FREEZING POINT DEPRESSIONS IN SODIUM FLUORIDE. EFFECT OF ALKALINE EARTH FLUORIDES1

1961 ◽  
Vol 65 (12) ◽  
pp. 2208-2210 ◽  
Author(s):  
Stanley Cantor
Keyword(s):  
Sodium Fluoride ◽  
Alkaline Earth ◽  
Freezing Point

FREEZING POINT DEPRESSIONS IN SODIUM FLUORIDE. II. EFFECT OF TETRAVALENT FLUORIDES1

1962 ◽  
Vol 66 (12) ◽  
pp. 2711-2713 ◽  
Author(s):  
Stanley Cantor ◽  
Terry S. Carlton
Keyword(s):  
Sodium Fluoride ◽  
Freezing Point

Melting and crystal structure of cryolite (3NaF, A1F 3 )

1957 ◽  
Vol 240 (1221) ◽  
pp. 160-172 ◽  
Keyword(s):  
Crystal Structure ◽  
Sodium Fluoride ◽  
Complex Anion ◽  
Freezing Point ◽  
Electrical Conductance ◽  
Fluoride Ions ◽  
Large Expansion ◽  
Aluminium Fluoride ◽  
Partial Dissociation ◽  
High Conductance

Measurements have been made of the electrical conductance of crystals and melts of sodium fluoride and of cryolite. The contraction in volume when these melts crystallize has also been determined. A new transition at about 880° C has been detected in cryolite. The new results have been combined with previous information on the crystal structures at various temperatures, and on the densities and viscosities of the melts as aluminium fluoride is added progressively to sodium fluoride. Entropies of fusion, and freezing-point depressions when various ions are added to the melts have also been considered. Various findings suggest that the complex anion [AlF 6 ] 3¯ undergoes partial dissociation to [A1F 4 ] ¯ and [F] ¯ in the melt; probably this already occurs in the crystal below the meltingpoint. Dissociation of some fluoride ions from the symmetrical [A1F 6 ] 3¯ and randomization of their positions in the crystal lattice would explain the high conductance σ S of the solid just below the melting-point, and the small increase of conductance to σ L on melting; for cryolite σ L / σ S is less than 10 compared with about 7000 for NaF. The comparatively large expansion in volume (25%) on melting cryolite is probably due to extensive formation of positional flaws.

Cryoscopic studies with molten fluorides. I. Depression of the freezing point of calcium fluoride by alkaline-earth fluorides and oxides and calcium silicates

1969 ◽  
Vol 47 (22) ◽  
pp. 4221-4228 ◽  
Author(s):  
H. Kojima ◽  
C. R. Masson
Keyword(s):  
Calcium Fluoride ◽  
Alkaline Earth ◽  
Freezing Point ◽  
Free Energies ◽  
Oxygen Ions ◽  
Low Concentrations ◽  
Molten Fluorides ◽  
Calcium Silicates ◽  
Nonideal Behavior ◽  
The Ideal

The depression of the freezing point of CaF2 by BaF2 and MgF2 is ideal in the limit of low concentrations, and excess partial free energies of CaF2 at finite concentrations are in accord with data for other systems. Limiting depressions due to SrF2, CaO, and SrO are each approximately 1/4, and due to BaO and MgO, 1/2, of the ideal values. Calcium orthosilicate behaves ideally on the basis of 1 SiO44− ion per molecule. For calcium metasilicate, the results are interpreted in terms of a distribution of fluorosilicate ions of general formula (SiO3)nF(2n+1)− in the melts. For Ca3SiO5, the depressions are complicated by the nonideal behavior of oxygen ions. From the phase diagrams at low concentrations, CaO behaves ideally in CaCl2, and MgO is ideal in MgF2. The results are discussed in terms of possible formation of solid solutions in some of these systems.

FREEZING POINT DEPRESSIONS IN SODIUM FLUORIDE. IV. EFFECTS OF TRIVALENT FLUORIDES

1963 ◽  
Vol 67 (12) ◽  
pp. 2766-2769 ◽  
Author(s):  
Stanley Cantor ◽  
Wilfred T. Ward
Keyword(s):  
Sodium Fluoride ◽  
Freezing Point

HVEM Cryomicroscopy of Frozen Hydrated PTK1 Cells

1990 ◽  
Vol 48 (1) ◽  
pp. 500-501
Author(s):  
E.T. O’Toole ◽  
G.P. Wray ◽  
J.R. Kremer ◽  
J.R. Mcintosh
Keyword(s):  
Liquid Nitrogen ◽  
Phase Contrast ◽  
Culture Medium ◽  
Low Dose ◽  
Ammonium Acetate ◽  
Freezing Point ◽  
Voltage Electron ◽  
Cold Stage ◽  
Humidity Chamber ◽  
Coated Carbon

Ultrarapid freezing and cryomicroscopy of frozen hydrated material makes it possible to visualize samples that have never been exposed to chemical fixatives, dehydration, or stains. In principle, freezing and cryoimaging methods avoid artifacts associated with chemical fixation and processing and allow one to visualize the specimen in a condition that is close to its native state. Here we describe a way to use a high voltage electron microscope (HVEM) for the cryoimaging of frozen hydrated PTK1 cells.PTK1 cells were cultured on formvar-coated, carbon stabilized gold grids. After three days in culture, the grids were removed from the culture medium and blotted in a humidity chamber at 35° C. In some instances, the grids were rinsed briefly in 0.16 M ammonium acetate buffer (pH 7.2) prior to blotting. After blotting, the grids were transferred to a plunging apparatus and plunged into liquid ethane held directly above its freezing point. The plunging apparatus consists of a vertical slide rail that guides the fall of a mounted pair of forceps that clamp the specimen. The forceps are surrounded by a plexiglass humidity chamber mounted over a dewar of liquid nitrogen containing an ethane chamber. After freezing, the samples were transferred to liquid nitrogen and viewed in a JEOL JEM 1000 equipped with a top entry cold stage designed and built by Mr. George Wray (Univ. Colorado). The samples were routinely exposed to electron doses of 1 e/Å2/sec, and viewed at a temperature of −150° C. A GATAN video system was used to enhance contrast and to estimate the correct amount of underfocus needed to obtain phase contrast at various magnifications. Low dose micrographs were taken using two second exposures of Kodak 4463 film. The state of the solid water in the specimen was determined by diffraction using a 30/μm field limiting aperture and a camera length of 1 meter.

Kinetics and mechanism of the reduction of selenium (IV) by iron (II) in presence of sodium fluoride

1973 ◽  
Vol 70 ◽  
pp. 918-922 ◽  
Author(s):  
R. K. Srivastava ◽  
V. K. Srivastava ◽  
M. N. Srivastava ◽  
B. B. L. Saxena
Keyword(s):  
Sodium Fluoride ◽  
Kinetics And Mechanism
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