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发表于 2006-7-12 13:55:51
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来自： 中国
IEC62321
! c* ^4 T8 p: }% R2 u% D' o" f9.7.2 Boiling-water-extraction procedure3 |) ]0 _1 O/ j5 ?, G6 Y& o) [$ X
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
: x0 ^# O# R4 W( A9 _get the total required surface area of (50±5) cm2.
9 p* K! L9 ^. g- xb) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally
: T3 m1 z7 t$ Nimmerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water9 b. S' Y7 I5 E. ^
continues to boil. Remove the sample(s), and cool the beaker and its content to room
2 I! c: H2 Y$ ^* F, }9 `temperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky8 M1 d5 C1 t3 K: o
or has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker
0 K* o$ ]( w' O gAdd 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into
S- l6 e0 w$ x7 S8 V' C, ^another dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and
" i( O9 @- U$ y5 L9 q1 fobserve the color against the other beaker which serves as the blank. A red color2 f0 X* s" f! D5 W0 Q2 Y/ {
indicates the presence of Cr (VI: ]8 t2 ~% H* }0 W
c) If the color developed during the test is difficult for the analyst to judge, transfer a portion3 V; g( [$ H% B+ |' U2 f
of the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs
2 m2 Q! A. A9 |$ D: A" uabsorbance in a colorimetric equipment against the blank.
' \$ { [" y/ E* E( i2 Q; ]3 w5 Ud) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of" h1 F) [& t8 k; R+ \6 ?7 W/ _
orthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and0 G$ S( S% e' f6 V
measure the absorbance as above.5 F' q7 J4 s* Z6 d
e) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in
* `+ U# d [( P! G- r9 u( J* ]9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs
, @$ Y7 s p2 o! U/ Fresult is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg6 f8 S0 ^6 t/ C4 m. p, K" A5 ^6 x% F
with 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
