ON THE ESTIMATION OF POTASH ANO PHOSPHORIC ACID. 39 



precipitate with alcohol of 98 per cent. Us removes any sulphates with a 

 slight excess of chloride of barium. He remarks that "the most essential 

 point of the whole method is the purity of the chloride of platinum, which 

 can be well proved by testing it with chemically pure muriate of potash. 

 This, of course, must yield 100 per cent. If more or less, the platimim solu- 

 tion has not been pure. If the platinum solution is correct, even less practised 

 hands will obtain exact results by the above method, which is now universally 

 applied in the manufactories of our place." 



The above replies and correspondence show conclusively the necessity for 

 independent experiments on mixtures containing known amounts of real 

 potash. 



Statement of Results of Analyses of Potash Salts. 



The information the Committee has received on this subject is limited to 

 the opinions of a few chemists. Without endorsing the whole of the fol- 

 lowing observations, the Committee beHeve that the subjoined remarks will 

 be read with interest and advantage. 



"It is quite likely that the sulphuric acid exists in these (kelp) muriates 

 not as sulphate of potash, but as the double salt 3K^ SO^ -t-J^a., SO^ 

 (discovered in kelp potash salts by Penny of Glasgow) ; and if so, the large 

 proportion of sulphates present in kelp muriates (usually from 4 to G per 

 cent.) would involve a shght alteration in the mode of stating the results, and 

 would introduce sodium sulphates to a small extent. This view, however, 

 even if proceeded upon in practice, would not interfere practically with the 

 commercial value of the sulphates. 



" There cannot be a doubt that the alkali present is carbonate of soda, both 

 from the fact of these muriates not being deliquescent, and the impossibilitj' of 

 the existence of carbonate of potash and chloride of sodium together without 

 mutual decomposition ; otherwise carbonate of potash could be made by the 

 simple process of mixing solutions of carbonate of soda and chloride of 

 potassium." 



Dr. Ulex, of Hamburg, writes : — 



"Potash, carbonate of potash, and pearlash generally contain sulphates 

 (which require to be removed carefully by a chloride-of-barium solution be- 

 fore estimating the potassium). The whole of the potassium is estimated as 

 chloride of platinum and potassium, and calculated to oxide of potassium. 

 The sulphuric acid present is precipitated with chloride of barium as sulphate 

 of baryta, the chlorine with a solution of silver as chloride of silver ; the former 

 is calculated to sulphate of potash, the chloiine to chloride of potassium. 

 The oxide of potassium equivalent to these two salts is subtracted from the 

 total oxide of potassium, and the remainder calculated to carbonate of potash. 

 Part of the sample is titrated with sulphuric acid and noted as carbonate of 

 potassium. Subtract from this the carbonate of potash previously found and 

 calculate the difference to carbonate of soda." 



Mr. W. Galbraith writes as follows : — 



" Muriates, which may be alkaline and contain sodium carbonate, and there- 

 fore will not contain calcium or magnesium soluble in water, I should state 

 thus, putting the stronger bases and salt-radicals first : — 



Potassium. Sulphate, 



c ,. Chloride. 



^<''^"™- Carbonate. 



