86 On the Analysis of Soils* 



process upon it. A given weight of it, for instance four 

 huiidred grains, must be heated red for half an hour in ^ 

 crucible, mixed with one third of powdered charcoal. The 

 mixture must be boiled for a quarter of an hour, in a half- 

 pint of water, and the fluid collected through the filter, and 

 exposed for some days to the atmosphere in an open vessel. 

 If any soluble quantity of sulphate of lime (gypsum) ex-r 

 isted in the soil, a white precipitate will gradually form in 

 the fluid, and the weight of it will indicate the proportion. 



Phosphate of lime, if any exist, may be separated from 

 the soil after the process for gypsum. Muriatic acid must 

 be digested upon the soil, in quantity more than sufficient 

 to saturate the soluble earths ; the solution must be evapo- 

 rated, and water poured upon the solid matter. This fluid 

 will dissolve the compounds of earths with the muriatic 

 acid, and leave the phosphate of lime untouched. 



It would not fall within the limits assigned to rliis paper, 

 to detail any processes for the detection of substances which 

 may be accidentally mixed with the matters of soils. Man- 

 ganese is now and then found in them, and compounds of 

 the barytic earth ; but ihise bodies appear to bear little re- 

 lation to fertility or barrenness, and the search for them 

 would make the analysis much more complicated, without, 

 rendering it more useful. 



XIV. Statement of Results and Products. 



When the examination of a soil is completed, the pro- 

 ducts should be classed, and their quantities added together; 

 and if they nearly equal the original quantity of soil, the 

 analysis may be considered as accurate. It must however 

 be noticed, that when phosphate or sulphate of lime are dis- 

 covered by the independent process XIII., a correction 

 must be made for the general process, by subtracting a sum 

 equal to their weight froni the quantity of carbonate of 

 lime obtained by precipitation from the muriatic acid. 



In arranging the products, the form should he in the 

 order of the experiments by which they were obtained. 



Thus, 400 grains of a good siliceous sandy soil may be 

 supposed to contain 



Of water of absorption 



Of loose stones and gravel, principally siliceous. 



Of undcconipounded vegetable fibres 



Of fiuc siliceous sand - - 



270 

 Brought 



