Showing papers on "Sodium chlorate published in 1990"

Chiral Symmetry Breaking in Sodium Chlorate Crystallization

Abstract: Sodium chlorate (NaClO3) crystals are optically active although the molecules of the compound are not chiral. When crystallized from an aqueous solution while the solution is not stirred, statistically equal numbers of levo (L) and dextro (D) NaClO3 crystals were found. When the solution was stirred, however, almost all of the NaClO3 crystals (99.7 percent) in a particular sample had the same chirality, either levo or dextro. This result represents an experimental demonstration of chiral symmetry breaking or total spontaneous resolution on a macroscopic level brought about by autocatalysis and competition between L- and D-crystals.

Contributions of autotrophic and heterotrophic nitrifiers to soil NO and N2O emissions

Abstract: Soil emission of gaseous N oxides during nitrification of ammonium represents loss of an available plant nutrient and has an important impact on the chemistry of the atmosphere. We used selective inhibitors and a glucose amendment in a factorial design to determine the relative contributions of autotrophic ammonium oxidizers, autotrophic nitrite oxidizers, and heterotrophic nitrifiers to nitric oxide (NO) and nitrous oxide (N2O) emissions from aerobically incubated soil following the addition of 160 mg of N as ammonium sulfate kg−1. Without added C, peak NO emissions of 4 μg of N kg−1 h−1 were increased to 15 μg of N kg−1 h−1 by the addition of sodium chlorate, a nitrite oxidation inhibitor, but were reduced to 0.01 μg of N kg−1 h−1 in the presence of nitrapyrin [2-chloro-6-(trichloromethyl)-pyridine], an inhibitor of autotrophic ammonium oxidation. Carbon-amended soils had somewhat higher NO emission rates from these three treatments (6, 18, and 0.1 μg of N kg−1 h−1 after treatment with glucose, sodium chlorate, or nitrapyrin, respectively) until the glucose was exhausted but lower rates during the remainder of the incubation. Nitrous oxide emission levels exhibited trends similar to those observed for NO but were about 20 times lower. Periodic soil chemical analyses showed no increase in the nitrate concentration of soil treated with sodium chlorate until after the period of peak NO and N2O emissions; the nitrate concentration of soil treated with nitrapyrin remained unchanged throughout the incubation. These results suggest that chemoautotrophic ammonium-oxidizing bacteria are the predominant source of NO and N2O produced during nitrification in soil.

The Effect of Chromate Addition on Cathodic Reduction of Hypochlorite in Hydroxide and Chlorate Solutions

Abstract: The cathodic reduction of chromate and its effect on the reduction of hypochlorite have been studied by cyclic voltammetry, using a rotating disk electrode of platinum in IM NaOH solution as well as in an electrolyte with a composition and temperature which were typical for industrial chlorate synthesis. It was found that in both electrolytes a thin film of presumably Cr(OH)3, with a thickness of only one or two molecular layers, is formed. After formation of this film in a cathodic sweep of the potential, the hypochlorite reduction reaction is almost completely inhibited in the reversed sweep, up to the potential region for dissolution of the formed film. From the experimental results and a theoretical analysis of the mass transfer rate of hypochlorite ions to the cathode surface, it is concluded that the addition of chromate to the electrolyte in the industrial chlorate process leads to the formation of a thin film on the cathode surface, which hinders electron transfer at the reduction of hypochlorite.

Simultaneous electrosynthesis of alkaline hydrogen peroxide and sodium chlorate

Abstract: Simultaneous electrosynthesis of alkaline hydrogen peroxide and sodium chlorate in the same cell was investigated. The alkaline hydrogen peroxide was obtained by the electroreduction of oxygen in NaOH on a fixed carbon bed while the chlorate was obtained by the reaction of anodic electrogenerated hypochlorite and hypochlorous acid in an external reactor. An anion membrane, protected on the anode side with an asbestos diaphragm, was used as the separator between the two chambers of the cell. The trickle bed electrode of dimensions 0.23 m high ×0.0362 m wide × 0.003 m thick was used on the cathode side. The anolyte chamber of the cell, 0.23 m high × 0.0362 m, wide × 0.003 m thick was operated at a fixed anolyte flow of 2.0 × 10−6 m3 s−1 while the oxygen loadings in the trickle bed was kept constant at 0.102 kg m−2 s−1. Other operating conditions include inlet and outlet temperatures of 27–33°C (anode side), 20–29°C (cathode side), cell voltages of 3.0–4.2 V (at current density of 1.2–2.4 kAm−2) and a fixed temperature of 70°C in the anolyte tank.

