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A selective test for organic sulphur compounds
JOURNAL
370
A SELECTIVE
TEST
R. I?. BXYFIELD*, De~avt~rucnt (A &mE~a) (Received
FOR
IT. CLARKE
of Applied January
4th.
ORGANIC
AND
E.
SULPHUR
OF CHROMATOGRAPHY
COMPOUNDS
R. COLE
O~qp~aic Chenaistqs.
Univemify
0~~ Neal
Souilr
Wales.
ICen.wi~ngto~w, N.S.
W,
1965)
INTWQDUCTION
gualitative tests for organic sulphur compounds suitable for use on paper chrGmatograms are comparatively few in relation to those available for most other classes of materials. Generally’ the presence of a functional centre is required, simple ‘examples being sulphoxides or thiols where advantage may be taken respectively of oxidising power or salt formation with heavy metals. One test that has been found useful involves exposure of the chromatogram to bromine vapour, blue-violet spots being produced on spraying with starch-iodide solution after removal of excess halogen in a current of warm airlp2. The key to this test appears to lie in the formation of a sulphur derivative containing “active” halogen, and superficially it is similar to tests applied to amino acids or proteins involving the use of chlorine 394. In these however, more drastic conditions are employed; prolonged exp’osure to the halogen followed by heat treatment probably leads to the formation of a N-chloro derivative as reactive intermediate, again detected with starch-iodide. Incidental to studies on the chemistry of sulphenamides (R*S*NH*R’; R = R’ or R + R’)t it was found that application of the bromine test immediately gave blue to violet spots, thus rendering unnecessary spraying with starch-iodide solution. This occurred when R’ was aryl. Now the sulphenamides may be regarded as condensation products, in the present work formed by the gradual addition of sulphenyl chlori.de to the amine, both in ether solution. R.S*CI
+ zI-1,N.R
->
R*S*NH.R’
+ Cl~NH,R
and it had been observed that a strong blue colour appeared on occasions towards the end of the addition. The colours obtained were reminiscent of those produced by the oxidation of aromatic amines, e.g. of aniline by hypochior~te, and it seemed possible therefore that even a very slight excess of the sulphe.nyl halide could act as an oxidising agent * * on the initially formed derivative. From this it appeared that a general test could be devised to embody in sitti formation from an organic sulphur * Glenfield Veterinary Research Station. * Oxidation in the present context is taken to inclucle the possibility e.g. to products of the phenothiazine type. l
J. Chromatog.,
=9 !r965)
370-374
of oxicla.tivc cyclizations,
SELECTIVE
TEST
FOR
ORGANIC
SULPEEUR
COMPOUNDS
371
compound of an “active” intermediate capable of acting on an aromatic amine to produce the coloured material. In principle, the selectivity of such a test lies in its restriction to those compounds capable of forming an intermediate of specific type, i.e. to simpler materials, sulphides and disulphides (or thiols as precursors). Thus the test depends on the presence of a sulphur atom which has not become subj ezt to inductive effects, Oxygenated materials such as sulphoxides, sulphones, sulphonic acids, in which the character of the sulphur atom has been affected by an electron demanding oxygen atom or atoms, would not be expected to react. The interpretation that the colour is probably due to an oxidation product of an aromatic amine was checked by comparative screening of variously structured compounds using aniline or an alkylamine. ESPERIMENTAL
PROCEDURE
Matevials Compounds used were either recrystallized commercial materials or prepared by standard methods to satisfactory analyses and physical constants.
were
Procedure “S$ot tests”. For better simulation of actual chromatograms and to overcome the tendency of materials to concentrate at the outer edges of circles formed during spotting, screening tests were carried out on Whatman No. I paper, using for development the reverse phase system previously described for disulphides2. The dry paper was then drawn through a solution of aniline (3% v/v) in light petroleum (b.p. 40-6o”), and the solvent allowed to evaporate in air. On immediately exposing to bromine vapour a positive test (generally a blue or mauve colour) was obtained within 30-60 sec. In the control tests either the treatment with aniline was omitted or the paper was similarly treated with ,a solution of benzylamine or butylamine before exposure to bromine. This step should not be delayed after evaporation of the light petroleum since, despite its high boiling point, aniline apparently evaporates very readily when spread over the paper in a thin film. RESULTS
Results with various classes of compounds, separated primarily to emphasize differences in the oxidation levels of the sulphur atom, are presented in Table I. Except where otherwise indicated the method has a sensitivity of the order 2-5 ,ug/cms. DISCUSSION
Two important features to observe are first, that best results are obtained in what might be termed a co-oxidation procedure, i.e. impregnation of the paper with aniline before exposure to bromin e is preferable to treating in the reverse order. Secondly tlie shade of colour m.a.y vary according to the length of treatment.with the halogen. This has been found to be due to indicator properties of the coloured product, blue with acid and reddish with excess aniline. Hence longer treatment producing J. Chomatog.,
rg (1965)
370-374
372 TABLE COLOUR No.
R. F. BAYFIELD,
V. CLARKE,
E.
