RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



On the action of certain plant acids on insoluble phosphates in 

 the presence of nitrates, G. Loges {Xetie Ztschr. Riibenz. Ind.^ 36 

 {1896), No. 16, pp. 173, 174). — Id experimeuts with H. von Liebig's 

 method,' in which 2 gm. of substance is digested for 4S hours, with occa- 

 sional shaking, with 5 gm. of acid potassium oxalate and U50 gm. of 

 water, 27 to 47 per cent of phosphoric acid of Thomas slag was dis- 

 solved, while 40 to 98 per cent of that in mineral phosphates went 

 into solution. The low solubility of the slag was probably due, as 

 pointed out by Emmerling,^ to the coating of the particles with oxalate. 

 By adding small amounts of nitric acid or nitrates this was overcome. 

 The calcium nitrate formed in this case reacts with the oxalate and sets 

 free the nitric acid, which forms more calcium nitrate, and thus the 

 cycle is repeated. A maximum solvent effect was obtained by adding 

 from 0.8 to 0.16 per cent of nitric acid to the solution, but in no case 

 was the solubility as high as with the mineral phosphates. This modifi- 

 cation was tested on a number of samples of slag, with the general 

 result of increasing the solubility about two and one half tunes. No 

 effect from the addition of nitric acid was observed in the case of the 

 mineral phosphate. 



Tests on slag of different degrees of fineness showed that the solu- 

 bility increased with the fineness of the i)articles. The lower solubility 

 of the coarse slag is claimed to be due to the fact that these particles 

 are coated with basic lime-iron silicate, which protects them from the 

 solvent action of the solution. Tartaric and citric acids did not influence 

 the solubility. 



Upon the determination of magnesium oxid as magnesium 

 pyrophosphate, H. Neubauer {Ztschr. angeic. Chem., 1896, No. 15, pp. 

 135-139). — After a long series of experiments, embodied in the article, 

 on the various influences bearing upon the accuracy of the determma- 

 tion of magnesium oxid as jjyrophosphate, the author arrives at the 

 following conclusions: 



The sodium phosphate should be added quickly to the solution made 



' Fiibling's laudw. Ztg., 1886, p. 65. 

 2Laudw. Vers. Stat., 30, p. 109. 

 192 



