Abstract: The inventors demonstrate herein that various Zintl compounds can be useful as thermoelectric materials for a variety of applications. Specifically, the utility of Ca3AlSb3, Ca5Al2Sb6, Ca5In2Sb6, Ca5Ga2Sb6, is described herein. Carrier concentration control via doping has also been demonstrated, resulting in considerably improved thermoelectric performance in the various systems described herein.

Abstract: A method for changing the color of a diamond. The method comprises placing the diamond in a substrate holder in a chemical vapor deposition (CVD) equipment. The CVD equipment is maintained at pressures near or below atmospheric pressure. A mixture of gases including hydrogen is introduced inside the CVD equipment. The introduced mixture of gases is energized by using microwave radiation to heat the diamond to temperatures above 1400° C. Then, the diamond is maintained at temperatures above 1400° C. for few seconds to few hours.

Abstract: Disclosed herein are a method of reductively bleaching a mineral slurry comprising adding in the mineral slurry an effective amount of a formamidine sulfinic acid (FAS) and an effective amount of a borohydride to reductively bleach the mineral slurry, compositions comprising a mineral slurry, a FAS, and a borohydride, and final products comprising a mineral obtained by the method disclosed herein.

Abstract: The present invention is directed to a method for changing the color of colored natural diamonds. The method includes placing a discolored natural diamond in a pressure-transmitting medium which is consolidated into a pill. Next, the pill is placed into a high pressure/high temperature (HP/HT) press at elevated pressure and elevated temperature for a time sufficient to improve the color of the diamond. The diamond may be exposed at elevated-pressure and elevated-temperature conditions within the graphite-stable region of the carbon-phase diagram—without significant graphitization of the diamond, or above the diamond-graphite equilibrium and within the diamond-stable region of the carbon-phase diagram. Finally, the diamond is recovered from said press. Colorless Type Ia and Type II diamonds may be made by this method.

Abstract: The present invention is directed to a method for treating discolored natural diamond, especially Type IIa diamond and Type IaA/B diamond with nitrogen as predominantly B centers, for improving its color. The method includes preblocking and preshaping a discolored natural diamond to prevent its breakage in a high pressure/high temperature (HP/HT) press, placing said discolored natural diamond in a pressure transmitting medium which is consolidated into a pill. Next, the pill is placed into a HP/HT press at elevated pressure and elevated temperature within the graphite-stable or diamond-stable range of the carbon phase diagram for a time sufficient to improve the color of said diamond. Finally, the diamond is recovered from said press. Colorless and fancy colored diamonds can be made by this method.

Abstract: The process for the brightening of continuously produced sodium hydrogensulfate obtained in the reaction of sodium chloride and concentrated sulfuric acid in molten sodium hydrogensulfate in a circulation reactor, wherein evolved hydrogen chloride and heating gases generated by an immersion burner are withdrawn at various sites and seed crystals are added for a faster conversion of initially formed metastable phases, is that from 0.01 to 0.05% by weight of aluminium oxide and/or from 0.5 to 1.5% by weight of magnesium oxide and/or magnesium sulfate and, optionally, additionally calcium sulfate are added as seed crystals.

Abstract: An aluminum hydroxide composition is disclosed, having diminished tendency to cause discoloration on heating at 177° C. of a plastic composition whose major polymeric component is polyvinyl chloride, comprising aluminum hydroxide and an amount, effective in diminishing discoloration, of at least one inorganic perchlorate salt selected from the group consisting of alkali metal perchlorates and alkaline earth metal perchlorates.

Abstract: The present invention is directed to a method for changing the color of colored natural diamonds. The method includes placing a discolored natural diamond in a pressure-transmitting medium which is consolidated into a pill. Next, the pill is placed into a high pressure/high temperature (HP/HT) press at elevated pressure and elevated temperature for a time sufficient to improve the color of the diamond. The diamond may be exposed at elevated-pressure and elevated-temperature conditions within the graphite-stable region of the carbon-phase diagram—without significant graphitization of the diamond, or above the diamond-graphite equilibrium and within the diamond-stable region of the carbon-phase diagram. Finally, the diamond is recovered from said press. Colorless Type Ia and Type II diamonds may be made by this method.

