THE RATE OF DEHYDRATION OF COPPER SULPHATE PENTAHYDRATE AT LOW PRESSURES OF WATER VAPOR

1953 ◽  
Vol 31 (2) ◽  
pp. 107-119 ◽  
Author(s):  
G. B. Frost ◽  
R. A. Campbell
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Copper Sulphate ◽  
Water Vapor Pressure ◽  
Gradual Decline ◽  
Induction Periods ◽  
Oxalate Dihydrate ◽  
Low Pressures

The rate of dehydration of copper sulphate pentahydrate has been determined over a range of low pressures of water vapor. It has been found that as the pressures are increased, the rate at first drops very rapidly; this drop is followed by a period of marked acceleration, which is followed in turn by a gradual decline. Copper sulphate pentahydrate has been found to be similar in this respect to manganous oxalate dihydrate, which has been hitherto regarded as unique in its behavior. The observed effects are probably due to amorphous to crystalline transitions occurring during induction periods, the durations of which have also been found to depend on water vapor pressure.

THE LOW PRESSURE DEHYDRATION OF MAGNESIUM SULPHATE HEPTAHYDRATE AND COBALTOUS CHLORIDE HEXAHYDRATE

1956 ◽  
Vol 34 (5) ◽  
pp. 591-599 ◽  
Author(s):  
R. W. Ford ◽  
G. B. Frost
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Magnesium Sulphate ◽  
Copper Sulphate ◽  
Water Vapor Pressure ◽  
Adsorbed Water ◽  
Vapor Pressures ◽  
Cobaltous Chloride ◽  
Chloride Hexahydrate ◽  
Initial Drop

Rates of dehydration under vacuum, and at a series of controlled water vapor pressures, have been carried out for powdered samples of magnesium sulphate heptahydrate and of cobaltous chloride hexahydrate. It has been found for the magnesium salt that as the pressures are increased, the rate at first drops rapidly, this decrease being followed by a period of acceleration which is followed in turn by a decline. The curves are similar to those previously reported for copper sulphate pentahydrate, but the changes occur over a much wider range of water vapor pressures. In the dehydration of cobaltous chloride hexahydrate the initial drop in rate with increase in water vapor pressure is not observed. The results are interpreted in terms of the crystallization of intermediate products in the presence of adsorbed water.

scholarly journals Water vapor pressure trends in south and southwest Iran

MAUSAM ◽  
2021 ◽  
Vol 68 (2) ◽  
pp. 335-348
Author(s):  
YOUNES KHOSRAVI ◽  
HASAN LASHKARI ◽  
HOSEIN ASAKEREH
Keyword(s):  
Time Series ◽  
Water Vapor ◽  
Vapor Pressure ◽  
Water Vapor Pressure ◽  
Sen’S Slope Estimator ◽  
Sen’S Slope ◽  
Ground Station ◽  
Mk Test ◽  
Slope Estimator ◽  
The Persian Gulf

Recognitionanddetectionofclimaticparameters inhave animportant role inclimate change monitoring. In this study, the analysis of oneofthe most importantparameters, water vapor pressure (WVP), was investigated. For this purpose, two non-parametric techniques, Mann-Kendall and Sen's Slope Estimator, were used to analyze the WVP trend and to determine the magnitude of the trends, respectively. To analyze these tests, ground station observations [10 stations for period of 44 years (1967-2010)] and gridded data [pixels with the dimension of 9 × 9 km over a 30-year period (1981-2010)] in South and SouthwestofIran were used. By programming in MATLAB software, the monthly, seasonal and annual WVP time series were extracted and MK and Sen's slope estimator tests were done. The results of monthly MK test on ground station observations showed that the significant downward trends are more considerable than significant upward trends. It also showed that the WVP highest frequency was more in warm months, April to September and the highest frequency of significant trends slope was in February and May. The spatial distribution of MK test of monthly gridded WVP time series showed that the upward trends were detected mostly in western zone and near the Persian Gulf in August. On the other hand, the downward trends through months. The maximum and minimum values of positive trends slope occurred in warm months and cold months, respectively. The analysis of the MK test of the annual WVP time series indicated the upward significant trends in the southeast and southwest zones of study area.  

Temperature and Water Vapor Pressure Effects on the Friction Coefficient of Hydrogenated Diamondlike Carbon Films

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Pamela L. Dickrell ◽  
N. Argibay ◽  
Osman L. Eryilmaz ◽  
Ali Erdemir ◽  
W. Gregory Sawyer
Keyword(s):  
Water Vapor ◽  
Friction Coefficient ◽  
Vapor Pressure ◽  
Water Vapor Pressure ◽  
Carbon Film ◽  
Transient Behavior ◽  
Carbon Films ◽  
Pressure Effects ◽  
Diamondlike Carbon ◽  
Gas Surface Interactions

Microtribological measurements of a hydrogenated diamondlike carbon film in controlled gaseous environments show that water vapor plays a significant role in the friction coefficient. These experiments reveal an initial high friction transient behavior that does not reoccur even after extended periods of exposure to low partial pressures of H2O and O2. Experiments varying both water vapor pressure and sample temperature show trends of a decreasing friction coefficient as a function of both the decreasing water vapor pressure and the increasing substrate temperature. Theses trends are examined with regard to first order gas-surface interactions. Model fits give activation energies on the order of 40 kJ/mol, which is consistent with water vapor desorption.

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