116 JSDC APRIL 1971 ; ASQUITH AND PURl

TABLE 4 Dependence of Uptake of Acid on Temperature Bath temperature

10 20 30 40 50 60

("C) Residual acid

(Yo) 5.34 6.34 7.03 7.15 7.90 8.14

The results obtained by immersing wool in a 5 % solution of sulphuric acid for various times are shown in Table 5 .

TABLE 5 Dependence of Uptake of Acid on Immersion Time

lmniersion time Residual acid (Yo)

20 s 4.09 40 s 5.05 60 s 5.66

5 niin 7.12 10 rnin 1.36 15 min 7.53 60 min 7.10 24 h 7,51

Experiments were also carried out with surfactants in the treatment bath. The results obtained contained many anomalies, so that no significant conclusions could be drawn. However, these anomalies are consistent with the results reported earlier by various workers (I).

Discussion Examination of various processing sequences has revealed that

fabric of satisfactory quality can be obtained by carbonising at any one of a number of points in the manufacturing sequence.

All pieces were judged to have been carbonised and dyed satis- factorily and to be of a satisfactory commercial standard, irrespective of the processing sequence. The physical properties of finished fabrics were satisfactory, except for the dry-cleaned fabrics, which is interesting since these were judged subjectively to be the best. The fastness properties, especially to the I S 0 3 washing test, of the dyeings vary. Dyebath exhaustion also varies with the processing sequence.

The sequence scour, alkaline mill, carbonise and dye appears to give the best results, especially if physical properties are considered. However, any of a number of sequences can be used in bulk practice to achieve commercially acceptable results.The method finally chosen may well depend on factors such as the amount of burrs present and their ease of removal, the storage time envisaged before neutralising or dyeing (since storage under acid conditions could be harmful if prolonged), the type of dyes or dyeing process to be employed and, finally, the relative cost and saving in chemical consumption of any individual method.

Correlation has also been obtained between the amount of acid retained in the wool and the temperature of the bath or the time of immersion. In the experiments based on temperature variation, the rate of change of acid absorbed is 0-06"/, acid/deg C. With regard to time of immersion, the rate of absorption is 0.65 "/,/niin over the range 0-5 min. Absorption is complete after 7 min, which is in agreement with previous results (3, 4).

* * * I thank Mr A. Buttle for assistance with the experimental work.

( M S . received 4 November 1970)

References I Park, J.S.D.C., 87 (Apr 1971) I l l . 2 Barritt, J. Textile Inst., 26 (1935) T87. 3 Pressley, Proc. Internat. Wool Text. Res. Conf., Austrulicr, ( 1955)

E389. 4 Mizell, Davis and Oliva, Amer. Dyestuff' Rep., 52 (1963) PSI :

Text. Research J., 32 (1962) 497.

Disulphide Exchange as a Method of Coloration of Animal Fibres R. s. AsQUITH AND A. K. PURI*

School of Coloitr Chemistry and Colour Technology, University of Bradford, Bradford

A dye containing a disulphide link has been prepared. Exchange reactions between the dye-disulphide and cystine in presence of thioglycollic acid have been shown to occur. Studies on the formation of mixed disulphides with wool cystine are described and evidence of the presence of the dye-fibre linkage is given. DisuIphide exchange may be a feasible niethod of dyeing wool at relatively

low temperatures.

Introduction When wool is treated with reducing agents such as thioglycollic

acid thiols are formed. Goddard and Michaelis (1) showed that this reaction takes place at pH > 10. Later Harris et al. (2) studied the reduction of the disulphide bond at neutral and acid pH values and postulated that the reaction was:

I I I I

I I I I

NH co CHCHzSSCHaCH + 2HSCHaCOOH

co NH

11 I co

2 t: HCH,SH + (SCH,COOH), I

AH I

Symmetrical disulphide

Cysteine *!'resent address: James Brown (Studley Wools) Ltd, Stone Hall Lane, Bradford 2

