Document 0JYL5K8Dp8djOxJjO1gKqNgVV

38-- Industrial Toxicology pH II Ih + 1196 TABLE 38-E THRESHOLD LIMIT VALUES FOR CHEMICAL SUBSTANCES IN WORKROOM AIR, 1973 (Continued) brated, in the laboratory, for re sponse to this specific quantitative and qualitative air-vapor mixture, and also to fractional concentra tions of this mixture, e g, 1/2 the TLV, 1/10 the TLV, 2 X the TLV, 10 X the TLV, etc ) TLV of mixture = f. TLV. u TLVs +' u TLV. + _L_ TLV. Example No 1 Liquid solvent contains (by weight) 50% heptane (TLV = 2000 mg/m3) 30% methylene chloride (TLV = 1740 mg/m3) 20% perchloroethylene (TLV = 670 mg/m3) TLV of mixture = ,]t ,02 2000 + 1740 + 670 11 0 00025 + 00017 + 0003 = 0 00072 = 1390 mg/m* Of this mucture 50% or 695 mg/m3 is hep tane, 30% or 417 mg/m3 is methylene chloride and 20% or 278 mg/m3 is perchloroethylene These values can be converted to ppm as follows Heptane2000 mg/m' = 500 ppm 1 mg/m3 = 0 25 ppm 695 mg/m3 = 174 ppm Methylene chloride1740 mg/m3 = 500 ppm 1 mg/m3 = 0 287 ppm 417 mg/m3 -- 119 ppm Perchloroethylene-- 670 mg/m3 = 100 ppm 1 mg/m3 = 015 ppm 278 mg/m3 = 42 ppm The TLV of this mixture = 174 + 119 + 42 = 335 ppm 1A c Independent effects Air contains 0 15 mg/m3 of lead (TLV, 0 15) and 07 mg/m3 of sul furic acid (TLV, 1) 015 0 15 = 1. ^-07 Threshold limit is not exceeded IB a General exact solution for mixtures of N components with additive effects and different vapor pressures U) c, , C, . t; + t,+ . c,, . (2) Ci + Cj + (2 1) Ci , C, . Y + ijr *4" + o 9 II + - i1 By the Law of Partial Pressures, (3) Ci -- api And by Raoult'ia Law, (4) p, = Fipi Combine (3) and (4) to obtain (5) C, = aF.p," Combining (1), (2,1) and (5), we ob tain (6) Fipi ( FiPpi' | F,,p,, T FiPi , F,pi T, t T, FDp0 and solving for T, (6 1) T FiPi 4- Fpi 4-____ + Fop.' Sel* + ^ + T, ' Ti ' F.p,, (6 2) T 2>.' EFiP!*T, T - Threshold Limit Value in ppm C = Vapor concentration in ppm p = Vapor pressure of component in solution p= Vapor pressure of pure compo nent F = Mol fraction of component in solution a = A constant of proportionality Subscripts 1,2, n relate die above quantities to components 1,2, n, respectively