Showing papers on "Sodium dichromate published in 1976"
Patent•
06 Feb 1976TL;DR: In the production of chromium oxide green pigment by heating a substantially stoichiometrically equivalent mixture of sodium dichromate dihydrate and an ammonium salt selected from the group consisting of the sulfate and chloride, the improvement which comprises dry mixing a mixture of dihydrates having a particle size less than 2 mm with the ammonium content less than about 0.5 mm, heating the resulting mixture over a period of about 15 minutes to a pigment-forming temperature of about 800° to 1100° C, calcining the mixture at a temperature in that range, and
Abstract: In the production of chromium oxide green pigment by heating a substantially stoichiometrically equivalent mixture of sodium dichromate dihydrate and an ammonium salt selected from the group consisting of the sulfate and chloride, the improvement which comprises dry mixing sodium dichromate dihydrate having a particle size less than 2 mm with the ammonium salt having a particle size less than about 0.5 mm, heating the resulting mixture over a period of about 15 minutes to a pigment-forming temperature of about 800° to 1100° C, calcining the mixture at a temperature in that range, and separating the formed pigment from the salts. To the mixture prior to heating there may be added sodium hydroxide solution, boron compounds such as borax and/or organic modifiers such as sawdust which improve the color and tinting strength of the resulting pigment. The pigments are brighter, and of higher tinting strength than heretofore produced.
9 citations
Patent•
06 Feb 1976TL;DR: A process for the production of chromium oxide green pigment comprising heating a mixture of ammonium dichromate with at least the stoichiometrically equivalent quantity of a sodium salt selected from the group consisting of chloride and sulfate over a period of at most about 15 minutes to a pigment-forming temperature of about 800 to 1100° C in the presence of about 1 to 45% water based on the weight of the mixture, calcining the mixture at a temperature in the above-mentioned range, and separating the formed pigment from the salts as discussed by the authors.
Abstract: A process for the production of chromium oxide green pigment comprising heating a mixture of ammonium dichromate with at least the stoichiometrically equivalent quantity of a sodium salt selected from the group consisting of chloride and sulfate over a period of at most about 15 minutes to a pigment-forming temperature of about 800 to 1100° C in the presence of about 1 to 45% water based on the weight of the mixture, calcining the mixture at a temperature in the above-mentioned range, and separating the formed pigment from the salts. The mixture may be formed in situ by reaction of sodium dichromate with ammonium chloride or sulfate in the presence of water. The presence during calcining of organic modifiers such as sawdust or of boron compounds such as borax increases, tinting strength and disproportionately affect color. The pigments are brighter, and of higher tinting strength than heretofore produced.
8 citations
TL;DR: When crystals of sodium dichromate dihydrate are heated at 1 atm pressure, the phase change Na2Cr2O7,2H2O → Na2cr2O 7,H 2O + saturated solution occurs at 82.8°C with the absorption of 17.6±0.95 kJ per mole of dihydrates as mentioned in this paper.
Abstract: When crystals of sodium dichromate dihydrate are heated at 1 atm pressure, the phase change Na2Cr2O7,2H2O → Na2Cr2O7,H2O + saturated solution occurs at 82.8°C with the absorption of 17.6±0.95 kJ per mole of dihydrate. A second phase change Na2Cr2O7,H2O → Na2Cr2O7 + saturated solution occurs at 91.1°C with the absorption of a further 12.4±1.5 kJ per mole of dihydrate.
TL;DR: A kinetic study of the oxidation of a series of substituted benzyl alcohols and benzaldehydes by neutral aqueous sodium dichromate has been completed in this article, showing that the aldehydes are more resistant to oxidation than the alcohols.
Abstract: A kinetic study of the oxidation of a series of substituted benzyl alcohols and benzaldehydes by neutral aqueous sodium dichromate has been completed. The aldehydes are more resistant to oxidation ...