AGRICULTURAL CHEMISTRY. 1007 



Jour. Cheni. Soc. [London], 96 (1909), No. 555, II, p. 92; Chem. Zentbl., 1909, 

 I, No. 3, !>. 210; Clidii. Abs., 3 (1909), No. 7, p. 763).— The perfected Jiiethod 

 proposed by the author is in brief as follows: In 500 cc. of a superphosphate 

 solution containing 20 gni, to the liter, precipitate the lime with exactly the 

 amount of normal itotassium oxalate required (this is determined by previous 

 titration of an aliquot of the solution), heat to about 70° C. until the granular 

 precipitate falls to the bottom, cool in a stream of water, make the volume to 550 

 cc, filter, and titrate 110 cc. of the filtrate with one-half-normal alkali solution, 

 using methyl orange or indigo methyl orange as indicator. To another portion of 

 110 cc. of the filtrate add 25 cc. of normal oxalate solution and titrate with the 

 same alkali solution, using phenolphthalein as indicator. The difference be- 

 tween the number of cubic centimeters obtained in the two titrations multiplied 

 by 0.0,')55 and by 50 gives the percentage of water-soluble phosphoric acid. The 

 number of cubic centimeters obtained in the first titration multiplied by the 

 same factors gives the percentage of free acid. 



The determination of nitrogen in calcium cyanamid, D. Girasoli (Atti R. 

 l.st. Incoiiujg. Napoli, 6. sei:, 59 (1907), pp. 13, l-'i). — The author reports a new 

 method, easily executed, sufficiently exact, and time saving. 



The calcium cyanamid is put into a glass tube connected on one side with a flask 

 in which steam is produced and on the other side with a condenser. The tube 

 is heated with a Bunsen lamp while steam is forced through and the distillate 

 is collected in a flask containing a known quantity of tenth-normal sulphuric 

 acid. The reaction is comi)lete when the distillate no longer gives an alkaline 

 reaction. The excess of sulphuric acid is titrated with a tenth-normal ammonia 

 solution, using phenolphthalein as an indicator. A table is appended com- 

 paring the results obtained with 3 samples by this and the Kjeldahl method. 

 A maximum difference of 0.13 per cent is shown. 



Comparative determinations of hardness in water, Klct (Mitt. K. Priifiiiig- 

 .sr/H.s7. Witsficrver. it. Abwasser. Berlin, 1908, No. 10, pp. 7-^-85; abs. in Chem. 

 Ztg., 32 (1908), No. 97, Repot., p. 632; Chem. Zentbl.. 1908, II, No. 25, p. 1953; 

 Jour. Chem. Soc. [London], 96 (1909), No, 556, II, p. 183; Csndhts. Ingen., 32 

 (1909), No. 16, pp. 270, 271). — Gravimetric analysis is considered the only 

 absolutely accurate method of determining hardness. For quick determination 

 Clark's soap method has value. The methods of Pfeiffer, Wartha, and Lunge 

 are considered unreliable. For temporary hardness the author titrates with 

 tenth-normal acid and methyl orange. "Carbonate" and "mineral-acid" hard- 

 ness are suggested as substitute terms for temporally and permanent hardness. 



The determination of the clay content of soils, C. C. PYetciikr (Science, n. 

 .st;-., 28 (190S). \o. 730, p. 930). — In the method described the amount of clay 

 is determined, after removing the coarser particles bj- centrifuging, by evaporat- 

 ing the clay water to dryness in enameled-ware cups having a capacity of about 

 300 cc. and weighing about 180 gm. The possibility of still further shortening 

 the process by determining the percentage of clay by difference is suggested. 



Shaking as a means of preparing soils for mechanical analysis, P, Kashin- 

 SKi (Zhiir. Opuitn. Agron. [Rush. Jour. Expt. Lttndir.], 9 (1908), No. .'/. pp. 

 Ji88-'i93). — The effect of shaking as compared with boiling was studied in the 

 mechanical analyses of three soils (one podzol, one alkali, and one chernozem). 

 The results are sunnned up as follows: (1) Shaking gives less i)articles with 

 the diameter less than 0.01 mm. and more particles of the diameter 0.25 to 0.05 

 than boiling does; (2) by increasing the volume of water in shaking these 

 difterences grew less; (3) for alkali and podzol soils the values obtained by 

 shaking and boiling are practically equal. The values differ strikingly iu the 

 case of chernozem soils. 



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