530. To Deodorize Fat for Making Perfumed Soap

530.    To Deodorize Fat for Making Perfumed Soap. Boil for 10 minutes 100 pounds of the fat with about 35 pounds water containing 6 ounces common salt and 3 ounces powdered alum; strain the water off, and let the fat rest for some hours before using.

531. To Prevent Fatty Substances from Turning Rancid

531.    To Prevent Fatty Substances from Turning Rancid. Boil for about 10 minutes with the salt and alum solution, as in last receipt; strain the water off, and then gently simmer the clarified fat with 4 ounces benzoin and 1 gallon rose water; skim off and let it cool. Fat thus treated will keep for years.

532. To Grain or Granulate Tallow

532.    To Grain or Granulate Tallow. Melt the tallow and stir it with twice its quantity of water at a blood heat until it is cold; strain the fat from the water, and dry by exposing it to a current of dry air. Tallow in this granulated form combines more readily with lye for soap-making purposes. (See No. 535 (To Keep Tallow from Turning Rancid).)

533. To Purify Tallow and Other Fats

533.     To Purify Tallow and Other Fats. Tallow and other fats are commonly purified by melting them along with water, passing the mixed fluids through a sieve, and letting the whole cool slowly, when a cake of cleansed fat is obtained. Another plan is to keep the tallow melted for some time, along with about 2 per cent, of oil of vitriol largely diluted with water, employing constant agitation, and allowing the whole to cool slowly; then to re-melt the cake with a large quantity of hot water, and to wash it well. Another method is to blow steam for some time through the melted fat. By either this or the preceding process a white hard tallow may be obtained. Some persons add a little nitre to the melted fat, and afterwards a little dilute-nitric or sulphuric acid, or a solution of bisul-phate of potash. Others boil the fat along with water and a little dilute nitric or chromic acid, and afterwards wash it well with water.

534. To Purify Bone Fat

534.    To Purify Bone Fat. Melt the fat with a small quantity of saltpetre (nitrate of potassa); then add sufficient sulphuric acid to decompose the saltpetre. The mass, after the scum is removed, becomes a light yellow color, and is completely deprived of all offensive smell and animal impurities.

535. To Keep Tallow from Turning Rancid

535.    To Keep Tallow from Turning Rancid. Cut 50 pounds tallow into slices, and boil it in about 21/2 gallons water containing 2 ounces alum and 4 ounces salt; strain the fat from the liquid, and wash it in clean water; put into a clean barrel twice as much water at a blood heat as there is grease, and dissolve in the water about 1 part of clean soap to 10 parts of the grease; next warm the grease to a blood heat and pour it into the barrel of water, stirring it together until cold; let it rest until the fat has risen to the surface, when the water must be drawn away through a hole in the bottom of the barrel, hitherto tightly corked. The fat in a granulated state must be thoroughly dried by exposure to a current of dry air; and, when perfectly dry, packed in barrels or other vessels. The graining of the fat at the same time greatly facilitates its combination with lye for the purposes of soap-making.