914 EXPERIMENT STATION RECORD. 



author concludes that the silver chlorid method, slightly modilied as described, and 

 the ammonium sulphate method are extremely accurate and satisfactory, the former 

 for standardizing solutions of hydrochloric and the latter of sulphuric acid. 



The determinatioii of available plant food in soils by the use of -weak acid 

 solutions, A. D. Hall and F. J. Plvmex (Jour. Chem. Soc. [London'], 81 {1902), 

 Xo. 470, jjp. 117-144). — "The authors have comjiared the amounts of phosphoric acid 

 that could be extracted from 19 different soils by a 1 per cent solution of citric acid, 

 by equivalent solutions of hydrochloric acid and acetic acid, by a saturated solution 

 of carbonic acid, and by an ainmoniacal solution of ammonium citrate, respectively. 

 Seven of these soils were from plats on the Broadbalk Field, Rothamsted, which had 

 been continuously manured in the same manner for 42 years previously; the remain- 

 ing 12 were soils of very varied origin, which had been the subject of crop experi- 

 ments and whose reaction to phosphatic manuring was well marked. 



"In the same 7 soils from the Broadbalk Field, the authors determined the potash 

 extracted by the same dilute solvents with the exception of ammonium citrate; tive 

 other soils of different origin, whose response or otherwise to potash manuring had 

 been tested by exiieriment, were also examined in the same way. 



"Determinations were also made of the phosphoric acid and potasli dissolved after 

 long digestion with strong hydrochloric acid, of the loss on ignition, and of the 

 earthy carbonates present in each soil. 



"The authors conclude: (1) That no sharp line of distinction can be drawn 

 between ' available ' and nonavailable phosphoric acid and potash in the soil, and 

 that any process of determining the 'available' constituents is an empirical one, 

 dependent on the strength and nature of the acid used. 



"(2) That the weak solvents give information as to the requirements of a given 

 soil for mineral manures of a far more trustworthy nature than that which is afforded 

 by such a solvent as strong hydrochloric acid. 



"(3) That of the acids examined, the 1 per cent solution of citric acid gives results 

 most in agreement with the recorded history of the soil, although there is evidence 

 that the same interpretation can not be put on results obtained from all types of 

 soil." 



Methods of analysis adopted for soils, fertilizers, feeding- stuflFs, wheat 

 and flour, and some miscellaneous substances, F. B. Guthrie {Agv. Gaz. Xcn' 

 South Wales, 12 {1901), Xo. S, ]>p. 905-915). — Details are given of the methods which 

 have been in use for several years in the laboratory of the Xew South Wales 

 department. 



A simple rapid eudiometric method of determining chlorin in chlorids and 

 hydrochloric acid, silver and phosphoric acid, E. Kn:GLEK( Z/.vcA/'. Anuhjt. ('hem., 

 40 {1901), Xo. 10, pp. 633-688; ahs. in Chem. Centhl., 1902^1, Xo. 1, p. 70).— The 

 method is based on the principle that when silver chlorid is treated with hydrazin 

 sulphate and sodium hydroxid solution the silver separates out in metallic form and 

 nitrogen is set free accordingto the following equation: 4AgCl-rN2H4.H2S04---NaOH = 

 4Ag-r4XaCl+Na.2S04n-6H20+X2. The method of procedure in case of phosphates 

 is as follows: Dissolve the phosphate in water strongly acidulated witli nitric acid. 

 To a quantity of this solution corresponding to from 0.15 to 0.16 gm. of phosphoric 

 acid, diluted if necessary to 50 to 60 cc, first add 1 to 2 gnu of silver nitrate dissolved 

 in about 10 cc. of water, then drop by drop a 10 per cent solution of sodium hydroxid 

 until the silver ])hosphate precipitate is not completely redissolved. .X^ld in the 

 same manner a 10 per cent solution of ammonia until the solution is alkaline, and 

 boil for about 5 minutes. Cool the solution, collect the precipitate on a small filter, 

 and wash with water, remo\-ing it to a flask by breaking the filter and Avashing it 

 out with about 50 cc. of water. Add about 3 cc. of concentrated nitric acid and 1 gm. 

 of sodium chlorid dissolved in water, close the flask and shake vigorously for h minute, 

 collect the precijiitate (jf silver chlorid on a small filter, and wash until it is free from 



