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CALCAREOUS MANURES— THEORY. 49 



boiling, let fall the carbonate of magnesia, if any liad been in tiie soil ; but 

 when any notable deposite is thus obtained, it will often be found to con- 

 sist more of carbonate of lime, than of magnesia. The following are ex- 

 amples of such products : 



One thousand grains of tide-marsh soil, (page 40, No. 4,) acted on by 

 muriatic acid in the pneumatic apparatus, gave out no carbonic acid gas, 

 and therefore could have contained no carbonate of lime. The precipitate 

 obtained from the same weighed sixteen grains ; which being again acted 

 on by sulphuric acid, evolved as much gas as showed that three grains had 

 become carbonate of lime, in the previous part of the process. 



Two hundred grains of alluvial soil from Saratoga Springs (page 41 No. 

 18,) containing no carbonate of lime, yielded a precipitate of twelve grains, 

 of which three was carbonate of lime— and a deposite from the alkaline 

 solution weighing six grains, four of which was carbonate of lime. 



Seven hundred grains of limestone soil from Bedford, Pennsylvania, 

 (part of the specimen marked 14, page 41,) contained about two-thirds of a 

 grain of carbonate of lime— and its precipitate of twenty-eight grains, only 

 yielded two grains : but the alkaline solution deposited eleven grains of the 

 carbonates of lime and magnesia, of which at least five was of the former, 

 as there remained seven and a half of solid matter, after the action of sul- 

 phuric acid.* 



From this process, there can be no doubt but that the soil contained a 

 proportion of some salt of lime, (or lime combined with some kind of acid,) 

 which being decomposed by and combined with the muriatic acid, was 

 then precipitated, not in its first form, but in that of carbonate of lime— it 

 being supplied with carbonic acid from the carbonate of potash used to 

 produce the precipitation. The proportions obtained in these cases were 

 small ; but it does not follow that the whole quantity of lime contained in 

 the soil was found. However, to the extent of this small proportion of 

 lime, is proved clearly the presence of enough of some acid (and that not 

 the carbonic) to combine with it. Neither could it have been the sulphuric, 

 or the phosphoric acid ; for though both the sulphate and phosphate of lime 

 are in some soils, yet neither of these salts can be decomposed by muriatic 

 acid. 



6th. The strongest objection to the doctrine of neutral soils is, that, if true, 

 the salt formed by the combination of the lime and acid must often be pre- 

 sent in such large proportions, that it is scarcely credible that its presence 

 and nature should not have been discovered by any of the able chemists 

 who have analyzed soils. This difficulty I cannot remove, but it may be 

 met (or neutralized, to borrow a figure from my subject,) by showing that 

 an equal ditficulty awaits those who may support the other side of the 

 argument. 



The theory of geologists of the formation of soils, from the decomposi- 



* The measurement of the carbonic acid £;as evolved was relied on to show the whole 

 amount of carbonates present — and sulpliuric acid was used to distinguish between 

 lime and magnesia, in the deposite from the alkaline solution. If any alumina or 

 mae^nesia had made part of the solid matter exposed to diluted sulphuric acid, the com- 

 binations formed would have been soluble salts, which would of course have remained 

 dissolved and invisible in the fluid. Lime only, of the four earths, forms with sulphuric 

 acid a substance but slightly soluble, and which therefore can be mostly separated in a 

 solid form. The whole of this substance (sulphate of lime) cannot be obtained in this 

 manner, as a part is always dissolved ; but whatever is obtained, proves that at least 

 two-thirds of that quantity of carbonate of lime had been present ; as that quantity of 

 lime which will combine with enough carbonic acid to make 100 parts (by weight) of 

 carbonate of lime, will combine with so much more of sulphuric aciil, as to form about 

 150 parts of the sulphate of lime, or gypsum. 



