Question

In the distillation of petroleum spirit, what property is exploited to separate the different components of the spirit?

Answer 1

`"The differential volatility of its components............?"`

Explanation:

Typically crude oil is distilled on a fractionating tower, and the volatile components are separated by boiling point; and the boiling points often corresponds (roughly) to chain length.

When we use petroleum ether in the laboratory, typically, we use `40` `""^@C-60` `""^@C` boiling point pet ether, `60` `""^@C-80` `""^@C` boiling point pet ether, `100` `""^@C-120` `""^@C` boiling point pet ether. The lower boiling pet ethers are the isomeric `C4-C5` alkanes and olefins, `60` `""^@C-80` `""^@C` boiling point pet ethers are the isomeric `C6-C7` alkanes and olefins.

An inorganic chemist will often take petroleum ethers from a supplier, and treat this with acidified, aqueous `KMnO_4` over an extended period (so as to oxidize any olefinic component). After 24-48 hours, the pet ether would be separated, carefully washed with fresh water, and then VERY carefully dried. The petroleum ether would then be used as `"olefin-free petroleum ether"` for the synthesis of certain metal complexes.