MANUFACTUEE OF BASIC SLAG. 



213 



TABLE LXI.— EFFECT OF COMPOSITION OF BASIC SLAG ON 



FACILITY OF GEINDING.i 



I. Poured slag, dark brown, hard and difficult to grind. 

 II. Block slag, grey, lamellar, friable, easily ground. 



III. Block slag, slate grey, firm, and easily ground. 



IV. Block slag, grey, firm, vesicular, less easily ground. 



V. Poured slag, dark brown, hard, brittle, difficult to grind. 

 VI. Block slag, brown, brittle, hard, difficult to grind. 

 VII. Block slag, grey, lumpy, difficult to grind. 



It follows from these figures that in general the chemical com- 

 position of basic slag has only a slight effect on its physical pro- 

 perties, whilst the percentage of oxide of iron would appear to 

 increase their resistance to grinding, as the following table show^s : — 



TABLE LXIL— SHOWING THE INFLUENCE OF THE KATIO OF THE 

 PEROXIDE OF IRON TO PROTOXIDE ON THE EASE OF GRIND- 

 ING OF BASIC SLAG. 



When the ratio of the peroxide of iron to the protoxide < 1 : 3 the 

 basic slag is generally easily ground, especially when the peroxide 

 of iron is in preponderant proportion, but when it is the protoxide 

 of iron which predominates the slags are hard and difficult to grind. 

 It is important to watch the sieves around the crusher, and see that 

 they are working well, so as to be able to remedy any defect forth- 

 with. With this end in view, the basic slag produced each time 



1 The translator has transposed the figures relating to lime and manganese. 