For some time it was believed that this postulate was correct and that any residual disulphide was present as cystine. Howevei., Kolthoff et al. (3) in 1955 and Eldjarn and Phil (4 ) in 1957 proved conclusively that a mixed disulphide is definitely formed when a thiol and a disulphide react together:

R'SSR' + RaSH + R'SSR" + R'SH

In 1959 Human and Springell (5), while studying the protein\ derived from wool by reduction with SsS-thioglycollic acid, proposed the formation of the mixed disulphide 8-carboxy- 8-aminoethylcarboxymethyl disulphide to account for t tic content of bound thioglycollic acid in the protein. This observa- tion was later supported by Zahn and Gerthsen (6). By paper chromatography, they found a new product-attributed to the mixed disulphide-in hydrolysates of wool fabrics set with thioglycollic acid. In earlier work (7), we confirmed the presence of the mixed disulphide in similar hydrolysates and quantita- tively estimated the amounts formed.

Milligan and Swan (8), in work on the dyeing of wool with thiosulphatoazo dyes, postulated that the dyes reacted with

Mixed disulphide

DISULPHIDE EXCHANGE AS A METHOD OF COLORATION O F ANIMAL FIBRES 117

cystine in wool as follows: WSSW + DSS0,- - + WSS0,- + WSSD . . . . ( i )

They used radioactively labelled sulphur in the dye molecule to show that the mixed disulphide was formed. OsterIoh (9), however, suggested that the dyes reacted with cysteine:

DSSO; + CySH + DSSCy + HS0,- He proposed that the mixed disulphide so produced transfers to form a symmetrical disulphide, since he was unable to find significant amounts of the mixed disulphide in hydrolysates of dyed wool.

Maclaren et a/. (10) have studied the reaction of partially oxidised disulphides with thiols and found that oxidation of disulphide leads to increased reactivity:

Dye Mixed disulphide

0 I1

I/ ii

RI-S-S -K1 + 2RaSH -- 2(R1SSR2) + H,O .. ..@) o

f R1SSR2 + RISOIH . . . . ( i i i ) R1-sS--S .HI + R”H -~

0 They have suggested the possibility of using the above reactions in the reactive dyeing of wool.

It is clearly possible that dyes can be covalently bound to wool via the disulphide bridge. This would have the advantage that the dye would be reactive only with disulphide-containing fibres, e.g. wool, and not with cellulosic fibres. This paper reports preliminary findings on the synthesis and reactions with wool of a dye of this nature.

Experimental PURIFICATION OF WOOL

The wool used and its purification have been described previously ( / I ) .

PREPARATION OF DISULPHIDE DYE

Tetrazotisation 4,4’-Dithiodianiline (4-5 g) was added to 100 ml of water at

45°C with stirring. Hydrochloric acid (11 g) was added at room temperature and the mixture stirred until a clear solution was obtained. This was cooled to 0°C and sodium nitrite (3 g) added until there was a slight excess of nitrous acid (as shown by means of potassium iodide paper). The solution was stirred for 30 min.

Coupling 8-Amino-l-naphthol-3,6-disulphonic acid (16 g) was dissolved

in a solution (100 ml) of sodium carbonate (16 g) at 45°C. The solution was cooled to 0°C and the tetrazo solution added to it rapidly with vigorous stirring. The reaction was allowed to proceed at 0°C for 3 h and at 20°C for 16 h. The reddish violet dye was salted out with saturated brine at room temperature and dried at 105°C.

Airification (12) To remove all traces of salt and starting materials, the dye

was dissolved in dimethylformamide (1 litre) at 35”C, the solution filtered through a No. 3 sintered-glass filter and the dye re- precipitated with acetone. This procedure was repeated three times. The resulting dye gave only one coloured component on chromatography.

1 REATMENT OL. DYE WITH THIOGLYCOLLIC ACID

A 2% solution of thioglycollic acid (50 ml) was added to a 1% solution (50 ml) of the dye with stirring at 60°C. The mixture was heated at 60°C for 1 * 5 h.

