Basicity:

Basicity can be understood either from ionic or from molecular nature of slag. The ionic nature of slag assumes slag to consist of ions. In slags, acidic oxides can accept one or several  ions, whereas a basic slag is a donor of ions. For example, 1 mole of can accept 2 moles  ions so that each tetrahedron in hexagonal structure becomes independent of each other. Similarly each mole of can accept 3 moles of  ions. Thus

(3)

                                               
Amphoteric oxides behave as bases in presence of acid or as acids in presence of a base:

(4)

                                                   
Bases can supply  ions

 

In a neutral slag enough oxygen ions will be present to ensure that each tetrahedron remains independent of each other. In binary , slag will become neutral when CaO is 66.7%, which corresponds to the formation of Slag will be basic only when CaO content is more than 66.7%. Basicity can be expressed in terms  ions which are in excess than that required, thus satisfying the requirements of acidic oxides. In 100 g of slag

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