RECEiVr WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



The determination of perchlorate in saltpeter, A. Dupre {Jour. Soc. Chem. Lid., 

 21 {1903), No. 13, pp. S25-S37).^Thii methdd jiroposed is as follows: Heat 10 and 

 20 gm., respectively, of this salt in nickel crucibles of about 70cc. capacity fitted with 

 a shaliovv-dish-sliaped, well-fitting cover, to a temperature of 545° C. for one hour. 

 The furnace or air liath recommended for this purpose is the (Gilbert modification of 

 L. Meyer's air bath. After cooling the fused mass of 20 gm. dissolve in warm water 

 and transfer the solution to a 200 cc. measuring flask, make up to the mark, and 

 witlidraw 25 cc. of the solution for a preliminary determination of chlorin by the 

 Mohr method. After this preliminary test add to a fresh portion of 100 cc. of the 

 solution an amount of standard silver solution (1 cc. ^0.001 chlorin) slightly more 

 than sufficient to precipitate all of the chlorin present (as shown by the preliminary 

 test), add 4 cc. of strong nitric acid, and heat fm sand bath to the boiling point (but 

 avoiding elmllition) for iialf an hour. Cool the solution, filter, wash the precipitate 

 thoroughly, add a little persulphate of iron to the clear filtrate, and determine the 

 silver by titration with stan<lard sohition of ammonium sulphocyanid according to 

 Volhard's method. Determine the chlorin by the same method in 10 gm. of the 

 saltpeter before heating. "The difference in chlorin before and after heating is the 

 measure of perchlorate present, provided, of course, that no other chlorin compound is 

 present. The titration may be repeated if desired, with the 10 gm. of saltpeter, using 

 the whole of the solution for one experiment." 



The determination of total phosphoric acid in Thomas slag, C. Aschman 

 {BuJ. Asaoc. Behji' ('him., 16 {1902), /ip. 140-142; ab.?. in Chem. Q'lilhl., 1902, II, No. 

 2, p. 155). — A slight modification of the author's previously descri))ed method (E. S. 

 R., 11, p. 507) is proposed. 



Note on the analysis of superphosphates, J. Legrand {Bui. Assoc. Beige Chim., 

 16 (l'.)02), pji. 14.3, 144; oh.s. ill Cliem. Cenlhl., 1902, IT, No. 2, p. i56').— Attention is 

 called to the fact that the cloudiness which appears in water solutions of superphos- 

 phates on standing is due to a mixture of iron and aluminum phosphates. 



Determination of sulphuric acid in soils, C. B. Williams {Jmir. Amer. Chem. 

 Soc, 24 {1902), No. 7, pp. 658-661). — A series of determinations of sulphuric acid in 

 soils by the method of the Association of Official Agricultural Chemists, and by a 

 modification of the same method in which the iron and alumina were first removed 

 by precipitation with l)arium sulphate, are reported, wliich show that nuich higher 

 results are (jl>tained by the modified method. This is apparently due to solution of 

 barium sulphate by either the ferric chlorid or aluminum chlorid or by both. 



A lime test for soils rich in lime and marls, M. Passon {Dent. Landu: Presse, 

 29 {1902), No. 6S, p. 5G2). — A descrii)tion, with explanation of method of use, of 

 the Passon apparatus, which has already been noted (E. 8. R., 13, p. 319). 



The determination of ammonia in waters, O. E.mmerling {Ber. Deut. Chem. 

 Gesell.,35 {1902), p. 2291; abs. in Chem. Ztg.,26 {1902), No. 68, Reperi.,p.214; Chem. 

 Centhl., 1902, II, No. 4, p. 298).— The ordinary method of direct determination of 

 ammonia by means of Nessler's reagent is condemned as inaccurate in presence of 



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