Volume 4, Issue 12, 01 December 1933
Index of content:
4(1933); http://dx.doi.org/10.1063/1.1745153View Description Hide Description
4(1933); http://dx.doi.org/10.1063/1.1745154View Description Hide Description
From knowledge of the electromagnetic field at the surface of a half‐space due to a prescribed oscillatory source, is determined the unknown variation with depth of the conductivity and the dielectric constant. Unique solutions exist for these quantities.
4(1933); http://dx.doi.org/10.1063/1.1745155View Description Hide Description
A theoretical expression for the evaporation of small spherical waterdrops in still air is developed from the general evaporation equation of Jeffreys. Experimental data for the evaporation of drops ranging from 25 to 2600 microns in diameter are obtained at several temperatures and relative humidities. After making approximate corrections for the cooling of the drops it is found that the results are in general agreement with the theoretical evapooration equation. Residual variations which are functions of the drop size and the difference between the water vapor density at the surface of the drop and at a distance from the drop are probably due to inaccuracies in the method used for computing the droptemperatures. The results of the paper furnish a means for computing the total time required for the complete evaporation of a drop of liquid water into a still atmosphere at any given temperature and relative humidity.
4(1933); http://dx.doi.org/10.1063/1.1745156View Description Hide Description
If liquid, initially saturating the pores of a soil, is allowed to drain from that soil, no such complete drainage as occurs in a simple capillary tube is observed; large quantities of liquid are retained. The quantity of liquid held by the soil immediately after drainage gradually alters; it decreases to a stationary value and the liquid so held finally arranges itself in a stable distribution. Whatever be the distribution, the bounding liquid surfaces are capillary ones and subject to the laws of thermodynamics and capillarity; the Kelvin relation, in general determines the curvatures. The problem is considered for an ideal soil, that is an assemblage of spheres, of a single size, packed at random. There are in the ideal soil three types of distribution. First, there is a pendular region where the liquid is retained in the form of single rings of liquid wrapped around the axis of each pair of adjacent grains in contact. Second, there is a funicular region, which may be considered to arise by coalescence of the rings; we have two or more grain contacts imbedded in a single liquid mass, that is, webs of liquid enmeshing two or more grain contacts and which may involve many grains of the packing. There is, finally, a saturation region in which all pores are completely filled. The limits of each of these zones are determined. The funicular zone is a zone of hysteresis and all values between a normal minimum and complete saturation are usually possible. To calculate the normal minimum distribution the actual packing is replaced by an average packing of grains in hexagonal array and equally spaced to give the required porosity. The funicular distribution is now in the form of single rings wrapped around the axis of each pair of grains of the packing. The volume of each type of ring is determined in terms of (σ/ρghr), where σ is the surface tension of the liquid and ρ its density, r the grain radius, and h the height of the ring above a free liquid reference plane. The average volume of each type of ring is obtained for all rings confined between two given planes. From the average ring volume and the number of such in each cc of packed space, the total retention in each zone above saturation is found. The distribution, that is, the liquid retained in any lamina at a height h above the free liquid, is also given. The results are compared with the data of King.