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发表于 2006-7-12 13:55:51
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来自： 中国
IEC62321
- X$ U& u" \. U9.7.2 Boiling-water-extraction procedure
# x6 F: I0 H5 h9 |! f1 |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 to9 \6 x- @4 y5 _7 H0 ~4 W, L
get the total required surface area of (50±5) cm2.$ P5 G! w5 S1 z* C7 K$ ^
b) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally. l O3 {- A* ? q& o7 R) p" E
immerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water0 Z& W8 U. L; j7 S
continues to boil. Remove the sample(s), and cool the beaker and its content to room; I9 Q# k" I- Q" C5 h
temperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky+ M, v0 {* L. u- G" i' D N1 @
or has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker+ w2 o5 f" S8 x/ e5 {
Add 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into) o& n% Z; R7 F3 J% h+ [) Z
another dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and( f, f0 Y s) \' r) q* t6 c
observe the color against the other beaker which serves as the blank. A red color
5 X1 f% T M+ K7 l1 pindicates the presence of Cr (VI( H8 C! d9 v3 t
c) If the color developed during the test is difficult for the analyst to judge, transfer a portion
4 B0 T4 j: e& B# k; cof the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs, Y$ W& w+ L) N, S3 F7 M5 I2 I
absorbance in a colorimetric equipment against the blank.; \( m8 U- Q2 N7 S: F" d
d) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of
* b( ^" q6 x5 iorthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and
3 D. y3 ?: J m n+ |4 b3 n: hmeasure the absorbance as above., o8 {2 z7 m. a
e) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in( Q) z" t. u8 t5 s- B$ q2 P' x
9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs4 c( p/ Q! h9 j& c4 g7 ~6 q
result is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg
6 H+ r0 D) e% X: v! y' X2 mwith 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
