OFFICIAL AGRICULTURAL METHOD 54! 



-with platinic chlorid solution. The best methods of executing 

 the analysis follow. 



463. The Official Agricultural Method. This method is based 

 on the processes at first proposed by Lindo 30 and Gladding, 31 

 and is given below as adapted to mixed fertilizers and mineral 

 potash salts. 32 



(1) Preparation of reagents. (a) Ammonium chlorid solu- 

 tion. Dissolve ico grams of ammonium chlorid in 500 cubic cen- 

 timeters of water, add from five to 10 grams of pulverized potas- 

 sium-platinic chlorid, and shake at intervals for six or eight hours. 

 The mixture is allowed to settle over night and filtered, and the 

 residue is ready for the preparation of a fresh supply. 



(b) Platinum solution. The platinum solution used contains 

 one gram of metallic platinum (2.1 grams of H 2 PtCl 9 ) in every 

 10 cubic centimeters. 



(2) Methods of making solution. (a) With potash salts and 

 mixed fertilizers. Boil 10 grams of the sample with 300 cubic 

 centimeters of water 30 minutes. In the case of mixed fertilizers 

 add to the hot solution a slight excess of ammonia and then suffi- 

 cient powdered ammonium oxalate to precipitate all the lime 

 present. Cool, dilute to '500 cubic centimeters, mix and pass 

 through a dry filter. In case of muriate and sulfate of potash, 

 sulphate of potash and magnesia and kainit, dissolve and dilute 

 to 500 cubic centimeters without the addition of ammonium and 

 ammonium oxalate. 



(b) With organic compounds. When it is desired to determine 

 the total amount of potash in organic substances, such as cotton- 

 seed meal, tobacco stems, etc., saturate 10 grams with strong sul- 

 furic acid, and ignite in a muffle at a low red heat to destroy 

 organic matter. Add a little strong hydrochloric acid, warm 

 slightly in order to loosen the mass from the dish, and proceed 

 as directed under (3) (a) below. 



(3) Determination. (a) In mixed fertilizers. Evaporate 50 

 cubic centimeters of the solution made according to (2), cor- 



80 Chemical News, 1881, 44 : 77, 86, 97, 129. 

 51 Division of Chemistry, Bulletin 7, 1885 : 38. 

 " Bureau of Chemistry, Bulletin 107, 1907 : n. 



