Question

dilute sulphuric acid was added in a test tube containing pieces of iron 2 sulphide and a paper strip dipped in lead acetali solution was brought over the mouth of the test tube which gas will be evolved during the reaction​

Answer 1

Answer:

Materials that contain sulfur can give off gases such as hydrogen sulfide or carbonyl sulfide, which cause silver and copper to tarnish. If possible, such materials should not be placed near objects that contain silver and copper, especially in a closed space like a display case. But what materials should be avoided? Some materials made from animal proteins contain sulfur wool, hair and feathers, for example but others, such as silk, contain almost none (Mills and White 1994). Rubber contains sulfur, but many plastics do not, although plastics with sulfur are being developed and used more extensively, especially since the 1990s (Kultys 2007). Furthermore, elemental sulfur (which cancan also cause silver to tarnish) can turn up in unexpected places (Benson 2012): as an adhesive, in inlays in furniture, as a strengthening material in hollow jewellery or in cement.

This Note describes a test for the presence of sulfur in materials. The test involves heating a small sample of the material in a glass pipette with a piece of moistened lead-acetate test paper. It is a destructive test, but it requires only a small sample, about 10 mg. The test is particularly useful when choosing materials for exhibits and display cases. When possible, the sulfur-containing material should be avoided in display cases that contain silver or copper, but if

the exhibit requires that the material and the metals be placed together, protective measures can be taken (Tétreault 2003).

In the test, a flame is used to heat the pipette until the material under test gives off fumes. Any hydrogen sulfide in the fumes will produce lead sulfide in the test paper and turn the paper black. This is a sensitive test for hydrogen sulfide, so only a small sample is needed to produce detectable levels of hydrogen sulfide, and there is only a small amount of lead in the test paper. (Nevertheless, it is recommended that the test be carried out in a well-ventilated area.)