METHODS FOR MELTING CAST IRON TO TEST ITS PHYSICAL QUALITIES.
Owing to the impracticability of judging pig metal by its fracture, the author has thought a Chapter on methods for melting small quantities to test its physical qualities wotild, in many cases, prove of value, especially where a founder was not in position to utilize chemistry.
There are three methods by which iron can be melted for testing its physical properties. One is to take the regular '' heats '' mixture, another to have a very small cupola expressly for melting light "heats," weighing from 50 to 500 pounds, and the third by means of a furnace and crucible similar to the principle used for melting brass, etc. By using metal from the first, we can at any period of a heat tell the physical properties of any mixture poured at that time. By using the small cupola we can, by proportioning a mixture in light charges, obtain a good approximate knowledge of the product to result from a like mixture in regular "heats," and also where there are several brands or grades of pig metal, each can be tested separately, to ascertain its physical properties, thus enabling" one to detect any brands that micfht be de-vity and weight per cubic inch of other metals, see Table 136, page 593.lity. With soft grades aluminum, can make tiu* metal sluggish, with excessive dross on its surface, just as can be the case by having too much silicon in a mixt lire.