number and name, concentration of active ingredient, toxicological data (LD50 and results of rabbit skin and eye irritation tests) and recommended labels (symbol; R- and S- phrases).

67/548/EEC on the approximation of laws, regulations and administrative provisions relating to the classification. packaging and labelling of dangerous substances,)

2. Bundesgesetzblatt, Part 1 (58) 1718. (Law dated 16 Sept 1980 concerned with protection against dangerous substances.)

3. Off. J. Europ. Commun., 26 (L257) 1. (Commission directive dated 29 July 1983 on the approximation of laws, regulahons and administrative provisions relating to the classification, packaging and iabelling of dangerous substances (83/467/EEC).)

REFERENCES 1. Off J Furop. Commun., 22 (L29) 10. (6th amendment of Directive

Crystal data for C.I. Pigment Yellow 60 A Whitaker

Department ojphysics, Brunel University, Uxbndge, Middlesex UB8 3PH

The single crystal data and X-ray powder pattern are reported for C.1. Pigment Yellow 60 11 -phenyl-3-methyl-4- (2'-chlorophenylazo)-5-pyrazolonej. The powder pattern has been indexedfrom cell dimensions given by single crystal measurements. The problems of multiple indexing have been reduced by comparing the powder data with obserued single-crystal intensities.

INTRODUCTION Crystalline materials give rise to an X-ray powder diffraction pattern which is related to the crystal structure and so is unique to that structure. It follows that not only is the pattern different for each pigment or dye, but is also different for different polymorphs of the same colorant. Thus the X-ray powder pattern may be used as a method of identification of the colorant and of the polymorph (if more than one exists). However, there is no way in which the powder pattern can be predicted from a knowledge of the chemical composition, and so for analytical purposes a bank of reliable standard data is required for interpreta- tion of the pattern. Without this standard data the method is useless

A very common method of obtaining the reference data is to obtain a pattern from a powder, but there are three objections to this. Firstly the powder may not be chemically pure, secondly it may be chemically pure but not crystallographically pure (i.e. it may contain more than one polymorph) and thirdly it may be crystallogra- phically a single phase but may differ from what the investigator believes it to be (e.g. it may contain molecules of crystallisation).

These objections may be overcome by using a powder specimen prepared from crushed single crystals, which gives data of greater reliability. In addition the intensities from the powder may be correlated with those from the single crystal as a further check. The present paper is one of a series[1-4] in which have been reported X-ray powder diffraction data obtained from crushed single crystals, with the aim of providing reliable X-ray data for analyhcal purposes. One earlier paper [l] examined the usefulness of X-ray powder diffraction to colour chemistry and gave a complete list of references to that date.

ORIGIN OF SPECIMEN C.I. Pigment Yellow 60 (C.I. 12705) has the molecular structure shown in Figure 1. No X-ray data have hitherto been reported on this pigment. Single crystals were prepared by making a saturated solution of the commer-

cial pigment Hansa Yellow 4R (Harshaw) in toluene at 85°C. This was placed in an oven and the temperature increased to 95°C to ensure complete solution and then cooled to room temperature over a period of three weeks.

Figure 1 - C.1. Pigment Yellow 60

OPTICAL EXAMINATION The recrystallisation gave predominantly blade-shaped crystals up to 6 . 0 ~ 1 . 9 ~ 0 . 5 m m in size, but there were some needle-shaped crystals and also a few massive crystals up to a size of 6 . 5 ~ 6 . 5 x 1 . 5 m m . Those crystals that were of sufficient thickness to observe the orientation of all three crystallographic axes indicated that the crystal class was triclinic.

The blade-shaped crystals had a monoclinic aspect with a monoclinic angle of about 62". In addition some crystals contained striations (growth lines) parallel to the breadth of the crystal. For the purposes of completing the morphological examination the a axis was defined along the length, b across the breadth of the blade and c through the thickness. With this orientation a=103", p=127" and y=62".

The colour was very variable and was dependent upon the thickness; thin crystals were yellow but as the crystals became thicker the colour became darker and redder, the colour changing through yellow-orange, orange to red- orange as the thickness increased.

