564 AGRICULTURAL ANALYSIS 



about one-tenth per cent, higher than are obtained by the offi- 

 cial processes. 



476. The Calcium Chlorid Method. Huston has proposed the 

 addition of calcium chlorid to the solutoin of a fertilizer in the 

 determination of potash, in order to furnish sufficient calcium 

 to form tricalcium phosphate with all the phosphoric acid present, 

 and thereby permit the use of platinum dishes in the lindo-glad- 

 ding method. 44 In testing this process de Roode found that when 

 sufficient calcium chlorid was added to combine with all the phos- 

 phoric acid present and then ammonia added in excess and a por- 

 tion of the solution filtered, no test for phosphoric acid could be 

 obtained ; but, that if in addition to the calcium chlorid and am- 

 monia, some ammonium oxalate or carbonate was added, a fil- 

 tered portion of the solution gave a test for phosphoric acid. 45 

 This is accounted for by the fact that the calcium phosphate, 

 which is precipitated by the ammonia, is changed by the ammo- 

 nium oxalate or carbonate into calcium oxalate or carbonate and 

 ammonium phosphate, so that the very object for which the cal- 

 cium chlorid was added is defeated by the addition of the ammo- 

 nium oxalate or carbonate. In order to make the use of calcium 

 chlorid effective it is necessary to filter the liquid from the precipi- 

 tate formed by the calcium chlorid and ammonia and then add 

 the ammonium oxalate or carbonate to the filtrate. This neces- 

 sitates two separate filtrations and makes the proposed method 

 of Huston as long as the old process. 



477. Moore's Potash Method for Fertilizers as Modified by 

 Veitch. In reviewing the methods used and proposed for estimat- 

 ing potash in fertilizers Veitch has suggested that the losses now 

 occurring may be partly or entirely overcome by using the method 

 of Moore, provided, of course, any potash is occluded in the 

 ammonia and ammonium oxalate precipitate in the lindo-glad- 

 ding method. 46 The addition of other bases, as proposed by Hare 



14 Division of Chemistry, Bulletin 43, 1894 : 26. 



* & Journal of the American Chemical Society, 1895, 17 : 46. 



** Journal of the American Chemical Society, 1905, 27 : 56. 



Fiinfter internationaler Kongress fiir angewandte Chemie ; Bericht, 

 1904, 1 : 486. 



Wiley, Principles and Practice of Agricultural Analysis, and Edition, 

 1906, 1 : 429. 



