By reference to market quotations it will be noted usually that the lower the ammonia content, the lower the price per unit of ammonia, consequently it behooves the maker to produce all the No. 1 tankage possible, and this is accomplished by cooking bone as raw bone and separately--in preference to tanking it. =Grease.=--Grease in fertilizers or dried tankage is a positive detriment. It is useless and valueless, consequently the point to be striven for is to lower the percentage of grease to the minimum. The best methods known are described under tanking. Some packers doing business on a large scale have “degreasing” plants where the grease is extracted by naphtha process, but, this is a highly specialized department and not desirable in a small plant. By careful attention the grease can be lowered to eight per cent on dry basis analysis. =Influence of Stick.=--The use of stick in tankage drying adds greatly to the average ammonia content. Dried stick separately analyzed yields 15¹⁄₂ per cent ammonia, greatly increasing the value of the product in which it is used. =Digester Tankage.=--This is a general name for the product sold to pig feeders for providing a nitrogenous element in their feeding. State Agricultural Departments and packers have been conducting campaigns for years introducing this as a feed. It is usually a No. 1 tankage made from freshly killed material and promptly dried. It is supposed to contain a stated protein content, which is really a multiple or unit based upon its nitrogen content, 5.137 being the factor. Stick is used in the digester tankage and with benefit provided it is kept sweet. In hog producing localities practically the entire output of tankage can be disposed of to the farmer for stock food purposes. =Slime.=--The slime scraped from intestines in the casing department has a high ammonia value and should be collected and cooked in a manner similar to the method used in cooking blood. =Drying.=--This operation consists of extracting the moisture from the tankage by means of air which is used as a vehicle to carry away the moisture. Various devices are employed for performing this function, such as barometric condensers, siphon tees, pipe condensers, and fan with air wash tower. There is some objection to all of these types, and each operator usually has some home-made device based upon experience. The fan is the more logical; it sweeps a large volume of air through the dryer by withdrawing it and passing it to the wash tower. The air carries away the moisture. To dry cheaply have a positive circulation of air through the dryer by keeping the inlet open, the fan attached to the air outlet connection. Single or multiple of dryers can be arranged on one fan. =Dryers.=--The principal apparatus in the fertilizer department is the dryer. Of these there are several types.