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A METHOD FOR THE ROUTINE EVALUATION OF DRY MASS FROM ELECTRON MICROGRAPHS
Author(s) -
Silvester N. R.,
Burge R. E.
Publication year - 1962
Publication title -
journal of the royal microscopical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0368-3974
DOI - 10.1111/j.1365-2818.1962.tb02063.x
Subject(s) - micrograph , electron micrographs , homogeneous , optics , rotation (mathematics) , scanning electron microscope , electron microscope , materials science , mathematics , physics , geometry , combinatorics
SYNOPSIS Under certain conditions the optical transmission of the negative of an electron micrograph is linearly related to the mass per unit area of the corresponding specimen. A polarizing microscope was modified so that the rotation of a polaroid in the system, which restored a photo‐multiplier current to a fixed value, was a measure of the transmission of a selected area of a micrograph placed on the stage. This null‐point method can be used in the routine evaluation of the dry mass of isolated specimens from their electron micrographs. The theory of the method is given and measurements on standard objects are described that demonstrate its validity of application. Optimum conditions for measurement are considered and experimental errors are discussed. The errors in the present measurements were estimated to be less than 6 p.c. The null‐point method was rapid and simple in operation and should be useful in statistical determinations of the mass of non‐homogeneous specimens.