Reduction of by-product formation in alkali chloride membrane electrolysis

Abstract: To obtain higher chlorine purity hydrochloric acid can be added to the feed brine of membrane cells in alkali chloride electrolysis. During the electrolytic process hydroxide ions migrate from the cathode compartment into the anode compartment. Hydrochloric acid neutralizes these hydroxide ions and, hence, formation of the by-products (oxygen in the anode gas and sodium chlorate in the anolyte) is reduced. With laboratory membrane cells the effects of varied amounts of hydrochloric acid on concentrations and current efficiencies of these by-products have been studied. Under normal operating conditions (with pH of feed brine between 2 and 11) the formation of by-products is not influenced by the addition of acid. Effects can only be observed at brine pH values<1. Maximum effects occur if the brine pH is 0.1 and the anolyte pH is 2. The latter value is the limiting pH given by the membrane suppliers. At this point 6.3 dm3 hydrochloric acid (37% HCl) per 1 m3 of the feed brine have to be added in order to obtain an anode gas with 0.4% oxygen by volume. The formation of sodium chlorate is completely suppressed. Problems connected with this process and its application to industrial electrolysis are discussed.

Chlorine dioxide generation from chloric acid.

Abstract: Chlorine dioxide, useful as a pulp mill chemical, is produced without producing sodium sulfate effluent for disposal, by effecting reduction of chloric acid in an aqueous reaction medium in a reaction zone at a total acid normality of up to about 7 normal in the substantial absence of sulfate ion and in the presence of a dead load of sodium chlorate added to and subsequently removed from the reaction medium. Chloric acid for the process is produced electrolytically from an aqueous solution of the deadload sodium chlorate and make-up quantities of sodium chlorate. The chloric acid reduction to produce chlorine dioxide may be effected using methanol or electrolytically.

Sparger system for discharge of bulk material from hopper cars

Abstract: A sparger system for removing sodium chlorate crystal and other particulate material in slurry or solution form from a tank car comprises a plurality of spray nozzles from which water is expelled as a flat spray initially to dissolve sodium chlorate so as to cavitate the mass of sodium chlorate chlorate crystals, which break off in lumps into the cavity and then to impact the walls and roof of the tank car to flush off residual sodium chlorate crystal. The slurry is collected in a sump and is dicharged therefrom, with additional sprays agitating the sump to break up clumps of sodium chlorate and to maintain the particulates in suspension.

Ion exchange removal of impurities from chlorate process liquors

Abstract: Disclosed is an improved method of operating a sodium chlorate crystal production system where a brine stream is electrolyzed to form sodium chlorate, the sodium chlorate is crystallized in a crystallizer, and the mother liquor from a crystallizer is recycled to the brine stream. The improvement comprises passing the mother liquor through a cationic chelating ion exchange column before it is returned to the brine stream, and operating the ion exchange column so that it removes, on the average, only the amount of calcium that enters the system in the brine stream.

Gas generating agent generating gas having same composition as clean air

Abstract: PURPOSE:To obtain a gas generating agent generating a gas having the same compsn. as air and forming residue having very low toxicity by blending sodium azide with sodium chlorate, aminotetrazole and a shaping agent. CONSTITUTION:This gas generating agent is composed of 18-38 pts.wt. sodium azide (NaN3), 44-64 pts.wt. sodium chlorate, 8-28 pts.wt. aminotetrazole and a proper amt. of a shaping agent or 20-40 pts.wt. sodium azide, 41-61 pts.wt. sodium perchlorate, 9-29 pts.wt. aminotetrazole and a proper amt. of the shaping agent. Sodium azide which is the least expensive stable azide is used as the nitrogen source of a generated gas having the same compsn. as air. Magnesium stearate, aluminum stearate, org. bentonite or silica, etc., rendering shapability and having no harmful effect on the generated gas is preferably used as the shaping agent.

Production of quinolinic acid

Abstract: PURPOSE: To obtain quinolinic acid useful as an intermediate for pressure- sensitive dyestuffs, agricultural chemicals and drugs from inexpensively obtainable raw materials under a mild condition in high yield by oxidizing quinoline through simultaneous addition of a chlorate and hydrogen peroxide. CONSTITUTION: Ouinoline is oxidized in an acidic aqueous medium such as sulfuric acid by simultaneous addition of a chlorate and hydrogen peroxide preferably in the presence of a ruthenium compound as a catalyst at 40°C to the reflux temperature of the reaction solution to give the objective quinolinic acid. Industrially inexpensively obtainable sodium chlorate is preferably as the chlorate and the amount of sodium chlorate used is preferably 0.5-0.8mol based on 1mol quinoline. The amount of hydrogen peroxide is 0.5-0.8mol. The amount of the acidic aqueous medium is 3-10 acid equivalents based on 1mol quinoline and the acidic aqueous medium has preferably 3-13 normal acid concentration. Ruthenium trichloride may be cited as the ruthenium compound of the catalyst and the amount of the ruthenium trichloride used is 10 -5 to 10 -2 mol based on 1mol quinoline. COPYRIGHT: (C)1991,JPO&Japio