A thermal analysis study of the one-stage decomposition of small (mg) quantities of carnallite, KCl. M a 2 , 6H20 + KCl+ MgO + 5Hz0 f + 2HCl f , showed that dehydration and hydrolysis require temperatures above 300 "C. Decomposition of greater amounts, and analysis of the products, showed that at 450 "C, 88 to 90% of the magnesium occurs as chloridefree high-purity periclase. At higher temperatures increasing amounts of chlorides remain in the periclase and are difficult to separate. Unglazed porcelain is a suitable material for the decomposition vessel.Technical carnallite contains NaCl (6 to 8 %), CaCI, (1 to 2%), sulphates (0.1 %) and bromide (0.4 to 0.5 %), which, with the possible exception of the bromides, will not decompose with the magnesium chloride. As a first approximation we may, therefore, view carnallite as pure KCI . MgClZ, 6Hz0.The one-stage decomposition of carnallite has now been investigated by thermogravimetry and differential thermal analysis, the combined results of which allow the chemical feasibility of the process to be reviewed. The results were then verified with increased amounts, permitting analysis of the product. 77 78 D. Ashboren

Ammonium chloride can be separated into its constituents, ammonia and hydrochloric acid, by treating it with a metal oxide. Whereas earlier it was shown that this separation is feasible for 14 different metals, when effected in two steps at two different temperatures, we now show that isothermal operation is possible, with the driving force consisting of concentration differences of NH4Cl and water vapor, respectively. The experiments with Fe2O3, MgO, NiO and PbO showed that the volatility of FeCl3 interferes when Fe2O3 is used, but the other oxides, which do not have volatile chlorides, serve well at temperatures of about 300°C.

Heating equimolar amounts of pure phosphoric and boric acids in aqueous solution yields, at 130°, a solid boron phosphate of the composition R = P2O5/B2O3 = 1:1.71. Increasing the calcination temperature to 575° increases R to 1:1.29 due to evaporation of boron‐values. Further heating to 850° causes no additional weight losses. The specific surface decreases monotonically with the calcination temperature, from 7.4 to 0.5 m2/g. X‐ray diffraction data indicate that up to 10 min heating at 800°, increased calcination temperature causes a monotonic decrease in the unit cell dimensions, while prolonged heating (48 h) at this temperature reverses this trend.

The two‐stage decomposition of ammonium chloride into ammonia and hydrogen chloride, with the aid of metal oxides, was investigated. Twenty‐one oxides were considered for this sequence, and 14 were actually tested and the temperature range of the reactions determined. The energy requirements for heating the metal chlorides from t1 to t2 were calculated. For Fe2 O3, the temperatures are 200° and 300°, respectively, and the heating requirement ca. 17 × 103 kcal/t NH4Cl converted.

Differential thermal analysis and X-ray diffraction of 12 different compositions in the phase diagram KCI-MgO disclose that there exists an area of solid solution, extending from ca. 30-80 equiv. % of MgO/2 (l0-55 wf. % MgO), and, depending on the composition, from ca. 759 0 _775 0 • Besides the solid solution solid MgO occurs in this area. No chemical reaction between the components takes place.