Electron microscopy; proceedings of the Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 348 G. SCHIMMEL Fig. 1. Monocrystalline calcium carbonate. Magnification : 90,000. Fig. 2. Calcium liydroxyde obtained from aqueous suspen- sion. Magnification 80,000. droxide precipitates from clear calcinated water in the form of smooth, compact spherulites (hemis- pheres). During the test they permitted the calcinated water to dry in the air on collodion films. Since then, these results have become the general scien- tific property of th
Electron microscopy; proceedings of the Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 348 G. SCHIMMEL Fig. 1. Monocrystalline calcium carbonate. Magnification : 90,000. Fig. 2. Calcium liydroxyde obtained from aqueous suspen- sion. Magnification 80,000. droxide precipitates from clear calcinated water in the form of smooth, compact spherulites (hemis- pheres). During the test they permitted the calcinated water to dry in the air on collodion films. Since then, these results have become the general scien- tific property of the lime industry; they are discussed, for instance, in the third volume of the book Zement-Cheniie by Dr. Hans Kuehl. We re- peated the investigations and obtained,at first,exactly the same photographs. When heating their prepara- tions by an intensive irradiation, the above-men- tioned authors observed a change in the spherulites, which they interpreted to be a transformation to calcium oxide. It has to be borne in mind, however, that it was not possible with the equipment used at that time to make electron diffraction diagrams. We, too, have observed corresponding changes, which we have analyzed by means of diffraction. Hardly any differences are detectable if the same spot is examined prior to and following an intensive irradiation. The proper diffraction patterns demon- strate, however, that the precipitations prior to the irradiation were of an amorphous nature and fol- lowing the irradiation of a crystalline one. Surpris- ingly, however, an evaluation of the diffraction pattern revealed calcium carbonate in a calcite structure to be present, rather than oxyde. Fig. 1 shows a monocrystalline section at which the hex- agonal symmetry of the calcite is clearly noticeable in the diffraction pattern. Radczewski, Miiller, and Eitel (1939) obtained spherulitic calcium carbonate as a residuum from dried calcium-bicarbonate solutions; however, they did not recognize the identity wi
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