236 Analysis of Soils. [Oct., 



which precipitates the humic acid in the state of a buff-colored 

 humate of lead. This precipitate is easily collected on the filters, 

 and is to be washed and dried at a steam heat, and weighed. 

 Then a portion of it is analyzed, and the proportion of humic 

 acid on the filter is calculated. If we now remove the subacetate 

 of lead from the solution by passing sulphydric acid gas through 

 it, we shall find that the solution is of a honey-yellow, and still 

 contains organic matters. Evaporate the solution to dryness in a 

 platina capsule, and you will obtain extract of humus, which ex- 

 tract I have ascertained is a compound of two distinct proximate 

 principles, one of which is precipitated by a solution of proto- 

 nitrate of mercury, and the other by nitrate of silver. These sub- 

 stances have not yet been analyzed or fully described. 



The insoluble substance called humine I do not find in the so- 

 lution of carbonate of ammonia and I regard it as a product of 

 evaporation at too high a temperature, for it does not appear 

 when we evaporate at a steam heat in vacuo. 



The insoluble organic matters remaining in the soil after diges- 

 tion with carbonate of ammonia may be called humine. It is 

 capable of being converted into humic acid or into the other or- 

 ganic acids by action of the atmosphere and slow decomposition 

 in the soil. Glucic and apoglucic acids probably exist in the 

 extract of humus, but I have not yet satisfied myself with regard 

 to them. I find them in brown sugar and in the sap of the ma- 

 ple and birch, and in saturated or " exhausted" bone black of the 

 sugar refinery. Bone black has the remarkable property of re- 

 taining apoglucic acid, and hence we obtain it most abundantly 

 from that substance after it has been used in refining sugar. 



It should be observed that if the soil contains phosphates de- 

 composable by carb. ammonia, that phosphoric acid will be thrown 

 down as a phosphate of copper with the crenate. Hence that 

 acid must be sought for and deducted from the crenate. I find it 

 in most of the crenate of copper obtained from peat, and some- 

 times it is in considerable quantity, giving a darker green color 

 to the crenate. 



In analyzing the apocrenate of copper we may either separate 



