Difference In Crystal Size Research Articles

Behavior of illite and chlorite during pressure solution of shaly limestone of the Kalkberg Formation, Catskill, New York

Textural and chemical changes occurring in illite and chlorite concomitant with pressure solution of limestone were studied in samples from the Kalkberg Formation of Catskill, New York, using XRD and TEM/AEM. Samples on one limb of an anticline are massive shaly limestones, but those on the other have undergone extensive pressure solution and well-developed cleavage is present. Illite and chlorite from the uncleaved shaly limestone are found in small individual packets (100–800 Å thick) dispersed throughout the carbonate matrix with crystal morphologies characteristic of burial diagenesis. Phyllosilicates from the limb more affected by pressure solution occur in larger units (>1 μm thick) as stacks of subparallel packets (150–500 Å thick). Such stacks are inferred to represent coalescence of smaller packets. These data imply that the phyllosilicates are largely passive during pressure solution of limestone; however, localized solution-recrystallization is required by the coherent to semi-coherent packet boundaries and the crystal morphologies present in the pressure solution sample. The largely passive role is in contrast with the more active role of phyllosilicates in many shales and slates. XRD data for illite show an increase in crystallinity in the pressure solution sample under isothermal conditions. Differences in illite crystallinity are adequately explained in large part by differences in crystal size with some contribution due to strain. The data demonstrate that illite crystallinity cannot be unambiguously used in determining absolute or even relative temperatures.

Estimation of solid‐liquid ratios in bulk fats and emulsions by pulsed nuclear magnetic resonance

AbstractSeveral pulsed nuclear magnetic resonance (NMR) methods were evaluated to estimate the solid fat content of fats and oil‐in‐water emulsions. The methods were checked with samples of paraffin oil or triolein containing known quantities of crystalline tristearate. A method based on the signal of solid fat (with use of a correction factor, the “f‐factor”) was rejected in this work for general use. Correct results were obtained with methods that used only the signal of the liquid phase. With emulsions, disturbances could arise due to the surfactant present and to possible solubilization of water in the oil phase, presumably by monoglycerides. Without these disturbances, solid fat content in emulsions could be estimated as in bulk fats, after correction of the liquid phase signal for the contribution of protons from the aqueous phase. The signal from fat crystals inside emulsion droplets differed from that of crystals of the same fat in bulk, which may have been due to difference in crystal size but not to difference in crystal modification. Measurements on natural cream showed that disturbances were also possible in this type of emulsion.

Growth of Lead Titanate (PbTiO3) Single Crystals

The phase diagram of PbO (massicot)-PbTiO3 system in PbO rich region was determined by X-ray diffraction and DTA measurement. On the basis of this diagram, single crystals of perovakite-type PLTiO3 were grown from the melt with PbO as flux. And it was also studied by using a mixture of PbO-H3BO3-PbTiO3.The following results were obtained.(1) PbTiO3 single crystals were tetragonal having the stoichiometric composition and the direction of the growth was [100].(2) The largest PbTiO3 single crystals (5mm×5mm×1mm) were obtained from the melt with the composition of PbO : PbTiO3=(80-70):(20-30) by mole percent.(3) There was no difference in crystal size between the crystals obtained by the cooling rate of 25°C/hr and that of 50°C/hr from the melt at 1100°C.(4) The translucent or partial translucent PbTiO3 single crystals were grown by adding 10 mole percent boric acid to the mixture of PbO:PbTiO3=(80-70):(20-30).(5) In PLO-H3BO3-PbTiO3 system, the region of the composition for obtaining single crystals of PbTiO3 was 10≤PbTiO3≤35, 25≤PbO≤85 and 0≤H3BO3≤52 mole percent and the translucent or partial translucent single crystals were grown in the region of 10≤PbTiO3≤30, 25≤PbO≤45 and 44≤H3BO3≤52 mole percent.

