220 



C. (T. T. MORISON. The amount of free lime and the compo- 

 sition of the soluble phosphates in Basic Slag. - The 



Journal of Agricultural Science, Vol. Ill, Part 2, October 1909. 

 Rothamsted Experiment Station. 



Basic Slag owes its value as a source of phosphoric acid to the 

 fact that it is essentially basic in its character, and can be used 

 on land where an acid manure of the character of superphosphate 

 is not to be recommended. 



As no figures were available on the subject it seemed interest- 

 ing to determine how much of the lime which it contains existed 

 in the free uncombined condition. 



The present analyses and Stead's work have fully established 

 that it is not tetracalcium phosphate which supplies the soluble 

 phosphoric acid in basic slag but a body in which the molecular 

 ratio of phosphoric acid to lime is 1:5. Of the total lime present 

 in the slag which was 38.62 j , 5.8 was as oxide or carbonate, 27.68 

 was combined in readily soluble form, leaving 5.17 combined with 

 the remainder of the phosphoric acid. V. F. Kroll in a preliminary 

 note (Stahl und Eisen no. 19, May 6th, 1908) says that the prin- 

 cipal constituents of basic slag is a compound hitherto unknown 

 consisting of a silico-phosphate of lime and ferrous iron, which 

 would seem to agree with the results obtained in the present paper. 

 The absence of crystals of tetra-calcium phosphate, which were un- 

 doubtedly obtained from basin slag by earlier observers and the 

 low percentages of free lime now found to be present in the slag, 

 may be correlated with the increased percentage of phosphoric 

 acid in slags of modern manufacture, less lime being nowadays 

 employed in the dephosphorisation process than formerly. 



J. HENDRICK. The Lime in Basic Slag. (Jour. Soc. Chem. Ind., 

 28, 1909, n. 14, pp. 775-778). E. S. J?., XXII, Jan. 1910. 



Chemical studies ot various samples of Thomas slag are reported 

 which "indicate that the basic lime in slag is not only a very 

 variable quantity, but that it consists of lime in various forms of 

 combination. A little of it is free caustic lime. The rest is in 

 combination, such as silicates and basic phosphates. A part of this 

 combined lime is readily liberated, and will probably readily act 

 in the soil as a base. Other portions are only liberated with greater 

 difficulty and slowly. As the conditions are very complex, it is im- 



