 | Acta Crystallographica Section B Acta Crystallographica Section B STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS |
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![[Figure 7]](bk0150fig7mag.jpg)
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Figure 7
(a) NH4Cl dependence of the cell dimensions of NH4Cl on temperature in the region of the transition at 242 K (measurements made with Cu Kα using the (024) plane of a single crystal). As numerical data are not given by Dinichert, enlargements of diagrams from his paper have been digitized and relabeled. Also, Dinichert's (diffraction) angle measurements were not on an absolute scale and had to be standardized by comparison with other measurements; it seems that Dinichert's values are in kX and should be multiplied by 1.00202 to place them on an Å scale. For clarity, the curves of the `cooling transition' have been shifted vertically by 0.01 Å. Adapted from Fig. 8 of Dinichert (1942  ). (b) NH4Cl – dilatometry of NH4Cl, values being taken from Table 1 of Smits et al. (1937; cf. their Fig. 4). In our diagram, molecular volumes have been converted into a mean cubic cell edge for comparison with Dinichert's results. We remind the reader that Dinichert gives separate results for each of the two phases, while dilatometry gives values for the system as a whole with varying proportions of the two phases as the transition progresses, thus the ordinate spread in the lower diagram is about twice as large as that in the upper diagram. |
![[Figure 7]](bk0150fig7.jpg)
| STRUCTURAL SCIENCE CRYSTAL ENGINEERING MATERIALS |
ISSN: 2052-5206