TREATMENT OF DYE WITH CYSTINE AND CYSTEINE

A 1% solution of cystine was prepared by dissolving the required amount in water containing a small quantity of hydro- chloric acid. This solution (25 ml) was added to a solution (50 ml) containing thioglycollic acid (0 .5 g) and dye (0.5 g). The mixture was heated at 60°C for 1.5 h.

A 1% solution of cysteine was prepared by dissolving the required amount in water. It was treated similarly, but in absence of thioglycollic acid.

THIN-LAYER CHROMATOGRAPHY OF TREATED DYE SOLUTIONS

Thin-layer chromatography was carried out on silica gel chromatogram sheets (Eastman Kodak), using a mixture (4:1:3:2) of propan-1-01, ethyl acetate, butan-2-01 and water as eluent.

TREATMENT OF DYE-THIOGLYCOLLIC ACID-CYSTINE UNDER CONDITIONS OF TOTAL WOOL HYDROLYSIS

A sample (5 ml) of the dye treated with cystine and thio- glycollic acid was taken and enough hydrochloric acid added to give a 6 - ~ hydrochloric acid solution. The solution was put in a sealed tube and heated at 110°C for 24 h. The solution was freeze-dried, redissolved in water and freeze-dried twice to remove all traces of hydrochloric acid.

IDENTIFICATION OF 3-(4-AMlNOPHENYLDISULPHENYL)ALANINE

Cysteine hydrochloride (0.5 g) was dissolved in water (50 ml) and added to dithiodianiline (0.8 g) dissolved in hydrochloric acid at 35°C. The mixture was maintained at 60°C for 1 h. Electrophoresis of the reaction mixture at pH 5.2 (6 kV) for 3 - 5 h showed that a new ninhydrin-positive material was present. This material, which is basic in nature (Rfcy= 1 - 83), was assumed to be the unpurified mixed disulphide. (Dithiodianiline gives a brownish colour with ninhydrin, in contrast with the purple colour obtained with amino acids.)

APPLICATION OF DYE TO WOOL

Wool was dyed by three methods: (1) Wool (0.50 g) was reduced with 2% thioglycollic acid at

60°C for 1 * 5 h at pH 2 and pH 9, respectively, and thoroughly rinsed in water. A 1% solution of the dye was prepared and reduced wool was added to it. Dyeing was carried out at 60°C for 1 h, under reflux, with frequent agitation.

(2) The dye (2.5 g) was dissolved in 250 ml of water at 50°C and thioglycollic acid (0.5 g) added. The mixture was heated at 60°C for 1.5 h. Aliquots (50 ml) were then withdrawn and adjusted to the required pH (2, 5, 7 or 9) with hydrochloric acid or sodium hydroxide. Wool (0.5 g) was added to these aliquots and dyeing carried out at 60°C for 1 -5 h with agitation. After dyeing, the wool was rinsed thoroughly in water. (3) Dye (10 g) was dissolved in 500 ml of water. Thioglycollic

acid (1 g) was added and the solution was heated at 60°C for 2.5 h. Urea (200 g) and Dispersol VP (ICI) (10 g) were then added to the solution and the volume made up to 1 litre. A woven wool fent (50 g) was padded with this dye solution to give an expression of 100%. The dyed material was batched for 24 h and rinsed thoroughly.

EXTRACTION OF DYED MATERIAL WITH PYRIDINE-FORMIC ACID

Dyed material was extracted with a mixture of pyridine and formic acid by the method of Cockett et al. (13) to remove all traces of the substantive dye.

HYDROLYSIS OF DYED WOOL

Dyed wool (0.025 g) was added to 2 ml of 6 - ~ hydrochloric acid containing 400 pI of 0.1 % thioglycollic acid. The mixture

118 JSDC APRIL 1971 ; ASQUITH AND PURl

was treated for 24 h at 110°C in a sealed tube, freeze-dried and washed with water twice to remove all traces of the acid.

