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22                         METALLURGY   OF   CAST
in founding as well as in furnace work. It is generally very essential in making coke that plenty of pure water be had. A drought can make water so scarce as to compel the use of mine water. Such usually contains enough sulphur to seriously affect the coke when quenching the fire. The process of coking has much to do in controlling the amount of sulphur in coke. Coke from the same mine and oven can and often does vary greatly in the percentage of sulphur. If sulphur is above .90 per cent it can often be told by the odor of escaping gases and the stifling fumes a furnace or cupola will emit, as compared with coke below .80 per cent. High sulphur can often be detected by the eye, due to its causing yellow spots or stains to appear on the surface of the coke. A quick test is made by heating pieces red-hot and dropping them into a pail of water. This drives off the sulphur to such a degree that, with a little practice, one can detect differences in the amount of sulphur coke may hold. The best way, of course, to determine the sulphur or other properties, is by chemical analysis.
Phosphorus in coke may be injurious and then again beneficial to both furnacemen and founders. This depends upon the percentage of phosphorus desired in any special brand or mixture of iron, as whatever phosphorus coke contains is generally taken up by the iron when being made or remelted. If, for example, regular Bessemer iron or castings calling for phosphorus not exceeding .10 is desired, the high phosphorus coke would certainly be injurious; but if it is foundry iron that is desired to make thin castings, then higher phosphorus coke is essential. The difference between phosphorus and sulphur is that it always............................Traces.