15 



3. DETERMINATION OP MANGANESE, CALCIUM, AND MAGNESIUM. 



As on page 78 of the "Methods," unchanged, save that the word "ash" is inserted after 

 "grams," line 2; add "The quantity of calcium found must be corrected for the calcium 

 added." 



4. DETERMINATION OF PHOSPHORIC ACID. 



(a) An aliquot portion of the hydrochloric-acid solution, corresponding to 0.2 to 1 gram 

 ash, is to be used for the determination by any of the methods described for total phosphoric 

 acid in fertilizers. 



(b) The determination can also be made in the plant substance as in (a 2 ), page 12 of the 

 "Methods," for phosphoric acid, using sufficient material to give from 0.2 to 1 gram ash 

 in the aliquot portion of the solution taken for the phosphoric acid determination. 



5. DETERMINATION OF ALKALIES. 



(a) An aliquot portion of the hydrochloric-acid solution (see 2) corresponding to 0.5 to 1 

 gram of ash is evaporated to dryness. Redissolve the residue in about 50 cc water, add 

 milk of lime or barium-hydroxid solution, which must be perfectly free from alkalies, until 

 no further precipitation is produced. 



(b) Potash may be determined as directed for potash in organic compounds (b), page 22 

 of the " Methods," using sufficient plant material to get from 0.5 to 1 gram ash in the aliquot 

 portion of the solution taken for the' potash determination. 



6. DETERMINATION OF SULPHUR (PROVISIONAL METHOD). 



Modified nitric-acid method as given above. 



Nineteenth Convention, 1902, Bui. 73. 



Insert the method of determining chlorin by ignition with sodium 

 carbonate as a provisional method : 



7. DETERMINATION OF CHLORIN IN PLANTS BY IGNITION WITH SODIUM CARBONATE (PRO- 

 VISIONAL.) 



Five grams substance in a platinum dish are impregnated with 20 cc of a 5 per cent solution 

 of sodium carbonate, evaporated to dryness, and ignited as thoroughly as possible. The 

 residue is extracted with hot water, filtered, and washed. It is returned to the platinum 

 dish, ignited to an ash, dissolved in nitric acid, and the chlorin determined by the Volhard 

 method. 



Twentieth Convention, 1903, Bui. 81, Cir. 13. 



The following method for the determination of sulphates is adopted 

 as provisional . 



PROVISIONAL METHOD FOR THE % DETERMINATION OF SULPHATES. 



Five grams substance are mixed well with 50 cc of a 1 per cent solution of hydrochloric 

 acid, allowed to stand half an hour, filtered, and washed with the dilute acid to 250 cc or 

 more. The liquid is heated to boiling, barium chlorid is added, and the determination com- 

 pleted in the usual way. 



