INTRODUCTION 



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TABLE I. RECORD OF THE EARLIEST MANUFACTURE OF BASIC SLAG 



(May, 1879) 



In the first blow it will be noted the phosphorus fell from 1-52 % 

 in the pig-iron to -18 % in the finished steel. 



When phosphorus has been removed to the required extent the 

 converter is tipped forward and the slag allowed to flow over the 

 top of the vessel into the slag pot where it is either allowed to cool 

 or tipped molten on to the slag heap. 



The production of steel by this process and the consequent accumu- 

 lation of phosphatic basic slag increased with great rapidity, and 

 attention was turned towards the possibility of using these basic slags 

 for fertilising purposes. It was at first considered that on account 

 of the insolubility of the phosphates in water the material would 

 be of little value for direct application. Attempts to obtain a suitable 

 fertiliser by dissolving the slag in acid proved unsuccessful. 



To Wrightson and Munro we owe the discovery in 1885 that if 

 basic slag is ground to a fine powder it has a very considerable 

 fertilising value. Their experiments were followed by many others 

 including the now classic experiments at Cockle Park, which were 

 commenced in 1896 by Professor Somerville and subsequently con- 

 tinued and developed by Sir T. H. Middleton and Prof. D. A. Gilchrist. 

 It is from the Cockle Park experiments that most of our information 

 concerning the practical use of basic slag has been derived. These 

 experiments continued over a period of 25 years do more than show 

 that basic slag has a high fertilising value. They demonstrate that 

 under the conditions at Cockle Park basic slag per unit of phosphoric 



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