Samuel S. Markowitz

KINETICS AND MECHANISM FOR THE CATALYTIC OXIDATION OF SULFUR DIOXIDE ON CARBON IN AQUEOUS SUSPENSIONS

Combustion-produced soot (carbonaceous) particles have been found to be efficient catalysts for SO{sub 2} oxidation, especially in the presence of liquid water. A kinetic study of the catalytic oxidation of SO{sub 2} on carbon particles suspended in solution has been carried out. The reaction was found to be first order with respect to the concentration of carbon particles, 0.69th order with respect to dissolved oxygen, between zero and second order with respect to S(IV) concentrations, and independent of the pH. Temperature studies were carried out, and an activation energy for this reaction was determined. A four-step mechanism is proposed for this carbon-catalyzed oxidation reaction.

THE HALF-LIFE OF FLUORINE-18

Radiochemically pure 18F has been prepared by three different methods and its decay has been followed with β proportional counters and γ-ray counters in an effort to measure the half-life accurately. Analysis by a computer program that used the method of least squares gave a weighted mean half-life of 18F and a weighted standard deviation of the mean as 109·72 ± 0·06 min.

Chemical effects following the 34S(n,γ)35S reaction in gaseous-sulphur compounds☆☆☆

Abstract The chemical behaviour of 35 S formed by the 34 S( n , γ) reaction has been studied in gaseous H 2 S, SO 2 , SF 6 , CH 3 SH, and thiophene. We obtained the reaction by sealing the gases in quartz ampules and irradiating them with thermal neutrons in the Livermore pool-type reactor (LPTR). Among the effects studied were those of pressure, surface area, and additive gases including argon, nitric oxide, oxygen and hydrogen. The 35 S was recovered in gaseous compounds and in deposits on the walls of the ampules; the chemical composition of both portions of activity was determined by aqueous chemistry using carriers. The results are consistent with a model in which the original molecule is broken up in the recoil process and the resulting fragments containing 35 S react with the surroundings only after they have slowed to thermal energies; in general, the final chemical form of the 35 S is determined by the chemical environment in which it is produced rather than by its original oxidation state or chemical form. However, irradiations of mixtures of several gases with NO gave results possibly indicating that the chemical form of the 35 S immediately after molecular disruption may depend upon the nature of the original molecule.

The half-life and the α-decay branching ratio of 207Po

Abstract 207 Po was produced via 3 He activation of lead samples. Polonium was chemically separated from the irradiated targets. Gamma and α spectra were measured with Ge(Li) and surface-barrier α counters, respectively. The decay of the 992-keV γ-ray of 207 Po was followed and a half-life of 5·84 ± 0·07 hr was obtained for 207 Po. The α-decay branching of 207 Po was measured to be 0·0210 ± 0·0023 per cent.

SULFUR DIOXIDE AS A RADICAL SCAVENGER IN ALKENE SYSTEMS.

The comparative efficiency of S0 2 and 0 2 as radical scavengers has been determined in the Τ + cyclohexene, Τ + transbutene, and Τ + n-butane gas phase systems. Τ was produced by recoil in the He(n, p)T reaction. 0 2 , the only scavenger currently in use in Τ + alkene systems, causes an anomalous increase in the butadiene-t yield from Τ + cyclohexene reactions. All other tritiated products from cyclohexene and transbutene + Τ reaction show similar scavenging trends. The use of S02 as a radical scavenger may be advantageous in some alkene systems although S02 fails to eliminate all thermal contributions to the HT yield in the Τ + n-butane system.

Design of a high-temperature neutron irradiation container

Abstract The design and construction of a neutron irradiation container in which all samples receive the same total neutron dose and the temperature is controlled to ±0.5° C in the 25°C to 200°C range is reported.

SCAVENGER EFFECTS IN THE RECOIL TRITIUM REACTIONS OF CYCLOHEXENE

Abstract The comparative efficiency of H2S, butadiene-d5, O2 and SO2 as radical scavengers has been determined in the T + cyclohexene gas phase system. The T was produced by recoil in the 3He(n, p)T reaction. Direct tritium substitution on cyclohexene yields cyclohexene-t which may undergo unimolecular decomposition to produce butadiene-t. In unscavenged samples butadiene-t is selectively depleted by reactions with H atoms produced by radiolysis. Neither SO2 nor H2S is sufficiently reactive with H atoms to protect butadiene-t from such depletion. The “hot” butadiene-t yield can only be determined by means of O2 or butadiene-d6 scavenging. All products except butadiene-t exhibit normal behavior with O2, SO2 or H2S scavenging.