SOIL. 



Fo-und to contain faline matter, and the foluble animal and 

 vegetable matters, if any exift in the foil. 



6. Examination of the Sand. — By the procefs of wafhing 

 and filtration, the foil is feparated into two portions, the 

 mod important of which is generally the finely divided 

 matter. A minute analyfis of the fand is feldom or never 

 neccfTary, and its nature may be deteded in the fame manner 

 as that of the llonts or gravel. It is always either fihceous 

 fand, or calcareous fand, or a mixture of both. If it confilts 

 wholly of carbonate of lime, it will be rapidly foluble in 

 muriatic acid, with effervefcence ; but if it confilt partly of 

 this fubltaiice, and partly of filiceous matter, the refpeftive 

 quantities may be afcertained by weighing the reiiduum 

 after the aftion of the acid, which muft be applied till the 

 mixture has acquired a four tafte, and has ceafed to efTer- 

 vefce. This refiduum is the filiceous part : it muft be 

 waflied, dried, and heated ftrongly in a crucible ; the dif- 

 ference between the weight of it and the weight of the 

 whole, indicates the proportion of calcareous fand. 



7 . Examination of the finely divided Matter of Soils, and 

 Mode of detcding mild Lime and Magnefta. — The finely divided 

 Blatter of the foil is ufually very compound in its nature ; 

 it fometimes contains all the four primitive earths of foils, 

 as well as animal and vegetable matter ; and to afcertain 

 the proportions of thefe with tolerable accuracy is the moft 

 difficult part of the fubjeA. The firft procefs to be per- 

 formed, in this part of the analyfis, is the expofure of the, 

 fine matter of the foil to the aftion of the muriatic acid. 

 This fubftance fiiould be poured upon the earthy matter 

 in an evaporating bafon, in a quantity equal to twice the 

 weight of the earthy matter ; but diluted with double its 

 Tolume of water. The mixture fliould be often ftirred, and 

 fuffered to remain for an hour, or an hour and a half, 

 before it is examined. If any carbonate of lime or mag- 

 nefia exilt in the foil, they will have been diilolved in this 

 time by the acid, which fometimes takes up likewife a little 

 oxyd of iron ; but very leldom any alumine. 



The fluid fhould be pafledthrough a filter; the folid matter 

 coUefted, wafhed with rain-water, dried at a moderate heat, 

 and weighed. Its lofs will denote the quantity of folid 

 matter taken up. The wafhings muft be added to the 

 folution, which, if not four to the talte, muft be made fo by 

 the addition of frefli acid, when a little folution of common 

 prufiiat of potafh and iron muft be mixed with the whole. 

 If a blue precipitate occurs, it denotes the prefcnce of 

 oxyd of iron, and the folution of the prufliat mult be 

 dropped in till no farther effcdl is produced. To afcertain 

 the quantity, it muft be collefted in the fame manner as 

 other folid precipitates, and heated red ; the refult is oxyd 

 of iron, which may be mixed with a little oxyd of man- 

 ganefum. Into the fluid freed from oxyd of iron, a folution 

 of neutrahzed carbonate of potafli muft be poured till all 

 the effervefcence ceafes in it, and till its tafte and fmell indi- 

 cate a confiderable excefs of alkaline fait. The precipitate 

 that falls down is carbonate of lime ; it muft be collected 

 on the filter, and dried at a heat below that of rednefs. 