ELECTROPHORETIC ESTIMATION OF 3-(4-AMlNOPHENYLDISULPHENYL)ALANINE

3-(4-Aminophenyldisulphenylfalanine was estimated electro- phoretically at pH 5 .2 by the method of Atfield and Morris (14). In the absence of a pure control sample, the colour yield with ninhydrin was taken as unity. All values given are therefore relative.

Discussion As a prerequisite to a study of the formation of mixed

disulphides containing a chromogen, it was necessary to prepare a suitable thiol-containing coloured compound. Several ap- proaches to produce these dyes either from known ‘reactive systems’ or by direct synthesis were unsuccessful, mainly because of the instability of the prepared thiol (owing to oxidation) or the decomposition (reduction) of the starting materials by thiol-introducing reagents.

Because of the lack of a suitable thiol, the alternative pos- sibility of using a coloured disulphide was considered. Among the colorants already known, only the disulphide pigments (15) for cotton seemed to offer a possible approach to the syn- thesis of a coloured disulphide. However, these colorants were unsuitable because of their insolubility in water. Using a modified method, a new water-soluble dye (I) was synthesised from dithiodianiline and 8-amino-l-naphthol-3,6-disulphonic acid:

correspond to those found on treatment with thioglycollic acid alone, for the reduced dye and the mixed disulphide between the dye and thioglycollic acid, and the third spot corresponds to that of the original dye. The fourth spot, far stronger than the others, was not observed in previous chromatograms (except as a faint spot in the mixture of dye reduced with cysteine). This was presumed to be the mixed disulphide formed between thc dye and cystine by the following reaction in the tertiary mixture: 2DSSD + 2HSCH2COOH + CySSCy -+ DSSCH2COOH -t DSSCy i

2DSH + CySSCHICOOH Spraying of the chromatogram with ninhydrin caused a noticc- able change in the colour of the fourth spot; the other spots were unaffected. Furthermore, the immobility of the spot is charac- teristic of the presence of large molecules containing the a-amino acid groupings with other solubilising groups (Table).

Rf Values in a Mixture (4:1:3:2) of Propan-1-01, Ethyl Acetate, Ethanol and Water

Dve 1 .oo Rf of dye

0.75 I , 2 h 0.0

STABILITY OF DYE-CYSTINE DERIVATIVE

Cystine was treated with a mixture of dye and thioglycollic acid and subsequently treated at the boil with hydrochloric acid (6 N), to simulate the conditions of total hydrolysis of the wool. During the latter treatment the solution was decoloriseti. Electrophoresis of the residual material showed a new compound

(1) Reddish violet dye

The reduction of the disulphide was first studied. Sodium borohydride decomposed the dye even in the cold, probably because of the reduction of the azo linkage. However, the colour was retained in the presence of thioglycollic acid. Treatment with 2% thioglycollic acid gave two spots on thin-layer chromato- graphy (Figure I). Neither of these corresponds to that of the

between the dye and thioglycollic acid and the other is the reduced form of the dye:

(Rfcy==l .83), basic in nature and giving a positive colour with ninhydrin.

Treatment of cysteine with 4,4’-diaminodithiophenol yielded the same product, together with cystine and unreacted 4,4’- diaminodithiophenol. In view of the easy formation of the other mixed disulphides (7), this product was assumed to be:

,CHCH,SS original dye; presumably one is the mixed disulphide formed H,N,

HOOC DSSD + HSCH,COOH --f DSSCHaCOOH + DSH 3(4-Aminophenyldisulphenyl)alanine ‘Dye’ Mixed disulphide Reduced dye Reduction with cysteine yielded three spots on thin-layer

chromatography. Two of them correspond to those of the original and the reduced dye, and the third-a very faint spot- appears near the origin. Reduction of dye with thioglycollic acid in presence of cystine yielded four coloured spots. Two of these

