This section is from the book "Mrs. Allen's Cook Book", by Mrs. Ida C. Bailey Allen. See also: The Conscious Cook: Delicious Meatless Recipes That Will Change the Way You Eat.
To prepare fat from corned beef, the soup kettle, etc. for frying, let it rise to the top of the liquid and solidify. Then remove it to the fat pan, add a little baking soda and cold water barely to cover, and let it cook slowly until the water has evaporated; or the water may be omitted, the soda and slices of raw potato being added to the fat instead. When the potato has become brown the fat will be clarified. Most of the odors and flavors of the meats and vegetables pass off in the steam from the water or from the water of the potato.
Remove all particles of flesh and bits of blood from the chicken fat. Let the fat stand for an hour in cold, salted water. Then drain from the water, put in an open pan, and try out slowly in the oven, pouring off the melted fat as fast as it accumulates. Goose fat may be treated in the same way.