4. On the Instability of the Double Sulphates M″SO₄.R′₂SO₄ + 6H₂O of the Magnesium Series

Abstract

By a number of observations made incidentally in the preparation of two of the double salts referred to in the heading, namely, the compounds of sulphate of potash with sulphate of magnesia and sulphate of ferrous oxide respectively, I had long come to suspect that these two salts at any rate are not perfectly stable in opposition to water. To settle the question, I have caused Mr James Eobson and Mr Andrew Hodge, two young chemists working in my laboratory, to inquire into the matter by systematic experiments. These were, in general at least, conducted according to the following scheme: —Starting from a known weight of sulphate of potash, this was dissolved in a proportion of hot water,* less than sufficient to hold the intended double salt in solution after cooling; there was then added a known weight of the di-valent sulphate amounting to exactly 1 or 1·1 or 1·2 … 1·5 times MgO or FeO per 1K2O used, the solution filtered hot into a basin, allowed to crystallise, and the crop of crystals produced examined.

Quantitative Depth Profile Analysis of Micrometer-Thick Multilayered Thin Coatings Using Step-Scan FT-IR Photoacoustic Spectroscopy

“…As mentioned before, the use of step-scan FT-IR spectroscopy with photoacoustic detection for depth-profiling studies of carefully designed polymer laminates has been well demonstrated. − The two approaches used were (I) the phase rotation method and (II) the direct analysis of the phase and magnitude spectra. , In the phase rotation method, a new rotated interferogram is calculated for a given angle a , where a is the phase angle used in the interferogram rotation. This calculation is possible because the two originally measured signals are orthogonal to each other; hence, any other angle between 0 and 360° can be computed by the trigonometrical transformation shown in eq 1 The phase (θ) and magnitude ( M ) spectra can be calculated from the in-phase ( I ) and 90° out-of-phase or quadrature ( Q ) components of the photoacoustic signal using eqs 2 and 3…”