768 



cell needs stimulation by such salts for the complete develo[)ment of its 

 functioning. Aso' has made similar discoveries as to the injuries due to 

 stronger concentrations of sodium fluorid and the favoring of growth by 

 very weak concentrations. Suzuki- has also found this to be true of 

 potassium iodid. Similar discoveries have often been observed by others. 

 Miani-' also reports the favorable action of copper solutions. 



2 : Superphosphate. We should briefly consider the brcakimj dou.m of 

 phosphoric acid in superphosphate and Thomas meal in many soils which are 

 rich in calcium and ferric oxid. In sour, marsh soil and sour meadow soil, 

 rich in humus, retention of the phosphoric acid in a soluble form predomi- 

 nates since w'ater, carbon dioxid, humic acid and some salts act as solvents. 

 In sandy soil containing humus but not acid the process of soluticjn is approx- 

 imately held in equilibruim with the process of transforming the dissolved 

 phosphoric acid into less soluble forms but in loamy soils, containing calcium 

 and iron, the process of decomposition preponderates, that is, the process of 

 transforming the soluble phosphoric acid into phosphates which are dissolved 

 with difficulty. Under such circumstances the use of Thomas meal in the 

 s[)ring would not be advisable. 



3: Gas phosphate. Rhodanammonium is found in different amounts 

 in the refuse of gas factories. This has attained a heightened agricultural 

 significance since a fertilizer, containing nitrogen, has been produced by the 

 purification of illuminating gas with superphosphate, and has been introduced 

 in trade as "(jas phosphate." The acid phosphate has taken up the ammonia 

 from the stream of illuminating gas but at the same time has retained the 

 Rhodanammonium. Because of the repeatedly proven poisonous quality of 

 this compound the purification of the fertilizer has been attempted by wash- 

 ing the gas phosphate with a concentrated solution of ammonium sulfate 

 in which the Rhodanammonium compounds are easily soluble. The amount 

 of Rhodan compounds contained could be reduced thereby to 0.9 per cent, 

 and, consequently, the direct use of this fertilizer has been recommended. 

 It is, in fact, distinguished by its large content of phosphoric acid and 

 nitrogen. 



The experimental results are contradictory in that favorable effects have 

 been observed on sandy soil and unfavorable effects on loamy soils. This 

 brought about the supposition that, in sandy soils, a more rapid decompo- 

 sition of the Rhodanammonium into ammonia, nitric acid and sulfuric acid 

 occurs whereby the poisonous effect is repressed. This hypothesis is con- 

 firmed by other experiments which demonstrate that in using the fertilizer 

 some weeks before seeding, no injuries appear, while severe losses take place 

 when it is used simultaneously with seeding. The same result was found 

 in using dust from a blast furnace containing i per cent. Rhodanammonium. 



1 Aso, Bull. Coll. Ag-ric. Tokyo; cit. Bot. Jahresber. 1902, p. 353. 

 - Suzuki, S. ibid. 



a Miana, D., t)ber Einwirkung von Kupfersulfat auf das Wachstum lebender 

 Pflanzenzellen. Ber. d. Deutsch. Bot. Ges. 1901, Part 7. 



