Chemistry Reference
In-Depth Information
98
0.96
2.4
-
-
143
1.0
2.8
4.1
7.9
197
1.2
2.1
5.5
8.8
394
1.2
2.6
4.9
8.7
591
1.5
2.4
5.0
8.9
985
1.1
3.6
5.9
10.6
1477
1.1
3.3
6.2
10.6
1804
1.2
4.5
6.0
11.7
2299
1.4
4.0
5.4
10.8
2803
1.2
3.7
5.2
10.1
3303
1.5
3.4
-
-
3801
1.0
3.3
5.3
9.6
4050
1.1
3.7
5.8
10.6
Av.
1.2
3.1
5.2
9.5
Max.
1.5
4.5
6.2
11.7
Min.
0.96
2.0
4.1
7.9
a
Inorganic
Source: Reproduced with permission from Elsevier Science [38]
octylamine. Chromium(III) remained almost quantitatively in the aqueous phase in the
concentration range 10
−9
-10
−6
M, whether or not iron or bismuth was present, However,
as about 95% of chromium(VI) was extracted by the same method, samples which may
contain chromium(VI) should be treated with ascorbic acid before extraction so as to
reduce chromium(VI) to chromium(III).
When the residue obtained by the evaporation of the aqueous phase after the extraction
was dissolved in 0.1M nitric acid and the resulting solution was used for electrothermal
atomic absorption spectrometry, a negative interference, which was seemingly due to
residual organic matter, was observed. This interference was successfully removed by
digesting the residue on a hot plate with 1mL concentrated hydrochloric acid and 3mL of
concentrated nitric acid. This process had the advantage that the interference of chloride
in the atomic absorption spectrometry, was eliminated during the heating with nitric acid.
Table 3.3 shows examples of the vertical distribution of each chromium species in the
Japan Sea and the Pacific Ocean samples which were collected during the summer of
1979.
For comparison, some of the results reported by other workers for chromium
concentrations in seawater are listed in Table 3.4. In most of these methods, co-
precipitation with hydrated iron(III) oxide was used to separate chromium(III) from
chromium(VI) and the chromium(VI) concentration was subsequently determined by
suitable reduction of chromium(VI) to chromium(III) before a further co-precipitation. In
Search WWH ::
Custom Search