R.
COLE
I TESTS Class
WITW of
VARIOUS
SULPWUR
COMPOUNDS
Colours
GOm$OUnd
obtained
With bromine
only
With br*onzine after aniline
Yellow, Yellow. Yellow, Yellow, Yellow,
quickly quickly quickly quickly quickly
Pink-mauve Pink-mauve Pink-mauve Mauve Pinlc-browngreen
d Thiol
n-Butyl mcrcsptan~ Dcnzyl mercaptan Thiophcnol Thiosalicylic acid Thioglycollic acid
Saclpltide Di-n-butyl sulphide Diphenyl sulphidc Phenothiazine p-Aminodiphenyl sulphide
Disul#ltide
Di-n-butyl clisulphide Diphenyl disulphideb Dibenzyl disulphide
O.vJlge?aaled derivative of molaosul$lGde (a) Sulphoxidc Diphenyl sulphoxide (b) Sulphoncs Diphenyl sulphone Sulphonal [(CI-Is),.C* (SO,*C,H,),] (c) Sulphonic acid $-Toluenesulphonic acid O.vygenated de&alive of disulpltide (a) Thiolsulphinate Phenyl benzenethiolsulphinate (Ph*SO*S* Ph) (b) Thiolsulphonate Benzyl benzylthiolsulphonate (I?11 CI-I,. so, * s * CH2* Ph) l
fades fades fades fades fades
Yellow, fades quickly Yellow, fades quickly Reddish blue Blue
Blue-mauve Blue-mauve Blue Blue
Yellow, Yellow. Yellow,
Reddish blue Blue-mauve Reddish blue
fades quickly fades quickly fades quickly
No colour
No colour
No colour No colour
No colour No colour
No colour
No colour
Yellow,
not permanent
Blue-mauve
Yellow,
not permanent
Pink-brown
Tl~iocarbonyz
Thiourea z-Thiobarbituric Thiocarbanilide Sodium diethyl
acid dithiocarbamate
~zcl~~~ur-~ailroge~a compoamds (a) Scphonamides (R- S. NH* R’) R’ Phenyl Phenyl Phenyl $EZ$~ $-Tolyl 2°% l?he\yl p-Chlorophenyl $-Chlorophenyl Phenyl $-Chlorophenyl p-Chlorophenyl N,N-Diethyleneoxy z-Benzothiazyl Piperidino z-Benzothiazyl
No No No No
colour colour colour colour
Blue-mauve Pink-brown Blue-mauve Pink-brown Blue-mauve Blue-mauve Blue-mauve No colour (IOO /Ag) No colour (50 chg)
Yellow orange Pink orange Orange yellow Deep orange yellow
Blue Mauve-blue Blue Blue-mauve Blue Mauve-blue Blue-mauve Pink-brown Pink-brown
(continued .I. Cltvonzalog.,
19 (1965) 370-374
on p. 373)
SELECTZVE
TABLE NO.
TEST
FOR
ORGANIC
SULFWUR
I (co+zlirtzc&) -Class
--
of cotn~ound
(b), S$pbinamiclos
Coloatrs obtained
(R Sv l
l
With browzine only,
With bronzisze after aniline
Blue-mauve Blue-grey Blue-grcy Blue-grcy
Faint Faint Faint Faint
No colour
No colour
NH *R’) 0
R
Phcnyl
Phenyl Phenyl p-Tolyl ~~lTconlyy: p-Tolyl (c) S%~l%$mides (R. SO,* NH * R’) SulphafWamicle~
@tolyl
373
COMPOUNDS
11Tested directly on spotted pspcr. b Same result Obtained \vit;h substituted
derivatives: disulphiclo. CJDecreased sensitivity, requires about 500 i.lg. d Developed &rec$ly with methanol 75 %.
