1817] SOILS FEKTILIZEBS. 727 



Chem. Indus., 35 {1916), No. 20, pp. 1073, 1974).— A number of samples of super- 

 phosphate were examined chemically and with a petrographic microscope, and 

 experiments were made on the conditions of equilibrium of the system, lime, 

 phosphoric- acid, and water at 75 and 100° O., and on the influence of various 

 factors on the physical properties of superphosphate. 



Contrary to the generally accepted view, the calcium sulphate present In 

 superphosphate prepared from mineral phosphates usually existed mainly or 

 entirely as anhydrate. Only in rare instances was it present chiefly or solely as 

 the dihydrate. In bone superphosphate, on the other hand, the dihydrate was 

 present more frequently. Monocalcium and dicalcium phosphates occurred 

 usually only in the hydrate form, but the anhydrous salts were also sometimes 

 present. 



The physical properties of superphosphate are considered to depend chiefly on 

 the amount of the liquid phase which is always present. The liquid phase Is 

 defined as the sum of the free water and the free phosphoric acid. Analyses 

 of numerous commercial samples of superphosphate indicated that in general 

 the best products in regard to dryness and friability are those in which the 

 liquid phase is less than 15 per cent. Products containing from 15 to 18 per 

 cent of liquid phase were still dry and friable, those containing 18 to 25 per 

 cent were slightly moist and caked when compressed, while those containing 

 more than 25 per cent of liquid phase were moist and caked readily. 



A discussion of the technical preparation of superphosphate is also included. 



The preparation of superphosphate from phosphorites, N. P. Koblikov {Iz 

 Rezul't. Veget. O^pytov Lab. Rabat (Rec. Trav. Lab. Agron.), Moskov. Selsk. 

 Khoz. Inst., 10 {1914), pp. 16-22). — A supei-phosphate containing 16.2 per cent 

 of water-soluble phosphoric acid was prepared from Perm phosphorite and 

 one containing nearly 12 per cent was prepared from Saratov phosphorite. 



Causes that influence the solubility of slowly soluble phosphates in citric 

 acid, A. AiTA (Ann. Chim. Appl. [Rmne], 6 (1916), No. 3-4, pp. 119-131, fig. 1; 

 abs. in Jour. Soc. Chem. Jndiis., 35 (1916), No. 20, p. 1074). — Experiments are 

 reported which showed that the solubility of the phosphoric acid of mineral 

 phosphates in 2 per cent citric acid was diminished in the presence of sodium 

 silicate or magnesium silicate, but increased in the presence of ferrous sulphate 

 or manganous sulphate in proportion to the concentration of the latter. In the 

 presence of ferric sulphate, ferric chlorid, or aluminum sulphate the solubility 

 increased more rapidly than the concentration of the added salts. It is con- 

 sidered probable that the phosphoric acid of basic slag is present as tricaleium 

 phosphate, and that its relatively high solubility in citric acid is due principally 

 to the effect of the aluminum and ferric ions present. From this, it follows 

 that the difference in price between the phosphoric acid of basic slag and of 

 mineral phosphates is not justified, and that the Wagner citric acid test can not 

 be considered satisfactory since it does not take into account the influence of 

 secondary constituents on the solubility of phosphoric acid. 



Valuation of water-soluble v. citrate-soluble phosphoric acid, E. J. Peanke 

 (Jour. Indus, and Engin. Chem., 9 (1917), No. 1, pp. 54, 55). — This is a critical 

 review of reports from the New York, New Jersey, and New England state ex- 

 periment stations in which the author attempts to show that the higher trade 

 valuation for water-soluble phosphoric acid over citrate-soluble phosphoric acid 

 Is unwarranted. He points out that " the retail cost of ' available ' phosphoric 

 acid in acid phosphate decreases as the proportion of water-soluble to citrate- 

 soluble increases. At present valuations for total phosphoric acid the organic 

 phosphates cost actually more per unit of citrate-soluble than does the available 

 in acid phosphate. Agricultural considerations are ruled out by definition fi'om 

 any connection with trade values, which are only market quotations." 



