On different Sorts of Lime ufed in Agriculture. 41§ 
. As the preceding method of eftimating the quantities of 
magnefia ‘and calcareous earth is liable to confiderable error, 
I afterwards examined them in the following manner, which 
feems capable of great exactnefs :—Twenty-five grains of 
each fubftance were diffolved, by marine acid, in a cup of 
platina, and, after the folution was evaporated to drynefs, 
it was made red-hot for a few minutes. The mafs remain- 
ing in the cup, which confifted of muriated lime, and of the 
magnefia freed from the acid, was wafhed out with water, 
and poured into a phial. There was then added to it a 
known quantity of diluted marine acid, fomewhat more 
than was fufficient to rediflolve the magnefia, and, after the 
folution, a certain weight of calcareous fpar, part of which 
would be diffolved by the fuperfluous acid. By the quantity 
of {par remaining undiffolved, it was learnt how much acid 
was required to diffolve the magnefia. The iron and argil- 
jaceous earth contained in fome fpecimens, were precipi- 
tated by the fpar, and therefore could not occafion any error. 
The calcareous fpar, however, diffolved more flowly where 
there was ar eiflaceous earth, as it became coated with its 
but this oritation was occafionally removed, and, in'‘al} 
the experiments, the fpar was left in the folution till it fuf- 
fered no further diminution, For this purpofe it was necef- 
fary to keep them flightly warm for fome days, during which 
time the phials were generally clofed, to prevent any efcape 
of the acid. 
The firft experiment in the following table was made upon 
known quantitics of magnefia and calcareous earth, to try 
the accuracy of the procels. For this purpofe, alfo, thé fe- 
tond was repeated upon a picce of limettone, previoufly pow- 
dered, to render every part of it of the fame quality. The 
firft column fhews the quantity of calcareous {par which 
Might have been diflolved by the acid required to take up 
the magnefia. The fecond fhews the correfponding quanti- 
ties of magnefia in 25 grains of each fubftance. The third 
exprefles the quantity of lime. This was inferred by fub- 
tracting the weight of the magnefia, and of the iron and 
clay, from 13.2 grains, the weight of the whole quantity of | 
earth in 25 grains of limeftone, This is probably not very 
: incorreét, 