Abstract: Gas flow is controlled to a feed gas consuming device depending on whether a contaminant gas is present. In one embodiment, hydrogen gas flow from a hydrogen gas generator to a hydrogen consuming device, such as a fuel cell, gas chromatograph or a flame ionization detector, is terminated when there is chemical contaminant breakthrough in the hydrogen gas flow. The apparatus relates to the use of a sensor for detecting a predetermined concentration of a chemical contaminant such as ammonia. In one embodiment the apparatus terminates the gas flow when a concentration of ammonia in the gas flow corresponds to a breakthrough (e.g., approximately in the range of 2.0% or greater). The apparatus prevents the ammonia-contaminated hydrogen from disabling such a hydrogen consuming device that would have otherwise received the contaminated gas flow.

Abstract: The present invention is directed to a method for treating discolored natural diamond, especially Type IIa diamond and Type IaA/B diamond with nitrogen as predominantly B centers, for improving its color. The method includes placing a discolored natural diamond in pressure transmitting medium powder which is consolidated into a pill. Next, the pill is placed into a high pressure/high temperature (HP/HT) press at elevated pressure and elevated temperature within the diamond stable range of the carbon phase diagram for a time sufficient to improve the color of said diamond. Finally, the diamond is recovered from said press. Colorless diamond can be made by this method.

Abstract: The present invention is directed to a method for treating discolored natural diamond, especially Type IIa diamond and Type IaA/B diamond with nitrogen as predominantly B centers, for improving its color. The method includes placing a discolored natural diamond in pressure transmitting medium powder which is consolidated into a pill. Next, the pill is placed into a high pressure/high temperature (HP/HT) press at elevated pressure and elevated temperature within the diamond stable range of the carbon phase diagram for a time sufficient to improve the color of said diamond. Finally, the diamond is recovered from said press. Colorless diamond can be made by this method.

Abstract: The present invention is directed to a method for treating discolored natural diamond, especially Type IIa diamond and Type IaA/B diamond with nitrogen as predominantly B centers, for improving its color. The method includes placing a discolored natural diamond in a pressure transmitting medium which is consolidated into a pill. Next, the pill is placed into a high pressure/high temperature (HP/HT) press at elevated pressure and elevated temperature within the graphite stable range of the carbon phase diagram for a time sufficient to improve the color of said diamond. Finally, the diamond is recovered from said press. Colorless diamond can be made by this method.

Abstract: A process for producing powders of perovskite-type compounds which comprises mixing a metal alkoxide solution with a lead acetate solution to form a homogeneous, clear metal solution, adding an oxalic acid/n-propanol solution to this metal solution to form an easily filterable, free-flowing precursor powder and then calcining this powder. This process provides fine perovskite-phase powders with ferroelectric properties which are particularly useful in a variety of electronic applications.

Abstract: Disclosed is a commercial grade of soluble silicate solutions, clear homogenous and water white essentially free of unreacted silica, made by dissolving in a closed container biogenetic silica, preferably rice hull ash, in a strong alkali solution, preferably sodium hydroxide in the presence of an agent, such as an active carbonaceous material, which prevents discoloration of the soluble silicates by absorbing and/or reacting with polyvalent metals, organic materials, and the like, in the biogenetic silica as it dissolves in and reacts with the alkali solution. The invention takes advantage of the residue of such active carbonaceous material on the biogenetic silica, such as rice hulls, left by commercial energy burning thereof which effectively prevents discoloration. A solid residue results from the method which is an active carbonaceous material including concentrated manganese from the biogenetic silica, both of which are valuable commercial products.

Abstract: A method for the qualitative determination of the visible levels of glycol and/or formaldehyde at significant concentrations greater than 10 ppm (10 ppm-10,000 ppm range) in a water sample, in which the sample is treated first with periodic acid, then with iodide-thiosulfate and finally with acetyl acetone to yield a yellow color without the benefit of heat. This yellow color is visible to the naked eye and proportional to the amount of contaminants ethylene glycol, propylene glycol and/or formaldehyde present in the original water sample.

Abstract: Kaolin clays are conditioned for the removal of colored titaniferous impurities by (A) first mixing the kaolin clay with a collector to condition the impurities, in the absence of a dispersant, but in the presence of sufficient water to yield a mixture having a solids content of at least 65 percent by weight and (B) then deflocculating the kaolin clay mixture at a pH of at least 4.0 with a dispersant in amounts sufficient to yield a kaolin clay slurry which is suitable for subsequent processing to remove colored titaniferous impurities.

