1910.] 



PUBLIC DOCUMENT — No. 31. 



79 



Brand of Slag. 



Phosphoric Acid avail- 

 able in Citric Acid 

 Solution. 



Phosphoric Acid avail- 

 able in Pot 

 Experiments. 



1, 



o 



3, 



4, 

 i), 

 6, 

 7, 

 8, 

 9, 

 10, 



n, 



100 



sr, 



81 

 72 

 73 

 76 

 39 

 48 

 42 

 4.5 

 38 



100 

 80 

 72 

 72 

 66 

 63 

 40 

 38 

 38 

 31 

 30 



Results similar to the above were secured by Maercker/ who 

 stated that '^ the results removed all doul)t that the citrate solu- 

 bility and plant experiments were so nearly proportioned that 

 one had the same right to ^•alue the slag according to its content 

 of phosphoric acid soluble in citrate solution as to value a super- 

 phosphate by its content of water soluble phosphoric acid." 



As a result of these investigations, the union of German ex- 

 periment stations, at its meeting at Kiel in September, 1896, 

 adopted the method of determining the relative value of the 

 slag according- to its phosphoric acid solubility in a S per cent, 

 citric acid solution, and did away with the previous standard 

 of total })hosphoric acid and fineness. 



Wagner as well as Maercker repeatedly called attention to the 

 fact that experiments both in the laboratory and with plants 

 gave positive evidence that those slags of like phosphoric acid 

 content which were ricliest in silicic acid gave the best results. 

 G. Hoyermann, working independently, came to similar con- 

 clusions. At the present time, according to Wagner, practically 

 all of the iron works treat the molten slag as it flows from the 

 converter with hot quartz sand, with the result that the avail- 



• Landw. Preese 1895, No. 82. 



2 Methofl Rliifflitly modified from the original. Present method described in Konifr's 

 Untersuchung landwirtschaftlich und gewerblich wichtiger Stoffe. Dritte Auflage, pp.173, 

 174. 



