of yttrium and cesium are concentrated in the plants. In addition, experiments have been completed on a fifth element rutheniua. The absorption of ruthenius from nutrient solution by Red Kidney Bean plants was studied az a fimetion of the ruthenium concen- tration and of the acidity of the solutdon (pH). Observations show thet the uptake of ruthenium ie dependent upon, but not strictly proportional te, the concentration of ruthenium added to the nutrient calture, and the uptake efficiency increases es the acidity increases. = The Project developed ui ingroved mathcd fer heemtization ef pestiole cise an airborne dust. The method has direct application to industrial hygiene Problems involving such ssasuremmts and should facilitate their solution. Heretofore, the usual msthods of sempling airborne dust have required snalysis of particle sise by time-consuming and tedious microscopic observations. The new technique involves collection on membrane filters vhich are then dissolved in an organic solvent. The resultant dust suspension is then analysed turbidinetrically (in terms of light falling on a photocell after passing through the suspension). ‘the concentration of the dust in the sample dees not affect the results of the particle-size determination, The turbidimetric msthod gives good accuracy and reproductibility of resulte, Radiation Instruments Progran Fourth Tripartite Conference on Instrumentation. Gaaaass Preliminary arrangements made the Canada, and the United Kingdom to hold a tripartite conference on ’ instrumentation at Harwell, Sngland, in May 195, On October 15 at Chalk River, Ontario a meeting will be held by the planning comittee of representatives from AEC, Chalk River, ood Harwell to establish an agenda for the confarunce, Items suggeated in preliminary discussions for the spring confer~ ence are pile instrumentation, chemical plant instrumentation, tran- iteas on instrumentationwithin the general areas of Health and Safety (Area 2), Isotopes (Area 3), Extraction Chemistry (Area 7), and Low- Fower Reactors (Area 9), SEY mete es | DOS ARCHIVES