Arriving at the laboratory, the half pigs from each car are drilled, equal amounts of the drillings being taken and mixed in an envelope which bears the name of the brand of iron, the number of the car, the date, etc. The sample pigs from each car are treated in this same way, each car being treated individually. The envelopes containing the drillings then go to the chemists. Frequently samples from fifteen or twenty cars of pig iron, with as many other samples of various derivation, are being analyzed at the same time for the four or six different constituents which it is necessary for the metallurgists to know and control in order that a highly satisfactory product may result. Though a hundred different determinations may be in progress at the same time, spelling “chaos” in the mind of one not entirely familiar with the details of the work, it will be interesting to single out and explain briefly how the samples are analyzed. [Illustration: CLOSER VIEW OF THE WEIGHING ] In such analytical work everything is based upon weight; i.e., constituents are determined and reported in percentages by weight. In chemical laboratory work everywhere the metric system is used, the cumbersome English system of weights and measures being practically impossible. Thus, the metric system is the international scientific standard. The unit taken is the gram, which is equivalent to ¹⁄₄₅₃ part of an avoirdupois pound. One gram of pig iron drillings is such an amount as could be held on an ordinary ten-cent piece. Working with such small amounts of the sample, exactness and skill are extremely necessary. The balances used are necessarily very delicate—just as delicate as were the scales upon which the jeweler weighed your diamonds—you remember, of course. On these balances we can weigh an inch-long mark made by an ordinary lead pencil. [Illustration: DISSOLVING IN ACIDS This is done under a hood that the irritating fumes given off may be kept from the room. ] As the results of the analysis have to be known inside of three or four hours that the cars may be quickly unloaded in order to avoid demurrage, which is the penalty for holding cars longer than the allowable time, separate portions of each sample are weighed out for determination of the silicon, manganese, sulphur, phosphorus, graphitic carbon, and combined carbon. These are necessary in order to determine that the iron is up to the quality specified in the purchase contract and also to provide for its most efficient use in the manufacture of iron castings.