AGRICULTURAL CHEMISTRY AGROTECHNY. 313 



made with pure dried ammonium clilorid dissolved in water with the aid of a 

 few drops of hydrochloric acid. 



In using the boric acid method in the Kjeldahl procedures it is advisable to 

 use a large excess of boric acid in the distillate collecting flask — i. e., 10 gm. 

 of boric acid in 100 cc. of water for from 200 to 300 cc. of distillate. If the 

 distillate amounts to only 100 cc. or less, 5 gm. of boric acid should be used. 



The ammonia present is to be titrated with the standard hydrochloric acid 

 solution, and not, as inadvertently stated in a previous abstract (E. S. R., 31, p. 

 lOS), the excess of boric acid. For this purpose the author recommends the em- 

 ployment of tenth-normal or fifth-normal hydrochloric acid solution, but dis- 

 courages the use of sulphuric acid. If Congo red is used the solution to be 

 titrated should be perfectly cool. 



Remarks on L. W. Winkler's work on the estimation of ammonia with, 

 the boric acid method, E. Bernard (Ztschr. Angeiu. Chem., 21 (1014), No. 102, 

 Aufsatzteil, p. 664)- — ^The boric acid method is deemed rapid and convenient 

 and yields very accurate results. 



The solubility of mineral phosphates in citric acid, G. S. Kobeetson (Jour. 

 Soc. Chcm. Indus., 33 (1914), No. 1, pp. 9-11; abs. in Ztschr. Angeto. Chem., 

 27 (1914), No. 64-G5, Referatenteil, p. 506). — Determining in the usual manner 

 citric acid soluble phosphoric acid in mineral phosphates destined for fertilizers 

 is said to yield erroneous results. A single extraction with citric acid will not 

 suffice and repeated extraction will dissolve almost all the phosphorus present in 

 the fertilizer. The yields obtained with mineral phosphates on experimental 

 plats are said to be as good as those given with slag or with bone meal. 



A convenient method for separating iron and aluminum, H. Bokck (Chem. 

 Ztg., 38 (1914), No. 1, p. 7, fig. 1; abs. in Ztschr. Angew. Chem., 27 (1914), No. 

 29, Referatenteil, p. 249). — The method depends upon the volatilization of the 

 iron from a mixture of iron and aluminum oxids by heating in hydrochloric 

 acid through which a current of air is being passed. It will yield constant 

 results only when a quartz boat is used. 



Copper sulphate of commerce and methods for determining copper therein, 

 F. Mach and P. Lederle (Landic. Vers. Stat., 84 (1914), No. 1-2, pp. 129-143). — 

 The fact that a sample of copper sulphate has a satisfactory appearance is not 

 sufficient evidence of its value for spraying purposes. The Windisch method "■ 

 for determining copper with sodium hypophosphite yielded low results, despite 

 the fact that the filtrate from the reduced copper does not give a reaction with 

 either ammonia or potassium ferrocyanid. Better results were obtained when 

 the copper reduced by sodium hypophosphite was collected in an Allihn tube 

 instead of roasting the precipitate as suggested by Windisch, but this method, 

 unless modified, is of value only when speedy results are desired. Rhead's^ 

 and Moser's " methods were tried and also found unsatisfactory. 



The following method, which embodies some of the essentials of the Rhead 

 and Moser methods, is recommended: Dissolve 10 gm. of the copper sulphate 

 in approximately 200 cc. of hot water, render slightly alkaline with ammonium 

 hydroxid, oxidize the ferrous iron with about 5 cc. of a 2 per cent hydrogen 

 peroxid solution (this is adequate for salts containing 2 per cent ferrous sul- 

 phate), keep the solution at the boiling point for two minutes, and filter off 

 the ferric hydrate. Wash the precipitate, dissolve in a little hot hydrochloric 

 acid, reprecipitate the iron with ammonia, filter, and add the washings there- 

 from to the original solution. JIake the iron-free solution slightly acid with 



"Ztschr. Analyt. Chem., 52 (1913), No. 1, pp. 1-13. 

 *Jour. Chem. Soc. [London], 89 (190G), II, pp. 1491-1495. 

 -^Chem. Ztg., 36 (1912), No. 117, pp. 1126, 1127. 



