The catalytic Hydrogenation of Benzene and toluene over evaporated films of Nickel and Tungsten

In the vapour-phase hydrogenation of benzene and toluene over evaporated films of nickel and tungsten there is some poisoning of the catalyst surface by adsorbed hydrocarbon residues, resulting in falling rates of hydrogenation. Activation energies and frequency factors are obtained from initial rates. On poisoned nickel, rates pass through a maximum at about 90 �C. The rate and extent of poisoning increase with temperature. Some cyclohexene is sometimes formed during the hydrogenation of benzene over nickel. The hydrogenation of cyclohexene over nickel is extremely rapid but strongly inhibited by benzene. On a benzene poisoned nickel surface cyclohexene disproportionates to benzene and cyclohexane, and this reaction also occurs to a small extent during hydrogenation of cyclohexene.

Thermodynomic data from Gas-Liqud partition Chromatography

Partition coefficients obtained from gas-liquid partition chromatography have been compared with those obtained in a static system to show that the former are true equilibrium values. The heats and entropies of solution have been obtained from the temperature dependence of the partition coefficients.

MASS TAGGING OF BLACK FLIES (Diptera: Simuliidae) WITH RADIOPHOSPHORUS

A new method for tagging large numbers of black flies (Simulium spp.) for flight range investigations is described. Radioactive adults that were readily detected with a Geiger counter were reared from larvae that had been kept for 24 hr. in a very dilute solution of radioactive phosphorus (0.2 μc. per ml.) and then returned to nonradioactive water to complete their development. The treatment did not visibly harm larvae or the adults that emerged from them. Larvae were reared in small containers of water circulated and aerated with air jets in the laboratory, and with a simple arrangement of stream-driven paddle wheels in the field. By this method, tagged larvae, pupae, and adults were produced which could be readily detected with a Geiger counter. In field tests, tagged larvae and pupae were found as far as 520 yd. downstream from the point of release. Tagged adults were taken in cages placed over radioactive larvae and pupae in the stream, but only one was recaptured in the open, and this only 100 yd. from the stream. Failure to capture more tagged adults was believed due mainly to inadequate collecting methods. A short treatment period is desirable when tagging large populations of black-fly larvae in the field because other methods, such as rearing in a small container for a long period of time, or treating the stream with a radioactive isotope, are impractical. This method would be applicable in studies on dispersal and predation of immature and adult stages of other insects of streams and ponds.

Study of adsorption on metals by the contact potential technique

The change in contact potential between metals due to physical adsorption of water vapour, isopropanol, and ethyl acetate has been studied. The plot of contact potential against relative vapour pressure showed a hysteresis loop, the behaviour varying for different methods of surface preparation. An initial irreversible potential change was always found, due to chemisorption. By studying the dependence of the contact potential on the temperature of one of the metal surfaces it has been possible to determine the change in work function of a gold surface due to physical adsorption.