TABLE 37 — PERCENTAGES OF IRON AND IMPURITIES IN WEAK AND STRONG CASTINGS.—SEEN ON PAGES 536 AND 537.
Chill Roll. Gun . Metal. Car Wheel. General Machinery. Stove Plate. Bessemer Iron.
Iron ..................... 95-l;)7 95.120 94.988 94. 100 92.473 93.782
Impui ities. '4.803 "4.880 5.012 5.900 7.527 6.218

Total .... 100.00 100.00 100.00 100.00 100.00 IOO.OO

Strength of largest bar ~ ................... V^3 4.3S5 4,263 3,786 3,011 2,860

Relative strength... 100. 87. 85., 75- 60. 57-
Relative estimated strength . . 100. 86, 84. 81.5 68.

Impurities in charcoal pig iron are less, as a rule, than in coke or anthracite pig iron. This causes the " iron " to be higher in the former metal. It is now conceded that this is a great cause for charcoal irons excelling1 coke or anthracite pig metal in making strong castings, when intelligently used. The advantages of having high " iron " in castings requiring strength are illustrated in steel metal. This was ably set forth in a paper treating of the importance of having high vi iron " in cast pig metal by the late Captain Henning of the Imperial Artillery, Berlin, Germany, before the local founclrymen's association, February 5, 1901, wherein he stated that steel castings show only .074 to 1.44 per cent, of impurities and 98.56 to 99.86 per cent. iron.
The results of the computation of iron as shown in Table 37 were first given by Mr. Whitney in a discussion of a paper by the author seen in Chapter LXIX. before the Foundry men's association, Philadelphia, December 2, 1896. During the above discussion Mr.good fluidity it is not to be understood, by the above, that it is necessary to have carbon above 3.75. To obtain good fluidity, extra silicon, phosphorus, and often manganese are necessary to be com-o.n. in ladle 1,772 Ibs. .100" -326 " I.IOO .242 3