. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. 350 E. KLEIN. Figs. 1-3. Carbon replicas of silver halide grams. /Ig. J, ammonia emulsion, silver bromide (carbon replica). Fig. 2, boiling emulsion (non-ammonia), silver bromide (carbon replica). Fig. 3, silver iodide emulsion (carbon replica). Fig. 4. Slightly etched silver bromide grains. ges and Mitchell (4) with a light microscope on large silver bromide single crystals is quite definitely brought about by clefts of less than 50 A in size; in other words, that the inner surfaces making th
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. 350 E. KLEIN. Figs. 1-3. Carbon replicas of silver halide grams. /Ig. J, ammonia emulsion, silver bromide (carbon replica). Fig. 2, boiling emulsion (non-ammonia), silver bromide (carbon replica). Fig. 3, silver iodide emulsion (carbon replica). Fig. 4. Slightly etched silver bromide grains. ges and Mitchell (4) with a light microscope on large silver bromide single crystals is quite definitely brought about by clefts of less than 50 A in size; in other words, that the inner surfaces making their appearance in this respect are less widely spaced. It would appear, therefore, that the sub-structure is only the result of displacements and spaces in the magnitude of one or a few lattice intervals.' Of course it is possible for sub-structure also to be present in the silver bromide crystals of normal photographic emulsions. Usually it is assumed (3) that inner surfaces in the crystal could arise from crystal growth due to grain conglomeration. However, examination of va- rious types of emulsion precipitations with an elec- tron microscope have confirmed that conglomeration is of importance only in the first stage of the preci- pitation, with the extremely fine grains. The growth of grain is due entirely to accumulation of the newly forming silver halide on grains already present and to Oswald ; Figs. 5-6 show a comparison of developed grains from the same silver bromide emulsion. Fig. 5: normal metolquinone developer; fig. 6: p-phenylene- diamine developer. The fine structure of the devel- oped silver is considerably coarser in the case of the /7-phenylenediamine development.'' Experiments on initial development show the for- mation of a single silver filament from a silver bro- mide crystal and also three etching pits alongside each other at angles of 120 to the centre of the crystal (2, 6) (fig. 7). This phenomenon has already been investigated by Ev
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