ELECTKON MICKOSCOrY 



A. B. 



Fig. 4. (a) Unshadowed carbon replica of Ilford H.P.3. photographic emulsion particles. X9,000 

 (b) The same, shadowed. 



in the light microscope and the region of 

 interest replicated while still in position and 

 transferred to a marked specimen support 

 grid, usually by means of a device attached 

 to the objective lens of the light microscope. 

 This enables electron and light micrographs 

 of the same portion of a specimen to be com- 

 pared. 









Fig. 5. Carbon extraction replica of chromium 

 molj'bdenum steel; the needles are molybdenum 

 carbide and the larger particles chromium carbide. 

 X1G,000. (After Nutting) 



Selected Area Techniques 



Various methods have been devised for 

 the study of selected areas of surfaces or 

 selected particles by means of replicas (14- 

 19). These areas or particles are first studied 



Applications of Replicas 



The field in which replicas have been most 

 widely used is metallography. For routine 

 work "Formvar" replicas have been em- 

 ployed; more recently carbon replicas have 

 been used both as simple replicas or extrac- 

 tion replicas. Similar techniques are em- 

 ployed in the examination of bulk specimens 

 such as clays and other minerals. 



The single-stage methods mentioned for 

 use with particulate specimens have been 

 widely employed in chemistry and biology. 

 Studies of photographic grains and the devel- 

 opment process and of wear particles give 



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