MANUFACTURE OF BASIC SLAG. 215 



that they possess covered and very dry warehouses. On the other 

 hand, the vendor takes a sample from each block by chipping off a 

 fragment vrith the hammer and takes a fair average sample at the 

 end of each month. The sample is crushed, mixed, and divided 

 into three parts ; one part is sent to the buyer, the other to the 

 sender, and the third is sealed and kept in reserve as a basis of 

 settlement in case of difference. The exchange of analyses on both 

 sides is made on a certain day, and the average is taken as a basis 

 when the difference between the two analyses does not exceed Oo 

 per cent P.,0^. If the difference be greater, the sample in reserve 

 is sent to an analytical station agreed on by both sides, and the 

 analysis which it supplies forms the sole basis of adjustment. The 

 cost of the analysis is borne by the party whose analytical results 

 are furthest from those of the analytical station. If the analytical 

 results on both sides differ to an equal extent from the experimental 

 station, the costs of settlement are defrayed equally by both parties. 



Basic slag is delivered to farmers without being mixed with other 

 manures. If it be mixed with potash salts it heats and gradually 

 solidifies ; the caustic lime acting on the magnesium chloride forms 

 magnesium oxychloride, which is a powerful cement ; if mixed with 

 sulphate of ammonia, the caustic lime acts on the ammoniacal 

 nitrogen and causes loss. Finally, if mixed with nitrate, the nitric 

 acid may be reduced into ammonia by iron, in the form of a fine 

 pow^der, and the ammonia expelled by the caustic lime. 



Customs in the Sale of Basic Slag.— From 1 July, 1895, 

 according to a decision of the Assembly of German Agricul- 

 turists, basic slags were sold on the basis of their phosphoric acid 

 soluble in citrate, without taking into account their total phosphoric 

 acid, nor the degree of fineness. 



But in its General Assembly held in 1898, the Union of Experi- 

 mental Stations decided no longer to use Wagner's citrate of 

 ammonia solution. It, moreover, found that steel works, to increase 

 the solubility of their basic slag in citrate, were adding to the cast- 

 iron not only silica, but more lime. The effect of this was to 

 increase the alkaline nature of the basic slag, and the Union esti- 

 mated that this increase in alkalinity justified the selection of a 

 solvent of greater acidity in the estimation of soluble phosphoric 

 acid. The 2 per cent solution of citric acid forms in fact a more 

 accurate method than citrate of ammonia for basic slag prepared 

 according to this new process. But Professor Wagner estimates 

 that the 2 per cent citric acid solution dissolves 7 per cent of PoO^ 

 more in basic slag, that is to say, it shows 16 per cent of soluble 

 phosphoric acid where the old method only showed 15 per cent. 



There is at the present time a tendency to value basic slag on 

 the basis of its total phosphoric acid content, according to cultural 

 experiments male on the subject by Meissl and Defert in Austria, 



