Practical investigations

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I am doing the wine investigatiom and I don't really understand how I'll use the colorimeter on ethanol solutions with silver nitrate, potassium dichromate and sulphuric acid

Igloo says
The oxidation of ethanol with acidified dichromate ions is a relatively slow process, but is known to be catalysed by silver ions, so that a fairly rapid reaction takes place without the need to apply heat.
 
The colour change during the process is from orange to green, and provided that the reaction is carried out in dilute solution, a colorimeter (fitted with a suitable filter, of course) will enable you to follow the reaction quite effectively.
 
To choose an appropriate filter you will need to experiment with a range of different ones, seeing which of them gives the greatest range of transmittance readings.
 
Once the filter has been chosen you will need to standardise the colorimeter using solutions of known concentration (either Cr₂O₇^2- or Cr³⁺, depending on the colour transmitted by the filter), before you start to carry out experiments on the wine itself.
 
Always carry out a risk assessment and check with your teacher before starting any practical work.

Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website. For further guidance see our tutorial on Risk Assessment.

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updated: 20 January 2006