HYSTERESIS IN SILICA GEL SORPTION SYSTEMS

1934 ◽  
Vol 10 (6) ◽  
pp. 713-729 ◽  
Author(s):  
L. M. Pidgeon
Keyword(s):  
Hysteresis Loop ◽  
Silica Gel ◽  
Sulphur Dioxide ◽  
Water System ◽  
The Other ◽  
Vapor Pressures ◽  
Large Pressure ◽  
Pressure Changes ◽  
Permanent Gases ◽  
Sorption Systems

The hysteresis which normally appears in the isotherms of the silica gel-water system has been attributed by Patrick to the presence of permanent gases in the system. Only one case has been found in which a reversible isotherm has been recorded in the silica gel-water system. For alcohol and benzene only one case of hysteresis has been reported. These results seem to be independent of the presence or absence of air or other gases.The sorption of water, benzene and ethyl alcohol has been examined using the sorption balance. A hysteresis loop appears for water only. This hysteresis may not be eliminated by special methods of evacuation and must be considered as a real effect. The isotherms of alcohol and benzene, on the other hand, are completely reversible. It has been shown that the dimensions of the hysteresis occurring in the water system may be affected by the manner of addition of vapor to the apparatus. Only when the vapor pressures remain reasonably constant during sorption are the dimensions of the effect evident. If very large pressure changes take place the hysteresis may disappear.A comparison of the isotherms for water showing hysteresis, and those of the sulphur dioxide system (upon which the original suggestion as to the cause of hysteresis was based) show that there is not necessarily any relation between the two.

Temporal variability of disinfection by-products concentration in urban public water system

2013 ◽  
Vol 14 (4) ◽  
pp. 393-398
Keyword(s):  
Drinking Water ◽  
Water Samples ◽  
Temporal Variability ◽  
Water System ◽  
The Other ◽  
Major Constituent ◽  
System P ◽  
Public Water System ◽  
Drinking Water Samples ◽  
By Products

The occurrence of trihalomethanes (THMs) was studied in the drinking water samples from urban water supply network of Karachi city that served more than 18 million people. Drinking water samples were collected from 58 locations in summer (May-August) and winter (November-February) seasons. The major constituent of THMs detected was chloroform in winter (92.34%) and summer (93.07%), while the other THMs determined at lower concentrations. Summer and winter concentrations of total THMs at places exceed the levels regulated by UEPA (80 μg l-1) and WHO (100 μg l-1). GIS linked temporal variability in two seasons showed significantly higher median concentration (2.5%-23.06%) of THMs compared to winter.

Pressure Gradients Affecting the Labyrinth during Hypobaric Pressure

1997 ◽  
Vol 106 (6) ◽  
pp. 495-502 ◽  
Author(s):  
Konrád S. Konrádsson ◽  
Björn I. R. Carlborg ◽  
Joseph C. Farmer
Keyword(s):  
Cerebrospinal Fluid ◽  
Eustachian Tube ◽  
Ambient Pressure ◽  
Pressure Gradients ◽  
Cochlear Aqueduct ◽  
Fluid Compartment ◽  
Large Pressure ◽  
Fluid Compartments ◽  
Pressure Changes ◽  
Considerable Pressure

Hypobaric effects on the perilymph pressure were investigated in 18 cats. The perilymph, tympanic cavity, cerebrospinal fluid, and systemic and ambient pressure changes were continuously recorded relative to the atmospheric pressure. The pressure equilibration of the eustachian tube and the cochlear aqueduct was studied, as well as the effects of blocking these channels. During ascent, the physiologic opening of the eustachian tube reduced the pressure gradients across the tympanic membrane. The patent cochlear aqueduct equilibrated perilymph pressure to cerebrospinal fluid compartment levels with a considerable pressure gradient across the oval and round windows. With the aqueduct blocked, the pressure decrease within the labyrinth and tympanic cavities was limited, resulting in large pressure gradients toward the chamber and the cerebrospinal fluid compartments, respectively. We conclude that closed cavities with limited pressure release capacities are the cause of the pressure gradients. The strain exerted by these pressure gradients is potentially harmful to the ear.

Determination of Sulfaquinoxaline, Sulfathiazole, Sulfamerazine, and Sulfamethazine in Feed Concentrates or Premixes

1973 ◽  
Vol 56 (6) ◽  
pp. 1475-1479 ◽  
Author(s):  
Ugo R Cieri
Keyword(s):  
Silica Gel ◽  
The Other ◽  
Uv Absorbance ◽  
The Individual

Abstract Sulfaquinoxaline is determined by its UV absorbance at about 358 nm, where the other 3 sulfonamides do not absorb. Sulfathiazole, sulfamerazine, and sulfamethazine are determined by a quantitative TLC procedure, based on the separation of the compounds on silica gel plates; the spots are extracted and the centrifuged extracts are analyzed spectro-photometrically. A method of calculating the total sulfonamide content, independent of the individual components, is also introduced.

