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发表于 2006-7-12 13:55:51
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来自： 中国
IEC623219 C/ ]9 K B- [0 t! n3 W1 K
9.7.2 Boiling-water-extraction procedure
9 Q9 P. w3 F0 s$ p2 ?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
; n0 O' V3 G! Y1 w7 tget the total required surface area of (50±5) cm2.
: j9 N: U+ g; Cb) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally
8 ?! q, F) W r" Simmerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water+ g6 x! I; Q9 }6 [ C4 v
continues to boil. Remove the sample(s), and cool the beaker and its content to room
$ b' Y! j% y9 P. m" k4 ^2 j4 V- o3 \; ytemperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky% X$ E: s$ P: [2 u2 g3 N5 P" h
or has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker% V( e9 G" l$ K6 H9 y" W0 J" J# S6 r
Add 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into+ T7 R& H/ R4 K" Y8 K
another dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and
8 ^2 G: d* J- i" \observe the color against the other beaker which serves as the blank. A red color
# X) V8 s- N4 w4 u3 {$ findicates the presence of Cr (VI9 W6 f( S# b) q& K8 ~! \
c) If the color developed during the test is difficult for the analyst to judge, transfer a portion5 E! n( d! b/ z8 o E
of the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs2 m- C( @3 L+ o* T$ V$ ~. \$ }
absorbance in a colorimetric equipment against the blank. Q6 J# J8 ~) r5 w6 t% m
d) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of; S y0 P4 v) e) C1 M: x2 X
orthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and$ A1 J; x$ c3 N o
measure the absorbance as above.& W% ^( P! f" p1 N g/ x% D' v3 R
e) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in7 Y2 l/ b. K2 K0 g- W$ s
9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs
, v0 \% z! |( ?% ^result is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg8 Z9 o& t$ J9 v' q' @# m: o: u
with 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