di-+chloro-,
blue-grcy blue-grey blue-grey blue-grey
di-t)-methoxy-
and
di-
hydrobromic acid as a by-product of amine bromination gives more intense’ blue shades. The necesbity for an aromatic amine is shown by the fact that no colour is obtained with disulphides using’ benzylamine, and of, course no background colour is obtained with aniline and bromine only. In more detail it is to be observed that neither diphenyl sulphoxide nor diphenyl sulphone responds to the test. On this point, the failure of oxygenated derivatives to respond, considerable interest attaches to the results with disulphides (R.S. S. R), thiolsulphinates (R SO 9S. R) , and thiolsulphonates (R *SO, *S R) as one group, and with sulphenamides (R Se NH R) , sulphinamides (R SO NH - R) , and sulphonamides (R*S02’NI-I*R), as another. Positive r@sults are given by disulphides and thiolsulphinates, which in the latter could be &tributed to the presence of the second sulphur atom, whose activity is not.inhibited by the adjacent sulphoxide group. The failure of the thiolsulphonates to respond mu& be associated with the more marked inductive influence of the sulphone group, now apparently sufficient to inactivate the unsubstituted sulphur atom. It is pertjtlent to recall other differences in reactivity, such as the capacity to affect the course of free radical processes - the thiolsulphinates are active inhibitors but the thiolsulphonates are without influence on these system@. The test with thiolsulphinates is so sensitive that if the bromination step is carried out first, then mere exposure CO aniline vapour is sufficient to produce a blue colour on the- paper. It must be noted that bluish colours are produced, from the sulphenamides themselves, i.e., in the absence of aniline. The shade of colour tends to become reddish and, depends on the length of exposure to bromine. This not only emphasizes the reactivity of the group but again focuses attention on the role of the aromatic amine. Colour ifltensity is enhanced by including the aniline treatment. At first sight the response of the sulphinamides appears to run contrary to expectation. Were, however, the test is very much less sensitive and it is not improbable that the result is due to products resulting from acid-catalyzed decollzposition on l
l
l
l
l
l
J. Clwomatog., 19 (wW
370-374
374
R. I?. BAYFIELD,
V. CLARICE,
E. R. COLE
the paper. The negative results with sulphonamides are in accordance with prediction, Results with aromatic sulphides are of interest. Diphenyl sulphide itself responds to the test but less readily than diphenyl disulphide. This is consistent with the lesser reactivity resulting from the inductive effects of the phenyl groups on the sulphur atom. Alkyl sulphides react more readily. The behaviour of these simple compounds reinforces the view that the reactive entity is a sulphenyl bromide. Indeed in these cases it is difficult to visualize any other reactive species. With the sulphenamides it is possible that the intermediate is formed by the back reaction under anhydrous conditions R*S*NI-I*R’
-j- IXBr b
R*S*l?;r
f
R’NEI,
using acid produced by the side reaction between bromine and the amine moiety. It is ,interesting to observe also that compounds such as $-aminodiphenyl sulphide also give a blue colour directly with bromine. This is presumably due to the fact that one molecule may fulfil the amine requirement of a second molecule. The fact that many compounds are able to give a yellow spot while exposed to the bromine, which although fading on removal nevertheless leads to a positive starch-iodide test,’ while still not responding to the aniline test, emphasizes the discrimination shown by the latter. A positive starch-iodide test therefore is due either to the formation of a species capable of liberating iodine and yet not able to oxidize aniline, the more demanding reaction, or to the physical occlusion of bromine, not easily removed in a current of air, at sites on the paper occupied by these compounds. ACICNOWLEDGMENT
The interest of the Director of the Glenfield Veterinary (Mr. J. C. KEAST) is gratefully appreciated.
Research
Station
A discriminating test probably depending on the formation of a sulphurhalogen compound as reactive intermediate, has been described for organic sulphur compounds in which the sulphur atom is at its lowest oxidation level. REFERENCES
I D. BARNARD AND E. R. COLE, Awal. China. Ada, 20 (1959) 540. E. R. COLE, Nnlztve,198 (1963) 1083. 3 H. N. RY~ON AND I?.W. G. SMITH. Natzcre,169 (1952) 922. 4 F. REINDXL AND W. HOPPE. Ber., 87 (1954) 1103. 5 R. F. BAYIQELD AND E:.R. COLE, Anal. Cl&n. Ada, in press. 6 D. BARNARD, L. I~ATEMAN, E. R. COLE AND J. I. CUNNEEN, Chew. Ind.
2
J. Chromatog,,
I9 (x965)
370-374
(Londoa),
(1958)
9x8.
