What is adsorption chromatography? Write its types.

$X$ and $Y$ have $R_f$ values of $0.75$ and $0.25$ respectively. In column chromatography,which component is obtained first?

Aniline-water mixture can be separated by

What criterion is followed for the selection of the stationary phase in chromatography?

Fill in the blanks:
$1$. In differential extraction from two layers,the .......... layer is above because .............
$2$. The organic solvent used in differential extraction is .......... in water.
$3$. If an organic compound is ......... soluble in an organic solvent,then the continuous extraction technique is used.
$4$. ........ solution is added to produce the precipitate of halide for the estimation of halogen.

The latest technique for the purification of organic compounds is