State whether the following statements are True or False:
$(i)$ The estimation of sulphur is detected by the weight of $BaSO_4$.
$(ii)$ $BaCl_2$ is added in the estimation of sulphur.
$(iii)$ The Carius tube is used in the estimation of sulphur.
$(iv)$ The magnesium mixture is added in the estimation of sulphur.

(A) $(i) - \text{True}, (ii) - \text{True}, (iii) - \text{True}, (iv) - \text{False}$.
Explanation:
$(i)$ In the Carius method,sulphur is oxidized to $H_2SO_4$,which is then precipitated as $BaSO_4$. The weight of $BaSO_4$ is used to calculate the percentage of sulphur.
$(ii)$ $BaCl_2$ is added to the solution to precipitate sulphate ions as $BaSO_4$.
$(iii)$ $A$ Carius tube is a sealed glass tube used for the digestion of organic compounds with fuming nitric acid.
$(iv)$ The magnesium mixture is used for the estimation of phosphorus,not sulphur.