Salicylaldehyde is treated with alkaline hydrogen peroxide and subsequently with dilute `HCl`. The product formed is

When borax is treated with aqueous solution of HCl the product formed is

The compound that gives hydrogen peroxide on treatment with a dilute cold acid is:

How is a dilute solution of hydrogen peroxide concentrated?

Aniline is treated with bromine water and the resulting product is treated with an aqueous soluition of sodium nitrite in presence of dilute HCl. The compound so formed is converted into tetrafluoroborate which is subsequently heated dry. The final product is