All of the following pages have been taken from the BDH Data Hazard Sheets. They have been reproduced by kind permission.
CHEMICALS USED : Sulphuric acid (18, 0.18 and 3 mol dm-3), l-Ascorbic acid, Potassium chromate (III), Potassium chromate (VI), Propanone, 1,5 Diphenylcarbazide (DiPC), Mercury (II) chloride, Cobalt (II) sulphate, Iron (III) chloride, Ammonium iron (II) sulphate, Barium (II) chloride.
ASSOCIATED RISKS : The higher concentration sulphuric acid (3 and 18mol dm-3) will both cause damage to the skin if in contact. Should the acid be splashed on the skin, it must be wiped off with a dry towel first followed by washing with running water for five minutes. In extreme circumstances, medical assistance should be sought.
SULPHURIC ACID If the acid (any concentration) is splashed into the eyes, the eye must be washed in running water for at least 10 minutes and medical attention sought IMMEDIATELY.
All spillages should first be neutralised with sodium carbonate powder and then wiped up with a damp cloth.
PROPANONE Propanone is highly flammable and should be kept from all sources of ignition (including static). The liquid is volatile and the resulting vapour is a mild anaesthetic. Prolonged exposure may result in giddiness, nausea and collapse (extreme!). The liquid must also not come into contact with the skin as it is a de-greasing agent and may cause sensitisation to occur. Should this happen, the skin affected must be cleaned with soap and water. All solutions must only be used in a fume cupboard.
Disposal of solutions containing propanone should be in the correct waste organic solvents bottle and NOT down the sink.
METAL IONS All of the metal ion solutions are in concentrations of 1.27mg dm-3. This will mean that they are all well within the limits set down (OES maximum TWA exposures). With the exception of the Cr(VI) and Hg(II) solutions, the metal ions at the concentration given above, may be disposed of down the sink without any due cause for alarm. The Cr(VI) and Hg(II) should be greatly diluted when being run to waste.
Due to the low concentrations, any skin contact should just be wiped off with a damp cloth.
1,5 DiPC This substance is light sensitive and is liable to deteriorate if kept in the light. It is only slightly soluble in non-polar solvents and in this practical, it is in a propanone solution.
The solid poses very little hazard to health, the major hazard comes from the carrier solvent (details on other side).
ASCORBIC ACID This poses very little risk in the concentration used for this experiment. All spills should be cleaned with water and run to waste.
OTHER RISKS : The only other significant risk comes from the water solutions used. These have (in four cases) been collected from natural ponds, streams or sewer outlets. As these have not been treated in any way, they must all be treated the same for this assessment.
I have assumed that they will all contain waste organic material and quite a number of undesirable 'bugs'. In addition to this, they may contain trace metal elements (such as iron, mercury, bismuth, chromium (III) and (VI) etc.). It is not my intention to determine if any of these are in the water (except Cr(VI)). The waters will all be filtered and treated with conc. Sulphuric acid (see other side for statement on acid) to dispose of any organic matter in the water. These will have posed the larger risk to health.
The metal ions should now not pose a problem (being in such low concentrations).
Cr(VI)/DiPC complex This complex will only cause a problem as the Diphenylcarbazide (DiPC) is in propanone. At the concentrations used, the complex will contain at the very most 1.27ppm of Cr(VI). The risk from the deterioration of Cr(VI) to the reduction product of Cr(V) will, at this concentration, not give any cause for concern (the maximum limit is far above this value).
All solutions used should be disposed of in a waste organic solvents bottle.
GENERAL Gloves, eye shields and a lab coat must be used when handling any of the materials listed above.
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