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发表于 2006-7-12 13:55:51
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来自： 中国
IEC62321+ d# e* d! Y' w- e
9.7.2 Boiling-water-extraction procedure4 o- |+ |/ ^; r. l. ?! X- n; E' ?
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& G4 y$ }' K4 Xget the total required surface area of (50±5) cm2.
( c) L. M3 u% H Z6 Y7 ]b) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally$ t; z q- m; [) D! ~3 F: X7 ~
immerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water* W" n3 A+ B6 I6 `2 r' r
continues to boil. Remove the sample(s), and cool the beaker and its content to room9 B2 `3 w& h6 A/ ^7 I) s( d
temperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky
9 C6 r; b' m! \6 n! @9 lor has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker2 D( w' t7 R5 l" t$ ?2 M
Add 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into) a) F# \5 w" u8 [4 @
another dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and/ p- M8 C: t5 S5 X
observe the color against the other beaker which serves as the blank. A red color
b: y' F, G' J4 m) zindicates the presence of Cr (VI
, i, }+ }5 g- |0 x- E4 Y7 [8 Tc) If the color developed during the test is difficult for the analyst to judge, transfer a portion' s: [" T0 j- {( r: K0 u
of the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs; c' \4 N5 y n( u9 |5 {9 Z' q( p: G; h
absorbance in a colorimetric equipment against the blank., f' k4 ^# }+ x
d) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of
+ y5 p$ G- \2 _* G' K7 e/ Oorthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and) @8 B- a" [- Y8 w# S9 ]
measure the absorbance as above.
: ?& E. P5 r" a9 v7 b0 A* Ie) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in1 B" A0 }4 t/ Q$ b& a. O
9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs
/ L$ K* m; [7 [+ v' o% iresult is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg# I- n1 [* S( p( q, @
with 50cm2 sample surface area used. |
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发表于 2006-7-11 09:49:34
