CALCAREOUS MANURES— THEORY. 35 



results are reported by one knowing very little of the science of chemistry, 

 < and whose limited knowledge was gained without aid or instruction, and 

 was sought solely with the view of pursuing this investigation. Appearing 

 under such disadvantages, it is therefore the more incumbent on me to 

 show my claim to accuracy, or to so explain my method as to enable others 

 to detect its errcflrs, if any exist. To analyze a specimen of soil completely 

 requires an amount of scientific acquirement and practical skill to which I 

 make no pretension. But merely to ascertain the absence of calcareous 

 earth, (or carbonate of lime,) or, if present, to find its quantity, requires 

 but little skill, and less science. 



The methods recommended by different agricultural chemists for ascer- 

 taining the proportion of calcareous earth in soils agree in all material 

 points. Their process will be described, and made as plain as possible. 

 A specimen of soil of convenient size is dried, pounded, and weighed, and 

 then thrown into muriatic acid diluted with three or four times its quantity 

 of water. The acid combines with, and dissolves the lime of the calcareous 

 earth, and its other ingredient, the carbonic acid, being disengaged, rises 

 through the liquid in the form of gas, or air, and escapes with effervescence. 

 After the mixture has been well stirred, and has stood until all efferves- 

 cence is over, (the fluid still being somewhat acid to the taste, to prove 

 that enough acid had been used, by some excess being left,) the whole is 

 poured into a piece of blotting paper, folded so as to fit within a glass fun- 

 nel. The fluid containing the dissolved lime passes through the paper, 

 leaving behind the clay and silicious sand, and any other solid matter ; over 

 which, pure water is poured and passed off several times, so as to wash off 

 all remains of the dissolved lime. These filtered washings are added to 

 the solution, to all of which is then poured a solution of carbonate of potash. 

 The two dissolved salts thus thrown together, {muriate of lime composed 

 of muriatic acid and lime, and carbonate of potash, composed of carbonic 

 acid and potash,) immediately decompose each other, and form two new 

 combinations. The muriatic acid leaves the lime, and combines with the 

 potash, for which it has a stronger attraction— and the muriate of potash 

 thus formed, being a soluble salt, remains dissolved and invisible in the 

 water. The lime and carbonic acid being in contact, when let loose by 

 their former partners, instantly unite, and form carbonate of lime, or calca- 

 reous earth, which being insoluble, falls to the bottom. This precipitate 

 is then separated by filtering paper, is washed, dried and weighed, and thus 

 shows the proportion of carbonate of lime contained in the soil,* 



In this process, the carbonic acid which first composed part of the calca- 

 reous earth, escapes into the air, and another supply is afterwards furnished 

 from the decomposition of the carbonate of potash. But this change of 

 one of its ingredients does not alter the quantity of the calcareous earth, 

 which is always composed of certain invariable proportions of its two 

 component parts ; and when all the lime has been precipitated as above 

 directed, it will necessarily be combined with precisely its first quantity of 

 carbonic acid. 



This operation is so simple, and the means for conducting it so easy to 

 obtain, that it will generally be the most convenient mode for finding the 

 proportion of calcareous earth in those manures that are known to contain 

 it abundantly, and where an error of a few grains cannot be very material. 

 But if a very accurate result is necessary, this method will not serve, on ac- 

 count of several causes of error which always occur. Should no calcareous 



* More full directions for the analysis of soils may be found in Kirwan's Essay on 

 Manures, Rozier's Cours Compiet, &c., and Davy's Agricultural Chemistry. 



