|
|
楼主 |
发表于 2006-7-12 13:55:51
|
显示全部楼层
来自： 中国
IEC623211 p8 l, Z0 t8 n, U' ^$ W9 C% P
9.7.2 Boiling-water-extraction procedure
$ k6 A+ F* _, L5 [2 c' p g6 oa) 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
8 ~, `( z; I8 ^5 Q4 S8 n6 [7 y- |get the total required surface area of (50±5) cm2./ H/ ~9 C% j, W* j: o( D
b) Heat in a suitable beaker (with volume graduation) 50ml of DI water to boiling and totally
: f# K; Q: {8 w& _5 zimmerse the sample(s) inside the beaker. Leach for exactly 5 minutes while the water) ]( K8 O8 E2 Y; I/ e6 ]4 `! N! W
continues to boil. Remove the sample(s), and cool the beaker and its content to room
, ^" \& Y$ O4 c7 M& _. }1 o, \5 itemperature. Fill up with DI water to 50ml if some water evaporated. If the solution is milky. Z! J8 N0 g; v1 I3 Q
or has a precipitate, filter it through a paper filter (0.45μm pore size) into a dry beaker! l+ T* b( t# ~9 u: x
Add 1ml of orthophosphoric acid solution (9.5 e) and mix well. Pour half the solution into2 z# V" @+ W0 Y: l
another dry beaker. Add 1ml test solution (9.7.1. a) to one of the two beakers, mix and
' m; q1 T i8 Q" c: ^observe the color against the other beaker which serves as the blank. A red color/ O q% R# t) o6 ~, f
indicates the presence of Cr (VI
' M( \6 I, @8 \0 Z' v0 M3 F' ]5 s1 yc) If the color developed during the test is difficult for the analyst to judge, transfer a portion; O+ ~7 b, I9 Y0 g
of the solution to an absorption cell. After a reaction time of 2 minutes, measure thebbs
( D6 J, W& M: {+ F- A6 U# |absorbance in a colorimetric equipment against the blank.( w1 V/ l: R2 N9 S5 C r
d) Dilute 1ml of 1mg/kg K2Cr2O7 standard solution (9.5 b) to 50ml with DI water. Add 1ml of
, _& N) `+ {* d2 porthophosphoric acid solution (9.5 e) and mix well. Add 2ml test solution (9.7.1 a), mix and
1 k# x J4 ?; Q9 d0 _+ bmeasure the absorbance as above.
. u4 Z1 C! m9 a& T. E$ L- be) If the absorbance value obtained in 9.7.2 c) is equal to, or greater than that obtained in
, C y; |( a, C, U) w9.7.2 d), the sample is considered to have a hexavalent chromium coating. If not, the testbbs
. \8 S% O# A6 ^result is negative. The detection limit for the boiling-water-extraction test is 0.02mg/kg
5 l) g A( Z, |' n8 ]$ vwith 50cm2 sample surface area used. |
|
[复制链接]
发表于 2006-7-11 09:49:34
