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发表于 2006-7-12 13:55:51
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来自： 中国
IEC62321 s/ Q* p4 k- w1 V' A; z# v5 n
9.7.2 Boiling-water-extraction procedure
# ~5 k% k' n) z$ M/ h3 Ha) 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
* Q x7 x/ _- }get the total required surface area of (50±5) cm2.; ^7 A; w: s9 J7 @, [+ z' [7 @
b) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally
3 ~7 \$ N! D) D2 A- O! S% jimmerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water/ @4 `/ I; q7 a+ z- \7 C( W% A
continues to boil. Remove the sample(s), and cool the beaker and its content to room( A: l I& H+ I& `# B# u; E
temperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky
' O6 |: N; M! M6 [/ W2 V- jor has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker
) }: L) b; e3 s" W d" u; mAdd 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into$ [' j' w* p* X, |
another dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and
6 `2 [+ `: O# k4 P% P0 X+ }observe the color against the other beaker which serves as the blank. A red color
; l# Q# q; V; Z/ E, i. uindicates the presence of Cr (VI ^! P8 ?, w# T# }' K c6 i2 B* e
c) If the color developed during the test is difficult for the analyst to judge, transfer a portion- b+ p% m) \& e7 W3 U
of the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs3 ]. d4 @) \+ M* m H
absorbance in a colorimetric equipment against the blank.
/ x( b; p* V! \, x3 md) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of3 |% W9 }* W# O7 E9 U
orthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and
6 c4 \3 U* Z0 R7 H3 i$ M- umeasure the absorbance as above.) z1 k+ H8 F# l& H' v. w1 r
e) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in% J: S I, _% Q- V& z
9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs+ a& G8 b# t- d: g! I) y3 B. @
result is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg. D/ W. S' e0 A+ K. O4 Y
with 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
