Volume 12, Issue 5, 01 May 1941
Index of content:
12(1941); http://dx.doi.org/10.1063/1.1712916View Description Hide Description
Constitution diagrams give in a small amount of space a great deal of information—the solid solutions and components present in an alloy—the ranges of temperature and compositions over which they are stable—information of very practical value to the metallurgist. The part played by x‐rays in ferreting out this information is described herein.
12(1941); http://dx.doi.org/10.1063/1.1712917View Description Hide Description
12(1941); http://dx.doi.org/10.1063/1.1712919View Description Hide Description
The reaction of hydrogen selenide and pigment zinc oxide at room temperature has been investigated, using electron and x‐ray diffraction as a means of examining the reaction product. It was found that hydrogen selenide reacts with zinc oxide to form zinc selenide as a coating around the zinc oxide particles. After approximately one‐tenth of the zinc oxide is converted to zinc selenide by this surface reaction, the resulting coating of zinc selenide prevents the continuance of the reaction. Since the effective depth of penetration of electrons under the conditions of electron diffraction is much less than the average diameter of the pigment particles used in this investigation, the electron diffraction photograms necessarily arise largely from the particle surfaces. For this reason electron diffraction was successfully used to demonstrate that the reaction proceeded in the manner described. The paper illustrates the applicability of electron diffraction to the general problem of the examination of the surfaces of pigment particles.
12(1941); http://dx.doi.org/10.1063/1.1712920View Description Hide Description
Data are presented showing flow and physical properties of cellulose acetate plastics made using five plasticizers (previously described by Kirkpatrick before the Society of Rheology) with cellulose acetates of 2.3 and 2.6 acetyl groups per C6 unit. Single plasticizers exert specific effects on flow and physical properties of the plastics. Mixtures of such plasticizers give plastics with properties which may be predicted by a simple proportion based on the amount of each plasticizer used. Results of Rockwell hardness,elastic modulus,impact strength, and water absorption tests of molded plastics are discussed. No general relation is found between flow properties of the plastics at molding heats and physical properties at room temperatures. An attempt is made to relate these results to the criteria for high elasticity set up by Houwink.
12(1941); http://dx.doi.org/10.1063/1.1712921View Description Hide Description
The author's general theory is applied to the calculation of the settlement through consolidation of a soil loaded uniformly on an infinite strip of constant width with particular reference to the nature of the settlement at the edge of the loaded area. The solution is obtained by first calculating the settlement produced by a suddenly applied load with sinusoidal distribution. The use of a Dirichlet integral and the principle of superposition leads then directly to the solution for the discontinuous loading.
12(1941); http://dx.doi.org/10.1063/1.1712922View Description Hide Description
12(1941); http://dx.doi.org/10.1063/1.1712923View Description Hide Description
By use of the method of Betz and Karrer the cathode drop of an arc has been measured for a number of electrodes, including copper,silver,iron and arc weldingelectrodes with and without coatings. The time for an arc to establish the cathode drop voltage measured from the time the ``last'' contact causes an appreciable voltage drop is found to be less than 40 microseconds. The cathode drop for copper is found to decrease with air pressure from 13 volts at atmospheric pressure to 8 volts at 0.1 mm of Hg pressure.