 The remaining fluid muft be boiled for a quarter of an 

 hour, when the magnefia, if any exift, will be precipitated 

 from it, combined with carbonic acid, and its quantity is 

 to be afcertained in the fame manner as that of the car- 

 bonate of lime. If any minute proportion of alumine 

 ihould, from peculiar circumftances, be diflolved by the 

 acid, it will be found in the precipitate with the carbonate 

 of lime, and it may be feparated from it by boihng it for 

 a few minutes with foap-ley, fufiicicnt to cover the folid 

 matter. This fubftance diftolvcs alumine, without afting 

 upon carbonate of lime. Should the finely divided foil be 



fufficiently calcareous to effervefce very ftrongly with acids, 

 a very fimple method may be adopted for afcertaining the 

 quantity of carbonate of lime, and one fufficiently accurate 

 in all common cafes. Carbonate of lime, in all its ftates^ 

 contains a determinate proportion of carbonic acid, i. e. 

 about 45 per cent., fo that when the quantity of this elaftic 

 fluid, given out by any foil during the folution of its cal- 

 careous matter in an acid, is known, either in weight or 

 meafure, the quantity of carbonate of lime may be eafily 

 difcovered. When the procefs by diminution of weight is 

 employed, two parts of the acid and one part of the matter 

 of the foil muft be weighed in two feparate bottles, and 

 very flowly mixed together, till the effervefcence ceafes ; the 

 difference between their weight, before and after the expe- 

 riment, denotes the quantity of carbonic acid loft ; for 

 every four grains and a half of which, ten grains of car- 

 bonate of lime muft be eftimated. The belt method of col- 

 lefting the carbonic acid, fo as to difcover its volume, is 

 by the pneumatic apparatus, the conftruftion and applica- 

 tion of which are defcribed below. The eftimation is, for 

 every ounce meafure of carbonic acid, two grains of car- 

 bonate of lime. The bulk may be meafured by the quan- 

 tity of water which is difplaced. 



8. Mode of afcertaining the Quantity of infoluble finely divided 

 animal and vegetable Matter. — After the fine calcareous 

 matter of the foil has been afted upon by muriatic acid, 

 the next procefs is to afcertain the quantity of finely 

 divided infoluble animal and vegetable matter that it con- 

 tains. This may be done with fufficient precifion, by 

 heating it to ftrong ignition in a crucible over a commoii 

 fire, till no blacknefs remains in the mafs. It fhould be 

 often ftirred with a metallic wire, fo as to expofe new fur- 

 faces continually to the air : the lofs of weight that it 

 undergoes denotes the quantity of the fubftance that it con- 

 tains deftruftible by fire and air. It is not poflible, without 

 nice and difficult trials, to afcertain whether this fubftance 

 is wholly animal or vegetable matter, or a mixture of both. 

 When the fmell emitted during the incineration is fimilar 

 to that of burnt feathers, it is a certain indication of fome 

 animal matter, or that which is analogous to it ; and a 

 copious blue flame at the time of ignition, almoft always 

 denotes a confiderable proportion of vegetable matter. In 

 cafi's when the experiment is needed to be very quickly 

 performed, the deftruftion of the decompofible fubftances 

 may be affifted by the agency of nitrate of ammonia, which 

 at the time of ignition may be thrown gradually upon the 

 heated mafs in a quantity of twenty grains for every hun- 

 dred of refidual foil. It promotes the diflipation, or affords 

 the principle neccflary to the combuftion of the animal and 

 vegetable matter, which it caufes to be converted into 

 elaftic fluids ; and it is itfelf at the fame time decompofcd 

 and loft. 



y. Mode ef feparating aluminous and fdiceous Matter and 

 Oxyd of Iron. — The fubftances remaining after the decom- 

 pofition and deftruftion of the vegetable and animal matter, 

 are generally minute particles of earthy matter, containing 

 ufually alumine and filex, with combined oxyd of iron, or 

 of manganefe. To feparate thefe from each other, the 

 folid matter (liould be boiled for two or three hours with 

 fnlphuric acid, diluted with four times its weight of water ; 

 t!ie quantity of the acid fliould be regulated by the quan- 

 tity of folid refiduum to be adted upon, allowing for every 

 hundred grains two draciim.;, or one hundred and twenty- 

 grain'; of acid. The fubftance remaining rftcr the aftion oi 

 the acid may be confidored as filiceous ; and it muft be 

 feparated, and its weight afcertained, after wafhing and 

 dryinr in the ufual manner. 



LI 2 The 



