AGRICULTURAL CHEMISTRY AGROTECHNY. 115 



verted into aldehyde with potassium permaiigauate in a solution containing 

 sulphuric acid. After the reduction of a sodium-silver solution by the aldehyde, 

 the excess of silver is determined. The equation representing the process is 

 Ag.04-CH3.CHOH.CO,H=Ag2+CH3.CHO+CO.+H20. 



Estimation of formic acid, T. Torquati {Rend. Soc. Chim. Ital., 2. scr., Jf 

 (1912), No. 11, pp. 307, 308; ahs. in Chem. Ztg., 37 (1913), No. 45, p. 456).— This 

 depends upon the reduction of mercuric to mercurous cblorid. The amount of 

 precipitated calomel corresiwnds to the formic acid present. 



Estimation of nitric acid, T. Tokquati (Rend. Soc. Chim. Ital., 2. ser., Jf. 

 (1912), No. 11, pp. 308-310; abs. in Chem. Ztg., 37 (1913), No. Jf5, p. //56).— The 

 method described is based ui)on the reduction of the nitric acid to nitrous oxid 

 by formic acid. 



Detection of nitrous acid when present with ferric salts, P. Artmann 

 (Chem. Ztg., 37 (1913), No. 49, p. 501).— The reaction is conducted as follows: 



In 100 cc. of water dissolve 8 gm. of pure disodium phosiphate and add about 

 0.2 gm. of potassium iodid; shake until the phosphate is dissolved and only a 

 white turbidity remains. Then acidify with 5 cc. of 4 times normal hydrochloric 

 acid solution and add 2 cc. of starch solution (zinc iodid starch was found to 

 serve well for this purpose). If 0.3 mg. or thereabouts of N2O3 is present a blue 

 coloration is obtained. If large amounts of ferric salts are present, the reaction 

 is accelerated. By this means as little as 0.1 to 0.2 mg. of N2O3 when present 

 with ferric salts to the extent of 500 mg. to the liter can be detected. 



The detection of nitrates and nitrites in sewag'e, A. Higginson (Chem. 

 News, 106 (1912), No. 2769, p. 306; abs. in Chem. Ztg., 37 (1913), No. 47, p. 

 480). — The nitrates in sewage can easily be converted into ammonia with a 

 copper zinc electrode contained in a solution of sodium hydroxid. The solution 

 is then distilled and the ammonia determined in the distillate. If too small 

 amounts of sodium hydroxid are used, the ammonia only passes over into the 

 distillate when the solution has been concentrated to a very small volume. 



The results obtained compare well with those given by the phenolsulphonic 

 acid method. 



A method for determining phosphoric acid, L. Moeser and G. Frank 

 (Ztschr. Anahjt. Chem., 52 (1913), No. 6, pp. 346-349; abs. in Chem. Ztg., 37 

 {1913), No. 74, Repert., p. 337). — From 0.3 to 0.5 gm. of the mineral under 

 examination is treated with 4 to 6 cc. of concentrated sulphuric acid and heated 

 to the boiling point on a sand bath for 10 to 50 minutes. After cooling, 30 to 

 40 cc. of 95 per cent alcohol and 2 cc. of a 10 per cent alcoholic potassium 

 hydroxid solution are added, shaken, cooled, filtered, and the precipitate washed 

 with alcohol. All of the buses remain on the filter, while the phosphoric acid is 

 contained quantitatively in the filtrate, which after dilution with an equal 

 volume of water is rendered slightly alkaline with ammonia and the phosphoric 

 acid precipitated with magnesia mixture. The phosiihoric acid is weighed as 

 magnesium pyrophosphate. 



Citro-phosphate solutions. — I, The homog'eneous equilibrium in aqueous 

 solution as studied by the cryoscopic method, U. Pratolongo (Atti R. Accacl. 

 Lincei, Rend. CI. Sei. Fis., Mat. e Nat., 5. ser., 20 (1911), I, No. 11, pp. 812-818; 

 abs. in Jour. Soc. Chem. Indus., 31 (1912), No. 4, P- 195). — A study on the nature 

 of solutions of calcium phosphates in citric acid and ammonium citrate, which 

 deals especially with the cryoscopic value of solutions of citric acid, of mono-, 

 di-, and tricalcium phosphates in citric acid, of diammonium citrate, and of 

 mono- and dicalcium phosphates in diammonium citrate. The results obtained 

 were at variance with those found by Ilerzfekl and Feuerlein," Barille (E. S. R., 



"Ztschr. Analyt. Cliem., 20 llSSlJ, pp. 101-208. 