The blade-shaped crystals were slightly pleochroic. When the breadth of the crystals was parallel to the plane of polarisation they were slightly redder (typical change from yellow-orange to reddish-orange), compared with when the breadth of the crystal was perpendicular to the plane of polarisation. These crystals exhibited oblique

JSDC Volume 104 May/June 1988 225

TABLE 1

5.16 200 5.169 51 3.174 301 3.181 11 2.382

2.325 i i i 4.408 3.031 131 3.036 11

2.306 440 { 020 4.355} 2.974 202 2.970 2(a) 4.28 121 4.277 10 2.859 220 2.863 12 4 13 220 4.139 15 212 2.730 2.256 { ] 8 2.179 3.69 12i 3.688 12 122 2.705 2.158

4.70 111 4.698 17 3.108 i2 i 3.114

4.00 021 4.006 11 2.722 I22 2.720

3.56 02i 3.558 29 f 322 2.6951 2.111

213 2.378

1.981 232 1.981 3 2.586 { iiE E::;:} 6 W! 1.950

103 2.446 412 1.937

10.35 100 10.339 38 300 3.446 8 30 110 8.279 7 3.398 { 22i 3.395} 100

5.40 210 5.368 6’181 66 5 3.231 { ii; ::$:} 4 2,413 4oi 2,412 4 1.893 133 1.894 :1

7.48 001 7.474 62 320 3.348 2,465 [ i22 2.469) 1.938 { 322 1.938} 5 6.17

1.847 242 1.844 4 113 2.342 403 1.833 422 2.324

140 2.303 1.787 312 2.267 231 2.175 8 323 2.154 6 1.700 442 1.697 5 133 2.110 4

233 2.307 i i 4 1.812

4

2.687 1 3 1 1 2.690) 9 2,019 041 2.018 } S i i 2.672 501 2.015

(a) Visible by eye but too weak to measure on photometer, intensity given IS half weakest measured

extinction on the blade face with an extinction angle of about 7” from the breadth in the acute angle of the aspect.

X-RAY EXAMINATION No symmetry was detected on Laue photographs, confirming the triclinic class. Crystals mounted with a, b and c along the rotation axis gave a=9.34+0.09& b = 1 1.86 f 0.12& C= 9.40 i 0.09A.

The intensity measurements for the crystal structure determination were obtained using an automatic diffrac- tometer. This was programmed to give a different unit cell, one closer to orthogonal.

The density (DO) was obtained by flotation in a mixture of trichloroethylene and benzene. The results of these measurements were: a = 11.1256f0.0010~ a = 80.708+0.009” b = 9.4507k0.0008A p =84.382+0.009” c = 7.5798k0.0009A y = 68.451 +0.007” V = 730.9+0.2A3 D, = 1.4211+0.0003 g/cm3

Space group PI or pi. DO = 1.420+0.003 g/cm3

The observed and calculated densities were in good agreement.

POWDER DATA The X-ray pattern was obtained using an 11.46 cm diameter Debye-Schemer camera and filtered cobalt radiation (CoK,,= 1.79021A) and the film photometered. The observed and calculated interplanar spacings and relative intensities are listed in Table 1. The Miller indices given are based on the unit cell from the diffractometer data. The problem of multiple indexing was reduced by reference to the observed single-crystal intensities. The patterns of the ‘as received’ and recystallised samples were in agreement.

REFERENCES 1. AWhitaker, J.S.D.C., 102(1986)66. 2. A Whitaker, J.S.D.C., 102 (1986) 109. 3. AWhitaker, J.S.D.C., 102 (1986) 136. 4. AWhitaker, J.S.D.C., 103 (1987) 270.

100 YEARS AGO From abstract of paper ‘Production of indigo in China’,

Journal, May 1888 In every farm there are a dozen or more large earthen jars fermentation. This process is aided by the application of a or kongs, with the capacity of a barrel, which are used for little slacked lime and frequent stirring, when the indigo is the manufacture of indigo. Those who engage extensively precipitated in the form of a dark blue sediment, which, in the manufacture have a large brick-lined tank built in when dried, forms the indigo of commerce, During the the ground, six or eight feet in depth, and of a diameter of process of manufacture, women with flowers in their hair ten or fifteen feet, with a capacity of many hundred (a universal custom in China) are not permitted to gallons. The plants are placed in these receptacles, and approach the kongs, as it is a belief that their presence is covered with fresh clear water, where they are allowed to prejudical to the quality of the indigo, and for a like reason lie for several days till the indican, a peculiar substance the kongs are removed to a situation protected from the contained in the juice of the plant, is decomposed by atmosphere of the fields.

226 JSDC Volume 104 May/June 1988