Purposes. These receipts in-. ; elude the preparation and appliance of such liquid colors as are used to tinge or impart color to matter generally. Their particular uses and appliances are specified in the receipt given for each preparation. In addition to those here given, a number of other receipts for coloring matter have been necessarily included under the respective headings of the special objects for which they are used, and will be readily found by consulting the index.

2615. Soluble Prussian Blue

2615. Soluble Prussian Blue. Add a solution of protosulphate of iron to a solution of prussiate of potash, and expose the precipitate to the air till it becomes blue, and wash it till the soluble salts are washed away. By continuing the washing, the blue itself dissolves, forming a deep blue solution, which may be evaporated without decomposition. Or, add a solution of persulphate of iron to a solution of ferroprussiate of potash, keeping the latter in excess; wash the precipitate until it begins to dissolve, and dry it. (See No. 2488 (Readers Patent Blue "Writing Fluid") for another method.)

2616. Chemique, or Chemic Blue

2616.     Chemique, or Chemic Blue. Sulphate of Indigo. To 7 or 8 parts of oil of vitriol, in a glass or earthen vessel, placed in cold water, add gradually 1 part of fine indigo in powder, stirring the mixture at each addition with a glass rod or piece of tobacco-pipe. Cover the vessel for 24 hours, then dilute with an equal weight of water. Sometimes it is sold without diluting. The German fuming acid answers best, 4 or 5 parts of it being sufficient for 1 of indigo. For dyeing silk, etc., carbonate of potash, soda, or ammonia, is added, to neutralize the acid, taking care not to add it in excess. (See Nos. 98 (To make Sulphate of Indigo) and 4791.)

2617. Liefchild's Patent Blue for Linen

2617.     Liefchild's Patent Blue for Linen. Mix 4 parts Chinese blue, 1 of Turn-bull's blue, and 1 of oxalic acid; gradually add boiling water until the whole is dissolved, and lastly 4 parts of sulphate of indigo. The latter is made with 1 part indigo, and 4 sulphuric acid, neutralized with carbonate of ammonia.

2618. Blue for Linen

2618.    Blue for Linen. The ordinary kinds of cake blue consist of indigo and starch.

2619. Solvents for Indigo

2619.    Solvents for Indigo. Indigo will dissolve in Venice turpentine heated to its boiling point, or in boiling paraffine, with the same blue color as the solution of sulphuric acid; and in petroleum it forms a carmine solution, while in spermaceti it produces a carmine-violet, and in stearic acid a blue color.

2620. Bluing for Clothes

2620.     Bluing for Clothes. Take 1 ounce of soft Prussian blue, powder it and put in a bottle with 1' quart of clear rain water, and add J ounce of oxalic acid. A tea-spoonful is sufficient for a large washing.