FERTILIZERS. 823 



The variation in citrate solubility is claimed to be due simply to vari- 

 ation in the saturation by the lime of the free citric acid in the reagent. 

 A slag rich in silica is poor in free lime. The citric acid is thus left 

 free to attack the phosphate and a high percentage of citrate solubility 

 is found. A slag poor in silica is rich in free lime and shows a low 

 citrate solubility. This explains why Paturel 1 found that when the 

 acid ammonium citrate was used in excess the citrate solubility of all 

 slags examined was greatly increased, and finally became practically 

 identical. 



In the pot experiments with oats, mustard, and wheat, a sandy clay 

 soil containing 0.65 per cent of phosphoric acid soluble in mineral acids 

 in the cold was used. The results show no constant relation between 

 the citrate solubility and the increase in crop produced or the amount 

 of phosphoric acid utilized by the crop. 



G-eneral fertilizer experiments, E. H. Hess (Pennsylvania Sta. R/>t. 

 1896, pp. 143-156). — This includes a summary of results obtained dur- 

 ing 1895 and 1896 in the combined fertilizer and rotation experiments 

 commenced at the station in 1883 (E. S. R., 8, p. 763), and a record of 

 the relative stand and yield of mixed clover and timothy in these 

 experiments during the same period. 



In 1895 the yield. of hay was higher than the stand noted in May 

 iudicated on the plats receiving nitrate of soda, and lower on those 

 receiving sulphate of ammonia. This is attributed to the season, which 

 was dry up to the middle of dune and thus probably more favorable to 

 the action of the nitrate of soda than to that of the sulphate of 

 ammonia. The season of 1896 was also dry and it was observed that 

 the yield was lower than the stand indicated on the plats receiving sul- 

 phate of ammonia and higher on those receiving dried blood. 



In both years the stand of clover decreased and that of timothy 

 increased as the amount of nitrogen applied increased. "The plats 

 receiving yard manure produced more hay than the stand indicated."' 



With the exceptions noted, the agreement between the stand and the 

 final yield was fairly close. 



Recent researches on reverted phosphoric acid, J. Stoklasa 

 (Ann. Agron., 23 (1897) N~o. 12, pp. 588-594). — Laboratory experiments 

 with salts of known composition led to the conclusion that the water- 

 soluble portion of superphosphates never contains acid ferrous phos- 

 phate, this salt changing almost immediately upon its formation into 

 di-tri-ferriphosphates of varying composition insoluble in water. The 

 addition of ferrous salts to soluble phosphates results in the formation 

 of di-tri-ferriphosphates unless an excess of free phosphoric acid is 

 present. Acid ferric phosphate may be found in superphosphates only 

 when there is at least 30 per cent of free phosphoric acid present. If 

 this is not the case, the acid ferric phosphate may be transformed into 

 mono-di-tri-ferriphosphate Fe 2 03(P203)2.8H 2 0. 



'Ann. Agron., 22 (1896>, p. 497 (E. S. R., 8, p. 681). 



