Shenstone, two classes are to be recognized: (I) Nataloins, which yield picric and oxalic acids with nitric acid, and do not give a red coloration with nitric acid; and (2) Barbaloins, which yield aloetic acid, C7H2N205, chrysammic acid, C 7 H 2 N 2 0 6, picric and oxalic acids with nitric acid, being reddened by this reagent.
When ignited, picric acid burns quietly with a smoky flame.
The more important picric powders are melinite, believed to be a mixture of fused picric acid and gun-cotton; lyddite, the British service explosive, and shimose, the Japanese powder, both supposed to be identical with the original melinite; Brugere's powder, a mixture of 54 parts of ammonium picrate and 45 parts of saltpetre; Designolle's powder, composed of potassium picrate, saltpetre and charcoal; and emmensite, invented by Stephen Emmens, of the United States.
By nitrating phenol with concentrated nitric acid, no care being taken to keep the temperature of reaction down, trinitrophenol (picric acid) is obtained (see Picric Acid).
The products of the action of nitric acid on cellulose are not nitro compounds in the sense that picric acid is, but are nitrates or nitric esters.
Hot concentrated nitric acid oxidizes it to picric acid and oxalic acid, whilst on treatment with hydrochloric acid and potassium chlorate it yields chloranil (tetrachloroquinone).
Alkaline potassium ferricyanide oxidizes it to picric acid.
With picric acid it forms a sparingly soluble picrate, which melts at 145 0 C. On the condition of phenanthrene in alcoholic solution see R.
From vegetable fibres silk is readily distinguished by the bright yellow colour it takes from a solution of picric acid, which does not adhere to vegetable substances.
The residue is dissolved in alcohol and to the cold saturated solution a cold alcoholic solution of picric acid is added.