Practical investigations
Read our general notes on Risk Assessment
I don't fully understand how I can find the percentage of alcohol in wine using an uncalibrated density bottle. The density bottles at school are small glass flasks about 50ml, and this is not what I was expecting to see.
Igloo writes ...
It’s not as difficult as it seems. First make sure that the bottle is clean and dry, and then weigh it accurately. Next fill it with de-ionised water, place the stopper inside and use a paper tissue to dry away any water which has oozed out. It is important that the bottle is completely dry on the outside. Next reweigh the bottle as accurately as you can, and then, after opening it, use a thermometer to measure the temperature of the liquid. Let’s assume that this is 20°C.
According to a book of data the density of pure water is 0.9982 g cm-3 at 20°C. Next, by subtraction, deduce the mass of water in the bottle, and divide by the density. This will give you the exact volume of the bottle.
Now repeat the procedure, using your distillate, and deduce its mass in the bottle. Together with the known volume you can deduce the density.
Since volumes and densities are greatly influenced by temperature, it is important that you carry out the experiment with the distillate at the same temperature that you used for the de-ionised water.
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: 01 December 2006
