CONVENTION OF OFFICIAL AGRICULTURAL CHEMISTS. 179 



Ou iuvitatiou, the Assistant Secretary of Agrieulture appeared before 

 the convention and delivered a brief address, 



Fertiliz('):s.—{\) Potash, — Tlie report ou potash was presented by H. 

 J. Wheeler. The work of the year on this snbject consisted principally 

 of tests of errors due to impurities in reagents and to double decom- 

 position of potassium-platinum chlorid due to the ammonium chlorid 

 wasli used in the Lindo-Gladding method. The following- changes in 

 the methods for potash were adopted : 



In the alternate method the time of boiling in preparing the solu- 

 tion was increased to 30 minutes and the number of cubic centimeters 

 of water used to 300, to conform with directions for the same operation 

 under the Lindo-Gladding method; the directions for preparing solu- 

 tions of organic substances containing potash were slightly modified 

 to make them more explicit, and the use of ether in washing the potas- 

 sium-platinum ehlorid obtained in the alternate method was disi^ensed 

 with. It w'as finally recommended that the reporter for next year con- 

 tinue the lines of investigation pursued during the past year, and in 

 addition make comparative tests of the methods in the presence of 

 maximum amounts of sulphates, and to investigate the value of adding 

 calcium chlorid to remove soluble phosphates in the determination of 

 potash in superphosphates by the Lindo-Gladding method, as proposed 

 by H. A. Huston. 



(2) Fhosphorie acid. — The report on phosphoric acid was submitted 

 by B. W. Kilgore. The subjects of investigation during the year were 

 (1) Eoss' method of direct determination of citrate soluble phosphoric 

 acid;' (2) treatment of the residue from the citrate solution with a 

 mixture of nitric and hydrochloric acids instead of igniting; (3) deter- 

 mination of phosphoric acid by titrating the yellow precipitate of 

 ammonium phosphomolybdate;^ and (4) methods of washing the pre- 

 cipitate with magnesia mixture. 



After discussion of the report ami the reading of special papers on 

 the subject of phosphoric acid, the following changes in ofiicial 

 methods were adopted : In the i)reparation of the solution of the 

 residue from digestion with citrate solution it is made optional whether 

 the residue is ignited and dissolved in hydrochloric acid or returned 

 to the digestion flask and treated with a solution of from 30 to 35 cc. 

 of nitric acid and from 5 to 10 cc. of hydrochloric acid ; and in the 

 directions for the preparation of dilute ammonia for washing it is speci- 

 fied simply that the solution shall contain 2i per cent of ammonia, the 

 wording in other parts of the method being made to conform to this 

 change. In view of the contradictory results with the Ross method of 

 direct determination of citrate-soluble phosphoric acid, it was recom- 

 mended that it be subjected to further trial before being passed upon 

 by the association. 



' U. S. Dept. Agr., Div. of Chein. Bnl. 38, p. 16; or Jonr. Am. Chem. 8oc., 16 (1894), 

 No. 5, p. 304. 



-Jonr. Am. Chem. Soc, 15 (1893), No. 7, ].. 3S2 ; 16 (1894), No. 1, p. 278. 



