Equilibration time. The equilibra- tion time will depend upon the length of time needed for the parent chemical to attain an equilibrium distribution between the solid phase and the aque- ous solution phase. The equilibration time shall be determined by the fol- lowing procedure:
Equilibration time. T h e eq u ilib r a- t io n t i m e will depe n d u po n t h e le n g t h of t i m e n eeded fo r t h e p a r e n t c h e m ic a l t o a tt a i n a n eq u ilib r i u m dis t r ib u t io n be t wee n t h e solid p h a se a n d t h e a q u e- o u s sol u t io n p h a se. T h e eq u ilib r a t io n t i m e s h a ll be de t e r m i n ed b y t h e fol- lowi n g p r oced ur e:
Equilibration time. T h e eq u ilib r a- t io n t i m e will depe n d u po n t h e le n g t h of t i m e n eeded fo r t h e p a r e n t c h e m ic a l t o a tt a i n a n eq u ilib r i u m dis t r ib u t io n be t wee n t h e solid p h a se a n d t h e a q u e- o u s sol u t io n p h a se. T h e eq u ilib r a t io n t i m e s h a ll be de t e r m i n ed b y t h e fol- lowi n g p r oced ur e:
( A) E q u ilib r a t e o n e sol u t io n co n- t a i n i n g a k n ow n co n ce n t r a t io n of t h e t es t c h e m ic a l wi t h t h e sedi m e n t o r soil i n a solid/sol u t io n r a t io eq u a l t o o r g r e a t e r t h a n 1⁄10 a n d p r efe r a bl y eq u a l t o o r g r e a t e r t h a n 1⁄5. I t i s i m po r t a n t t h a t t h e co n ce n t r a t io n of t h e t es t c h e m ic a l i n t h e eq u ilib r a t i n g sol u t io n (1) does n o t exceed o n e- h a lf of i t s sol u bili t y a n d
(2) s h o u ld be 10 pp m o r less a t t h e e n d of t h e eq u ilib r a t io n pe r iod.
