Although the main aim of many analysts is to apply increasingly sensitive methods in the field of ecology and health, it is extremely important that conclusions are not drawn solely from analytical results. The impact of chemi- cals on the environment or even on human beings can be properly assessed only by evaluation of data derived from suitable toxicity experiments supported by analytical measurements.

So the efforts of analysts and toxicologists must be regarded as complimentary in the support for authorities dealing with the practicable regulation and control of harm- ful chemicals.

* * *

The members of the Analytical Subcommittee of ETAD thank Dr R Anliker and Dr E A Clarke, ETAD, Basle, for many helpful discussions.

REFERENCES 1. Anliker, Swiss Chem, 2 (9) (1980) 30. 2. Clarke and Anliker, 'Handbook of Environmental Chemistly', Vol.3IPart

3. Venkatamaran, 'The Analytic Chemistry of Synthetic Dyes' (New York:

4. Kubota, Ecotox. Environ. Safety, 3 (1976) 256. 5. Hansch and Leo, 'Substituent Constants for Correlation Analysis in

6. Rekker, 'The Hydrophobic Fragmental Constant' (Amsterdam: Elsevier,

7. Hansch et al., J. Med. Chem., 16 (1973) 1207. 8. Anliker, Clarke and Moser, Chemosphere, 10 (1981) 263. 9. OECD Guidelines for Testing of Chemicals, OECD 1981.

A, Ed. Hutzinger (Berlin: Springer-Verlag, 1980) 181.

Wiley & Sons, 1977).

Chemistry and Biology' (New York: Wiley and Sons, 1979).

1977).

10. Anliker, Swiss Chem, 3 (1/2) (1981) 25. 11. Jensen, New Scientist, 32 (1966) 612.

Crystal Data for C.I. Pigment Yellow 98 A Whitaker Department of Physics Brunel University Uxbridge Middlesex

The single-crystal data and X-ray powder pattern are reported for C.I. Pigment Yellow 98 (a-ll-hydroxyethyl- idene)acet-Fmeth yl-4-chloroanilido- a-azo-(4'-chloro- 2'-nitrobenzene)). The powder pattern has been indexed from the cell dimensions given by the single-crystal measurements; the problems of multiple indexing have been reduced by comparing the powder data with observed single-crystal intensities.

INTRODUCTION This article is one of a series [1,21, in which have been reported X-ray powder diffraction data obtained from crushed single crystals, with the aim of providing accurate X-ray data for analytical purposes. One of the earlier papers [I] gives a complete list of articles up to that date.

ORIGIN OF SPECIMEN C.I. Pigment Yellow 98 (C.I. 11717) has the molecular struc- ture shown in Figure 1. No X-ray data have been reported on this pigment.

Figure 1

Single crystals were prepared by making a saturated solution of the commercial pigment, ARCT-031 Fastona

Yellow 98 (ex Blythe Burrell Colours Ltd) in toluene at 85°C. This was placed in an oven and the temperature increased to 95°C to ensure complete solution of the pigment. The solution was slowly cooled to room temperature over a period of two and a half weeks.

OPTICAL EXAMINATION The crystals appeared to take up one of two forms: (a) Prismatic crystals up to 1 mm in size and triclinic in

shape (b) Blade- or needle-shaped crystals up to 0.7~0.5~0.3

mm in size with hexagonal or monoclinic aspect; in the latter case the angle was 117"; many of these crystals were three dimensional and indicated a crystal of the triclinic class; a majority of crystals were of this second form.

For the purposes of completing the morphological examination the crystallographic axes were defined by the morphological axes; for those crystals with monoclinic aspect,b was along the length, c across it anda through the thickness. With this definition a=117", p=90" and y=llOo. These crystals exhibited oblique extinction on the blade face with an extinction angle of about 46"from the length in the acute angle of the monoclinic aspect.

For those crystals with a hexagonal aspect, b was along the length, a across it and c through the thickness, these crystals had faces of the forms (IOO}, {OIO}, (510) and (001 ). On these crystals the extinction was again oblique with an extinction angle of about 48" or 42" from the length in y. The shape of the crystals made it difficult to decide which of the end angles was y.

X-RAY EXAMINATION No symmetry was detected on Laue photographs, confirm- ing the triclinic class.

Crystals mounted with b and c along the rotation axis

JSDC Volume 100 April 1984 123

TABLE 1

X-ray Powder Data for C.I. Pigment Yellow 98

dabs - _. - hkl - dcalc I dabs hkl

7.56 100 7.594 28 7.24 i i i 7.295 23 2.697 1 iii 6.54 i i o 6.529 11

i i 2 5.536 2.584 302

2.449 ( g g g 5.48 55; 13

2.404 {zli 5.00 121 4.981 32 4.74 1 i i 4.764 16

2.286 {;:; 4.43 120 4.419 9 4.10 012 4.066 8 3.94 201 3.938 33 (330

102 3.79 200 3.69 112

121 3.52 121

3.271 223

3.062 232 3.160 2 i i

342 3'800 1 27 2.170

3.403 2.109 1325

3.775 3.706 15 3.524 15 205

3.354 I 100 2.049 033 3.347 232 3.268 21 3.143 18 3.055 18 32 i

' I 3 2'972 1 9 1.978 i l l , 257 2'980 { 231 2.969

1.936 314 2'752 { 130 2.751

2.696 050 1.906 2.691 2.681 2.582 15 1.897

2'4451 8 1.866 { ;:y 1 6 2.432 1.868 255 1.854

2.382 1.846 { ;:: i:::: 1 5

2.282 233 1.840

8

2.181

2.157 2.156

2.105 2.104 1 2.046 2.030 2.018 1.998 1.992

1.968 1.933 6

I 7

1.808 135 {911 1.747 125

4 54 1.678 { 046

436

1.625 (::: 1.348 {6i4 262

1.273 435 656

1.819 1.81 5 1.812 1.798 1.746 5 1.682 1.677 I .676 1 l 1

1.622 I 1.343 1 1.272 5 1.265 1.255 1.254

give b=10.60r0.11 A, c=12.33*0.12 A, a was indirectly calculated as 8.47 A. Combining these values with those of the angles obtained from the morphological examination gives a unit cell volume of 910 A3.

The intensity measurements for the crystal structure determinarion were obtained from an automatic diffrac- tometer of the National X-ray Crystallographic Service. This was programmed to give a different unit cell.

The density was obtained by flotation in a mixture of trichloroethylene and carbon tetrachloride. The results of these measurements are:

a = 8.297r0.001 A a = 113.14-+.0.01" b = 10.551 t0.002 A /3 = 67.84t0.01" c = 11.856~0.001 A y = 107.88t0.01"

V = 868.4-10.04 A3 D, = 1.565t0.001 g/cm3 2 - 2 Do = 1.562r0.001 g/cm3

Space group PI or Pi.

POWDER DATA The X-ray pattern was obtained with an 11.46 cm Debye-Scherrer camera and filtered cobalt radiation (CoK,,=1.79020 A) and the films photometered. The observed and calculated 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 recrystallised and as-received compound are in agreement with each other.

REFERENCES 1. Whitaker, J.S.D.C., 99 (1983) 121 2. Whitaker, J.S.D.C., 99 (1983) 157.

The calculated and observed densities are in reasonable agreement.

124 JSDC Volume 100 April 1984