1920] AGRICULTURAL CHEMISTRY AGROTECHNY. 13 



" The precipitate formed in titrating the soil extract obtained by the Hop- 

 kins method absorbs the indicator to a marked extent. Tlie end result depends 

 upon the temperature, time, and amount of indicator used. 



" The acidity of tlie first portions of tlie neutral salt extracts of an acid soil 

 increases with increase in concentration of the neutral salts. 



" The difference in absorption of calcium and potassium from solutions of 

 their bases by an acid soil may be accounted for by precipitation effects. 



" There is a marked basic exchange when a neutral salt solution is added to 

 an acid soil, by which alumina is carried into solution. This, however, does 

 not account for the total acidity of the solution. 



" When acid soil is extracted with ix)tassium acetate solution, a portion of 

 acetic acid may be distilled off from the extract, showing the presence of free 

 acid. 



" Exchange of acid radicals when an acid soil is treated with a neutral salt 

 solution was not noted." 



A rapid and accurate method for determining nitrogen in nitrate of 

 soda by the modified Devarda method and the use of the Davisson scrubber 

 bulb, C. A. Butt {Jour. Indus, and Engin. Chem., 12 (1920), No. 4, pp. 352- 

 35 Jf). — The procedure described involves the use of the Davisson scrubber 

 (E. S. R., 40, p. 806) in the method essentially as described by Allen, a modi- 

 fication of which by Davisson and Parsons has been previously noted (E. S. R., 

 40, p. 711 ) . The technique is as follows : 



The sample is put through a 10-mesh sieve and mixed tlioroughly, 17,034 gm. 

 being then weighed into a 500 cc. volmetric flask, dissolved in 300 cc. of water, 

 cooled, and made up to volume. After mixing thoroughly, 25 cc. of the soluticm 

 is pipetted into a Kjeldahl flask of 500 to 650 cc. capacity, and to this are added 

 300 cc. of water, 3 gm. Devarda's alloy (75 per cent of which will pass a 

 20-mesh sieve), and 3 to 5 cc. 45° Baum4 NaOH. The flask is connected at once 

 with the Kjeldahl distilling apparatus fitted with the Davisson scrubber into 

 which has been drawn 20 or 30 cc. of water, and the distillation conducted 

 simultaneously with the reduction, the boiling being so regulated that from 

 175 to 200 cc. of distillate is collected in about one hour. The ammonia is ab- 

 sorbed in 21 cc. of n/2 H2SO4 and titrated as usual with methyl red as 

 indicator. 



Analyses are reported which indicate that exceptionally accurate results are 

 obtained with this method, and that the presence of 1 gm. of sodium chlorid 

 or sodium carbonate in the sample has no appreciable effect on the determina- 

 tion. 



The determination of iodid and bromid in mineral waters and brines, 

 W. F. Baughman and W. W. Skinner {•Jour. Indus, and Engin. Chem., 12 

 {1920), No. Jf, p. 358). — In this paper some results are reported of the iodid and 

 bromid content of mixtures of iodid, bromid, and chlorid, as determined by 

 combining the ferric sulphate method for iodid described in a previous contri- 

 bution (E. S. R., 41, p. 12) with the chromic acid method for bromid (E. S. R., 

 42, p. 8). The general procedure is as follows: 



The iodin is determined in one sample by the permanganate method. From 

 another sample, which should contain not more than 0.1 gm. of bromin as 

 bromid nor more than 10 gm. of total solids, the iodin is removed by oxidation 

 with ferric sulphate and distillation with steam, the distillate beuig received 

 in a potassium iodid solution. The residue in the distilling flask is transferred 

 to a beaker, heated to boiling, and treated with annuonium or sodium hydroxid 

 to precipitate the iron. After filtering and washing the precipitate with hot 

 water the filtrate is evaporated to dryness and the bromid determined in the 

 residue by the chromic acid procedure. 