Crystal Growth of Pb(ZrxTi1-x)O3 by Flux Method

Single crystals of perovskyte-type Pb(ZrxTi1-x)O3 were grown by flux method using a mixture of PbO-H3BO3-Pb(Zr0.52Ti0.48)O3. The following results were obtained.(1) The largest single crystal (2.5mm×2.5mm×1mm) was obtained from the melt with the composition of Pb(Zr0.52Ti0.48)O3: flux=25:75 (weight percent), where the composition of flux is; PbO: H3BO3=50:50 (mol percent).(2) Single crystal Pb(Zr0.25Ti0.75)O3 having the shape of square pyramid was usually obtained from the center of the crucible.(3) There was no difference in crystal size between the cooling rate of 25°C/hr and that of 50°C/hr for crystal growth from the melt at 1000-1100°C.(4) The region of the composition for obtaining single crystals of Pb(ZrxTi1-x)O3 was respective 40≤PbO≤63, 12≤H3BO3≤22 and 20≤Pb(Zr0.52Ti0.48)O3≤45 at weight percent in the PbO-H3BO3-Pb(Zr0.52Ti0.48)O3 system.

Structural Studies of Subpolar Glacier Ice

Structural studies including orientation of respectively bubbles, foliation plane and englacial moraine particles as well as ice fabric studies have been carried out on subpolar glacier ice from the Kebnekaise region in northern Swedish Lapland. Most of the work was done in a cold laboratory, work on the glacier itself was restricted to achieve complementary information such as velocity and direction of ice movement and strain-rate measurements.The ice crystals, which were taken from the snout of Isfallsglaciären, were very large. One crystal was found to be at least 26 cm long. No difference in crystal size could be detected in the uppermost 15 m in this part of the glacier. Although the ice crystals are complexly shaped a definite dimensional orientation has been found.The ice fabrics also display a very anisotropic pattern consisting of six point maxima at constant angular distances from each other. The pattern is independent of the structural type of ice present, but seems to fit a combination of Kamb's theory of crystal orientation in a general stress field and Brace's corresponding theory for a uniaxial stress field.

CALCIUM CRYSTALLURIA IN RECURRENT RENAL-STONE FORMERS

The volume of crystals excreted by controls and stone-forming patients was measured in fresh urine at body temperature. Six male patients with idiopathic recurrent renal-stone disease had a sustained crystalluria on a normal but constant dietary intake of calcium, phosphorus, oxalate, and fluid. Below pH 6.2 the crystals consisted only of calcium oxalate and above pH 6.2 mainly of calcium phosphate. Six healthy male controls investigated under the same conditions of diet and fluid intake excreted significantly less crystalline calcium oxalate than did the stone-formers. Separate oral doses of calcium citrate and sodium oxalate further enhanced the crystalluria of the stone-formers but had little effect in the controls. The difference between the two groups was due mainly to a difference in crystal size rather than crystal numbers. The calcium-oxalate crystalluria in the recurrent stone-formers was mainly of octahedral crystals of calcium oxalate dihydrate, often in aggregates up to 200 μ in diameter, whereas in the controls the calcium oxalate was in the form of very small particles with little or no aggregation. The increased crystalluria of the stone-formers was assor ciated with increased concentrations of calcium and oxalate in the urine.

The Constitution, Reactivity and Thermal Change of Phosphate Ores

Abstract Tests were made on twenty-five samples of phosphate ores from all over the world deposits. All of the samples consisted of apatite, plus small amounts of calcite and other minerals. The apatite crystals of the sedimentary ores ranged in size from around 0.05 μ (Gafsa, North Carolina, etc.) to around 0.5μ (Taiba), while those of igneous ores reached 100 μ. The difference between the ores in their reactivity with citric, hydrochloric and nitric acid was mainly due to the difference in crystal size. The decomposition of the ores by a mixture of sulfuric and phosphoric acids was seriously affected by the coating of calcium sulfate crystals on the surface of the ores, and also by the aluminum and iron present in the acids and ores. The lattice constant, a0, of the apatite of the ores ranged from 9.340 to 9.422 Å; it was generally smaller for the ores which had larger F2/P2O5 ratios. Upon calcination above 500°C, the a0 value of the apatite which had an excess of fluorine increased and approached that of true fluorapatite. The reactivity of the ores with the acids generally decreased upon calcination due to the sintering of the grains and the crystal growth. For ease of decomposition by a mixture of sulfuric and phosphoric acids, the calcined ore should contain a small amount of carbon dioxide. Tests also were made on the amount of organic matter and its decrease upon calcination.