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A method to determine the indicatrix of small crystals

Published online by Cambridge University Press:  14 March 2018

N. Joel
N. Joel*
Affiliation:
Birkbeck College Research Laboratory, London
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Extract

In the course of the investigation of the crystal structure of sodiumthyroxine- dl it appeared to be necessary, in order to find the approximate orientation of the molecule, to determine the orientation of the indicatrix and the values of the principal refractive indices.

The crystals are flat and very thin (about 0-03 mm. thickness), and when put on a glass slide they all lie on their (100) face. This suggested the use of the universal stage, but the high birefringence of the crystals prevented it from giving good results. Moreover, as the crystals belong to the triclinic system and have no regular contour, it would have been difficult to refer the indicatrix to the unit cell. The interference figures seen when the crystals lie on a glass slide were mis-oriented, though sufficient to determine the sign of the indicatrix, and no clear interference figures could be seen when the crystals were far from horizontal.

To overcome these difficulties the method which follows was developed, and proved to be very useful for all uniaxial crystals and highly birefringent biaxial crystals, whatever their habit.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 29 , Issue 210 , September 1950 , pp. 206 - 214
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1950

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References

1 Bernal, J. D. and Carlisle, C. H., Journ. Sci. Instruments, London, 1947, vol. 24, p. 107.Google Scholar

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2 Weisz, O. and Cole, W. F., Journ. Sci. Instruments, London, 1948, vol. 25, p. 213.CrossRefGoogle Scholar

3 Jeffery, J. W., Acta Cryst. Cambridge, 1949, vol. 2, p. 15. [M.A. 10–525.]Google Scholar