Finding the Percentage of Copper in a Brass Alloy

Finding the percentage of copper in a Brass alloy

Aim: Brass is an alloy of copper and zinc. This alloy has many uses ranging from coinage to non- ferrous fittings on ships. Many domestic taps use brass where contact with water occurs.

I have been provided with a sample of brass which is bout 150 years old and I have been asked to quantitatively analyse it, using colorimetry, to find the percentage of copper present.

Method of analysis

1. Using a fume cupboard, I firstly placed 30cm3 of distilled water into a 250cm3 conical flask then slowly adding 15cm3 of concentrated nitric acid. I stirred it using a glass rod.

2. I then weighed out accurately 1.5g of the antique brass filings subsequently adding it to the diluted nitric acid in the fume cupboard.

3. Leaving the mixture for some minutes until all the brass was dissolved and allowing poisonous nitrogen dioxide gas to evaporate.

4. Afterwards I removed the solution from the flask and quantitatively added it to some distilled water in a 250cm3 volumetric flask making sure it went up to the mark using distilled water and mixing well.

5. I was then provided with 100cm3 of copper sulphate solution. This solution contained 1.6g of copper in a 250cm3 of solution. The next step was to dilute the copper sulphate solution with distilled water to make all six solutions on the table I was given.

6. I switched on the colorimeter and allowed it to warm up for five minutes, I then placed a 700nm filter in the colorimeter and zeroed the instrument using a cuvette filled with distilled water.

7. I filled six cuvettes with the solution labelling them A to F this was from the more concentred to the less concentred solution. I then found the absorption value for each of them.

8. I then filled another cuvette with the brass solution I had made earlier and measured the absorption of the solution.

chemical Molecular formula Hazard Hazard symbol Prevention

Potassium permanganate KMno4 Eye: can cause severe eye irritation and possible burn may.

Skin: may harmful if absorbed through the skin cause skin irritation and possible burns.

Inhalation: causes respiratory tract, irritation with possible burns and can cause headache.

Eyes: wear appropriate protective goggle.

Skin: wear appropriate gloves to prevent skin exposure.

Clothing: wear appropriate protective clothing to prevent skin exposure (lab coat).

Wash hands: if contact with the chemical.

Nitric acid HNo3 Eye: can cause severe eye irritation and possible burn may.

Skin: may harmful if absorbed through the skin cause skin irritation and possible burns.

Inhalation: causes respiratory tract, irritation with possible burns and can cause headache.

Eyes: wear appropriate protective goggle.

Skin: wear appropriate gloves to prevent skin exposure.

Clothing: wear appropriate protective clothing to prevent skin exposure (lab coat).

Wash hands: if contact with the chemical.

Copper sulphate CUSO4

5H2o Eye: can cause severe eye irritation and possible burn may.

Skin: may harmful if absorbed through the skin cause skin