334 SECTIONAL TRANSACTIONS.— A. 



Dr. J. D. Bernal, F.R.S. — X-rays and the food and chemical industries 

 (10.40). 



The range of methods based on X-ray crystal diffraction have only begun 

 to be used in the chemical industry, and it is not nearly well enough realised 

 what possibilities they offer. So far, most work has been done in the use 

 of X-rays as an auxiliary in the analysis of complex compounds, particularly 

 natural products, vitamins, hormones, etc., and there they have shown 

 that as an auxiliary method they are capable of shortening the ordinary 

 chemical work by a very large factor. Their immediate practical utility 

 may, however, be even greater. 



X-rays provide an ideal method for standardising chemical products at 

 all stages of manufacture and they are more sensitive than chemical analysis 

 in that they detect differences of texture and body. 



Their value in applied chemistry has been shown by their elucidation of 

 the problem of bleaching powder which had baffled chemists for a century. 



It can safely be claimed that the use of X-ray methods is likely to be 

 equivalent in value to the chemical industry to such techniques as electro- 

 chemical analysis. 



Mr. J. T. Randall and Mr. H. P. Rooksby. — X-rays and the 

 electrical industry (11.5). 



Although it is impossible to describe all the applications of X-rays which 

 have been of value in the electrical industry, the following items have been 

 chosen from recent investigations of interest. 



Fluorescent materials are now of considerable importance in connection 

 with colour modification of discharge lamps and television, and in our first 

 example we show how the colour of fluorescence depends in certain instances 

 on the crystal structure, and how, when solid solutions are possible, the 

 colour of fluorescence may vary in a continuous way with the lattice constant. 

 Specks of dirt hardly visible to the eye sometimes produce large fluorescent 

 discolorations, and the specks may be identified by X-rays. 



Another example is taken from metallurgy. When molybdenum sheet 

 is successively rolled in two directions at right angles, after annealing 

 characteristic fractures occur at 45° to the directions of rolling ; the reasons 

 for this can be understood from a study of X-ray orientation diagrams. 



It is now well known that the differences between amorphous carbon and 

 graphite are ones of degree, and this has led us to some interesting distinc- 

 tions between the X-ray photographs of natural and artificial graphite. 

 Some of the reflections observed by Finch in electron-diffraction photo- 

 graphs have been shown to appear in X-ray patterns of certain natural 

 graphites, while these lines do not appear for any artificial graphite. 



Dr. A. J. Bradley. — X-rays and the permanent magnet industry 

 (11.40). 



Powerful permanent magnets are made of alloys with a composition near 

 to that of FcaNiAl. Their properties can be explained by X-rays. Powder 

 photographs of slowly cooled Fe-Ni-Al alloys have given an entirely new 

 phase diagram with many surprising features. The main single-phase 

 areas are face-centred cubic (a) and body-centred cubic ((3). It was formerly 

 thought that the intermediate area was simply an (a + P) region, but this 

 is only correct at high temperatures. On cooling the alloy, the receding P 

 boundary leaves a new two-phase area consisting entirely of body-centred 



