818 EXPERIMENT STATION RECORD. 



in nitrate of soda, and changes in laws. Comparative tests by 19 sta- 

 tions of the inolybdic and Bottoher citrate methods for determining the 

 citrate-solnble phosphoric acid in Thomas slag are reported. As a result 

 of this work, the citrate method was made optional, although in cases 

 of dispute Wagner's molybdic method is to be used. 



By applying the Loges method the Halle Station found in 107 samples 

 of nitrate of soda from 0.27 to 5.04 per cent of perchlorate, averaging 

 0.94 per cent. The general occurrence of this substance in nitrate was 

 shown by reports from other analysts. P. Wagner briefly reported 

 results of pot experiments with different amounts of perchlorate on oats 

 and rye. He found that the rye plants ceased to grow when the nitrate 

 of soda used contained 12 per cent of perchlorate; the oat plants died 

 when the amount reached 18 per cent. 



No change was made in the methods of seed testing. 



It seemed to be the consensus of opinion that the best preparation 

 for station assistants consists in a good, general training in analytical 

 chemistry, the necessary technical skill required being easily acquired 

 in the laboratory. 



A new solvent for distinguishing the phosphoric acid in various 

 phosphates, W. Hoffmeister (Landw. Vers. Stat., 50 (1898), JSTo. 5-6, 

 pp. 363-379). — The author claims that humic acid furnishes a more reli- 

 able means of distinguishing between different phosphates than the 

 citrate solutions commonly used. The humic acid is prepared as fol- 

 lows: Extract wood lignin with ammonia vapor, precipitate the humic 

 acid in the ammoniacal solution with dilute hydrochloric acid, collect 

 the precipitate on a filter, wash and dry. Extract with alcohol and 

 again dissolve the humic acid in ammonia, precipitate, wash, and dry. 



The method proposed for the examination of the phosphate is as fol- 

 lows: Dissolve 15 gm. of the humic acid in dilute ammonia 1 and pour 

 the solution into a 2 liter flask containing some sand. Add 5 gm. of 

 the phosphate and 1 liter of water; shake the contents of the flask and 

 pass a moderately rapid current of carbon dioxid through the solution 

 for 12 days, adding ammonia 1 frequently; pour off the solution; wash 

 the sand; combine the wash water with the solution previously poured 

 off; make up to a definite volume; filter, aud evaporate four-fifths of 

 the filtrate to dryness with the addition of hydrochloric acid; treat the 

 residue with water containing a little hydrochloric acid; filter, wash, 

 and make up the filtrate to 100 cc. Use portions of this solution for 

 the determination of phosphoric acid, etc. 



A slag containing 10.7 per cent of citrate-soluble phosphoric acid 

 according to Wagner's method gave 10.43 and 10.38 per cent soluble in 

 humic acid by the author's method. In bono meal and fermented bone 

 meal 1.01 and 1.48 per cent of phosphoric acid respectively were dis- 

 solved in the humic acid. When the slag was very finely ground the 

 two methods gave practically identical results— 18.53 per cent by the 



1 The amount of ammonia to he used is not stated. 