Abstract: Disclosed is a method of manufacturing potassium sulfite from a potassium hydroxide feedstock. A feedstock is tested for the presence of iron and, if the feedstock contains less than 0.3 ppm of iron, it is reacted with sulfur dioxide in an aqueous solution to form potassium sulfite. Alternatively, potassium sulfite that has a yellow or brownish color can be decolorized by adding about 0.02 to about 0.8 wt % hypophosphorous acid to it.

Abstract: Salt compositions which have been discolored during sterilization by means of radioactive radiation such as gamma and/or beta irradiation of the type which causes such discoloration are substantially restored to the original color by treatments disclosed herein. Methods for restoring the original color of such salts, including heating to specified temperatures for specified periods of treatment are also disclosed.

Abstract: For bleaching natural chalk, an aqueous suspension consisting of 50 to 80% by weight fine-grained natural chalk and 50 to 20% by weight water and containing 0.1 to 1.5% by weight, based on the dry weight of the chalk, of a dispersant and optionally containing a hydrogen peroxide stabilizer or activator or a salt of hydrogen peroxide with a divalent metal is prepared, the suspension is wet ground to reduce the particle size until about 9/10 of the particles have a grain size of <4, the suspension is mixed with hydrogen peroxide or a salt of hydrogen peroxide with a divalent metal at temperatures between 50.degree. and 99.degree. C. and at a specific pH-value or at an alkaline pH, respectively, and stirred intensively until it is mixed and foaming commences, the suspension is allowed to stand until foam formation is complete and then the foam formed is separated with the dark particles contained therein.

Abstract: A method for preparing a chlorosilane sample to enable colorimetric detection of the presence of minute amounts of boron impurities is provided. Detection of boron impurities below five parts per billion is contemplated.

Abstract: A method of processing naturally occurring kaolin clay wherein ion exchange resins are utilized to remove charged soluble impurities from the clay thereby eliminating the filtration step required in conventional clay beneficiation process. Further, by saturating the ion exchange resin utilized with a bleaching agent, ferric ions in the clay will be reduced to soluble ferrous ions and removed from the clay without the conventional acid leaching.

Abstract: A process for the whitening of phosphogypsum comprising treating a phosphogypsum in aqueous suspension with an amount of ozone equal to at least 150 parts by weight per million parts by weight of phosphogypsum calculated as Ca SO.sub.4.2H.sub.2 O, the pH of the aqueous suspension being lower than or equal to 3, to yield a whiteness grade of phosphogypsum higher than 75, according to French Standard NF Q 03-038.

Abstract: The present invention relates to a method for the manufacture of phosphatic products having a very low fluorine content from wet process phosphoric acid.According to the invention the fluorine in the wet process phosphoric acid is removed in the form of potassium fluosilicate, by the reaction of its fluoride components with KH.sub.2 PO.sub.4 formed insitu from KCl or K.sub.2 SO.sub.4 and an amine phosphate salt, the latter resulting from phosphoric acid and an amine selected from the group consisting of a primary--secondary--or tertiary aliphatic amine, a quaternary ammonium base or mixtures thereof. Examples of suitable amines and quaternary ammonium bases are: tri-n-octylamine, ethyl di-n-octylamine, di-n-dodecylamine, di-n-decylamine, tricaprylamine, tri-iso-octylamine etc. The amine constituent appears in the form of a water-immiscible liquid, preferably in conjunction with an organic solvent in which the aliphatic amines and their salts are soluble.

Abstract: A method for producing kaolin pigments of improved coated brightness and opacity is provided in which kaolin is degritted, heated to the level of substantially minimum brightness and then leached. The kaolin may be comminuted before treatment, after heating or after leaching to control particle size distribution.

Abstract: The invention provides a process for the production of zeolite A from kaolin by conversion of the kaolin into meta-kaolin followed by reaction of the meta-kaolin in an aqueous alkaline medium, wherein the conversion of the kaolin into the meta-kaolin is conducted at temperatures of between 700.degree. and 950.degree. C. in the presence of alkaline earth compounds and optionally in the presence of uncolored halides and/or halogens, wherein the process may be conducted under reducing conditions and in the presence of alkali metal compounds.

Abstract: Method for improving the brightness of limestone utilizing a flocculating agent and a bleaching agent where the pH of the slurry is between about 7 and 9.

