The Electrical Conductivity of Solutions of Certain Electrolytes in Organic Solvents

The study of the electric conductivity of solutions in organic solvents has brought to light many interesting relations. In many such solvents the same general relation obtains as is found in the case of aqueous solutions, viz., the molecular conductivity increases regularly with increasing dilution. In the great majority of these no limiting value of the molecular conductivity is obtainable, however great the dilution employed

An Improved Heating Apparatus for Maintaining Constant Temperatures in Work With Polarimeters and Refactometers

In the course of some work upon the effect of temperature upon the specific rotation of optically active substances in solution, it was found necessary to maintain constant temperatures over long periods of time. The conditions demanded that the heating apparatus be one which is simple and convenient and at the same time one which permits the easy reproduction of any given temperature

Environmental epidemiology: challenges and opportunities.

Epidemiology is struggling increasingly with problems with correlated exposures and small relative risks. As a consequence, some scholars have strongly emphasized molecular epidemiology, whereas others have argued for the importance of the population context and the reintegration of epidemiology into public health. Environmental epidemiology has several unique features that make these debates especially pertinent to it. The very large number of environmental exposures require prioritization, and the relative risks are usually very low. Furthermore, many environmental exposures can be addressed only by comparing populations rather than individuals, and the disruption of both local and global ecosystems requires us to develop new methods of study design. The population context is also very important to consider in risk management decisions because of the involuntary nature of most environmental exposures and the diversity of possible outcomes, both health- and nonhealth-related. Studies at the individual or molecular level tend to focus the research hypotheses and subsequent interventions at that level, even when research and interventions at other levels may be more appropriate. Thus, only by starting from the population and ecosystem levels can we ensure that these are given appropriate consideration. Although better research is needed at all levels, it is crucially important to choose the most appropriate level, or levels, of research for a particular problem. Only by conducting research at all these levels and by developing further methods to combine evidence from these different levels can we hope to address the challenges facing environmental epidemiology today

The Influence of Solvent upon the Optical Rotation of Di-Ethyl Tartrate

A determination of the specific rotation of di-ethyl tartrate in various mixed-solvents has been made at 25° and 30°, using two different concentrations of the ester. The solvents used were ethyl alcohol, methyl alcohol, benzene and toluene and the binary mixtures of each solvent with each of the remaining solvents. The mixed solvents were made on a mol fraction basis

The Thermal Decomposition of Hexane at High Pressures

The thermal decomposition of n-hexane has been studied at pressures between 14,000 and 15,000 lbs., at temperatures between 430° and 520°\u27 and for heating periods varying from a few minutes to two hours

The Solubility of Certain Substituted Benzoic Acids in Typical Salt Solutions at 25°

The solubility of the ortho-, meta- and para aminobenzoic acids, of the ortho-, meta- and para hydroxybenzoic acids, and of ortho- and meta nitrobenzoic acids in typical salts solutions at 25° has been determined. The salts were sodium chloride, barium chloride, potassium sulphate and magnesium sulphate

A Study of the Potentials and the Activities of the Metals in Zinc Amalgam Cells

The electromotive forces of cells containing zinc amalgam electrodes in a saturated solution of zinc sulphate, have been determined at 18°, 25 ° and 30°. The concentration of the zinc in the amalgams varied from N = 0.000302 to that of a two-phase amalgam, N = 0.0638

The Influence of Strong Electrolytes upon the Rate of Inversion of Sucrose at 25°

The rate of inversion of sucrose by hydrochloric acid in some typical salt solutions was studied at 25°. In every case the molalities of the sucrose and of the acid were fixed at 0.1 m and 1.0 m, respectively; the concentration of the salts ranging from 0.05 m to 1.0 m. For each salt the inversion coefficient varies rectilinearly with the molality. The order of decreasing influence upon the coefficient is BaCl2 , NaCl, KCl. The order is exactly reversed when considered with respect to ionic strength. The velocity is decreased by potassium sulfate, due to the formation of the HSO4 ion. The results are discussed from the standpoint of dipole orientation and ionic charge

Heat of Adsorption on Charcoal of Certain Organic Vapors

Previous work on the heat of adsorption has been carried out by the use of the ice calorimeter adapted only to those liquids of appreciable vapor pressure at 0°C., and affording no investigation of the effect of temperature upon the heat of adsorption. In the present paper there is described a method for studying the heat of adsorption at different temperatures by employing a sensitive thermo-couple in a calorimeter system consisting of a known weight of low specific heat oil in a Dewar flask. With this arrangement we find that a change of 1 microvolt in the thermocouple reading corresponds to 0.06 calories per gram of charcoal