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发表于 2006-7-12 13:55:51
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来自： 中国
IEC623211 i7 _/ i3 x, X, a0 {
9.7.2 Boiling-water-extraction procedure
' h" K [# z v/ q! \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. N% j6 m) V3 L- W3 j6 q0 l
get the total required surface area of (50±5) cm2.
' W9 D# C6 p9 L# t9 V- pb) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally
" d, s) _- ]4 K; b5 k z2 wimmerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water
) [. I4 j- F3 R4 X) m/ rcontinues to boil. Remove the sample(s), and cool the beaker and its content to room
0 Q+ X7 u/ ^6 m8 z. P, Ztemperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky) f* z1 z" f8 D5 P" g4 \( |( ~
or has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker
5 G& K9 U# X. f/ k3 ]: h- a, FAdd 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into
, r/ r6 z5 d' t0 N2 Z% }! t4 W( y, x- qanother dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and
$ q# o7 o) U6 yobserve the color against the other beaker which serves as the blank. A red color$ i1 ]- o* n' O& L2 S
indicates the presence of Cr (VI
+ G7 C# F% t- ]* R) }; z0 Yc) If the color developed during the test is difficult for the analyst to judge, transfer a portion
4 |. O6 n1 L4 L: p8 Jof the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs) ~- | v, z6 C' d: ^1 D* V; q' h
absorbance in a colorimetric equipment against the blank.
2 ~$ s3 ?$ k) i% m' J0 yd) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of
* r! i% j' p1 W, Aorthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and
: Y; @5 }9 O) o$ h- u' S! Y: {measure the absorbance as above.! j0 v3 M) a# p6 [2 {
e) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in
2 y- P% _6 _4 r. S6 S8 |6 a& l9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs+ q1 _$ [' D/ P/ p4 K1 x" C
result is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg
7 V8 f8 ]0 {- h& P+ Awith 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
