Qualitative Tests on Silver Compounds

Cool and allow to stand for complete precipitation. Filter the precipitate under suction. Wash on the filter with three 5 cm 2 M sulphuric acid and then with five 5 cm water at 70 C. Dry at 110 C and weigh. Calculate the percentage yield. 

The complex can be analysed by adding a slight excess iron(Il) chloride solution in HCl. This will be oxidised to iron(lll) chloride and copperflll) will be reduced to copper(II) chloride. Since the two chlorides absorb at different parts of the spectrum, they can be determined spectrophotometrically. 

Weigh out accurately about 0.20 g of your preparation into a Buchner flask, with a bung carrying a separating funnel. Prepare 0.05 M iron(ll) chloride in 1 M HCl and place immediately in the funnel. Apply suction to the flask, and allow about 20 cm of the solution to be added to the solid. Ensure that the solid has dissolved and that maximum colour has developed. Transfer the contents of the flask quantitatively to a measuring flask and make up to 1000 cm using 1 M HCl. Measure the absorbance in a 10 mm stoppered or vacuum cell at the wavelengths chosen above. Calculate the % Cu in your preparation and hence work out its % purity. 

The majority of silver salts are insoluble and generally precipitate as white solids. Among the few soluble salts, the most important are the nitrate, the fluoride and the oxochloro-compounds. In the tests for anions in earlier chapters 3-8, tests with silver nitrate were mentioned. The following summarises these tests. To a neutral solution of each of the following salts, add silver nitrate solution dropwise and shake to check the possibility of solubility in excess. Test the solubility of any precipitate separately in dilute or cone, ammonia or in dilute nitric acid. Use sodium or potassium salts of the anions  

To a drop of the silver salt solution on a watch glass add a drop of potassium chromate solution. 

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