Abstract: A process for treating a clay mineral of the kandite group comprising forming a fluid aqueous suspension of the clay mineral, the suspension having a solids content in the range of from 60% to 75% by weight and a pH in the range of from 7.0 to 11.0 and the suspension containing a dispersing agent to deflocculate the clay mineral; and treating the fluid suspension of clay containing the dispersing agent with a water-soluble reducing bleaching agent under alkaline pH conditions for a time sufficient to give the desired improvement in brightness of the clay. Preferably, the clay mineral suspension is subjected to a particle size separation process at said solids content to reduce the percentage of particles larger than 10.mu.m to not more than 3% by weight. Advantageously, the viscosity of the clay mineral suspension during the particle size separation process is below 2 poise.

Abstract: Method for the manufacture of ferrosilicon nitride is disclosed. The method produces ferrosilicon nitride with a silicon nitride content of 65% to 85% by weight by oxidizing the metallic iron which is present in the ferrosilicon nitride in an aqueous medium in the presence of selected oxidizing agents while forcing a mixture of air and steam through the aqueous medium.

Abstract: A method of reducing discoloration of alumina which is caused by exposure of said alumina to high temperatures is disclosed. The method comprises adding an effective amount of an inorganic oxidizing agent (e.g. H.sub.2 O.sub.2 or NaOCl) to the alumina prior to exposing it to the high temperature.

Abstract: A method of producing citrine crystals comprising the step of growing citrine crystals under hydrothermal conditions by the temperature difference method in a high-pressure autoclave on crystalline quartz seeding plates oriented in parallel with the pinacoid crystallographic plane {0001} or with planes inclined at an angle within the range of up to 20.degree. with respect to said pinacoid plane using a charge comprising crystalline quartz and aqueous solutions of potassium carbonate with a concentration of from 5-10 wt.%. Said solutions contain iron introduced in the autoclave in the form of metallic iron in an amount of from 2-20 g per lit. of the solution, as well as nitrites or nitrates of alkali metals or potassium permanganate which are introduced in the autoclave in an amount of from 1-20 g per lit. of the solution. The above-described method of growing citrine crystals is carried out at a crystallization temperature of from 300.degree.-345.degree. C, under a pressure of from 300-1500 kg/cm.sup.

Abstract: A process for producing amethyst crystals involving growing of colorless quartz crystals by a hydrothermal method of a temperature drop in a high-pressure autoclave on crystalline quartz seed plates oriented parallel to the crystallographic planes of the major {1011} and minor {1101} rhombohedrons using crystalline quartz as a charge. Said growing is effected from aqueous solutions of potassium carbonate or potassium hydroxide having a concentration ranging from 4 to 7 wt.% and containing iron introduced into the autoclave in the form of metallic iron or in the form of its oxydic or hydroxydic compounds in an amount ranging from 5 to 30 g/l of the solution. The growing process is effected at a crystallization temperature within the range of from 300.degree. to 500.degree. C. under a pressure ranging from 200 to 1,700 kg/cm.sup.2 and a crystal growth rate of from 0.05 to 0.5 mm/day.

Abstract: In the purification of impure titanium tetrachloride comprising adding an agent to said titanium tetrachloride and thereafter distilling off purified titanium tetrachloride while leaving the impurity in the distillation residue, the improvement which comprises employing as said agent at least one amine of the formula ##EQU1## in which R.sub.1 and R.sub.2 each independently is hydrogen, alkyl or alkenyl of up to 6 carbon atoms, cycloalkyl of 5 to 7 carbon atoms, or aryl, andR.sub.3 is cycloalkyl of 5 to 7 ring carbon atoms, or aryl, orR.sub.2 together with R.sub.3 is butylene, pentylene or hexylene, in which eventR.sub.1 is hydrogen, alkyl of up to 6 carbon atoms or aryl.The preferred agents are aniline, cyclohexylamine, N,N-dimethyl-aniline, diphenylamine, 2,3-dimethyl-aniline and 2,6-dimethyl-aniline. The process serves to remove vanadium impurities.

Abstract: Metal cyanide complexes of a single metal or mixed-metal complexes in which a metal is complexed with cyanide. The metals preferably include .[.magnesium, beryllium, aluminum,.]. chromium, titanium, zirconium, thorium, yttrium and cobalt and nickel in addition to the lanthanide metals. An aqueous solution is prepared and the complex is isolated by crystallization with a stoichiometry of the metals determined by their proportions in the solution.