Chemical analyses test
Organic matter content (Mass loss using H2O2)
The organic content can be determined using several methods, often depending on the type of soil. The two main methods used are the loss-of-ignition method and a chemical method using hydro-peroxide (H2O2).
To find out the organic matter content of soil with the use of H2O2, the sample is firstly oven dried at 105° Celsius for a period of 16-24 hours after which its dry weight is established. Next, a measured amount of the sample is transferred into an Erlenmeyer, to which, after adding water, the H2O2 is added. - H2O2 causes any organic material to oxidize - After a long soak, followed by the cooking of the solution, the remainder of the liquid is left to evaporate. The final suspension is then dried and weight to determine the loss of mass and calculate the organic matter content.
Carbonate content (Mass loss using HCl)
The carbonate content can be determined using several methods, often depending on the type of soil. The two main methods used are the loss-of-ignition method and a chemical method using hydrochloric acid (HCL).
The chemical method to determine the carbonate content is more or less similar to the organic matter content, yet the chemical used is much different. Again first the soil sample is oven dried at 105° Celsius for a period of 16-24 hours after which its dry weight is established. Next, a measured amount of the sample is transferred into an Erlenmeyer, to which, after adding water, HCL is added. - HCL only reacts with the carbonate in the soil, and is not affected by any organic matter still present - After a long soak, followed by the cooking of the solution, the remainder of the liquid is left to evaporate. The final suspension is then dried and weight to determine the loss of mass and calculate the carbonate content.
Another method to find out the carbonate content of soil is through the volumetric method. Again, the sample is firstly oven dried at 105° Celsius for a period of 16-24 hours. Next, an excess of hydrochloric acid (HCL) is added to the sample to decompose any carbonates present. The reaction of the HCL with any carbonates present produces carbon dioxide (CO2). The volume of CO2 produced by the sample is measured using a ‘Scheibler’ apparatus and is compared with the volume produced by pure calcium carbonate. Lastly the carbonate content of the soil sample can be calculated.
Determination of pH (in soil)
The soil sample is oven dried over 16-24 hours, after which it mixed with a potassium chloride solution (KCL). Following a fifteen hour soak the suspension is shaken once more after which the pH can be tested.
Sulphate, chloride and pore water salinity
These tests are outsourced to Omegam laboratoria B.V. in Amsterdam, the Netherlands.
Methylene blue test
In order to test the presence and activity of (swelling) clay minerals in soil, the methylene blue test can be conducted. The test is based on the absorption capability of methylene blue by the clay particles in the soil. Based on the amount of methylene blue solution absorbed by the soil, the percentage of clay particles can be calculated. Furthermore, the activity of the clay with respect to e.g. its swelling capacity can be determined.
