salicylic

Further examination indicated the presence of salicylic acid, a gummy material, having the properties of tragacanth and glycerin.

Then add a drop of ferric chlorid solution, and a violet color will be produced if salicylic acid is present.

Formaldehyde, boric acid or salicylic acid may be added to preserve the milk.

A purple or violet coloration proves the presence of salicylic acid, which in turn indicates the presence of saccharin.

This test cannot be used if salicylic acid was used as a preservative in the original product.