Iron Sulfides Formed from Aqueous Solution at Low Temperatures and Atmospheric Pressure

1964 ◽  
Vol 72 (3) ◽  
pp. 293-306 ◽  
Author(s):  
Robert A. Berner
Keyword(s):  
Aqueous Solution ◽  
Atmospheric Pressure ◽  
Low Temperatures ◽  
Iron Sulfides

scholarly journals The behaviour of visual purple at low temperature

1941 ◽  
Vol 179 (977) ◽  
pp. 151-159 ◽  
Keyword(s):  
Aqueous Solution ◽  
Low Temperature ◽  
Low Temperatures ◽  
Room Temperature ◽  
Absorption Curve ◽  
Quantum Yields

Visual purple is soluble and stable in a mixture of glycerol and water (3:1). At room temperature the spectrum of such a solution is identical with that of the aqueous solution. At — 73° C the peak of the absorption curve is higher and narrower than at room temperature, and it is shifted towards longer waves. The product of photodecomposition at — 73° C has a spectrum in ­ dependent of pH and is at low temperatures thermostable and photostable, but at room temperature it decomposes therm ally to indicator yellow. The primary product appears to be identical with transient orange. The quantum yields of the photoreaction at low and at room temperature are of the same order.

Cerium Tetrafluoride. I. Preparation and reactions

1965 ◽  
Vol 18 (7) ◽  
pp. 959 ◽  
Author(s):  
WJ Asker ◽  
AW Wylie
Keyword(s):  
Aqueous Solution ◽  
Water Content ◽  
Water Vapour ◽  
Hydrogen Fluoride ◽  
Low Temperatures ◽  
Cerium Dioxide ◽  
Lattice Parameters ◽  
Refractive Indices ◽  
Dissociation Pressure ◽  
Cerium Trifluoride

Pure anhydrous cerium tetrafluoride is best prepared by fluorinating cerium dioxide at 350-500�. A monohydrate can be obtained from aqueous solution in a variety of ways, but it cannot be dehydrated without decomposition. It loses water "zeolitically" in vacuum, showing relatively small changes in lattice parameters for loss of 70% of its water content. Thereafter the lattice collapses, forming well-crystallized cerium trifluoride and poorly crystallized "anhydrous" cerium tetrafluoride. The refractive indices of anhydrous monoclinic cerium tetrafluoride have been measured and its fluorine dissociation pressure at 500� shown to be less than 0.5 mm. At higher temperatures the tetrafluoride sublimes incongruently, and at 835-841� it melts with extensive decomposition into a fluorine-poor liquid and a fluorine-rich vapour. Cerium tetrafluoride is easily reduced to the trifluoride by ammonia and by water vapour at low temperatures. At higher temperatures it is quantitatively converted by water vapour to cerium dioxide and hydrogen fluoride. When heated with cerium dioxide it is reduced to the trifluoride with liberation of oxygen.

scholarly journals Dissolution of cellulose using a combination of hydroxide bases in aqueous solution

Cellulose ◽  
2019 ◽  
Vol 27 (1) ◽  
pp. 101-112 ◽  
Author(s):  
Beatrice Swensson ◽  
Anette Larsson ◽  
Merima Hasani
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Microcrystalline Cellulose ◽  
Low Temperatures ◽  
Dynamic Rheology ◽  
Organic Base ◽  
Single Base ◽  
Solvent Quality ◽  
Solvent Stability

Abstract In order to further understand the role of the cation when dissolving cellulose in aqueous solutions of hydroxide bases, different bases were combined in solution. Up to 5 wt.% of microcrystalline cellulose was dissolved using a combination of NaOH and the organic base tetramethylammonium hydroxide (TMAH) in water at low temperatures. Thermoscans of solutions containing both NaOH(aq) and TMAH(aq) indicated that cellulose interaction with TMAH seems to be favoured over NaOH. Dynamic rheology measurements of the solutions revealed that combining the two bases delayed gelation significantly when compared to cellulose dissolved in NaOH(aq) or TMAH(aq) alone. Intrinsic viscosity of cellulose in the combined NaOH- and TMAH(aq) solutions was slightly higher than that of the single-base solutions, indicating a slight increase in solvent quality. This shows that combining bases may lead to synergies that improve solvent stability without requiring the use of other additives. Graphic abstract

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