Abstract
The reagent and sample volumes for the Marcali method for the determination of toluenediisocyanate (TDI) in air have been modified to accommodate the 1961 revision of the Threshold Limit Value (TLV = 0.02 ppm). A lightweight, easily portable assembly which includes the “Uni-Jet” Constant Rate Air Sampler, reagents, and a compact set of permanent liquid color standards for the range 0.01 to 0.08 ppm was developed for field surveys. A similar unit, modified to provide permanent liquid color standards in a visual comparator adapted to the required 10-cm light path, was completed for the Ranta determination of combined TDI and TDI urea. A satisfactory laboratory test, based on the Marcali method for TDI, has been developed for traces of MDI (methylene-bis-(4-phenylisocyanate)) in air. The method easily detects 0.01 ppm MDI in a one cubic foot air sample.