MIXING CASTS OF PIG IRON AT FURNACE, ETC. 143
analysis of that one cast stand for the chemical properties of the four or five casts which the furnace has made that day. It is not to be understood that many furnaces follow this practice. However, such a practice should not be tolerated by any furnace claiming to grade iron by analysis, and is little better than trying to achieve desired results in re-melting by judging the grade of pig iron by its fracture or hardness. Every furnace cast should be analyzed and the metal of each cast kept separate when piled in the yard or shipped on cars, so that when the founder receives the iron he has not, in connection with an ill-mixed cast of iron, a chemical guess, but a true analysis to guide him aright in re-melting his pig iron. Give the founder a true analysis of a well sampled cast of pig iron, in connection with having it well mixed, or cast from one ladle, as in sandless pig, before the pig iron is charged into a cupola, and he will find that chemistry is a guide that can be relied upon in assisting him to obtain the grades of iron he desires in his castings.tive assurance of obtaining certain'bodies of iron that would be uniform in analysis, without having to resort to mixing each cast of iron. These are all factors which strongly recommend the use of sandless pig iron. For methods of calculating percentages of silicon, sulphur, etc., as found in iron, to obtain averages for making mixtures, see Chapter XXXVI.