jpio] CARBON, PHOSPHORUS AND NITROGEN IN SOILS 99 



Digestion of the soil itself and also the extracted matlere noire 

 with a solution of potassium hydrogen phosphate failed to add any 

 phosphorus which was not again recovered by treatment with 

 hydrochloric acid. This was conclusive evidence to Schmoeger 

 that the phosphorus did not exist as absorbed phosphorus and must, 

 therefore, exist in organic combination. Two possibilities sug- 

 gested themselves to Schmoeger: first, the phosphorus existed in 

 the form of lecithin ; second, it existed as nuclein. Lecithin was 

 found to be present only in traces. The characteristic property of 

 nuclein to "split-off" its phosphorus in the form of phosphoric 

 acid, when heated, under pressure in the presence of water, to a 

 temperature of I5o-i6o was utilized by Schmoeger. The soil 

 under examination, treated in this way, yielded as much soluble 

 phosphorus as did the ignited soil. This experimental evidence 

 led him to conclude that nuclein or some closely allied bodies were 

 present in the soil. 



Later Schmoeger (39) confirmed his previous work and pro- 

 duced additional evidence in favor of his view that nuclein or simi- 

 lar bodies existed in the soil. Table 3 shows some of the results 

 obtained. 



TABLE 3. PERCENTAGE OF SULFURIC ACID AND PHOSPHORUS SOLUBLE IN 



DILUTE ACID 



Since sulfur is regarded by many authors as being a constitu- 

 ent of plant nuclein, the increased solubility of this substance to- 

 gether with the phosphorus when the soil was treated as indicated 

 alx>ve, was regarded as evidence in favor of his assumption. 



In a later article (40) he showed, by similar treatment, that 

 analogous bodies existed in the moor grass out of which the moor 

 soil was formed. This was regarded as additional evidence in favor 

 of his view. 



Tacke (33) observed that the drying out of soil rendered the 

 phosphorus available. There were three possible explanations sug- 

 gested to him : first, the phosphorus existed in the soil in organic 

 combination which was destroyed by the process of drying; second, 

 it existed in the soil in the colloidal form as suggested by Van Bem- 

 melen; third, the drying out of the soil gave rise to substances of 

 a strong acid nature which acted upon the insoluble phosphorus 

 compounds rendering the phosphorus soluble. 



