J. J. Rowe’s research while affiliated with United States Geological Survey and other places

Melting and subsolidus relations in the system K2SO4MgSO4CaSO4 were studied using heating-cooling curves, differential thermal analysis, optics, X-ray diffraction at room and high temperatures and by quenching techniques. Previous investigators were unable to study the binary MgSO4CaSO4 system and the adjacent area in the ternary system because of the decomposition of MgSO4 and CaSO4 at high temperatures. This problem was partly overcome by a novel sealed-tube quenching method, by hydrothermal synthesis, and by long-time heating in the solidus. As a result of this study, we found: (1) a new compound, CaSO4·3MgSO4 (m.p. 1201°C) with a field extending into the ternary system; (2) a high temperature form of MgSO4 with a sluggishly reversible inversion. An X-ray diffraction pattern for this polymorphic form is given; (3) the inversion of β-CaSO4 (anhydrite) to α-CaSO4 at 1195°C, in agreement with grahmann; (1) (4) the melting point of MgSO4 is 1136°C and that of CaSO4 is 1462°C (using sealed tube methods to prevent decomposition of the sulphates); (5) calcium langbeinite (K2SO4·2CaSO4) is the only compound in the K2SO4CaSO4 binary system. This resolved discrepancies in the results of previous investigators; (6) a continuous solid solution series between congruently melting K2SOP4·2MgSO4 (langbeinite) and incongruently melting K2SO4·2CaSO4 (calcium langbeinite); (7) the liquidus in the ternary system consists of primary phase fields of K2SO4, MgSO4, CaSO4, langbeinite-calcium langbeinite solid solution, and CaSO4·3MgSO4. The CaSO4 field extends over a large portion of the system. Previously reported fields for the compounds (K2SO4·MgSO4·nCaSO4), K2SO4·3CaSO4 and K2SO4·CaSO4 were not found; (8) a minimum in the ternary system at: 740°C, 25% MgSO4, 6% CaSO4, 69% K2SO4; and ternary eutectics at 882°C, 49% MgSO4, 19% CaSO4, 32% K2SO4; and 880°, 67·5% MgSO4, 5% CaSO4, 27·5% K2SO4.

The binary system K2SO4CaSO4 was studied by means of heating-cooling curves, differential thermal analysis, high-temperature quenching technique and by means of a heating stage mounted on an X-ray diffractometer. Compositions and quench products were identified optically and by X-ray. Limited solid solution of CaSO4 in K2SO4 was found. There is a eutectic at 875°C and 34 wt. per cent CaSO4. Calcium langbeinite melts incongruently at 1011°C. The melting-point of CaSO4 (1462°C) was determined by the quenching technique using sealed platinum tubes. The only intermediate crystalline phase found in the system is K2SO4·2CaSO4 (calcium langbeinite).

Solutions in contact with solid amorphous silica at room temperature tend to become supersaturated. Experiments carried out over long periods of time show that steady states of supersaturation, 120 to 170 ppm, may persist for months. Eventually, however, the colorimetrically detectable dissolved silica in contact with silica gel decreases to about 115 ppm. Dissolved silica in waters collected from hot springs (p;H range 6.0 to 8.5) also slowly polymerizes and approaches 115 ppm. Extrapolation to 25°C of solubility data taken at high temperatures also yields a value of about 115 ppm for the solubility of amorphous silica. It is concluded that in nearly neutral solutions 115 ppm is the solubility of amorphous silica at 25°C, the differential heat of solution, ΔH, is 3.35 kcal/mole, and the standard free energy of solution, ΔF°25°C, is approximately 3.7 kcal/mole.

The join between the compositions K2Mg2(SO4)3 and K2Ca2(SO4)3 was studied by means of high-temperature equilibrium quenching techniques and by means of a heating stage mounted on an X-ray diffractometer. Complete solid solution exists in the system, but at 25°C members of the solid solution series are isometric only in the composition range 0–73·5 wt. per cent K2Ca2(SO4)3. At compositions richer in K2Ca2(SO4)3 than 73·5 wt. per cent, members of the series are optically biaxial. At higher temperatures members of the solid solution series are isometric at successively more calcium-rich compositions and pure K2Ca2(SO4)3 is isometric above about 200 ± 2°C. The system is not binary, as mixtures richer in K2Ca2(SO4)3 than 42 wt. per cent decompose with the formation of liquid and CaSO4.

Study of the interferences of silica and sulfate in the flame-photometric determination of calcium in thermal waters has led to the development of a method requiring no prior chemical separations. The interference effects of silica, sulfate, potassium, sodium, aluminum, and phosphate are overcome by an addition technique coupled with the use of magnesium as a releasing agent.

The solubility of quartz in water was investigated by three sets of experiments 1. (1) at 1000 atm P H 2 O and temperatures ranging from 45° to 300°C 2. (2) at water pressures appropriate for the coexistence of three phases, gaseous water, liquid, and quartz, at temperatures ranging from 69° to 240°C 3. (3) a long term study of the dissolution of quartz grains which were continuously tumbled in water at room temperature. Saturated silica solutions in equilibrium with quartz were obtained in a few days at temperatures above 100°C. Equilibrium is shown by reproducible results for runs of different durations and by the precipitation of quartz from initially supersaturated solutions. The differential heat of solution derived from the data obtained at 1000 atm pressure is 5.38 kcal/mole. At room temperature and pressure, highly supersaturated silica solutions were obtained by continuously rotating quartz grains and water in plastic bottles at 75 rev/min. In one run the amount of silica in solution increased to a maximum value of 395 p.p.m. after 370 days. Another run reached 80 p.p.m. silica after 386 days and then dropped to 6 p.p.m. silica. It is concluded that quartz was precipitated at room temperature from this supersaturated solution and that 6 p.p.m. is essentially the true solubility of quartz at 25°C. In contrast to the runs rotated at 75 rev/min, quartz grains, and also silica glass grains, continuously rotated in water at rev/min, each contributed less than 1 p.p.m. colorimetric silica into solution after 1 year. Thus, vigorous agitation of the liquid is necessary to remove dissolved silica from the vicinity of surfaces of both quartz and glass. Two significant factors that may have contributed to the formation of supersaturated silica solutions in the runs rotated at 75 rev/min at room temperature are 1. (1) stresses and structural irregularities at the surfaces of the crushed quartz grains, which contributed silica into solution more readily than well crystallized quartz 2. (2) the very slow rate at which dissolved silica polymerizes to species appropriate to act as nuclei for quartz growth. At the termination of the runs rotated at 75 rev/min, spikelike projections were present on many of the quartz grains. These are interpreted as indicating that abrasion was not the dominant cause for the great supersaturations which were obtained.