In the estimation of phosphorus in an organic compound,phosphorus is $NOT$ weighed in the form of which of the following substances?

$0.259 \ g$ of an organic compound gives $0.350 \ g$ of $BaSO_4$ upon treatment. Calculate the percentage of sulphur in the compound. (Atomic masses: $Ba = 137, S = 32, O = 16$) (in $\%$)

In an estimation of bromine by Carius method,$1.6 \ g$ of an organic compound gave $1.88 \ g$ of $AgBr$. The mass percentage of bromine in the compound is..........
(Atomic mass,$Ag = 108, Br = 80 \ g \ mol^{-1}$)

In sulphur estimation,$0.157 \ g$ of an organic compound gave $0.4813 \ g$ of barium sulphate. What is the percentage of sulphur in the compound?

Quantitative measurement of nitrogen in an organic compound is done by the method:

In the estimation of nitrogen,$0.3 \ g$ of an organic compound was digested,and the evolved ammonia was passed into $100 \ mL$ of $0.1 \ M \ H_2SO_4$. The excess acid required $20 \ mL$ of $0.5 \ M \ NaOH$ for complete neutralization. What is the organic compound?