Trace mild acid-catalysed Z→E isomerization of norbornene-fused stilbene derivatives: intelligent chiral molecular photoswitches with controllable self-recovery

Stilbene derivatives are long known to undergo “acid-catalyzed” Z→E isomerization, where a strong mineral acid in high concentrations is practically demanded. Such severe reaction conditions often cause undesired by-reactions and...

Mechanisms of carbon monoxide hydrogenation yielding formaldehyde catalyzed by the representative strong mineral acid, H2SO4, and Lewis–Brønsted superacid, HF/AlF3

The HAlF4 superacid was predicted to effectively reduce the activation barriers of the carbon monoxide hydrogenation mechanism.

A Gasometric Procedure to Measure Residual Lime in Container Substrates

Unreacted residual limestone in the container substrate is key in buffering pH change over time. Our goal was to develop a substrate test protocol to measure residual lime [in units of CaCO3 equivalent (CCE)] by applying a strong mineral acid (HCl) to a substrate sample and measuring the evolved CO2 gas with a gasometric method based on a Chittick apparatus. In one experiment, CaCO3 was added to a substrate that had previously been neutralized to pH 7.35 with Ca(OH)2 so that there would be minimal CaCO3 reaction with the substrate at this high pH. The gasometric method was then used to estimate residual CCE. Measured CCE and applied CaCO3 were similar, indicating reliable CCE estimation. In a second experiment, a pH titration method was used to quantify the relationship between substrate-pH and milliequivalents of reacted base and provided an additional validation of the estimated reacted and residual CCE. The gasometric method demonstrated declining residual CCE over time as a dolomitic limestone reacted to raise substrate-pH and increasing residual CCE as applied CaCO3 concentration increased. Residual CCE in a substrate is an important property that should be considered for pH control and management in greenhouse crop production. Our results indicate that the gasometric system may be useful for optimizing lime application rate, lime source, or management of residual CCE during crop production.

Comparison of the Behavior of Trace Elements During Acid Leaching of Ashes from Several Coals

ABSTRACTThe leaching of fly ash from eastern U.S. coals with strong mineral acid is the initial step in a series of potential processes for producing useful and marketable materials from the ash. This initial leaching step removes most, or all, of the more soluble (generally amorphous) materials from the ash and leaves an inert residue, believed to be mostly mullite and silica. Chemical analyses of the leachate and the residual inert materials indicate the original distribution of the trace elements in the phases. Significant differences in crystallography, composition and leaching behavior have been noted in ash samples from coals from various regions, of various types, and sometimes even in ash samples from the same or similar coals. Trace element analyses of fly ash leachates provide a useful means of studying coal characteristics and of determining how the trace elements are incorporated in various types of fly ashes.

In-Situ Leaching Of Crownpoint New Mexico Uranium Ore. IV. Laboratory Study Of Strong Leaching Systems: Oxidant-Sulfuric Acid

Mobil Research and Development Corporation Field Research Laboratory Dallas, Texas Abstract In this paper we present laboratory data on the effectiveness of a fairly severe leaching system ---- sulfuric acid (H2SO4) and an oxidant ---- in recovery of uranium from refractory Crown- point uranium ore. In combination with a strong mineral acid such point uranium ore. In combination with a strong mineral acid such as H2SO4, oxidants such as oxygen or hydrogen peroxide (H202) should be able to degrade the organic matter intimately associated with uranium in slow-leaching uranium ores, thus increasing exposure of the uranium mineral sites to contact by the leachate. Scoping batch leach tests showed that a leachate such as H2SO4 with H2O2 and with ferric ion added gave good racoveries at a fast rate from Crownpoint refractory ore. For detailed study of the H2SO4-oxygen system, a composite core was fabricated with ore segments from several wells in an area In which ore leached slowly with mild leachates. With this system, comprising 0.5% H2SO4, 24.5 gm/liter Na2SO4, 1 gm/liter NaCl and 0.2 gm/liter CO2 with 800 psig (~520 kPa) 02, 65% recovery of uranium was observed rapidly in about 30 pore volumes. This is almost double the recovery observed with a mild leaching system (02-NaHC03) in the same number of pore volumes. Plugging that occurred twice during the leach run appears related to movement of feldspar and quartz fines rather than gypsum deposition.

Synthesis of 3-isoxazolols revisited. Diketene and (β-ketoesters as starting materials

3-Isoxazolols can be made in good yields from β-ketoesters or diketene and hydroxylamine, provided that pH is kept at about 10 throughout the reaction, and that the reaction mixture is quenched with an excess of strong mineral acid. This suppresses the formation of 5-isoxazolones, which are otherwise normally the main products of the reaction.

Acidic Precipitation in South-Central Ontario: Recent Observations

Precipitation in south-central Ontario, with mean pH between 3.95 and 4.38 and frequent event pH's of < 4.0, is more acidic than that in the Sudbury, Ontario, region and in Scandinavia, and as acidic as that in the northeastern USA. As in New England, a major component of the total acidity is strong mineral acid. Because most lakes in south-central Ontario have very low buffering capacities (10–200 μeq∙L−1), high acid loadings are likely to lead to acidification of many lakes and streams in the forseeable future. Although it is not yet possible to estimate the time required for this to happen, there is already some evidence of declining buffering capacity in a few lakes. Key words: acidic rain, buffering capacity, acidic lakes, precipitation, alkalinity