What is the relationship between CaO and CaCO3 in soil simple ? especially in calcareous soil.
Thanks you
Dear Tabrika Ilyass, usually CaO is converted to Ca(OH)2 in presence of H2O (it's a quick and exothermic reaction). The formed Ca(OH)2 maybe converted into CaCO3 in presence of CO2. Thus, CaCO3 is dominant species in soil compared to CaO. Best regards Nils
Thanks you geatly for your interaction dear Nils, is a logical reponse to my question. Laboratory analysis of my soil simples (10) showed the same CaO content but different value of CaCO3. In your opinion, it's logical ?
Yes it is quite logical. There can not be same value for CaO and CaCO3..
Agricultural lime ( CaCO3 ). , chalk powder or limestone, is used as a cheap way to neutralize the acidic soil, making it suitable for cultivation.
Dear Tabrika Ilyass ,
First I would ask the lab. about how CaO and CaCO3 were measured. If CaO was derived from measuring Ca (by Atomic absorption or ICP) then being converted to CaO, whereas CaCO3 was measured by titration with and acid (e.g., HCl), then same CaO values in many soils could yield different CaCO3 values in those soils. That is because acid titration cmight be consumed by other bases, such as MgO, K2O, especially in calcareous soils.
* Calcium is found in hard water in the form of calcium carbonate (CaCO3) . *The carbon dioxide formed is removed immediately so that the reaction is preceded until the completion of the process in accordance with Le-Chatelier’s principle.
CaCO3 → CaO +CO2
This reaction is reversible and exothermic in nature in the forward directio . - -* In the presence of water, it forms slaked lime. This process is called slaking of lime.
CaO+H2O → Ca (OH)2
A SIMPLE METHOD TO IDENTIFY MARL SOILS
ABSTRACT An experimental investigation was carried out to propose a simple, practical method, to identify marl soils in the laboratory and to classify the soils. The percentage of calcium carbonate (CaCO3) of the soil was determined with three different methods: (1) TGA (ThermoGravimetric Analysis); (2) “sequential” LOI (Loss on Ignition); and (3) chemical reaction following ASTM C 25. The sequential LOI test has the advantage that both organic and calcium carbonate content of the soil can be determined with a conventional furnace. X-Ray Diffraction (XRD), pH, and Atterberg limits tests were also conducted. The percentage of CaCO3 determined from the sequential LOI tests agreed very well with those from the TGA tests and from the chemical tests. No correlation was found between the percentage of CaCO3 and organic content in the soil. As the organic content of the soil increases, the liquid limit (LL) increases, and the plasticity of the soil increases. As the CaCO3 content of the soil increases, the LL of the soil decreases and the soil becomes less plastic. The geotechnical engineering properties of marl soils depend on organic content and CaCO3 content, and so the soils should be classified in terms of both organic content and calcium carbonate content .
No correlation was found between the percentage of CaCO3 and .... (CaCO3) decomposes intocalcium oxide (CaO) and carbon dioxide (CO2).
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