234 AjJj^endix 



Potash, (a) Muriate, free from, sulphate. A weighed quantity of 

 the sample 5 grm. of a high-grade, 10 grm. of a low-grade muriate 

 is dissolved in water, and the solution, filtered if necessary, made up 

 to 500 c.c. To 50 c.c. of this a few drops of hydrochloric acid and 

 10 to 20 c.c. of a solution of platirric chloride containing 10 grm. 

 platinum in 100 c.c. water are added. Evaporate over the water- 

 bath to a syrup, cool, treat with alcohol of sp. gr. 0-864. Collect the 

 precipitate on a weighed filter paper, wash with alcohol as above, 

 dry at 100 C, and weigh. 



Or, as a simpler and equally accurate process: 



To 50 c.c. of the solution filtered from the 500 c.c. above add 7 to 

 12 c.c. of a 20 per cent, solution of perchloric acid (sp. gr. 1-125): 

 concentrate till white fumes are copiously evolved: redissolve the 

 precipitate in hot water: add 'a few drops of the perchloric acid 

 solution and again concentrate to the fuming stage. Cool. Stir the 

 residue with 20 c.c. alcohol of sp. gr. 0-816 to 0-812. Allow the pre- 

 cipitate to settle, filter by decantation through a weighed filter paper 

 or a Gooch crucible: wash with alcohol saturated with potassium 

 perchlorate; dry at 100 C. and weigh. 



(6) 8alts containing sulphate. Boil a weighed quantity of the 

 sample (5 to 10 grm.) with about 300 c.c. water and 20 c.c. hydro- 

 chloric acid in a 500 c.c. flask. Barium chloride is added drop by 

 drop till precipitation of the sulphuric acid is complete. Any excess 

 of barium chloride is then removed by careful addition of sulphuric 

 acid. Cool, and make up to 500 c.c A portion of the solution is 

 filtered, the precipitate washed, and the potassium in 50 c.c. of the 

 filtrate determined as above either by the platinum chloride or the 

 perchlorate method: as in (a). 



(c) Guxtnos, mixed fertilisers, etc. 10 grm. of the sample are gently 

 ignited to destroy organic matter, heated for 10 minutes with 10 c.c. 

 of concentrated hydrochloric acid, and finally boiled with 300 c.c. 

 water. Filter into a 500 c.c. flask, raise to the boiling point, and add 

 a slight excess of powdered barium hydrate. Cool, make up to 

 500 c.c, and filter. To 250 c.c. of the filtrate add ammonium hydrate 

 and ammonium carbonate, and then, while boiling, a little powdered 

 ammonium oxalate. Cool, make up to 500 c.c, and filter. Evaporate 

 100 c.c of the filtrate in a porcelain dish, heat the residue first in an 

 air-bath and then very gently over a low flame till all volatile matter 

 is driven off, but keep the temperature below dull redness. Moisten 



