1838] 



FARMERS' REGISTER 



617 



between the weight of ihc soil nnd tliat of the 

 water will p;ivc ilie lesuii.* Tiius, if the bottle 

 contains tour huiulred (Trains of water, and s:a\us 

 Uvo hundred ijrains wiien lialf filled with water 

 and hall" with soil, the specific gravity of the soil 

 will be 2; that is, it will be twice as heavy as 

 water; and if it gained 165 fjrains, its specific 

 gravity would be 1825, water beinti 1000. 



It is of importance that the specific gravity of a 

 soil slionid be known, as it afibrds an indication of 

 the quantity of animal and vegetable matter it 

 contains ; these substances being always most 

 abundant in the lighter soils. 



The other physical properties of soils should 

 likewise be examined before the analysis is made, 

 as they denote, to a certain extent, tlieir composi- 

 tion, and serve as guides in directing the experi- 

 ments. Thus, siliceous soils are generally rough 

 to the touch, and scratch glass when rubbed upon 

 it ; ferruginous soils are of a red or yellow colour; 

 and calcareous soils are soft.t 



1. Soils, though as dry as they can be made by 

 continued exposure to air, in ail cases still contain 

 a considerable quantity of water, which adheres 

 with great obstinacy to the earths and animal and 

 vegetable matter, and can only be driven off from 

 them by a considerable degree of heat. The first 

 process of analysis is, to free the given weight ol" 

 soil from as much of this water as possible, with- 

 out in other respects affecting its composition ; and 

 this may be done by heating it for ten or twelve 

 minutes over an Argand'slamp, in a basin of por- 

 celain, to a temperature equal to 300 Fahrenheit; 

 and if a thermometer is not used, the proper de- 

 gree may be easily ascertained, by keeping a piece 

 o]' wood in contact with the bottom of the dish; 

 as long as the color of the wood remains unalter- 

 ed, the heat is not too high; but when the wood 

 begins to be charred, the process must be stopped. 

 A small quantity of water will, perhaps, remain 

 in the soil even after this operation, but it always 

 affords useful comparative results ; and if a higher 

 temperature were employed, the vegetable or ani- 

 mal matter would undergo decomposition, and in 

 consequence the experiment be wholly unsatisfac- 

 tory. 



The loss of weight in the process should be 

 carefully noted, and when in 400 grains of soil it 

 reaches as high as 50, the soil may be considered 

 as in the greatest degree absorbent, and retentive of 

 water, and will generally be found to contain much 

 vegetable or animal matter, or a large proportion 

 of aluminous earth. When the loss is only from 

 20 to 10, the land may be considered as only 

 slightly absorbent and retentive, and siliceous 

 earth probably forms the greatest part of it. 



2. None of the loose stones, gravel, or large 

 vegetable fibres, should be divided from the pure 

 soil till after the water is drawn off; for these bo- 

 dies are themselves often highly absorbent and 

 retentive, and, in consequence, influence the fer- 

 tility of the land. The next process, however, 

 after that of heating, should be their separation, 

 which may be easily accomplished by the sieve, 

 after the soil has been gently bruised in a mortar. 



* It may be more accurately and easily accomplish- 

 ed by weighing it in air and in water in a light phial 

 carefully counterpoised. — J. D. 



t Clay soils, breathed on, emit a peculiar odor, 

 called the earthy.— J. D. 

 Vol. VI.— 78 



The weights of the vegetable fibres or wood, and 

 of gravel and stones, should be separately noted 

 down, and the nature of the last ascertained ; if 

 calcareous, they will eflervesce with acids ; if sili- 

 ceous, they will be sufficiently hard to scratch 

 glass; and if of the common aluminous class of 

 stones, they will be soft, easily cut with a knile, 

 and incapable of effervescing with acids. 



3. The greater number of soils, besides gravel 

 and stones, contain larger or smaller proportions 

 of sand of diderent degrees of fineness ; and it is 

 a necessary operation, the next in the process of 

 analysis, to detach them from the parts in a state 

 of more minute division, such as clay, loatn, marl, 

 vegetable and animal matter, and the matter so- 

 luble in water. This may be effected in a way 

 sufficiently accurate, by boiling the soil in three or 

 lour times its weight of water; and when the tex- 

 ture of the sod is broken down, and the water 

 cool, by agitating the parts together, and then 

 suffering them to rest. In this case, the coarse 

 sand will generally separate in a minute, and the 

 finer in two or three minutes, whilst the highly- 

 divided earthy, animal, or vegetable matter, will 

 remain in a state of mechanical suspension for a 

 much longer time ; so that by pouring the water 

 from the bottom of the vessel, after one, two, or 

 three minutes, the sand will be principally sepa- 

 rated from the other substances, which, with the 

 water containing them, must be poured into a 

 filter, and after the water has passed through, col- 

 lected, dried, and weighed. The sand must like- 

 wise be weighed, and the respective quantities 

 noted down. The water of lixiviation must be 

 preserved, as it will be found to contain the saline 

 and soluble animal or vegetable matters, if any 

 exist in the soil. 



4. By the process of washing and filtration, the 

 soil is separated into two portions, the most impor- 

 tant of which is generally the finely-divided matter. 

 A mipute analysis of the sand is seldom or never 

 necessary, and its nature may be detected in the 

 same manner as that of the stones or gravel, it 

 is always either siliceous sand, or calcareous sand, 

 or a mixture of both. If it consist wholly ol' car- 

 bonate of lime, it will be rapidly soluble in muria- 

 tic acid with effervescence ; but if it consist partly 

 of this substance, and party of siliceous matter, 

 the respective quantities may be ascertained by 

 weighing the residuum after the action of the 

 acid, which must be applied till the mixture has 

 acquired a sour taste, and has ceased to effervesce. 

 This residuum is the siliceous part; it must be 

 washed, dried, and heated strongly in a crucible ; 

 the diSisrence between the weight of it and the 

 weight of the whole indicates the proportion of 

 calcareous sand. 



5. The finely-divided matter of the soil is usu- 

 ally very compound in its nature; it sometimes 

 contains all the four primitive earths of soils, as 

 well as animal and vegetable matter; and to 

 ascertain the proportions of these with tolera- 

 ble accuracy is the most difficult part of the sub- 

 ject. 



The first process to be perfowned in this part of 

 the analysis is the exposure of the fine matter of 

 the soil to the action of muriatic acid. This sub- 

 stance should be poured upon the earthy matter in 

 an evaporating basin, in a quantity equal to twice 

 the weight of the earthy matter ; but diluted with 

 double fts volume of water. The mixture should 



