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发表于 2006-7-12 13:55:51
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来自： 中国
IEC62321
5 k" l) n: }1 Z X9.7.2 Boiling-water-extraction procedure* g: y$ @' t1 C
a) The sample to be tested shall have a surface area of (50±5) cm2. For small parts, such asfasteners, or samples with irregular surface shapes, use a suitable number of samples to3 L& {% _/ H; Y( x
get the total required surface area of (50±5) cm2.& X" r+ j% k6 k0 [) w' i+ I
b) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally& ~& H8 o, @6 D: i9 }
immerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water2 c* n, Z% u' N5 R: U! |5 G4 H
continues to boil. Remove the sample(s), and cool the beaker and its content to room, k$ e8 {: i& H" G# } r) _
temperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky7 r& _- c, ]1 S3 T0 k' m9 t
or has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker" Q) A9 S* W% _& R/ a
Add 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into
8 @, @* y7 Z& [0 O3 u1 J# Sanother dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and! [% K4 z/ `* J- W
observe the color against the other beaker which serves as the blank. A red color
3 L# i% r' Y6 Mindicates the presence of Cr (VI
2 k, i* K" A7 x a/ H, C9 n. ~c) If the color developed during the test is difficult for the analyst to judge, transfer a portion
8 w* o( ], Q$ ]% p, V% ~* Lof the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs
1 `/ n- \- I5 Q& S! T8 m9 `6 x: nabsorbance in a colorimetric equipment against the blank.& y8 G1 R& n7 L
d) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of* ]& N5 o3 ~+ i* s: Q- v
orthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and
+ n' J/ q# Z, p o0 pmeasure the absorbance as above.
1 l% Z# r& f$ H. we) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in
! M+ ]: ^3 @% U; j9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs" P1 F$ K+ s q; g
result is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg
( C5 t5 O1 B f+ ~with 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
