204 METALLURGY OF CAST IRON. metalloids shall cover every element in cast iron excepting the iron. This implies that one or all of the elements — carbon, silicon, sulphur, manganese, and phosphorus — are classified as metalloids, and this classification the author has accepted for all his writings. To have a clear understanding of the influence of these metalloids in affecting the character of iron or castings, a study of the following chapters is necessary.one or different kinds of atoms. Where molecules are formed of different kinds of atoms, the mass is called a compound. There are now about seventy different kinds of atoms or elements, among which are classed carbon, iron, manganese, phosphorus, silicon, and sulphur. Table 130, at the close of this work, gives the chemical and atomic weights of various elements.