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发表于 2006-7-12 13:55:51
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来自： 中国
IEC62321
. V; u0 ?( a* O8 O& F' K a9.7.2 Boiling-water-extraction procedure
* J: x7 P; V! @" Ra) 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
' x! F! X, g: j+ \% q& eget the total required surface area of (50±5) cm2.
! t2 T( d1 \7 m6 Cb) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally T Q7 ^4 Z; n$ w: [. y% s
immerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water% r+ r' ?6 @0 J" Y: R/ `' I; f
continues to boil. Remove the sample(s), and cool the beaker and its content to room% d8 R/ l$ F5 k9 p2 A
temperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky
' w7 x: H+ _% N+ R4 L( Bor has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker
1 R* y5 I8 T, @! P) f% ?5 ^Add 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into
1 x% j3 V+ D; Manother dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and
6 {" i/ G# @# ~9 ^observe the color against the other beaker which serves as the blank. A red color
1 y# |4 w% {2 Nindicates the presence of Cr (VI
# z5 a, ^" s8 B P! H4 ` ?c) If the color developed during the test is difficult for the analyst to judge, transfer a portion% r8 M0 K( N( h; G3 h
of the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs
3 ?8 l0 V P0 M) l' P: E, W+ |absorbance in a colorimetric equipment against the blank.
% f8 l; R& p; i! Cd) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of$ k2 w! M- @) t
orthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and
! U6 I. B6 ]3 w Umeasure the absorbance as above.
9 g) m8 H: m$ e8 }9 ne) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in, C" }' {( W: X3 O. i
9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs/ W3 J9 j) t7 z5 K7 B: W; ]: w
result is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg
1 r9 p; Z0 ?; m, d# ^9 V0 bwith 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
