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LOSS   OK    IRON    |JV    OXIDATION   IN    CUPOLAS.          317
broken in pieces about 4 inches square, and melted it in comparison with the rolls or heavier iron, as seen in tests 15 and i 6. This ^-inch plate iron was cast especially for the purpose and used the day following-, so that it was perfectly free from all rust or dirt scale, its coat being* only that of the film of oxide formed on its surface while in the green sand mould. The loss of this 2^-inch plate will be seen to be about 5 per cent., and this can be taken as a good test for this character of flat-faced surfaces, when charged in the form of clean scrap, not exceeding- i inch in thickness. It will be well to state that the iron used for pouring' the chilled or sandlcss gray roll bodies used throughout all the heats herein described (form shown in Fig. 58) were taken from one of our regular shop cupola heats and would average about 1.70 silicon, .045 sulphur, .50 manganese, and .10 phosphorus. Owing to this iron being moderately high in silicon and fairly-low in sulphur, it would only chill, to a depth of about J.j' of an inch in the small rolls shown. Such a depth of chill on the surface of the rolls used for the heats litMvin described, would agree fairly well with that found in general gray pig irons that had been cast in chills instead of sand molds, and. L believe all will concede it to be an iron well suited for tests on the comparative oxidation of chilled and, sand-cast pig metal. Table 67 would show that greater silicon and manganese were lost on the high beds than the low beds of fuel. Another interesting point, which may surprise many, is that the slag which came from the stove plate iron, as seen in Table 6S, has a less percentage of iron in it than that, which came from the heavier or sandless gray roll iron. While this is shown as such, it doeslate obtained.        .           ,      '    S<> Ibs,	sy Ibs	<jl Ibs	fi Ibs