ANALYSIS. 



ANALYSIS. 



ble, it may be considered as partly vegetable ex- 

 tract. If its smell when exposed to heat be like 

 that of burnt feathers, it contains animal or albu- 

 minous matter; if it be white, crystalline, and not 

 destructible by heat, it may be considered prin- 

 cipally as saline matter. The saline compounds 

 contained in soils are very various. The sul- 

 phuric acid combined with potash or sulphate 

 of potash is one of the most usual. Common 

 salt is also veiy often found in them ; likewise 

 phosphate of lime, which is insoluble in water, 

 but soluble in muriatic acid. Compounds of 

 the nitric, muriatic, sulphuric, and phosphoric 

 acids, with alkalies and earths, exist in some 

 soils. The salts of potash are distinguished 

 from those of soda by their producing a pre- 

 cipitate in solutions of platina ; those of lime 

 are characterized by the cloudiness they occa- 

 sion in solutions containing oxalic acid ; those 

 of magnesia by being rendered cloudy by so- 

 lutions of ammonia. Sulphuric acid is detected 

 in salts by the dense white precipitate it forms 

 in solutions of baryta ; muriatic acid, by the 

 cloudiness it communicates to solution of nitrate 

 of silver ; and when salts contain nitric acid, 

 they produce scintillations by being thrown 

 upon burning coals. 



9. Should sulphate or phosphate of lime be 

 suspected in the entire soil, the detection of 

 them requires a particular process upon it. 

 A given weight of it, for instance, 400 grains, 

 must be heated red for half an hour in a cruci- 

 ble, mixed with one third of powdered char- 

 coal. The mixture must be boiled for a quarter 

 of an hour in a half pint of water, and the 

 fluid collected through the nitre and exposed 

 for some days to the atmosphere in an open 

 vessel. If any notable quantity of sulphate of 

 lime (gypsum) existed in the soil, a white pre- 

 cipitate will gradually form in the fluid, and 

 the weight of it will indicate the proportion. 



Phosphate of lime, if any exist, may be 

 separated from the soil after the process for 

 gypsum. Muriatic acid must be digested upon 

 the soil in quantity more than sufficient to sa- 

 turate the soluble earths : the solution must 

 be evaporated, and water poured upon the 

 solid matter. This fluid will dissolve the com- 

 pounds of earths with the muriatic acid, and 

 leave the phosphate of lime untouched. It 

 will not fall within the limits assigned to this 

 article to detail any processes for the detection 

 of substances which may be accidentally 

 mixed with the matters of soils. Other earths 

 and metallic oxides are now and then found in 

 them, but in quantities too minute to bear any 

 relation to fertility or barrenness, and the 

 search for them would make the analysis much 

 more complicated, without rendering it more 

 useful. 



10. Where the examination of a soil is com- 

 pleted, the products should be numerically 

 arranged and their quantities added together, 

 and if they nearly equal the original quantity 

 of soil, the analysis may be considered as ac- 

 curate. Ii must, however, be noticed that when 

 phosphate or sulphate of lime are discovered 

 by the independent process just described (9), 

 a correction mnst be made for the general pro- 

 cess, by subtracting a sum equal to their 

 weight from the quantity of carbonate of lime 



86 



obtained by precipitation from the muriatic 

 acid. In arranging the products the form 

 should be in the order of the experiments by 

 which they were procured. Thus I obtained 

 from 400 grains of a good silicious sandy soil 

 from a hop garden near Tonbridge Kent, 



Grains. 



Of water of absorption - .... 19 



Of loose stones and gravel, principally silicious 53 

 Of undecomposed vegetable fibres - - 14 



Of (in i; silirious sand 212 



Of minutely divided matter, separated by agitation 

 and filtration, and consisting of Grains. 



Carbonate of lime (chalk) - - 19 

 Carbonate of magnesia 3 



Matter destructible by heat, princi- 

 pally vegetable - - - - 15 



Silica 21 



Alumina ------ 13 



Oxide of iron ----- 5 



Soluble mftuer, principally common 



salt and vegetable extract 3 



Gypsum ------ 2 



Loss ... - 21 

 400 



The loss in this analysis is not more than 

 usually occurs, and it depends upon the im- 

 possibility of collecting the whole quantities 

 of the different precipitates, and upon the pre- 

 sence of more moisture than is accounted for 

 in the water of absorption, and which is lost 

 in the different processes. 



When the experimenter is become acquaint- 

 ed with the use of the different instruments, 

 the properties of the re-agents, and the rela- 

 tions between the external and chemical quali- 

 ties of soils, he will seldom find it necessary to 

 perform, in any one case, all the processes 

 that have been described. When his soil, for 

 instance, contains no notable proportions of 

 calcareous matter, the action of the muriatic 

 acid (7.) may be omitted. In examining peat 

 soils, he will principally have to attend to the 

 operation by fire and air, and in the analysis 

 of chalks and loams, he will often be able to 

 omit the experiment by sulphuric acid (9.). 



In the first trials that are made (adds Davy) 

 by persons unacquainted with chemistry, they 

 must not expect much precision of result; ma- 

 ny difficulties will be met with ; but, in over- 

 coming them, the most useful kind of practical 

 knowledge will be obtained ; and nothing is so 

 instructive in experimental science as the de- 

 tection of mistakes. The correct analyst 

 ought to be well grounded in general chemical 

 information; but perhaps there is no bettei 

 mode of gaining it than that of attempting 

 original investigations. In pursuing his ex- 

 periments, he will be continually obliged to 

 learn the properties of the substances he is 

 employing or acting upon ; and his theoretical 

 ideas will be more valuable in being connected 

 with practical operations, and acquired for the 

 purpose of discovery. 



Such were the excellent rules for analysis 

 prescribed by Sir Humphry Davy. With the 

 still more simple directions of the Rev. W. 

 Rham, I shall conclude this paper. 



A portion of the earth to be analysed may 

 be dried in the sun or near a fire until it leels 

 quite dry in the Hand. It is then reduced to 

 powder by the fingers, or by rolling it on a 

 deal board with a wooden roller, so as to sepa- 



