Riassunti VERIFICATO
Riassunti LABORATORI - Chimica del Terreno
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- Total Limestone Calculation:
- Utilizes the "calcimetro di Scheiber" to measure CO2 produced from soil's reaction with hydrochloric acid (CaCO3 + 2HCl → CaCl2 + H2O + CO2).
- Results are expressed as % CaCO3.
- High calcareous soil (>10%) can lead to insolubilization of phosphorus and iron.
- Soil pH Calculation:
- Involves mixing 10g of soil with 25ml of pure or distilled water.
- After agitation and settling, the pH is measured using a portable pH meter.
- Active Limestone Calculation (for total limestone >10%):
- Measures limestone reacting with ammonium oxalate (COONH4)2, considering crystal structure (calcite/aragonite) and fineness.
- Procedure includes reacting 2g of soil with 0.5ml of 0.2N ammonium oxalate, agitation, filtration, and subsequent titration with 0.1N potassium permanganate in both blank and sample tests.
- The percentage of active CaCO3 is calculated from the titrated volumes.
- Texture Determination:
- Based on the sedimentation of soil particles in a liquid, following Stokes' Law.
- 10g of fine soil is mixed with 200ml of water and sodium hexametaphosphate to separate sand, silt, and clay.
- Utilizes an "Esenwein sedimenter" for sequential sedimentation of sand (after 12 min), silt (after 20 hours), and remaining clay.
- Particle fractions are determined by weighing dried samples taken at specific intervals.
- An "optimal soil" (franco) typically contains 70% sand, 20% silt, and 10% clay.
- Organic Matter Determination:
- Uses the Walkley-Black wet method.
- Soil (0.5-1g) reacts with 1N potassium dichromate and concentrated sulfuric acid, causing carbon oxidation and chromium reduction.
- Both blank and sample titrations are performed with potassium permanganate to calculate the organic carbon percentage.
- Cation Exchange Capacity (CSC) Determination:
- Involves three main steps:
- Barium Saturation: 2g of soil is treated with 10% barium chloride to replace all adsorbed cations. The supernatant is discarded.
- Magnesium Replacement: 25ml of 0.1N magnesium sulfate is added to replace the adsorbed barium.
- Titration: The resulting supernatant (containing the released magnesium) is titrated with EDTA using Eriochrome Black T indicator, comparing blank and sample values to determine CSC (meq/100g).
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