In this laboratory the citrate method has been found to give nearly agreeing results with the old process. It is much shorter and less expensive; and is recommended most favorably for practical use, suggesting, however, that with every new kind of phosphate or phosphatic fertilizer varying notably in composition from the standard, the work should be checked at first by comparison with the molybdenum method. BASIC PHOSPHATIC SLAGS. =69. History and Manufacture.=—The basic process for the manufacture of Bessemer steel is known in Europe as the Thomas or Thomas and Gilchrist process, and the slags rich in phosphate, one of the waste products of the process, are known by the same name. In this country all the phosphatic slags which have been made in the manufacture of steel have been obtained working under the patents of Reese, and, when prepared for the market, are known as odorless phosphate. The only place where these slags have been made in this country is Pottstown, Pennsylvania. In Europe they are extensively manufactured, in England, France, and Germany, and their use for agricultural purposes has increased until it is quite equal to that of superphosphates. The quantity of basic slag manufactured in Germany in 1893 was 750,000 tons; in England 160,000; in France 115,000, making the total production of central Europe about 1,000,000, a quantity sufficient to fertilize nearly 5,000,000 acres. =70. Process of Manufacture.=—The principle of the process depends upon the arrangement of the furnaces, by means of which the phosphoric acid in the pig iron is caused to combine with the lime which is used as a flux in the converters. A general outline of the process is as follows: The pigs, which contain from two to four per cent of phosphorus, are melted and introduced into a Bessemer converter lined with dolomite powder cemented with coal-tar, into which has previously been placed a certain quantity of freshly-burned lime. For an average content of three per cent of phosphorus in the pig iron, from fifteen to twenty pounds of lime are used for each 100 pounds of pig iron. As soon as the melted pig iron has been introduced into the converter, the air-blast is started, the converter placed in an upright position, and the purification of the mass begins. The manganese in the iron is converted into oxid, the silicon into silica, the carbon into carbon dioxid and oxid, and the phosphorus into phosphoric acid. By reason of the oxidation processes, the whole mass suffers a rise of temperature amounting in all to about 700° above the temperature of the melted iron. At this temperature the lime which has been added, melts, and, in this melted state, combines with the phosphoric acid, and the liquid mass floats upon the top of the metallic portion, which has, by this process, been converted into steel.