The exactly weighed portions are put into clean, numbered beakers, which are small pieces of high grade glassware that will stand sudden changes of heat and cold. Some of these portions are dissolved in nitric acid, some in hydrochloric acid, others in combinations of acids. In each case the drillings go into solution in the acids, and after various treatments of boiling, evaporating, filtering, etc., well known to those of the chemical profession, the desired results are obtained. In some cases it is by actually weighing a constituent which has been filtered out and burned to ash of a constant known composition, in others it is by comparison of color with standards of known composition, and sometimes it is by other means. [Illustration: FILTERING SILICONS After evaporating the excess acid, baking dry, cooling, and redissolving in weaker acid, the silicon compound formed may be filtered out. The iron and other soluble constituents, now in solution, pass through the filter, which is of pure, porous, unglazed paper. ] In all of this analytical work the chemist must take care to lose not one drop of the solution or one grain of the ash from the burned “precipitate,” as the “filtered out” constituent is called. The pig iron is always bought upon guarantee that it will contain a certain percentage of silicon—the element which in cast iron is known as a “softener.” But this is not the only thing necessary in the iron that is purchased. It must also show proper specified quantities of manganese, phosphorus and carbon, which also are very desirable elements in iron castings, and as little of that undesirable element, sulphur, as possible. Therefore they pay in proportion to the content of silicon, manganese, phosphorus, and carbon—and penalize the seller for sulphur. [Illustration: “BURNING OFF” THE SILICONS The paper and contents, in a little crucible, are placed in a red-hot muffle furnace. The paper is such pure cellulose that it leaves no weighable ash. That which remains after burning is silicon oxide, which is a perfectly white, fine sand. This is very carefully weighed. (Ordinary sand is silicon oxide usually slightly colored with iron.) ] The laboratory holds copies of the contracts upon which these materials were bought. If, upon comparison, the analysis obtained complies with the terms of the contract, an O. K. unloading slip is made out and the receiving department is given directions into what raw-material bin in the receiver building it shall be unloaded. If not fully up to the standard called for in the contract, the purchasing department is notified and the car is either rejected or accepted upon some proper terms of adjustment if it can be used without detriment to the product in which it is to be utilized.