FERTILIZERS. 



33 



Relation between amount of sodium carbonate used in fusion and the citrate solubility of 



the product. 



The presence of feldspar in fusing- apatite with sodium carbonate is 

 important, since a high citrate solubility can not otherwise be obtained. 

 Fusions with and without feldspar gave the following results: Pure 

 apatite with 2 parts sodium carbonate, 37 per cent citrate solubility; 

 with 3 parts sodium carbonate, 72 per cent; 83 parts pure apatite and 

 17 parts pure feldspar with 20 parts sodium carbonate, 04 per cent; 83 

 parts pure apatite and 17 parts pure feldspar with 30 parts sodium car- 

 bonate, 01 per cent. 



The raw material for the manufacture of the Wiborgh phosphate is 

 found in enormous quantities in Sweden in the Gellivare iron ore, from 

 which the magnetic iron has been separated, leaving a finely divided 

 refuse product of silicic apatite; four-fifths of the latter consists of pure 

 calcium phosphate and one-fifth mainly of feldspar, with some quartz, 

 mica, and hematite. The phosphoric acid content of the raw material 

 reaches 35 per cent. 



Fertilizer experiments. — Preliminary experiments made with Wiborgh 

 phosphate during 1890 indicated that the phosphoric acid contained 

 therein possessed a greater value than Thomas slag, approaching that 

 of the water-soluble phosphoric acid in superphosphates. The experi- 

 ments were continued on a somewhat larger scale in 1897 with oats 

 grown in sandy soil and with peas and sugar beets grown in marsh soil. 

 The Thomas phosphate used had a citrate solubility of 88 per cent. 

 The glass cylinders used were 50 cm. high, 25 cm. in diameter, with a 

 surface of 0.05 sq. meter. They were filled with 25 kg. sand in the oat 

 experiments and with 15.5 kg. of marsh soil in the pea experiments. 

 In case of the oats a basal fertilizer of 300 kg. potash (sulphate), 100 

 kg. nitrogen (nitrate), 2,000 kg. powdered marble, 200 kg. salt, and 200 

 kg. land plaster was applied; in case of the peas, 300 kg. potash (sul- 

 phate) and 200 kg. salt. The results obtained with the first two crops 

 are summarized in the following table: 