On electrophoresis it gave the same Rf value as the product obtained after hydrolysis of the dye and cystine treated with thioglycollic acid. Presumably, it is formed from the dye-cystine disulphide by reduction of the azo linkage, during the hydrolysis at higher temperatures in the presence of a free thiol-containing compound (thioglycollic acid):

H ~ = N ~ + ~ ~ N = N ~ Na03S \ / S0,Na

HSCHiCOOH + CySSCy I NaO$ \ / S0,Na

C y S S e + N a HO NH,

- NaOJS \ / S0,Na I

HSCH2COOH-HC1 1

DISULPHIDE EXCHANGE AS A METHOD OF COLORATION OF ANIMAL FIBRES 119

Q d

Q

8 DSSThy

DSSD

DSH

n na PureDye DThy BCY SH D ~ ~ S S C Y T W

Figure 1- Thrri-layer chromatography of treated dye solutions using a rnixture (4:1;3:2) of propan-1-01, ethyl acetate, butan-1-01 and water

The presence of this mixed disulphide in reaction mixtures would suggest that the dye-cystine mixed disulphide is relatively stable to acid hydrolysis in so far as the disulphide link is con- cerned. However, Osterloh (9) was unable to find any similar compounds in the hydrolysates of wool dyed with thiol sul- phatoazo dyes, although Milligan e t a/. (8) had previously found evidence of their presence by the indirect method of radioactive labelling. Under the conditions of hydrolysis of the mixture, the presence of some free thiol compounds is important if re- arrangement is to be prevented. Sanger (16) reported that, with other proteios, the presence of a trace of thiol inhibits interchange back to symmetrical disulphide. Such interchange does occur iq the absence of traces of thiol. With trace quantities of added thiol (7) it was possible to recover from wool hydroly- sates mixed disulphide formed between cystine in wool and thioglycollic acid without appreciable interchange occurring. Accordingly, although such additions would undoubtedly increase the degradation of the dye in wool (by reduction of the azo linkage), additions of trace quantities were made to estimate the amounts of mixed disulphide formed. In the absence of such thiol, no m&ed disulphide was detected, indicating that re- arrangement had occurred. Presumably similar changes had occurred in the work reported by Osterloh (9).

The above findings are supported by the work of Klotz et al. (19) on the interaction of thiol groups of soluble proteins with disulphide compounds. Reaction of the thiol groups with a coloured disulphide compound (11) showed that the thiol

r

(m groups of serum albumin and 8-lactoglobulin react with the disulphide quantitatively to give the mixed disulphide. Thiol groups produced in the interchange take no further part in the reaction.

On the other hand, the thiol groups of ovalbumin react with the disulphide in a manner analogous to the reaction of low- molecular-weight mercaptans, i.e.

R'SH + R2SSRa + R2SSR' + RPSH RZSSR1 + R'SH + R'SSR' + R2SH

It would therefore seem that, with high-molecular-weight proteins (of which wool is an example), the mixed disulphide is more stable.

APPLICATION TO WOOL

Three different methods were used to apply the dye to wool and in all dyeings the wool was highly coloured. In the first method, in which wool is reduced before dyeing, visual examina- tion showed that dyeing is much more effective at pH 9 than

at pH 2. One drawback of this method is that wool is badly degraded by the thioglycollic acid and the handle is adversely affected. In the second method wool was dyed with a solution of dye prereduced with thioglycollic acid. Visual examination showed that the intensity of the dyeing decreased with pH as follows pH 2 > pH 9 > pH 7 > pH 5. Damage to wool is very considerably eliminated. To determine whether any reaction had taken place between the wool and the dye, the dyeings were extracted with pyridine-formic acid to remove all traces of substantive unreacted dye. A considerable amount of dye was retained by the wool after continued extractions, thus indicating that the dye had bound more permanently to the fibre.

