2 METHODS OF ANALYSIS. 



mix, and test again, as before. Repeat this process until a neutral reaction is 

 obtained. Add sufficient water to make the specific gravity 1.09 at 20 C. 



(c) MolyMate solution. Dissolve 100 grams of molybdic acid in 144 cc of 

 ammonium hydroxid, specific gravity 0.90, and 271 cc of water; slowly and 

 with constant stirring, pour the solution thus obtained into 489 cc of nitric 

 acid (specific gravity 1.42), and 1,148 cc of water. Keep the mixture in a warm 

 place for several days, or until a portion heated to 40 C. deposits no yellow 

 precipitate of ammonium phosphomolybdate. Decant the solution from any 

 sediment and preserve in glass-stoppered vessels. 



(d) Ammonium nitrate solution. Dissolve 200 grams of commercial ammo- 

 nium nitrate in enough water to make the volume of the solution 2 liters. 



(e) Magnesia mixture. Dissolve 22 grams of recently ignited calcined mag- 

 nesia in dilute hydrochloric acid, avoiding an excess of the latter. Add a little 

 calcined magnesia in excess, and boil a few minutes to precipitate iron, alumina, 

 and phosphoric acid ; filter ; add 280 grams of ammonium chlorid, 261 cc of 

 ammonium hydroxid of specific gravity 0.90, and water enough to make the vol- 

 ume 2 liters. Instead of the solution of 22 grams of calcined magnesia, 110 grams 

 of crystallized magnesium chlorid (MgCl 2 6H 2 O) may be used. 



(f) Dilute ammonium hydroxid for washing. This solution should contain 

 2.5 per cent of ammonia (NH 8 ). 



(fir) Magnesium nitrate solution. Dissolve 320 grams of calcined magnesia 

 in nitric acid, avoiding an excess of the latter ; then add a little calcined mag- 

 nesia in excess ; boil ; filter from the excess of magnesia, ferric oxid, etc., and 

 dilute with water to 2 liters. 



(2) TOTAL PHOSPHORIC ACID. 



(a) Methods of making solution. Treat 2 grams of the sample by one of the 

 methods given below. After solution, cool, dilute to 200 or 250 cc, mix, and 

 pour on a dry filter. 



(Oj) Ignite and dissolve in hydrochloric acid. 



(a 2 ) Evaporate with 5 cc of magnesium nitrate, ignite, and dissolve in hydro- 

 chloric acid. 



(a s ) Boil with from 20 to 30 cc of strong sulphuric acid, adding from 2 to 4 

 grams of sodium or potassium nitrate at the beginning of the digestion and 

 a small quantity after the solution has become nearly colorless, or adding the 

 nitrate in small portions from time to time. A Kjeldahl flask marked at 250 cc 

 is recommended. After the solution is colorless add 150 cc of water and boil 

 for a few minutes, cool, and make up to mark. 



(a 4 ) Digest with strong sulphuric acid and such other reagents as are used 

 in either the plain or modified Kjeldahl or Gunning method for estimating 

 nitrogen. Do not add any potassium permanganate, but after the solution has 

 become colorless add about 100 cc of water and boil for a few minutes, cool, 

 and make up a convenient volume; 2.5 grams of substance and a digestion 

 flask marked at 250 cc are recommended. 



(a,) Dissolve in 30 cc of concentrated nitric acid and a small quantity of 

 hydrochloric acid and boil until organic matter is destroyed. 



(a 8 ) Add 30 cc of concentrated hydrochloric acid, heat, and add cautiously, in 

 small quantities at a time, about 0.5 gram of finely pulverized potassium chlo- 

 rate to destroy organic matter. 



(a 7 ) Dissolve in from 15 to 30 cc of strong hydrochloric acid and from 3 to 

 10 cc of nitric acid. This method is recommended for fertilizers contaiping 

 much iron or aluminum phosphate. 



