SECTION CONTENTS
ii Table of contents
1.i Why is chromium so important?
1.ii Complex theory
fig. 1 Complex form by model
fig. 2 Complex form by X-ray diffraction method
1.iii Final oxidation state after complexation
1.iv Methods of detection
1.vi Complex colour: d - d shift or electron transfer
1.vii The original practical.
Re-print of Journal of Chemical Education, Vol.71 1994
1.viii Changes to the published method
Table 1 - Formulation of interfering ion solutions with Cr(VI)
2.ii H2SO4 0.18mol dm-3 & 3mol dm-3
2.iii 1,5 - Diphenyl carbazide.
2.iv l-Ascorbic acid
3.i Re-written practical
Table 2 - Chromium(VI)-DiPC and acid standards
Equation 1 - Conversion of absorbance from transmission
Table 3 - Formulation of interfering ion solutions with Cr(VI)
4 RESULTS
4.i The solutions
4.ii Calibration curve from standards
4.iii Water samples - collection points
4.iv Preparation of water samples
4.v Results from Cr(VI) solution used.
Table 4a - Calibration curve, week 1
Table 4b - Calibration curve, week 2
Table 4c - Calibration curve, week 3
4.vi Results from interfering ions
Table 5 - Interference from other ions
4.vii Results from water samples
Table 6 - Water sample absorbance values
4.viii Results from reduction by ascorbic acid
Table 7 - Reduction by ascorbic acid
4.ix Graphs
Graph 1 - Week 1 calibration curve
Graph 2 - Week 2 calibration curve
Graph 3 - Week 3 calibration curve
APPENDICES
iii Bibliography
v. CHEMICAL DATA HAZARD SHEETS
vi. Thanks
vii. Technology used.