The reaction of chloroform with alcoholic $$KOH$$ and p-toluidine forms

The reason for double helical structure of $$DNA$$ is operation of

A red solid is insolvable in water. However it becomes soluble if some $$K{\rm I}$$ is added to water. Heating the red solid in a test tube results in liberation of some violet colored fumes and droplets of a metal appear on the cooler parts of the test tube. The red solid is :

A pressure cooker reduces cooking time for food because