ANALYSIS OF SUPERPHOSPHATE 133 



phosphate, diluted with water to 200 c.c, filtered, and 

 the phosphate estimated in the filtrate as in (a). 



{d) Total Phosphate. — Two grams of the super- 

 phosphate are added to 30 c.c. of concentrated hydro- 

 chloric acid and heated. About 0-5 gram of potassium 

 chlorate is then added and the mixture boiled gently 

 until all the phosphates are dissolved and the organic 

 matter destroyed. The solution is diluted to 250 c.c. 

 and filtered. Fifty c.c. are abstracted, neutralised with 

 ammonia, and mixed with 15 grams of ammonium 

 nitrate. The phosphate is then precipitated with 

 ammonium molybdate and estimated in the usual 

 way. 



118. Calcium. 



The whole of the calcium in an aliquot part of 

 the original solution prepared for the water soluble 

 phosphate (116 ia)^ p. 130) is precipitated as oxalate 

 by ammonium oxalate and weighed as CaO after 

 ignition (see 83, p. loi). 



119. Alkali Salts. 



The residue from estimation of the organic matter 

 (114) is extracted thoroughly with water, the solution 

 evaporated, if necessary, to about 150 c.c, and heated 

 on the water-bath to 100° C. Barium-chloride solution 

 is added drop by drop in slight excess, and then, 

 without filtering, baryta water, also in slight excess. 

 The liquid is again heated, filtered, and the precipitate 

 washed. To the filtrate and washings is added i c.c. 

 of strong ammonia, then a strong solution of ammonium 

 carbonate, and finally, to the hot liquid, i gram of 

 powdered ammonium oxalate. The liquid is allowed 

 to stand for some time, the precipitate filtered and 

 washed, and the filtrate evaporated down to dryness 



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