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发表于 2006-7-12 13:55:51
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来自： 中国
IEC62321
7 z d/ b0 |' v! ?9.7.2 Boiling-water-extraction procedure( ^) i8 Q& h. o4 {
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 to: O6 }& {) R6 Q/ P2 ]) b" F4 ?, r9 ^% B
get the total required surface area of (50±5) cm2.
4 n$ N8 b9 y* C2 z9 f7 ^b) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally
3 y2 u# |* | Q. A: Y0 ?* ?immerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water8 Q% C5 Q4 f5 Z* n3 h6 k' U
continues to boil. Remove the sample(s), and cool the beaker and its content to room
, m9 i p9 Q6 a; atemperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky
9 n4 N: [; U. {3 G$ r- U/ ^4 Dor has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker5 l4 } I' z! {5 d% K2 u# @' `+ |
Add 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into
- c' R7 f% k3 z+ `% ~+ @6 ?0 R, Eanother dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and6 T, W. v2 f6 ]2 h$ Y5 L+ O
observe the color against the other beaker which serves as the blank. A red color8 T- i" h" L* [' M) U
indicates the presence of Cr (VI! f2 B" X2 E* Q1 w. V6 {% V# u
c) If the color developed during the test is difficult for the analyst to judge, transfer a portion- a2 o! {! a( d
of the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs
: ]& F S, K9 |4 Yabsorbance in a colorimetric equipment against the blank.
" g( D- U+ W3 `( K3 O2 ~6 r6 t Zd) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of
* }( P; Q! s: ? A* |) zorthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and
% `9 S% v% v9 tmeasure the absorbance as above.
9 L" X' f Q# @1 h' V# y! Je) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in
6 u3 }& E$ H& ^5 ~/ V' K6 q |5 b6 f8 ^9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs
8 p* m$ {) }( l5 t, ]result is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg
& [& H# V) n' Wwith 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
