Chemistry Reference
In-Depth Information
1.5×10
−2
mol L
−1
Reduction of SO
4
to sulphite by HCl-
acetic anhydric and
spectrophotometric determin-ation of
sulphide as Fe(III) phenanthroline
complex
510 -
[723]
Source: Own files
The automatic equipment consists of a control unit connected to the titrator. This contains
a photocell, the resistance of which is 2 and 250k, respectively, in the directions forward-
backward. The cell is connected via a switch either to the mirror galvanometer
(Ri=420MΩ, current for maximum scale deflection=0.57µA) (manual titration), or to a
follower (Ri=400MΩ) with an accompanying linear amplifier in the control unit
(automatic titration). The follower and the linear amplifier are built from operational
amplifiers.
The current from the photocell gives a voltage drop over the input of the follower
which is amplified in the subsequent step. The amplified signal may be somewhat
unstable and an RC-step is therefore used as an attenuation circuit.
Table 2.48
Results of analyses of pure sulphate solutions
Sulphate concn. given,
µmol L
−1
Sulphate concn. found
Stand, dev
µmol L
−1
% rel
1.0
1.3
0.7
54
2.0
2.3
0.7
30
3.0
3.2
0.5
16
5.0
4.5
0.4
9
7.5
7.4
0.4
5
10.0
9.8
0.4
4
20.0
19.2
0.6
3
40.0
39.8
0.9
2.3
50.0
50.0
1.0
2.0
60.0
60.4
1.4
2.3
a
Calculated from six determinations
Source: Reproduced with permission from Springer Verlag [722]
Ion exchange with barium iodate achieved by passing the sample through a column of
homologously precipitated barium iodate, leads to the following reaction [714]
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