(2) Methods of making solution. 



(a) With potash salts and mixed fertilizers. Boil 10 grams of the sample with 

 300 cc of water thirty minutes. In the case of mixed fertilizers, add to the hot 

 solution a slight excess of ammonia and then sufficient powdered ammonium 

 oxalate to precipitate all the lime present. Cool, dilute to 500 cc, mix and pass 

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

 ash and magnesia and kainit, dissolve and dilute to 500 cc 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 like cotton seed meal, tobacco stems, 

 etc., saturate 10 grams with strong sulfuric acid, and ignite in a muffle at a low 

 red heat to destroy organic matter. Add a little strong hydrochloric acid and 

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

 under (3) (a). 



(3) Determination. 



(a) In mixed fertilizers. Evaporate 50 cc of the solution made according to 

 (2), corresponding to 1 gram of the sample, nearly to dryness, add 1 cc of dilute 

 sulfuric acid (1 to 1), evaporate to dryness and ignite to whiteness. As all the 

 potash is in form of sulfate, no loss need be apprehended by volatilization of 

 potash, and a full red heat must be maintained until the residue is perfectly 

 white. Dissolve the residue in hot water, using at least 20 cc for each decigram 

 of K 2 O, add a few drops of hydrochloric acid and platinum solution in excess. 

 Evaporate on a water bath to a thick paste and treat the residue with 80 per cent 

 alcohol, sp. gr. 0.8645, avoiding the absorption of ammonia. Wash the precipi- 

 tate thoroughly with 80 per cent alcohol both by decantation and on the filter, 

 continuing the washing after the filtrate is colorless. Wash finally with 10 cc of 

 the ammonium chlorid solution (1) (a), to remove impurities from the precipi- 

 tate and repeat this washing five or six times. Wash again thoroughly with 80 

 per cent alcohol and dry the precipitate for thirty minutes at 100. The precipi- 

 tate should be perfectly soluble in water. 



(b) Muriate of potash. Dilute 25 cc of the solution, prepared according to (2) 

 (a), with 25 cc of water, acidify with a few drops of hydrochloric acid, add 10 cc 

 of platinum solution and evaporate to a thick paste. Treat the residue as under 

 (3) (a). 



(c) Sulfate of potash, sulfate of potash and magnesia, and kainit. Dilute 

 25 cc of the solution, prepared according to (2) (a), with 25 cc of water, acidify 

 with a few drops of hydrochloric acid and add 15 cc Of platinum solution. Evap- 

 orate the mixture and proceed as directed under (3) (a), except that 25 cc por- 

 tions of ammonium chlorid solution should be used. 



(b) OPTIONAL METHOD.* 

 (1) Preparation of reagent. 



Platinum solution. The platinum solution used is the same as that described 

 under the Lindo- Gladding method. 



(2) Method of making solution. 



The solution is prepared as directed under the Lindo -Gladding method, omit- 

 ting in all cases the addition of ammonia and ammonium oxalate. 



* The Lindo-Gladding method is preferable in the presence of soluble sulfates. 