Wool dyed by the second method was investigated further. Hydrolysis of pyridine-extracted wool (6-N HCl) again gave a relatively colourless solution (i.e. colour of dye was lost). The hydrolysates did not indicate the presence of any new amino acids other than those for wool treated in a blank bath, with the exception of a faint trace of 3-(4-aminophenyldisulphenyl)- alanine, the compound previously found in hydrolysates of cystine treated with dye and thioglycollic acid. It would appear therefore that, under the conditions used, the azo linkage is reduced and either the mixed disulphide is not formed or the conditions of hydrolysis are such as to cause rearrangement to the symmetrical disulphide. Since it has already been reported that trace quantities of thiol inhibit disulphide interchange, 400 pl of 0.1 % thioglycollic acid were added to hydrolysates. Amino-acid analysis and electrophoresis showed that the mixed disulphide 3-(4-aminophenyldisulphenyl)alanine was present. It would appear that the previous failure to isolate such a product (9) was due to the rearrangement of mixed disulphide during hydrolysis in the absence of inhibiting thiol groups.

Figure 2 shows the amounts of mixed disulphide formed at different pH values. The results tally in part with the visual appearance of the dyed wool, which is dyed deepest at pH 2 and least at pH 5. However, the results for wool dyed at pH 9 differ from that of visual examination, where somewhat more mixed disulphide was expected because of the high coloration of the wool. Examination by electrophoresis of hydrolysates of wool dyed at pH 9 revealed a new spot, very near that for the mixed disulphide, with a slightly higher Rfey value (2.25). This could be a monosulphide formed between the dye and the wool cystine; similar monosulphides have been reported (7) for re- action between a thiol and disulphide.

20

pH of solution

Figure 2-Efect of p H on amount of 3-(4-arninophenyldisulphenyl)- alanine in dyed wool

Using urea-assisted cold pad-dyeing (18) under acid condi- tions, level dyeings were obtained, and extractions with pyridine indicate a high degree of fixation.

120 JSDC APRIL 1971 ; CHAPMAN AND WHlTAKER

Disulphide exchange may be a feasible method of dyeing wool at relatively low temperatures without the need for preliminary partial oxidation of the disulphide bond as previously suggested (8). * * *

We thank the International Wool Secretariat for a grant to one of us (A.K.P.). (MS. received 25 October 1970)

References I Goddard and Michaelis, J. Biol. Chem., 112 (1935) 361. 2 Patterson, Geiger, Mizel and Harris, J . Res. Nat. Bur. Stand., 27

3 Kolthoff, Stricks and Kapoor, J. Amer. Chem. SOC., 77 (1955) 4733. (1941) 89.

4 Eldjarn and Pihl, J. Biol. Chem., 225 (1957) 604. 5 Human and Springell, Australian J. Chem., 112 (1959j 608. 6 Zahn and Gerthsen, J.S.D.C., 75 (1959) 604. 7 Asquith and Puri, Text. Research J. , in press. 8 Milligan and Swan, ibid., 31 (1961) 18. 9 Osterloh, Melliand Textilber., 44 (1963) 57. I0 Maclaren and Kirkpatrick, J.S.D.C., 84 (1968) 564. I1 Asquith and Garcia-Dorninguez, ibid., 84 (1968) 155. 12 Mehta, Ravikrishnan and Chitale, ibid., 78 (1962) 552. 13 Cockett, Rattee and Stevens, ibid., 85 (1969) 113. 14 Atfield and Morris. Biochem. J.. 81 (1961) 606. 15 Martin-Marietta Corpn, USP 3,225,025 (i963). 16 Sanger, Nature, 171 (1953) 1025. 17 Asauith and Puri. Text. Research J.. 39 (1969) 95. 18 Lewis and Seltzer, J.S.D.C., 84 (1968) 501. 19 Klotz, Ayers, Ho, Horowitz and Heiney, J. Amer. Chem. Suc., 80

’

(1958) 2132.

