METHOD EMPLOYED BY HOLLAND 77 



monium molybdate in a liter of water and pouring the solution 

 into a liter of nitric acid of 1.20 specific gravity. 



(2) A 10 per cent, solution of ammonium nitrate. 



(3) Strong and dilute ammonia, the latter being between two 

 and five-tenths and three per cent, and of 0.988 specific gravity.. 



(4) Magnesia mixture made by dissolving no grams of crys- 

 tallized magnesium chlorid, 140 grams of ammonium chlorid, and 

 700 cubic centimeters of ammonia of 0.96 specific gravity in 

 water and bringing the solution to two liters. 



(5) Ammoniacal citrate solution, made by dissolving 500 grams 

 of citric acid in a liter of water, and mixing with four liters of 

 10 per cent, ammonia of 0.96 specific gravity. 



Manipulation. Place 20 grams of the substance in a mortar 

 together with some cold distilled water or pure rain water, stir, 

 and decant the water and suspended matters into a liter flask. 

 After this has been repeated several times, rub up the residual 

 mass and wash it all into the flask. Fill up to about 900 cubic 

 centimeters and allow to stand two hours (24 hours in the case 

 of double phosphates with more than 22 per cent, of soluble phos- 

 phoric acid) ; shaking repeatedly, or shaking continuously, for 

 half an hour. Fill up to the liter mark and filter through a dry 

 filter. Add 100 cubic centimeters of molybdate solution for each 

 100 milligrams of phosphorus pentoxid present, to portions of 

 25 or 50 cubic centimeters for each determination, warm to about 

 80 for an hour, filter, and wash the precipitate with the ammo- 

 nium nitrate solution. Add a little molybdate solution to the 

 filtrate, warm, and, if a fresh precipitate be observed, it is to be 

 added to the first. The precipitate is dissolved in ammonia and 

 hydrochloric acid carefully added until the precipitate caused by 

 it only slowly redissolves on stirring. The phosphoric acid is 

 precipitated from the clear liquid, which is still ammoniacal, with 

 magnesia mixture, using 10 cubic centimeters for each 100 'milli- 

 grams of phosphorus pentoxid present. This is added, drop by 

 drop, and the liquid kept stirred during the addition. Allow to 

 stand at least two hours, filter, wash with dilute ammonia, dry, 

 and ignite, at first with a very small flame, and finally with the 

 blast-lamp or in a Rossler furnace. To insure burning to white- 



