32 On the Analysis of Soils. 



sand, or a mixture of both. Tf it consist wholly of car- 

 bonate of Hine, it will be rapidly soluble in muriatic acid, 

 with ettervcscence : but if it consist partly of this sub- 

 stance, and partly of siliceous matter, the respective quan- 

 tities may be ascertained by weighing the residuum after 

 the i.ction of the acid, which must be applied till the mix- 

 ture has acquired a sour taste, and has ceased to effervesce. 

 This residuum is the siliceous part : it nuist be washed, 

 dried, and heated strongly in a crucible : the diftcrcnce be- 

 tween the weight of it "and the weight of the whole, indi- 

 cates the proportion of calcareous sand. 



IX. Examination of Ihe Jinely divided Maifcr of Soils, 

 and Mode of dcttcfing mild Livic and Magnesia. 



The finely divided matter of the soil is usually very com- 

 pound in its nature ; it sojnetimes contains all the four 

 primitive earths of soils, as well as animal and vegetal)le 

 matter; and to ascertain the proportions of these with to- 

 lerable accuracy, is the most difficult part of the subject. 



The first process to be performed, in this part of the ana- 

 lysis, is the exposure of the line matter of the soil to the 

 action of the muriatic acid. This substance should be 

 poured upon the earthy matter in an evaporating bason, in 

 a (quantity ei|ual to twice the weight of the earthy matter; 

 but diluted with double its volume of water. The mixture 

 should be often stirred, and suffered to remahi for an hour 

 or an hour and a half before it is examined. 



If any carbonate of lime or of magnesia exist in the soil, 

 thev will have been dissolved in this time by the acid, w inch 

 sometimes takes up likewise a little oxide of iron ; but very 

 seldom any alunhne. 



The ihud should be passed through a filter ; the solid 

 mailer collected, washed with rain water, dried at a mode- 

 rate heat, and weighed. Its loss will denote the quantity 

 of solid matter taken up. The washings must be added to 

 the solution ; wiiich, if not sour to the taste, must be made 

 so by the addition of fresh acid, when a little solution of 

 common prussiaieof potash niust be mixed with the whole. 

 If a blue precipitate occurs, it denotes the presence of 

 oxide of iron, and the solution of the prussiate nuist be 

 dropped in till no further effect is produced. To ascertain 

 its quantity, it must be collected in the same manner as 

 othtr solid precipitates, and heated red : the result is oxide 

 of iron. 



Into the fluid freed from oxide of iron, a solution of 

 neutralized carbonate of potash must be poured till all ef- 

 fervescence 