370
A SELECTIVE
TEST
R. I?. BXYFIELD*, De~avt~rucnt (A &mE~a) (Received
FOR
IT. CLARKE
of Applied January
4th.
ORGANIC
AND
E.
SULPHUR
OF CHROMATOGRAPHY
COMPOUNDS
R. COLE
O~qp~aic Chenaistqs.
Univemify
0~~ Neal
Souilr
Wales.
ICen.wi~ngto~w, N.S.
W,
1965)
INTWQDUCTION
gualitative tests for organic sulphur compounds suitable for use on paper chrGmatograms are comparatively few in relation to those available for most other classes of materials. Generally’ the presence of a functional centre is required, simple ‘examples being sulphoxides or thiols where advantage may be taken respectively of oxidising power or salt formation with heavy metals. One test that has been found useful involves exposure of the chromatogram to bromine vapour, blue-violet spots being produced on spraying with starch-iodide solution after removal of excess halogen in a current of warm airlp2. The key to this test appears to lie in the formation of a sulphur derivative containing “active” halogen, and superficially it is similar to tests applied to amino acids or proteins involving the use of chlorine 394. In these however, more drastic conditions are employed; prolonged exp’osure to the halogen followed by heat treatment probably leads to the formation of a N-chloro derivative as reactive intermediate, again detected with starch-iodide. Incidental to studies on the chemistry of sulphenamides (R*S*NH*R’; R = R’ or R + R’)t it was found that application of the bromine test immediately gave blue to violet spots, thus rendering unnecessary spraying with starch-iodide solution. This occurred when R’ was aryl. Now the sulphenamides may be regarded as condensation products, in the present work formed by the gradual addition of sulphenyl chlori.de to the amine, both in ether solution. R.S*CI
+ zI-1,N.R
->
R*S*NH.R’
+ Cl~NH,R
and it had been observed that a strong blue colour appeared on occasions towards the end of the addition. The colours obtained were reminiscent of those produced by the oxidation of aromatic amines, e.g. of aniline by hypochior~te, and it seemed possible therefore that even a very slight excess of the sulphe.nyl halide could act as an oxidising agent * * on the initially formed derivative. From this it appeared that a general test could be devised to embody in sitti formation from an organic sulphur * Glenfield Veterinary Research Station. * Oxidation in the present context is taken to inclucle the possibility e.g. to products of the phenothiazine type. l
J. Chromatog.,
=9 !r965)
370-374
of oxicla.tivc cyclizations,
SELECTIVE
TEST
FOR
ORGANIC
SULPEEUR
COMPOUNDS
371
compound of an “active” intermediate capable of acting on an aromatic amine to produce the coloured material. In principle, the selectivity of such a test lies in its restriction to those compounds capable of forming an intermediate of specific type, i.e. to simpler materials, sulphides and disulphides (or thiols as precursors). Thus the test depends on the presence of a sulphur atom which has not become subj ezt to inductive effects, Oxygenated materials such as sulphoxides, sulphones, sulphonic acids, in which the character of the sulphur atom has been affected by an electron demanding oxygen atom or atoms, would not be expected to react. The interpretation that the colour is probably due to an oxidation product of an aromatic amine was checked by comparative screening of variously structured compounds using aniline or an alkylamine. ESPERIMENTAL
PROCEDURE
Matevials Compounds used were either recrystallized commercial materials or prepared by standard methods to satisfactory analyses and physical constants.
were
Procedure “S$ot tests”. For better simulation of actual chromatograms and to overcome the tendency of materials to concentrate at the outer edges of circles formed during spotting, screening tests were carried out on Whatman No. I paper, using for development the reverse phase system previously described for disulphides2. The dry paper was then drawn through a solution of aniline (3% v/v) in light petroleum (b.p. 40-6o”), and the solvent allowed to evaporate in air. On immediately exposing to bromine vapour a positive test (generally a blue or mauve colour) was obtained within 30-60 sec. In the control tests either the treatment with aniline was omitted or the paper was similarly treated with ,a solution of benzylamine or butylamine before exposure to bromine. This step should not be delayed after evaporation of the light petroleum since, despite its high boiling point, aniline apparently evaporates very readily when spread over the paper in a thin film. RESULTS
Results with various classes of compounds, separated primarily to emphasize differences in the oxidation levels of the sulphur atom, are presented in Table I. Except where otherwise indicated the method has a sensitivity of the order 2-5 ,ug/cms. DISCUSSION
Two important features to observe are first, that best results are obtained in what might be termed a co-oxidation procedure, i.e. impregnation of the paper with aniline before exposure to bromin e is preferable to treating in the reverse order. Secondly tlie shade of colour m.a.y vary according to the length of treatment.with the halogen. This has been found to be due to indicator properties of the coloured product, blue with acid and reddish with excess aniline. Hence longer treatment producing J. Chomatog.,
rg (1965)
370-374
372 TABLE COLOUR No.
R. F. BAYFIELD,
V. CLARKE,
E.
