234 



INDUSTRIAL APPLICATIONS OF PHASE MICROSCOPY 



the study of surface roughness (Hershman, 1945) should be easier seen 

 and evaluated with the phase microscope. 



9. RUBBER 



The phase microscope is useful for the investigation of the homoge- 

 neity of rubber and for the examination of fillers. With the 1.8-mm 

 phase objective it is possible to distinguish five different phases in one 

 specimen. Fillers, such as carbon, channel and chrome blacks, silica, 

 etc., may be examined within the limits of the light microscope, a-nd 



Fig. VI. 6. Emulsion of rubber and resin, 800 X. Left, brightfield. Center, dark- 

 contrast (A — ) phase. Right, bright-contrast phase. 



for this the 0.07A+0.25X diffraction plate in an oil immersion objective 

 is recommended, although the same transmission in an A— plate would 

 be appropriate when dark contrast is preferred. Lesser transmissions 

 are not so good for such fine detail. 



In a two-phase system (Fig. VI. 6) it is possible to identify the con- 

 tinuous and the dispersed phases when their refractive index is known. 

 As was pointed out in Chapter IV the greater path is bright with an A-1- 

 and dark with an A— diffraction plate. In this specimen the two phases 

 show with brightfield because the inner phase was slight amber in color. 

 Examining a number of the inner-phase glol^ules we note that they are 

 bright with the A+ and dark with the A— objective, which indicates 

 that the inner phase is of the higher refractive index. In this case it was 

 known that the resin had a higher index than the rubber and therefore 

 this is a resin-in-rnhber emulsion. To avoid possil)le ambiguities, 

 particles of several sizes should be examined for consistent behavior in 

 reversing contrast. 



10. TEXTILES 



A Zeiss phase microscope placed at the disposal of the Hochst works 

 of I. G. Farbenindustrie led to early trial and discovery of its utihty in 



