RECENT WORK IN AGRICULTURAL SCIENCE. 



AGRICITLTTJRAL CHEMISTRY. 



Determination of sodium and potassium in silicates, J. E. Thomsen {Jour. 

 Amer. Chem. Soc, 30 (WOS), No. 3, pp. .'{20, Ji21; abs. in Chcm. Abs., 2 {1908), 

 ?;o, 17, pp. 235.li, 2355). — It is stated that the following method has been found 

 rapid and satisfactory for the determination of sodium and potassium in clay 

 and silicates which can be decomposed by sulphuric and hydrofluoric acid : 



" One gm. of clay is decomposed by means of sulphuric and hydrofluoric 

 acids, and the excess of sulphuric acid expelled in a hot-air bath. The residue 

 is then dissolved in water and powdered barium hydroxid added to the boiling 

 liquid to alkaline reaction. The solution is decanted and filtered, and the resi- 

 due boiled again with water and thoroughly washed. Carbon dioxid is passed 

 into the filtrate in excess, the solution evaporated to 50 cc, 25 cc. of alcohol 

 (96 per cent) added, and the solution filtered and the residue washed with 50 

 per cent alcohol. A measured excess of tenth-normal hydrochloric acid is then 

 added to the filtrate and the solution boiled to expel the carbon dioxid, litmus 

 being used as an indicator and more acid being added, if necessary, to give a 

 permanent acid reaction after boiling. The titration is then finished with 

 tenth-normal sodium hydroxid. The solution is evaporated to dryness in plati- 

 num, dried at 110° and finally at very faint redness, and the residue of potas- 

 sium and sodium chlorids weighed. The amount of each metal can be calcu- 

 lated on the following principle : 

 Let a=No. of cc. of tenth-normal HCl used less the No. of cc. of tenth-normal NaOH. 



b=aXA 0.00585=weight of NaCl equivalent to sum of NaCl+KCl. 



c=weight of NaCl+KCl formed less the weight of NaCl corresponding to the 

 weight of NaOH used. 



x=weight of Na. 



y= weight of K. 



_, , 58.5 ^58.5 

 Then b=23;o5X+3g^y. 



58.5 . 74.6 

 ^~23.05 ^"^" 39.15 y- 

 y=2.432 (c-b). 



23.05/" 74.6 \ 

 = 58:5C*^-39.150=^^-^^^^^"^-^^^- 



Determination of potash in soils, L. Ronnet {Ann. Chim. Analyt., 13 

 {HJOi^), Xo. //, pp. l.'il-lJfS). — The method proposed is as follows : Treat 25 gm. of 

 the soil in a porcelain dish with a flat bottom 11 cm. in diameter with nitric 

 acid until effervescence ceases. Add 25 cc. more of the acid and heat for 5 

 hours on a sand bath. Precipitate sulphuric acid with a few drops of saturated 

 solution of barium nitrate. Evaporate to dryness and heat in a muffle at a low 

 red heat until nitrous vapors disai)pear, the nitrates of iron and aluminum 

 are completely decomposed, and the nitrates of calcium and magnesium par- 

 tially decomposed. Take up in a little water and precipitate lime with 10 to 20 

 gm. of oxalic acid according to the lime content of the soil. Warm under cover 



417 