R.
COLE
I TESTS Class
WITW of
VARIOUS
SULPWUR
COMPOUNDS
Colours
GOm$OUnd
obtained
With bromine
only
With br*onzine after aniline
Yellow, Yellow. Yellow, Yellow, Yellow,
quickly quickly quickly quickly quickly
Pink-mauve Pink-mauve Pink-mauve Mauve Pinlc-browngreen
d Thiol
n-Butyl mcrcsptan~ Dcnzyl mercaptan Thiophcnol Thiosalicylic acid Thioglycollic acid
Saclpltide Di-n-butyl sulphide Diphenyl sulphidc Phenothiazine p-Aminodiphenyl sulphide
Disul#ltide
Di-n-butyl clisulphide Diphenyl disulphideb Dibenzyl disulphide
O.vJlge?aaled derivative of molaosul$lGde (a) Sulphoxidc Diphenyl sulphoxide (b) Sulphoncs Diphenyl sulphone Sulphonal [(CI-Is),.C* (SO,*C,H,),] (c) Sulphonic acid $-Toluenesulphonic acid O.vygenated de&alive of disulpltide (a) Thiolsulphinate Phenyl benzenethiolsulphinate (Ph*SO*S* Ph) (b) Thiolsulphonate Benzyl benzylthiolsulphonate (I?11 CI-I,. so, * s * CH2* Ph) l
fades fades fades fades fades
Yellow, fades quickly Yellow, fades quickly Reddish blue Blue
Blue-mauve Blue-mauve Blue Blue
Yellow, Yellow. Yellow,
Reddish blue Blue-mauve Reddish blue
fades quickly fades quickly fades quickly
No colour
No colour
No colour No colour
No colour No colour
No colour
No colour
Yellow,
not permanent
Blue-mauve
Yellow,
not permanent
Pink-brown
Tl~iocarbonyz
Thiourea z-Thiobarbituric Thiocarbanilide Sodium diethyl
acid dithiocarbamate
~zcl~~~ur-~ailroge~a compoamds (a) Scphonamides (R- S. NH* R’) R’ Phenyl Phenyl Phenyl $EZ$~ $-Tolyl 2°% l?he\yl p-Chlorophenyl $-Chlorophenyl Phenyl $-Chlorophenyl p-Chlorophenyl N,N-Diethyleneoxy z-Benzothiazyl Piperidino z-Benzothiazyl
No No No No
colour colour colour colour
Blue-mauve Pink-brown Blue-mauve Pink-brown Blue-mauve Blue-mauve Blue-mauve No colour (IOO /Ag) No colour (50 chg)
Yellow orange Pink orange Orange yellow Deep orange yellow
Blue Mauve-blue Blue Blue-mauve Blue Mauve-blue Blue-mauve Pink-brown Pink-brown
(continued .I. Cltvonzalog.,
19 (1965) 370-374
on p. 373)
SELECTZVE
TABLE NO.
TEST
FOR
ORGANIC
SULFWUR
I (co+zlirtzc&) -Class
--
of cotn~ound
(b), S$pbinamiclos
Coloatrs obtained
(R Sv l
l
With browzine only,
With bronzisze after aniline
Blue-mauve Blue-grey Blue-grcy Blue-grcy
Faint Faint Faint Faint
No colour
No colour
NH *R’) 0
R
Phcnyl
Phenyl Phenyl p-Tolyl ~~lTconlyy: p-Tolyl (c) S%~l%$mides (R. SO,* NH * R’) SulphafWamicle~
@tolyl
373
COMPOUNDS
11Tested directly on spotted pspcr. b Same result Obtained \vit;h substituted
derivatives: disulphiclo. CJDecreased sensitivity, requires about 500 i.lg. d Developed &rec$ly with methanol 75 %.
