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476 HYPOSULPHITE OF SODIUM.

Synonym—Thiosulphate of Sodium.

Na2S2O3,5H2O.

Test.—24-8 grains decolorise 1000 grain-measures of the volumetric solution of iodine.

INDIGO.

C8H5NO.

A blue pigment prepared from various species of Indigofera, Linn. ISINGLASS.

The swimming bladder or sound of various species of Acipenser, Linn., prepared, and cut into fine shreds.

LITMUS. A blue pigment prepared from various species of Roccella, DC.

LITMUS PAPER, BLUE. Unsized white paper steeped in solution of litmus, and dried by exposure to the air.

LITMUS PAPER, RED. Unsized white paper steeped in solution of litmus which has been previously reddened by the addition of a very minute  quantity of acid, and dried by exposure to the air.

OXALIC ACID OF COMMERCE. Oxalic acid (H2C204,2H2O), not quite pure.

OXALATE OF AMMONIUM.

(NH4)2C204,H2O.

Take of