282 ^EXPERIMENT STATION RECORD. 



Experiments have been reported wliicli indicated that liydrated phos- 

 pliates of aluniinuin and iron were more effective as fertilizers tlian 

 tricalcium pliospliate. It is claimed that tbe citrate-solubility is not 

 a true index of the availability of phosphate in the soil, because the 

 same phosphate produces very different effects upon different kinds of 

 soil, as has been frequently shown by field experiments. Among' the 

 more important of such experiments those carried out by Gerlach,^ 

 Ulbricht,^ and Tacke^ are noted. 



The unreliability of the citrate method as api)lied to bone meal is 

 shown by citations of the v»"ork of Kellner, Kozai, and Mori," C. Antz,^ 

 and L. Gebek.'' Gebek's investigations showed that the citrate solu- 

 bility of bone meal varied directly with the content of gelatin, and 

 this is in conformity with the general opinion that raw bone decom- 

 poses in the soil more quickly than steamed bone. It is suggested that 

 these results may be partially explained by the fact that the phos- 

 phate of lime is dehydrated and thus rendered more insoluble by the 

 action of the heat in steaming. Other exiierimenters, including Kell- 

 ner, have obtained results in field experiments which indicate that the 

 steamed bone is quicker in its action than the raw bone. In conclusion 

 the author claims that the Wagner method is valuable as a comparative 

 test, but that quantitative exactness can not be claimed for it. 



Investigations are reported on the citrate solubility of Thomas 

 slag with reference (1) to the relation between the proportions of the 

 solvent and the material to be tested, (2) the time of digestion, (3) the 

 basicity of the material, and (4) the temi^erature and time of digestion 

 are reviewed at some length, as well as a <;oinparison of the results 

 obtained by this method with those obtained in field experiments, and 

 comparisons of a citrate solution containing 2.4 per cent of citric acid 

 with the ordinary Wagner solution on 7 samples of slag. 



A study of the chemical constitution of Thomas slag led to the con- 

 clusion that the citrate-solubility of slag is due to the presence of tetra- 

 calcium phosphate, and that the presence of a considerable amount of 

 silicic acid is not a sure indication that the i>hosphate is highly soluble. 

 A slag containing 11.21 per cent of citrate-soluble phosphoric acid was 

 found to contain only 3.88 per cent of silicic acid, while one which 

 showed 4.03 per cent of citrate-soluble phosphoric acid contained 7.24 

 per cent of silicic acid soluble in ammonium citrate. It is claimed that 

 a slag which is rich in lime may be free from silicic acid and still show 

 a high solubility in citrate. This fact is utilized in the process of E. 

 Bartz,' in Avhich phosphorite is mixed with the molten slag, the phos- 

 phoric acid of the former being rendered soluble in citrate by the i)rocess. 



iLiindw. Vers. Stat., 46 (1895), p. 208 (E. S. R., 7, p. 488). 



'-^Laiulbote, 1889, p. 821; Agr. Chem. Vers. Stat., DaLme, 1894 (E. S. R., 6, p. 626). 

 3 Mitt. Ver. Ford. Moorknlturs, 1894, p. 345. 

 -•Landw. Vers. Stat., 43 (1894), p. 1-14 (E. S. R., 4, p. 861). 

 6 Chem. Ztg., 19 (1895), p. 1875 (E. S. R., 7, p. 293). 

 «Zt8chr. angew. Chem., 1894, p. 193 (E. S. R., 7, p. 398). 

 'Chem. Ztg., 1895, p. 1273; see also E. S. R., 7, p. 198. 



