Volume 13, Issue 2, 01 February 1945
Index of content:
13(1945); http://dx.doi.org/10.1063/1.1723999View Description Hide Description
The overvoltage for the discharge of hydrogen on a mercurycathode has been measured at 25°C in sulfuric acid solutions in the concentration range 0.125 to 9.65 molar. In dilute solution, the overvoltage is independent of the acid concentration, the cathodereaction being the discharge of a proton from water. At concentrations in excess of 2.83 molar, the overvoltage decreases approximately as a linear function of the weight percentage. Evidence is presented to show that in this region, the cathodereaction involves the hydrogen sulfate molecule, H2SO4. Preliminary results on phosphoric acid solutions also show a drop in the overvoltage as the concentration is increased beyond 1 molar.
Amphipathic Character of Proteins and Certain Lyophile Colloids as Indicated by Absorption Spectra of Dyes13(1945); http://dx.doi.org/10.1063/1.1724000View Description Hide Description
A characteristic change of spectral absorption of certain dyes as between water and organic solvents is shown to appear in aqueous solutions of gelatin or of the colloidal detergent, cetyl pyridinium chloride. This behavior is attributed to a bilateral character of lamellar micelles of such bodies, the elementary lamellae being polar and hydrophile on one side, non‐polar and organophile on the reverse side. The possibility is indicated of diagnosing such amphipathic characteristics by comparative spectrophotometric measurements with suitable dyes.
13(1945); http://dx.doi.org/10.1063/1.1724001View Description Hide Description
The quasi‐chemical method in the investigation of the equilibrium distribution of atoms in the pairs of neighboring sites in a superlattice is generalized by considering groups containing large numbers of sites. The generalized method may be used to obtain successive approximations of the free energy of the crystal. The labor of integration is avoided by the introduction of a Legendre transformation. In order to analyze the fundamental assumption underlying the method more closely, the number of arrangements of the atoms for given long‐distance order is calculated and the hypothesis of the non‐interference of local configurations discussed. The method is applied to the calculation of the free energy in the different approximations discussed in this paper, including Bethe's second approximation and a simple approximation for the face‐centered cubic crystal Cu3Au.
13(1945); http://dx.doi.org/10.1063/1.1724002View Description Hide Description
Previous theoretical treatments of the thermodynamics of high‐polymer solutions have assumed that the entropy of mixing is independent of the magnitude of the heat of mixing. The present treatment considers energy interactions on a molecular scale and includes these in the configurational partition function. This leads to the derivation of expressions for the heat of mixing and the entropy of mixing which reflect the effect of solvent‐solute interaction. One result of particular interest is an explicit expression for the temperature dependence of osmotic pressure.
13(1945); http://dx.doi.org/10.1063/1.1724003View Description Hide Description
The appropriate quantum‐mechanical Hamiltonian is set up according to the method of Wilson and Howard for investigating rotation‐vibration energies to second‐order approximation. The vibrational term G is derived explicitly as a function of the anharmonic constants, Coriolis parameters, etc. The elements are given for the secular determinant required for evaluation of the rotational term F including dependence on Coriolis interactions, centrifugal stretching, effective moments of inertia, etc. Selection rules are discussed.
13(1945); http://dx.doi.org/10.1063/1.1724004View Description Hide Description
It is shown that, contrary to Mache's model of the progressive extinction of a flame from the burner rim, a combustion zone cannot vanish within a combustible stream. The depth of penetration of the quenching of the explosive reaction by the burner wall is calculated from values of burning velocity and critical boundary velocity gradient for flashback; it is compared with the limiting distance between plane‐parallel plates and the limiting tube diameter for flame propagation. The thermal expansion of the gas normal and parallel to the combustion zone is discussed. An experimental analysis and discussion of partial entrance of the combustion zone into the burner tube (tilted flame) and partial attachment to the burner rim are given. New data have been obtained on hydrogen and acetylene flames. For instantaneous flashback, the boundary velocity gradients are independent of tube diameter, as expected; these gradients are not a satisfactory criterion for flame stability because flashback can be readily induced by tilted flames. The limit of the tilted‐flame range is represented by the semitheoretical equation g is the boundary‐velocity gradient, Su the burning velocity, and R the tube diameter. The boundary‐velocity gradients for blow‐off are again found constant over the laminar flow range. The compression of acetylene‐oxygen streams by the combustion zone has been measured. The burning velocities calculated from these and additional thermodynamic data agree well with those determined from gas flow and cone surface.