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MIXING    AND    MET,TING   SCRAP   IRON.                 293
erally found in their foundry iron, in all the three mixtures. By such a method any founder having had experience in following chemistry to any degree will soon know what " grade " the above mixtures of <'j             pig metal would give were they poured into castings
.1^          ranging from stove plate up to bodies six inches thick,
*            and then, when sorting scrap in " grades," they would
,            simply be contrasted with the '' grade '' produced by the
imaginary pig mixture which had been taken to define a base for a grade desired. By following such a method as this, it is very evident that the grading of scrap iron could be reduced to a very satisfactory system, in all work where it is economical to utilize scrap iron. As a general thing, founders are desirous of utilizing
'           .all   the   outside   scrap   possible   in   mixture  with  pig-
metal, because it can generally be bought for less than pig iron. With work that permits a good leeway in
A         the grade or mixture obtained, such as floor plates,
\            furnace  castings  and heavy machinery not requiring
much finishing, etc., scrap iron can often compose the greater part of the mixture, especially so if silicon pig-has been used to soften the scrap. In the case of stove plate or light machinery castings requiring much finishing, much more care is necessary in attempting
t           to use much outside scrap iron.    The same is to be
said of chilled work where definite results are to be insured. In many chill work specialties it is often very poor economy to adopt the practice of utilizing any
i;           outside   scrap;   but,   of  course,   shop  scrap,   such   as
5J"*""         gates, etc., every shop must work up in mixture with
its pig metal. An all-pig mixture, of which a correct analysis has been given, enables the founder to be
;           much more positive in obtaining desired results than93. The War Department at first refused to accept cupola iron as gun iron, but when it was fully demonstrateduois Iron Co., Illinois Steel Co., Jefferson Iron Co., Kittan-ning Iron & Steel Co., C. A. Kelly Plow Co., Lebanon Furnace, Longdale Iron Co., Lackawanna Iron & Steel Co., Logan Iron........................   16,720     "                                     t-