246 E. A. Schneider — Analysis of a Soil, etc. 



coarser portions of this soil the alkaline earth phosphates pre- 

 dominate, owing to undecomposed apatite, while in the finer 

 portions which contain more of the oxides of iron and alumina 

 they change into phosphates of iron and alumina. This sup- 

 position is confirmed by the researches of E. Peters* and 

 Warington, Jr.f 



Should we now attempt to decide about the degree of fer- 

 tility of the soil, it would not be sufficient to know how much J 

 phosphoric acid is contained in the soil, and with what bases 

 it is combined ; we ought also to know if the conditions in 

 the soil are favorable to the decomposition or solution of the 

 phosphates, particularly those of iron and alumina, so that 

 the phosphoric acid could become available as plant-food. 



Being aware of the omnipresence of the phosphates of iron 

 and aluminum in the soil, Thenard§ has attempted to solve this 

 question. By a laboratory experiment he showed that the 

 available form of phosphoric acid — phosphate of calcium — is 

 formed by a double decomposition of the phosphates of iron 

 and aluminum and a soluble modification of calcium silicate. 

 "We must confess that even if that should be the true explana- 

 tion of the phenomenon we are unable to trace those conditions 

 in nature. 



I have not made determinations of nitrogen and ammonia in 

 the soil owing to lack of material, and other determinations 

 have been omitted for the same reason. 



The results of this investigation may be summarized as 

 follows : 



1. The action of hydrochloric acid on soils is far from uni- 

 form. This is seen when we compare the results obtained by 

 extracting the Rockland Eidge soil with hot and cold hydro- 

 chloric acid, and the results which Grouven has published. 



2. It is probable that plant-roots derive then* nutrition from 

 the finest sediments of the soil, from the clay. But this does 

 not make necessary that the clay should be the richest of all 

 sediments in plant-food. Such may be only the case if the 

 coarser sediments consist of quartz-sand. 



3. Hydrochloric acid corrodes powerfully not only the finest 

 sediments of the soil, but also the coarsest. We have good 



I. 1 00 grm. silt coutain -42 grm. P 2 5 . 



II. 100 grm. sed. -25 mm h. v.-8 mm h. v. contain -24 grm. P 2 5 . 



The acetic acid has therefore dissolved 1-76 per cent of the total P 2 5 con- 

 tained in the silt and 1/41 per cent of the total P 2 5 contained in sediments -25 mm 

 h, T- _8 mm h. v. This experiment would have been probably more decisive if the 

 sediments -25 mm h. v.-8 mm h. v. had been converted by trituration to the same 

 degree of fineness as the silt possesses. 



* Annalen der Landvvirthschaft. vol. xlix. p. 31. 



\ Journ. of the Chem. Soc, new series, vol. vi, 1868. p. 5. 



+ •' A soil may contain many thousand pounds of phosphoric acid or of nitrogen 

 and yet be iu a poor condition." — R. Warington. The Chemistry of the Farm, p. 17. 



§ Comptes rendus, 1858, vol. xlvi, p. 212. 



