D 4373 - Astm

This test method covers the quantitative determination of the carbonate content (primarily calcium carbonate, CaCO₃) in soils, using a gasometric method. It is suitable for both fine-grained and coarse-grained soils, as well as soft rock and aggregate materials.

Or directly from a pre-established calibration curve using pure CaCO₃.

The method relies on the chemical reaction between carbonates present in the soil and hydrochloric acid (HCl). The reaction produces carbon dioxide (CO₂) gas. astm d 4373

| Step | Action | |------|--------| | 1 | Dry the soil sample at 105°C to a constant mass. | | 2 | Crush soil to pass a No. 200 (75 µm) sieve. | | 3 | Weigh a specimen (typically 1–10 g, depending on expected carbonate content). | | 4 | Place specimen into the reaction vessel. | | 5 | Add HCl (without allowing contact until sealed) into a separate chamber or capsule within the vessel. | | 6 | Seal the gas-measuring apparatus. | | 7 | Tip the apparatus to allow acid to contact the soil. | | 8 | Record the maximum gas pressure or volume reading after reaction stabilizes (usually 1–2 minutes). |

Carbonate content (%) is calculated as:

[ CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2 \uparrow ]

[ \textCarbonate (%) = \frac\textCO_2 \text pressure/volume reading\textDry soil mass \times \textCalibration factor ] This test method covers the quantitative determination of

D4373 – 14 (or current active version: 2021)