Closure to “Discussion of ‘Detection of Soil Removal in Metal Cleaning by the Radioactive Tracer Technique’ [ J. C. Harris, R. E. Kamp, and W. H. Yanko (pp. 430–432)]”

Abstract

a decided commercial success, and there may be many other applications such as the one suggested in this paper.The very low pressures recorded in this paper are a tribute to the excellent construction of the apparatus and also to the pumping capacity of the large diffusion pump which was used. A question arises as to whether the results obtained at 0.05 microns are any different than those that would be obtained at 5 or even 50 microns. This point is of importance because the 0.05 mieron pressure would be very difficult to maintain on a commercial scale.The use of a vacuum in distillation has two main purposes: to protect the metal or metals from oxidation and to increase the rate of evaporation. Pidgeon reported that in the ferrosilicon-dolomite process no improvement in yield was noted at two microns as compared with 100-200 microns. St. Clair and Spendlove of the U. S. Bureau of Mines have reported careful determinations on the rate of evaporation of zinc versus residual gas pressures; one series of tests showed no increase in rate below pressures of 100 microns. A second series of tests are not as conclusive; there seems to be some improvement below 100 microns but the data are scattered. P. C. Carman writing in the 1948 Transactions of the Faraday Society states that in the distillation of liquids or the evaporation of solids the following equation gives the relation between rate of evaporation and the residual gas pressure when P is less than r W= Wo(l -P)where W = rate of evaporation, Wo = the maximum rate, P = the pressure above the liquid or solid, and ~ is the saturation vapor pressure of the solid or liquid.Taking Run No. 4 as an example, at 600~ the vapor pressure of magnesium would be close to 880 microns. The distillation rate under a residual gas pressure of 0.05 microns according to the above equation would be 99.9944 per cent of the maximum rate. At a residual gas pressure of 5 microns the measured rate would be 99.44 per cent maximum, and at 50 microns it would be 94.4 per eent maximum.This loss of 5.6 per cent in the evaporation rate resulting from operation at 50 microns rather than 0.0.5 microns is not very serious as it could be compensated for by a temperature increase of 2~ At lower temperatures the difference in evaporating rates between operating pressure of 0.05 and 50 mierons would be greater; at higher temperatures it would be less.R. R. ROGERS AND G. E. VIENS: Dr. Sehleehten's remarks deal largely with the effect of pressure on evaporation rate and yield. Since only one pressure was used in the work which we have reported, our paper does not eontain any conclusions with regard to the effect of pressure. We were concerned particularly with the efficiency with which the alloying metals could be removed from the magnesium, i.e. with the efficiency with whieh the magnesium could be refined. We also wished to determine the lowest temperature at which the process could be operated satisfactorily. Obviously the success of the process would be determined to a considerable extent by these two...

A double label radiotracer approach to detergency studies

“…However, with increasing knowledge of the composition of natural mammalian wax (3) and the publication of experiments which cast some doubts on carbon black as a reliable representative of the organic and inorganic material likely to occur in soils (4,5), there has been a trend toward the use of more sophisticated soils together with a trend toward more accurate methods of analysis for the soil used. Thus Harris et al (5) in 1950 used a carbon-14 tagged amide and hydrocarbon on metal as one of the earliest labeled soils in detergency studies. Ashcraft (4) used carbon-14 labeled tristearin and carbon black in a study of the relative removal of these two soil components from cotton fabric.…”

Cationic Adsorption and Exchange as Shown by Radio-calcium Tracer Studies

“…In a note, Hensley, Long, and Willard (11) described briefly their work on the reaction of radioactive ions in aqueous solutions on glass and metal, surfaces. The applications of the radioactive tracer technique to metal cleaning was recently described by Harris, Kamp, and Yanko (10). In this study an organic compound was labeled with carbon-14 and was then added to the oil used for soiling the test panels.…”