ANALYSIS. 



burning a known quantity of earth 

 thoroiigiily dried by means of the ox- 

 yde of copper, aided by a current of 

 oxygen, that the carbon and hydrogen 

 may be determined. But the most 

 important point of all is to ascertain 

 the amount of azote inchided in the 

 organic remains of the soil ; and we 

 have, happily, precise means in our 

 elementary analysis of ascertaining 

 the quantity of azote from which the 

 amount of azolized organic matter 

 may be accurately inferred. 



It may be very useful to determine 

 the presence or absence of carbonate 

 of lime in a soil ; this knowledge 

 would, of course, guide us in our ap- 

 plications of lime, marl, &c. Two ! 

 modes may be employed for this pur- 

 pose ; 1st, the soil may be treated by 

 nitric acid slightly diluted with water. 

 Any etfervescence will denote the 

 presence, in all probability, of carbon- 

 ate of hme. I say in all probability, 

 because the disengagement of car- 

 bonic acid gas under such circum- 

 stances generally indicates the pres- 

 ence of carbonate of lime ; it is not, 

 however, a special character, because 

 the disengagement may be due to the 

 presence of any other carbonate. It 

 is well to boil the acid solution upon 

 the sample of soil that is analyzed ; 

 the part which is not dissolved is 

 thrown upon a filter and washed with 

 distilled or rainwater boiling hot. 

 Into the clear filtered liquor which 

 results from all the portions of water 

 used in the washing, a little ammonia 

 is added ; if any precipitate falls, it 

 is collected upon a filter and washed : 

 to the new liquors obtained by this 

 washing, a solution of oxalate of am- 

 monia is added. If there be any lime 

 present, it is thrown down in the 

 state of oxalate, and the liquor, hav- 

 ing been left at rest for five or six 

 hours, becomes completely clear ; the 

 addition of a few drops of the solu- 

 tion of oxalate of ammonia to this 

 clear fluid satisfies us whether the 

 whole of the lime has been precipita- 

 ted or not. The oxalate of lime is 

 received upon a filter, waslied, and 

 dried ; it is then thrown into a plati- 

 num capsule along with the piece of 

 B2 



filtering paper upon which it was col- 

 lected, and is heated to a dull red, un- 

 til the paper of the filter is complete- 

 ly consumed and no farther trace of 

 carbon appears ; the capsule is then 

 taken from the fire, or from over the 

 spirit lamp, and cooled ; when cold, 

 the matter which it contains is moist- 

 ened with a concentrated solution ot 

 carbonate of ammonia. 



The matter is then dried, great 

 care being taken that nothing is lost 

 by particles flying out, and the cap- 

 sule is again heated to a dull red ; 

 when cold, it is weighed accurately, 

 and the quantity of matter contained 

 then becomes known. This matter 

 is carbonate of lime, 100 of which 

 represents 56-3 of lime and 43-7 of 

 carbonic acid. I have said that in 

 arable soil other carbonates may be 

 met with besides that of lime ; calca- 

 reous soils, for example, very com- 

 monly contain carbonate of magne- 

 sia. If we would ascertain the quan- 

 tity of this earth, the mode of pro- 

 ceeding which I have just particular- 

 ly indicated enables us to do so ; we 

 have but to evaporate the liquid from 

 which the oxalate of lime was depos- 

 ited, and then to calcine the product 

 of the evaporation in a platinum cap- 

 sule. Any nitrate of magnesia which 

 may exist there will be decomposed 

 at a dull red heat, as well as any ox- 

 alate of ammonia which may have 

 resulted from ammonia added in ex- 

 cess. By treating the residue of the 

 calcination with water, we obtain the 

 magnesia, which, being washed, has 

 only to be calcined, and its weight 

 ascertained by weighing. 



2. If we would be content with a 

 simple approximation, we may judge 

 of the quantity of calcareous carbon- 

 ate contained in a vegetable soil by 

 measuring the quantity of carbonic 

 acid which we obtain from it. We 

 counterpoise upon the scale of a bal- 

 ance a vial containing some diluted 

 nitric acid ; we weigh a certain quan- 

 tity of the earth to be analyzed, and 

 this is added by degrees to the acid. 

 If the earth contains carbonates, ef- 

 fervescence ensues. The liquid is 

 shaken with care, and having waited 



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