Practice Assignment 08
A better bit of butter?
There is a debate at the moment, that there is too much salt in our diet. Salt is added to butter to improve its taste and to extend its shelf life. But how much salt is there in the butter we eat? Your task is to find out. Working in pairs, determine the percentage of salt in a sample of butter. Then compare with other pairs to see how much salt there is in the different varieties of butters available.
What you have to do
-
Get a copy of the Standard Procedure
SP 0008:2005 Determining the salt content of butter. Read it carefully. - Collect all the equipment and reagents that you need. Remember nitric acid is corrosive, especially when hot. Always wear eye protection.
- Divide your butter sample (approximately 2 g) into two halves.
- Carefully follow the procedure on the sheet
SP 0008:2005, including repeating the procedure with the second portion. - Calculate the percentage of salt for each of your results, and the mean of your two results.
- Check the accuracy of your analysis by looking at the ingredients list on the label of your butter.
- Compare your results with those from different butter samples analysed by other students.
Some hints
- Always swirl your flask when titrating. If you are right-handed, swirl with your right hand and operate the burette tap with your left. If left-handed, do the reverse.
- Remember to add the potassium thiocyanate slowly, drop by drop, towards the end point.
- Don’t forget to carry out a blank test.
Some questions
Write up your results in your laboratory notebook.
- Why is salt added to butter?
- When is salt added in the process of butter making?
- Why did you add concentrated nitric acid?
- Why did you add silver nitrate solution?
- How could you alter your procedure to improve your results?
- Do you prefer salted or unsalted butter? (Give a reason)