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发表于 2006-7-12 13:55:51
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来自： 中国
IEC62321
( j9 t$ f. Y/ L. i$ _9.7.2 Boiling-water-extraction procedure
9 \7 R( A8 Q: u* G G0 `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
/ O' |9 o2 W( b8 ]* lget the total required surface area of (50±5) cm2.
& m I3 a6 S; W- L+ Q7 wb) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally
: A1 k& d- C* |0 }* t. r; simmerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water
6 @! K! O. `, Scontinues to boil. Remove the sample(s), and cool the beaker and its content to room
l' p9 c5 Q1 l5 p% Stemperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky- c3 m0 W. T- m' U( ]) b
or has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker9 G) Y7 [7 l0 x+ ^& x" a
Add 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into. d3 t: z: Q2 H( u# O
another dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and
) F4 d) \: K" f3 Hobserve the color against the other beaker which serves as the blank. A red color
/ ^6 E6 L8 `$ E _% sindicates the presence of Cr (VI0 F6 M4 F! s/ I; I$ p
c) If the color developed during the test is difficult for the analyst to judge, transfer a portion
" \+ p( k) b# L. ]8 O2 G# cof the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs
& X+ A a% N6 K, w4 }4 v( rabsorbance in a colorimetric equipment against the blank.( D1 Z, l; t3 e" `( V& ^( k. [) k' ]
d) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of
; q- O- r7 ^2 U) Z ~2 o) C! aorthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and1 Y5 M# D' X$ u/ U1 @
measure the absorbance as above.
* ?5 Z! b F3 x7 Je) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in
& h6 O! j. L! E9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs9 e; ~* k. C0 [, B" z
result is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg
" `0 p! a+ H% T% D4 }( E# ^with 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
