THE METHOD OF SOIL ANALYSIS. 



The following method for the analysis of soils has been adopted by 

 this division, and is essentially the same as that described by Spren- 

 gel and Otto in SprengePs Bodenkunde, 1837, p. 370, depending on the 

 principle that in order to judge of the fertility of a soil, it u necessary 

 to determine not only what are its elementary constituents, but like- 

 wise the manner in which they are combined. With this view Spren- 

 gel and Otto treated a sample of the soil successively with water, dilute 

 hydrochloric acid, strong sulphuric acid, and by fusion with an alkaline 

 carbonate. The constituents of the soil soluble in water were supposed 

 to be actually available as plant food ; those which were soluble in 

 dilute acids as available for that purpose after being subjected to the 

 action of carbonic acid and the humous acids of the soil ; the rest as 

 available only after the soil had been subjected for a considerable time 

 to atmospheric influences, assisted by the mechanical operations of till- 

 age. This mode of proceeding was originally based upon the suppo- 

 sition that the constituents of the soil which are to nourish the plant 

 must be presented to it in the state of solutiou, a viow which can no 

 longer be regarded as correct. Hence the treatment of the-sample of 

 soil with water, with strong sulphuric acid, and by fusion with an alka- 

 line carbonate, has not been followed, because it was considered that 

 the estimation of the constituents soluble in dilute acids was the most 

 important as showing the total amount of those constituents present in 

 the soil as readily available as plant food. This was formerly made on 

 the residue left after exhausting the soil with boiling water, but as this 

 mode of operation is no longer regarded as of much importance, the 

 soil is now directly treated with the dilute acids after the removal of 

 the stones and coarser particles. 



The mode of operation pursued and the precautions to be observed 

 have been stated at length, as where such small quantities are obtained 

 the greatest care is necessary in all manipulations to obtain accurate 

 results. References have been made, in all cases, to Fresenius's Quan- 

 titive Analysis. Results obtained from different portions of the same 

 sample of soil have been found to agree very closely, thus establishing 

 the accuracy of the methods employed, where all precautions are ob- 

 served. 



The strength of the acids used and the time employed for digestion is 

 that found by Professor Hilgard, from investigations made by Dr. R. 

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