ANALYSIS. 



ANALYSIS. 



by continued exposure to air, in all cases 

 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 consi- 

 derable degree of heat. The first process 

 of analysis is to free the given weight of 

 soil from as much of this water as possible, 

 without, in other respects, affecting its compo- 

 sition, and this may be done by heating it for 

 ten or twelve minutes over an Argand lamp 

 in a basin of porcelain to a temperature equal 

 to 300 Fahrenheit; and if a thermometer is 

 not used, the proper degree may be easily as- 

 certained by keeping a piece of wood in con- 

 tact with the bottom of the dish ; as long as 

 the colour of the wood remains unaltered 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 vege- 

 table or animal matter would undergo decom- 

 position, and, in consequence, the experiment 

 be wholly unsatisfactory. 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 con- 

 sidered as only slightly absorbent and retentive, 

 and silicious 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 bodies are often themselves highly ab- 

 sorbent and retentive, and in consequence in- 

 fluence the fertility of the land. The next 

 process, however, after that of heating, should 

 be their separation, which may be easily ac- 

 complished by the sieve, after the soil has 

 been gently bruised in a mortar. The weights 

 of the vegetable fibres or wood, and of the 

 gravel or stones, should be separately noted 

 down, and the nature of the last ascertained ; 

 if calcareous, they will effervesce with acids ; 

 if silicious, they will be sufficiently hard 

 to scratch glass ; and if of the common alumi- 

 nous class of stones, they will be soft, easily 

 cut with a knife, and incapable of effervescing 

 with acids. 



3. The greater number of soils, besides 

 gravel and stones, contain larger or smaller 

 proportions of sand, of various 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 divi- 

 sion, such as clay, loam, marl, vegetable and 

 animal matter, and the matter soluble in water. 

 This may be effected in a way sufficiently ac- 

 curate, by boiling the soil in three or four times 

 its weight <~,i water, and when the texture of 

 the soil 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 



84 



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 princi- 

 pally separated from the other substances, 

 which, with the water containing them, must 

 be poured into a filter, and after the water has 

 passed through, collected, dried, and weighed. 

 The sand must likewise 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 ani- 

 mal or vegetable, if any exist in the soil. 



4. By the process of washing and filtration, 

 the soil is separated into two portions, the most 

 important of which is generally the finely di- 

 vided matter. A minute analysis of the sand 

 is seldom if ever necessary, and its nature 

 may be detected in the same manner as that 

 of the stones or gravel. It is always either 

 silicious sand, or calcareous sand, or a mixture 

 of both. If it consist wholly of carbonate of 

 lime, it will be rapidly soluble in muriatic 

 acid, with effervescence ; but if it consist 

 partly of this substance, and partly of silicious 

 matter, the respective quantities may be ascer- 

 tained by weighing the residuum after the ac- 

 tion of the acid, which must be applied till the 

 mixture has acquired a sour taste, and has 

 ceased to effervesce. This residuum is the 

 silicious part ; it must be washed, dried, and 

 heated strongly in a crucible : the difference 

 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 

 usually very compound in its nature ; it some 

 times contains all the four primitive earths or 

 soils, as well as animal and vegetable matter- 

 and to ascertain the proportions of these with 

 tolerable accuracy is the most difficult part of 

 the subject. 



The first process to be performed in this part 

 of the analysis, is the- exposure of the fine 

 matter of the soil to the action of muriatic 

 acid. This substance 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 its volume of 

 water. The mixture should be often stirred and 

 suffered to remain 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, they 

 will have been dissolved in this time by the 

 acid, which sometimes takes up likewise a 

 little oxide of iron, but very seldom any alu- 

 mina. 



The fluid should be passed through a filter, 

 the s^'lid matter collected, washed with rain- 

 water, dried at a moderate heat, and weighed. 

 Its loss will denote the quantity of solid matter 

 taken up. The washings must be added to 

 the solution, which, if not sour to the taste, 

 must be made so, by the addition of fresh acid, 

 when a little solution of prussiate of potassa 

 and iron must be mixed with the whole. If a 

 blue precipitate occurs, it denotes the presence 

 of oxide of iron, and the solution of the prus- 

 siate must be dropped in, till no farther effect 



