APPENDIX. 



235 



ing. Evaporate the solution and washings to complete dryness on a water bath. 

 Take up with dilute hydrochloric acid, heating if necessary, and filter out the silica. 

 Evaporate filtrate and washings to about 10 cc, add 2 cc of concentrated nitric acid, 

 and just neutralize with ammonium hydroxid. Clear up with nitric acid, avoiding 

 an excess. Heat at 40 to 50 on water bath, add 15 cc of molybdic solution, keeping at 

 this temperature for from one to two hours. Let stand over night, filter, and wash 

 free of acid with a one-tenth per cent solution of ammonium nitrate and, finally, 

 once or twice with cold water. Transfer filter to beaker, and dissolve in standard 

 potassium hydroxid (1 cc = 0.2 mg P), titrate the excess of potassium hydroxid with 

 standard nitric acid, using phenolphthalein as indicator. 



87404 Bull. 10700 17 



