116. Nitrate of Iron

116.    Nitrate of Iron is used in the dye-house for various purposes. Its principal use is for dyeing Prussian Blue, and is obtained as follows : Take 4 parts nitric acid and 1 part water in a glass or stoneware vessel; place it in a warm bath, and add clean iron so long as the acid continues to dissolve it with effervescence ; take out any iron that remains undissolved, and, after settling for 1 hour, the clear solution is ready for use. The fumes given off during the operation should be guarded against, being deleterious to health and injurious to any metal or vegetal with which they come in contact. This solution should be kept in the dark, as it loses some of its strength by exposure to fight.

117. Chloride of Iron

117.    Chloride of Iron is another salt used in the dye-house for dyeing silks and woolens a deep blue, and is preferred, for that purpose, to copperas. It is prepared for use thus: To 4 parts hydrochloric acid add 2 parts water, and apply a gentle heat; then add iron in pieces, or filings, so long as it continues to be dissolved; then pour off the clear liquid into a basin, and evaporate, when greenish colored crystals of chloride of iron will be obtained. This salt crystallizes with difficulty, deliquesces in the air, and should not be exposed. Instead of evaporating and crystallizing, the solution may be put in a bottle and reserved for use.

118. To make Iron Liquor

118.    To make Iron Liquor. Into a large cast-iron boiler, or pot, a quantity of iron turnings, hoops or nails, are introduced, and acetic acid - the crude pyroligneous acid from the distillation of wood - is poured in upon them. The strength of the acid is generally of 5° Baum'e, or specific gravity 1.035. A temperature of 150° Fahrenheit is maintained till the solution of protoacetate of iron is obtained. During the solution of the iron much tarry matter separates, which is skimmed off, and the solution frequently agitated, to free it, as much as possible, from the tar. As soon as a strength is gained of a specific gravity of 1.09, at 60° Fahrenheit, the solution is allowed to cool, for a further quantity of impurities to separate. When clean turnings are operated on, the process of solution is completed in 5 to 7 days.

119. To make up a Blue Vat

119.    To make up a Blue Vat. Take 1 pound indigo, and grind in water until no grittiness can be felt between the fingers; put this into a deep vessel - casks are generally used - with about 12 gallons water; then add 2 pounds copperas, and 3 pounds newly-slaked lime, and stir for 15 minutes; stir again after 2 hours, and repeat every 2 hours for 5 or 6 times; towards the end, the liquor should be of a greenish yellow color, with blackish veins through it, and a rich froth of indigo on the surface. After standing 8 hours to settle, the vat is fit to use.

120. To make Blue Stone

120.    To make Blue Stone. Sulphate of copper is known in commerce as Blue stone, Roman vitriol, and Blue vitriol, and may be prepared by exposing pure copper in thin sheets to the joint action of dilute sulphuric acid and air; or by treating freshly precipitated oxide of copper with diluted pure oil of vitriol; or by boiling the metal with oil of vitriol, either in the concentrated state or diluted with an equal bulk of water. These are the simplest ways of obtaining this salt, which may be reduced to a crystalline form by evaporation. The crystals assume a well-defined rhomboidal form of a fine sapphire-blue color.