructose. mannosc and gal~to~~ con~unIc 21 L4u1\al;nt, requires 48. They have been estmintcd on this bn\lc The con\ll,lipl tcbn ot ‘CII col~pcr(IIl) at rooni temperature bv these sugars lndlcatcs that their owd~t~on ‘it ~~~~~III.I~~ ccr.>pcrd:tue I> mcomplere Beck’ standardized copper(lII) agamct glucose at room tenlpcrntcuc, L1\siln-~n; lii~ consamption ot S
Short communications
351
TABLE I.-STOICHIOMETRY OF OXIDATJON OF SOME SUGARS DlTELLURAToCUPRATE(I~~)
BY POTASSIUM
Equivalents of Cu(lI1) consumed per mole of sugar Sugar taken, ml
0.035M Cu(II1) taken, ml
a
b
C
24.1; 24.0 24.0; 24.0 241 24.1 24.1 24.0 24.0 24.1 241 24.1 24.0 20.1 20.0 20.0 20.0 20.1 20.1 20.0 48.1
O.OOlMGlucose
20
40
80
15 9
O*OOlMFructose
25
30
10.1
18.2
3.0
85
11.8
80
11.8
12.9
3.0
8.0
20
10.1
14.1
3.0
18.0
248
0 OOlM Mannose
25 3.0 1.0 0+048M Galactose 1.0 15 05 0 OOO!J9M Arabmose 3 0 40 2.0 1.0 O+OllM Xylose 0 OOOSMSucrose
1.0 1.0 3.0 4.0
equivalents of Cu(III) per mole of glucose. Our results in Table I indicate that the consumption of copper(IH) at room temperature- increases with standing time and hence the standardization agamst glucose cannot be recommended. Recks found that mannose stabilixed copper(II1) but our observations mdrcate that this sugar is also oxidizable and can be estimated like the others. Chemical Laboratories University of Aihzkabad Allahabad, India
s. CHANDRA K. L. YADAVA
titrimetric determination of glucose, fructosemannose, galactose, arabinose, xylose and sucrose with potassium ditelluratocuprate(III) is described. On heating, pentoses and hexoses consume 20 and 24 equivalents of copper(III) per mole respectively, and sucrose consumes 48 equivalents. Summary-The
R&.tnnt%On d&it le dosage titrimetrique des glucose, fructose mannose, galactose, arabinose, xylose et sucrose par le dttelluratocuprate(III) de potassrum. Par chauffage, les pentoses et hexoses consomment 20 et 24 CQurvalents de cuivre(III) par mole respectrvement, et le sucrose consomme 48 equivalents. ZusannnenfasstrttR-Die titrimetrische Bestimmung von Glucose, Fructose, Mannose, Galactose, Arabinose, Xylose und Sucrose mit Kahumditelluratocuprat(II1) wird beschrieben. In der H&e verbrauchen Pentosen und Hexosen 20 bxw. 24 Aquivalente Kupfer(II1) pro Mol. Sucrose 48. REFERENCES 1. M. Votis, Rec. Trav. Chim., 1925,44,425. 2. L. Malaprade, Compt. Rend., 1937,204,979. 3. L. Malatesta, Gazz. Chim Ital., 1941.71,467, 4. G. Reck, Mlkrochemie, 1950, 35, 169.
580.
Short commumcattons
352
5. Idem, ibid., 1951, 38, 152. 6. Idem, ibid., 1953, 40,258. 7. Zdem, rbld., 195 1, 38, 1, 8. Idem, ibid., 1952, 39,22; 1952,39, 147; Mlkrochrm. Acta, 1956, 977. 9. Idem, Anal. Chim. Acta, 1953,9,241. 10. D. A. Keyworth and K. G. Stone, Anal. Chem , 1955, 27, 833. 11. L. JenSovskf, Chem. Lsty, 1956,50,1103.
Tnlanta
1968. Vol.
15. pp. 352 to 356
Pcrgamon
Press. Prtntcd ID.Northern Irela.ld
Spectrophotometric titration of bismuth with EDTA (Recewed 12 ApriI 1967. Accepted 5 May 1967)
THE development of a sample and efficient method for the estrmation of phosphate m technical sugar solutron&* made it necessary to determine bismuth. The method was based on the procedure due to Vancea* for estimation of phosphate in pure solution; phosphate was precipitated quantrtatrvely by adding a known amount of bismuth at pH 4.5 and then the excess of bismuth was determined. In the past bismuth has been determined gravrmetrically,4-’ tttrrmetrrcally,8-10 and color~n~etr~cally.11-‘8 We have developed a new spectrophotometric titratron of bismuth with EDTA, usmg the non(III)salicylate complex as indicator. EXPERIMENTAL Reagents
Stock soluttons of 0 02M bismuth nitrate, aon(II1) rutrate and EDTA were made in doubly drstdled water. Salicvhc , acid solution. 0.OSM. was nrenared in 50”/, ethanol. The bismuth and iron solutions were standardized against the EDTA, th&r& and sahcycc acid respectively being used as indicators. The buffer used was prepared by mtxmg 100.0 ml of l*OM sodmm acetate and 240.0 ml of 1 OM nitric acid and diluting to 500 ml with water. Procedure
Known quantities of the standard soluttons of iron and bismuth were transferred by pipette to 25-ml standard flasks, followed by addition of 5 ml of 0.05M salicyhc acid. The pH was adjusted to 0.5 by addition of 10 ml of sodium acetate-mtric acid buffer. Increasing quantities of 0.02M EDTA were then added to the flasks, and enough ethanol to give a final concentration of 20% v/v. The solutions were diluted to the mark with water and mixed. The absorbances were then measured at
0
0.4
0.8
I2
‘2 0
2.4
2 8
3 2
3.7
42
46
SO
J
ml of EDTA
FIG. I.-Titration
curves for bismuth wrth EDTA in presence of 0 OlM sahcychc acid. Bsmuth, Ltmole: I-10; 2-20; J-30; 4-40.