Common use of Phase 2—Screening test Clause in Contracts

Phase 2—Screening test. (1) Intro- duction and purpose. (i) Phase 2 meas- urements provide approximate solar photolysis rate constants and half-lives of test chemicals in PW and SHW. If the photoreaction rate in SHW is sig- nificantly larger than in PW (factor of > 2X) then the test chemical is subject to indirect photoreaction and Phase 3 is necessary. Phase 2 data are needed for more accurate Phase 3 measure- ments, which require parallel solar ir- radiation of actinometer and test chemical solutions. The actinometer composition is adjusted according to the results of Phase 2 for each chem- ical, to equalize as much as possible photoreaction rate constants of chem- ical in SHW and actinometer. (ii) In Phase 2, sunlight photoreaction rate constants are meas- ured in round tubes containing SHW and then mathematically corrected to a flat water surface geometry. These rate constants are not corrected to clear-sky conditions.