380 liLMATK OF LIMK I.N TlIK SOIL,. 



Its presence may be detected by the deposition of minute crystals on the 

 sides of the vessel during the evaporation of the solution obtained by 

 boiling the soil in distilled water. Or, its presence may be inferred if, 

 after observing that oxalate of ammonia causes a precipitate in one 

 small portion of the solution, it be found that nitrate of baryta also 

 throws down a white precipitate from another small portion. 



3°. In the state o/ phosphate. — This compound is probably present, 

 though always in small })roportion, in every soil which is capable of 

 raising a nutritious vegetation. It may be readily detected by treating 

 500 grains of the dry soil for 12 hours with dilute muriatic acid, and oc- 

 casionally stirring. If to the filtered solution caustic ammonia be add- 

 ed, a brownish precipitate will usually fall. If this precipitate be se- 

 parated, and treated with acetic acid (vinegar), it will all dissolve if no 

 phosphoric acid be present. If this experiment be carefully performed, 

 and a residue remain undissolved, the presence of phosphoric acid in 

 the solution, and of phosphate of lime in the soil, may be safely inferred. 



4°. In the state of silicate, lime rarely exists in the soil in any con- 

 siderable quantity. It is chiefly in such as are derived from the decay 

 of the trap rocks or of some varieties of granite (sienite), that silicate 

 of lime is to be expected to occur. 



If, after being treated with dilute sulphuric acid, as above described, 

 the soil be digested for some hours at a gentle heat with concentrated 

 muriatic acid — a solution will be obtained from which ammonia will 

 again throw down a brown precipitate. If oxalate of ammonia now 

 cause a white precipitate of oxalate of lime, and if, on evaporating to 

 dryness, the solution leave a portion of silica insoluble in acids, we may 

 infer that the soil most probably contains some lime in the state of sili- 

 cate. 



5°. In the state of carbonate, lime is generally supposed most usually 

 to exist, and most abundantly in all soils. If on pouring dilute muri- 

 atic acid upon a soil, a visible effervescence or escape of minute bubbles 

 of gas manifest itself, or if, when the experiment is made in a tube 

 closed at one end, and inverted over water or mercury, bubbles of gas 

 collect in the upper end of the tube — the soil contains some carbonate. 

 If after ammonia has been added to the solution, oxalate of ammonia 

 throws down a white precipitate of oxalate of lime — the soil contains 

 carbonate of lime. 



6°. In the state ofhumate. — In combination with humic acid (Lee. 

 XIII., § 1,) lime exists most frequently in soils which abound in vege- 

 table matter — in peaty soils, for example, to which quick-lirne or marl 

 of any kind has been added for the purpose of agricultural improve- 

 ment. The presence of lime in the state of humate is only to be detect- 

 ed by carefully determining the relative weights of the carbonic acid 

 given off' during the action of dilute muriatic acid upon the soil, and of 

 the lime contained in the solution thus obtained, (see Appendix.) If for 

 every 100 grains of carbonic acid there be more than 77-24 grains of 

 Xxme, the remainder or excess has existed in the soil in combination with 

 humic or some analogous organic acid.* 



* To such analogous acids belong the crenic and apocrenic acids (Lee. Xlll., § 1.) The 

 existence of these acids in the soil is by no means problematical. According to Professor 

 Hermann, of Moscow, they exist in the rich black sof. 'Tchornoi Zem.) of Little Russia, 

 to the amount of 4 per cent. 



