Grease varies so greatly in composition and consistency that it can hardly be classed as a distinctive oil or fat. It is obtained from refuse, bones, hides, etc., and while it contains the same constituents as tallow, the olein content is considerably greater, which causes it to be more liquid in composition. Grease differs in color from an off-white to a dark brown. The better qualities are employed in the manufacture of laundry and chip soap, while the poorer qualities are only fit for the cheapest of soaps used in scrubbing floors and such purposes. There is usually found in grease a considerable amount of gluey matter, lime and water. The percentage of free fatty acid is generally high. The darker grades of grease are bleached before being used. This is done by adding a small quantity of sodium nitrate to the melted grease and agitating, then removing the excess saltpeter by decomposing with sulphuric acid. A better method of refining, however, is by distillation. The chrome bleach is also applicable. ROSIN (COLOPHONY, YELLOW ROSIN, RESINA). Rosin is the residue which remains after the distillation of turpentine from the various species of pines. The chief source of supply is in the States of Georgia North and South Carolina. It is a transparent, amber colored hard pulverizable resin. The better grades are light in color and known as water white (w. w.) and window glass (w. g.). These are obtained from a tree which has been tapped for the first year. As the same trees are tapped from year to year, the product becomes deeper and darker in color until it becomes almost black. The constituents of rosin are chiefly (80-90%) abietic acid or its anhydride together with pinic and sylvic acids. Its specific gravity is 1.07-1.08, melting point about 152.5 C., and it is soluble in alcohol, ether, benzine, carbon disulfide, oils, alkalis and acetic acid. The main use of rosin, outside of the production of varnishes, is in the production of laundry soaps, although a slight percentage acts as a binder and fixative for perfumes in toilet soaps and adds to their detergent properties. Since it is mainly composed of acids, it readily unites with alkaline carbonates, though the saponification is not quite complete and the last portion must be completed through the use of caustic hydrates, unless an excess of 10% carbonate over the theoretical amount is used. A lye of 20deg. B. is best adapted to the saponification of rosin when caustic hydrates are employed for this purpose, since weak lyes cause frothing. While it is sometimes considered that rosin is an adulterant for soap, this is hardly justifiable, as it adds to the cleansing properties of soap. Soaps containing rosin are of the well known yellowish color common to ordinary laundry soaps. The price of rosin has so risen in the last few years that it presents a problem of cost to the soap manufacturer considering the price at which laundry soaps are sold. ROSIN SAPONIFICATION.