Preparations, sulphinate coordination, and thermal decomposition of some bismuth triarenesulphinates

1972 ◽  
Vol 25 (10) ◽  
pp. 2107 ◽  
Author(s):  
GB Deacon ◽  
GD Fallon
Keyword(s):  
Thermal Decomposition ◽  
Acetic Acid ◽  
Sulphur Dioxide ◽  
Glacial Acetic Acid ◽  
The Other

Bismuth triarenesulphinates, Bi(02SR)3 [R = Ph, p-MeC6H4, p-ClC6H4, 2,4,6-(Me2CH)3C6H2, and p-MeCONHC6H4], have been prepared by reaction of bismuth triacetate with the appropriate arenesulphinio acids in glacial acetic acid, and the first two compounds have also been obtained by reaction of triphenyl-bismuth with the appropriate mercuric arenesulphinates. The sulphur-oxygen stretching frequencies of the bismuth sulphinates are indicative of O-sulphinate coordination, and the compounds are considered to be polymeric with bridging O-sulphinate groups and six-coordinate bismuth. Thermal decomposition of Bi(O2SR)3 (R = Ph, p-MeC6H4, or p-CIC6H4) under vacuum gave the corresponding triarylbismuth compounds and sulphur dioxide, the preparation of tri-p-chlorophenylbismuth being accompanied by formation of di-p-chlorophenyl sulphone and S-p-chlorophenyl p-chlorobenzenethiosulphonate. Pyrolysis of the other triarenesulphinates did not yield organobismuth compounds.

Activated Shale Creep and Potential Micro-Annulus Investigated in the Field

2021 ◽  
Author(s):  
Andreas Bauer ◽  
Matteo Loizzo ◽  
Laurent Delabroy ◽  
Tron Golder Kristiansen ◽  
Kristian Klepaker
Keyword(s):  
Core Sample ◽  
Inversion Algorithm ◽  
Log Data ◽  
Sealing Capacity ◽  
Large Pressure ◽  
Elastic Rebound ◽  
Zonal Isolation ◽  
Pressure Changes ◽  
Drilling Muds ◽  
The Impact

Abstract It has been demonstrated that creeping shales can form effective hydraulic well barriers. Shale barriers have been used for many years in P&A of wells in Norway. More recently, shale barriers for zonal isolation have also been used in new wells where shale creep was found to occur within days. In some cases, shale creep is activated by a reduction in annulus pressure, in other cases shale creep sets in without any active activation, possibly by time-dependent formation-pressure changes. However, the presence of thixotropic fluids (drilling muds) in the annulus may prevent full closure of the annulus as it requires large pressure differentials to squeeze the fluid out of a microannulus. Furthermore, elastic rebound of an actively activated shale barrier could result in a microannulus and hence a possible leakage pathway. Improved logging technology is needed for identifying shale barriers and the presence of micro-annuli in shale-barrier zones. We use cement bond log data and standard bond logging criteria to evaluate the quality of the shale well barriers (Williams et al., 2009). In addition, in order to detect microannuli on the outside of the casing, a new inversion algorithm for the bond logging data was developed and tested on field data. Later, we had the chance to apply the inversion algorithm to bond-log data obtained in the laboratory with a miniature bond-logging tool inside a cased hollow-cylinder shale-core sample place. It turned out that both the micro-annulus widths and shale velocities determined by the inversion technique were too high. By constraining the shale velocities to more realistic values, the updated microannulus widths were smaller and more consistent with the experimental results. Small microannuli may not cause any measurable leakage along the well, especially if filled with a thixotropic fluid. However, more studies are needed to quantify the impact of microannuli on the sealing capacity of shale barriers.

Quantitative Fluorodensitometric Measurement of Aflatoxin B1 with a Flying-Spot Densitometer. II. Comparative Study of B1 Measurements in Spiked and Naturally Contaminated Peanut Products

1972 ◽  
Vol 55 (6) ◽  
pp. 1310-1315
Author(s):  
P R Beljaars ◽  
F H M Fabry ◽  
M M A Pickott ◽  
M J Peeters
Keyword(s):  
Comparative Study ◽  
Silica Gel ◽  
Aflatoxin B1 ◽  
Peanut Butter ◽  
Reference Method ◽  
Amyl Alcohol ◽  
The Other ◽  
Coefficients Of Variation ◽  
Tlc Plates ◽  
Flying Spot

Abstract Peanut butter extracts and samples spiked with 5-40 μg anatoxin B1/kg were analyzed, together with naturally contaminated peanut products, by 3 extraction procedures: the official Dutch method (KB), he Liem et al. method (methanol), and the IUPAC method. The last procedure was selected as a reference method, since it has international application. KB extracts were separated on silica gel G plates with a mixture of chloroform-acetone (90 + 10), whereas IUPAC extracts were separated similarly on MN-G-HR plates. Methanol extracts were resolved on silica gel II plates, using chloroform-trichloroethylene-n-amyl alcohol-formic acid (80 + 15 + 4 + 1) as the developing solvent. After development, plates were scanned with a reflectance flying-spot densitometer. With such techniques, average recoveries for spiked peanut butter extracts ranged from 99 to 105%, with variation values of 11-12%. Recovery values of 69% (KB method) and 84% (methanol and IUPAC methods) were obtained for spiked peanut butter samples. Coefficients of variation ranged from 13 to 15% for fluorodensitometric measurements. Innaturally contaminated peanuts and peanut products , precision values were 13.6% for fluorodensitometric measurements compared to 36% for visual estimations . Both the methanol and IUPAC methods yield extracts suitable for densitometric analysis after spotting on TLC plates; the analytical results obtained are comparable. Extracts from the KB method contained more interfering fluorescent material than the other 2 methods

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