Leeds University Library

Calcite

Calcite, CaCO3 and the calcite series of crystals-sodium nitrate, NaNO3; dolomite CaMg (CO3)2; rhodochrosite, MnCO3 and Chalybite, FeCO3

On p58 (figure 9a) is a sketch of a calcite rhomb with an axial angle of 101° 54' and a table (figure 9b) in which the calculated and observed reflection angles from five crystal faces are compared.

On p95 the complete experimental data for 1st, 2nd etc order reflections is summarised and is reproduced, as Table IV, in WLB's paper The Analysis of Crystals in the X-ray Spectrometer(16).

Original data for spectra from calcite (p95 of notebook) (Fig 10a) and its reproduction in Table IV of WLB paper, The Analysis of Crystals in the X-ray Spectrometer (Fig 10b)(16).

The data for the 1st, 2nd etc. order reflections from the (111) plane in calcite is compared to the other crystals in the calcite series in Table II as shown in figure 11a (and also in the graphical form, in fig 37 in the 1915 book, X-rays and Crystal Structure(8). The data in the notebook upon which these comparisons are based can be seen in figure 11b.

The importance of these comparisons is that the Braggs made use of the intensity measurements to support their proposed structures of the calcite series of crystals as consisting of alternate layers of metal (Na, Ca, Mn, Fe) atoms and CO3 planar groups. As the scattering power of the metal atoms approaches that of the CO3 groups the first order reflections become weaker, an observation consistent with their proposed structures.