di-+chloro-,
blue-grcy blue-grey blue-grey blue-grey
di-t)-methoxy-
and
di-
hydrobromic acid as a by-product of amine bromination gives more intense’ blue shades. The necesbity for an aromatic amine is shown by the fact that no colour is obtained with disulphides using’ benzylamine, and of, course no background colour is obtained with aniline and bromine only. In more detail it is to be observed that neither diphenyl sulphoxide nor diphenyl sulphone responds to the test. On this point, the failure of oxygenated derivatives to respond, considerable interest attaches to the results with disulphides (R.S. S. R), thiolsulphinates (R SO 9S. R) , and thiolsulphonates (R *SO, *S R) as one group, and with sulphenamides (R Se NH R) , sulphinamides (R SO NH - R) , and sulphonamides (R*S02’NI-I*R), as another. Positive r@sults are given by disulphides and thiolsulphinates, which in the latter could be &tributed to the presence of the second sulphur atom, whose activity is not.inhibited by the adjacent sulphoxide group. The failure of the thiolsulphonates to respond mu& be associated with the more marked inductive influence of the sulphone group, now apparently sufficient to inactivate the unsubstituted sulphur atom. It is pertjtlent to recall other differences in reactivity, such as the capacity to affect the course of free radical processes - the thiolsulphinates are active inhibitors but the thiolsulphonates are without influence on these system@. The test with thiolsulphinates is so sensitive that if the bromination step is carried out first, then mere exposure CO aniline vapour is sufficient to produce a blue colour on the- paper. It must be noted that bluish colours are produced, from the sulphenamides themselves, i.e., in the absence of aniline. The shade of colour tends to become reddish and, depends on the length of exposure to bromine. This not only emphasizes the reactivity of the group but again focuses attention on the role of the aromatic amine. Colour ifltensity is enhanced by including the aniline treatment. At first sight the response of the sulphinamides appears to run contrary to expectation. Were, however, the test is very much less sensitive and it is not improbable that the result is due to products resulting from acid-catalyzed decollzposition on l
l
l
l
l
l
J. Clwomatog., 19 (wW
370-374
374
R. I?. BAYFIELD,
V. CLARICE,
E. R. COLE
the paper. The negative results with sulphonamides are in accordance with prediction, Results with aromatic sulphides are of interest. Diphenyl sulphide itself responds to the test but less readily than diphenyl disulphide. This is consistent with the lesser reactivity resulting from the inductive effects of the phenyl groups on the sulphur atom. Alkyl sulphides react more readily. The behaviour of these simple compounds reinforces the view that the reactive entity is a sulphenyl bromide. Indeed in these cases it is difficult to visualize any other reactive species. With the sulphenamides it is possible that the intermediate is formed by the back reaction under anhydrous conditions R*S*NI-I*R’
-j- IXBr b
R*S*l?;r
f
R’NEI,
using acid produced by the side reaction between bromine and the amine moiety. It is ,interesting to observe also that compounds such as $-aminodiphenyl sulphide also give a blue colour directly with bromine. This is presumably due to the fact that one molecule may fulfil the amine requirement of a second molecule. The fact that many compounds are able to give a yellow spot while exposed to the bromine, which although fading on removal nevertheless leads to a positive starch-iodide test,’ while still not responding to the aniline test, emphasizes the discrimination shown by the latter. A positive starch-iodide test therefore is due either to the formation of a species capable of liberating iodine and yet not able to oxidize aniline, the more demanding reaction, or to the physical occlusion of bromine, not easily removed in a current of air, at sites on the paper occupied by these compounds. ACICNOWLEDGMENT
The interest of the Director of the Glenfield Veterinary (Mr. J. C. KEAST) is gratefully appreciated.
Research
Station
A discriminating test probably depending on the formation of a sulphurhalogen compound as reactive intermediate, has been described for organic sulphur compounds in which the sulphur atom is at its lowest oxidation level. REFERENCES
I D. BARNARD AND E. R. COLE, Awal. China. Ada, 20 (1959) 540. E. R. COLE, Nnlztve,198 (1963) 1083. 3 H. N. RY~ON AND I?.W. G. SMITH. Natzcre,169 (1952) 922. 4 F. REINDXL AND W. HOPPE. Ber., 87 (1954) 1103. 5 R. F. BAYIQELD AND E:.R. COLE, Anal. Cl&n. Ada, in press. 6 D. BARNARD, L. I~ATEMAN, E. R. COLE AND J. I. CUNNEEN, Chew. Ind.
2
J. Chromatog,,
I9 (x965)
370-374
(Londoa),
(1958)
9x8.