Correspondence The Editor does not hold himsetf responslbte for the opinions expressed by correspondents

X-ray Powder Diffraction Data for some Azo Pigments Although the optical properties of some azo pigments have

been investigated (I), X-ray data are scanty. The only X-ray crystallographic studies which have been undertaken are a study of the twinning of Para Red (2) and the determination of the crystal structure of C.I. Pigment Yellow 1 (Hansa Yellow G) and its chlorine analogue (3). In neither case are any X-ray powder data reported.

X-ray powder diffraction data that can be used for identifying unambiguously the following pigments have been obtained : C.I. Pigment Yellow 1 (Hansa Yellow G), C.I. Pigment Yellow 3 (Hansa Yellow IOG), C.I. Pigment Yellow 4 and C.I. Pigment Red 2 (4). Further, the mono- and di-bromo analogues of C.I. Pigment Yellow 3 (Hansa Yellow 10G) [4-chloro-2-nitrophenyl- azo-2-bromoacetoacetanilide (5) and 4-bromo-24trophenylazo- 2-bromoacetoacetanilide (6)] were synthesised and examined.

The X-ray powder diffraction patterns were obtained by placing a finely crushed sample in a Philips powder-diffraction camera (diameter 11.48 cm) and irradiating it with CoKa radiation (h= l .79020 A) at 35 kV and 12 mA for 12 h. The interplanar spacing d of the atomic planes producing the various diffraction lines was found using Bragg’s equation nh=2d sin 8. The diffraction lines were photometered to give peak optical densities, which were then normalised to a maximum value of loo.

As a check on the reliability of the diffraction pattern, as well as on the purity of the specimen, it was decided to index the diffraction lines, i.e. to assign hkl values to the atomic planes producing each line. This is a difficult task in dealing with complex compounds and can be satisfactorily achieved only if unit-cell dimensions are known. These dimensions were obtained by examining single crystals of each specimen in turn using oscilla- tion and Weissenberg techniques.

From the X-ray patterns (Figure) it would appear that C.I. Pigment Yellow 3 (Hansa 10G) and both its analogues are isomorphous.

X-ray powder di#+action patterns of C.I. Pigment Yellow 3 (A) and irs mono- ( B ) and di- ( C ) bromo analogues

The indexed X-ray powder patterns for all six materials are

S . J. CHAPMAN given in the Table. DEPARTMENT OF CHEMISTRY

WATFORD WATFORD COLLEGE OF TECHNOLOGY

DEPARTMENT OF PHYSICS BRUNEL UNIVERSITY LONDON W3 23 November 1970

A. WHlTAKER

I Hannam and Patterson, J.S.D.C., 79 (1963) 192. 2 Grainger and McConnell, Acta Cryst., A25 (1969) 422. 3 Mez, Ber. Bunsenges. Phys. Chem., 72 (1968) 389. 4 Material obtained by courtesy of Dr D. Patterson, private comniuni-

5 Patterson, private comniunication (1968). 6 Chapman and Mijovic, Chem. andlnd., (I 970) 955.

cation (1967).

C.I. Pigment Yellow I *

(C.I. 11680) rf l / I , t hkl

10.16 100 020 9.28 26 011 7-27 25 021 6.25 5 110

X-ray Powder Diffraction Patterns of Am Pigments Monobronio Dibromo analogue 01’

C. 1. Pigment C.I. Pigment C.1. Pigment analogue of (2.1. C.I. Pigment Yellow 3 Yellow 4 Red 2 Pigment Yellow 3 Yellow 3

(C.I. 11710) (C.I. 11665) (C.I. 12310) ((2.1. 11710) (C.I. 11710) d Z/I,t hkl d l/l,t hkl d l/llt hkl d Z/Z,t hkl d l/lJ hkl

15.38 19 020 10.38 37 010 10.73 79 002 7.70 7 040 15-22 24 020 7.45 5 040,021 9.30 6 001 10.12 11 100 7.22 1 021 7-33 7 021 6.87 33 111 7.98 18 Oil 8.56 6 011 6.81 38 111 6-94 35 1 1 1 5.57 1 1 041 6.85 1 100 7-14 7 102,012 6.52 9 210 6-42 3 121