Question

why is testing box used in preparation of sulphuric acid ​

Answer 1

Sulfur dioxide has many impurities such as vapours, dust particles and arsenous oxide. ... In this process, the gas is washed with water, and dried by sulfuric acid. In the dusting tower, the sulfur dioxide is exposed to a steam which removes the dust particles.

Answer 2

The product is known as fuming sulphuric acid or oleum. This can then be reacted safely with water to produce concentrated sulphuric acid - twice as much as you originally used to make the fuming sulphuric acid. The mixture of sulphur dioxide and oxygen going into the reactor is in equal proportions by volume.