What is the procedure for determining the content of organic matter in a soil sample?


a. Take a 300g sample of material that has passed through sieve No. 10 and heat it in an oven at 110°C until constant mass. Take a 30g sample of soil (A) and place it in a crucible in a muffle for 6 hours. After 6 hours, remove the sample and let it cool to determine its mass (B). Calculate the organic matter content as a percentage.
b. Take a 1500g sample of material that has passed through sieve No. 4, dry it in an oven at 110°C until constant mass, and let it cool. Take a 250g sub-sample and place it in a Griffin volumetric flask. Add 30ml of distilled water and stir with the stirrer until a slurry is obtained. Then, with the help of a burette, add increments of 0.5ml of Methylene Blue solution and stir for one minute. After each dose, the absorption of the dye solution by the sample is checked by performing a color test on filter paper to detect the presence of free dye.
c. Take a 20g portion of soil prepared for the liquid limit test. Reduce the water content of this soil portion until it can be rolled without sticking to the hands, continuously spreading or mixing it on a glass plate. Once this procedure has been carried out, rolls of 1/8 inch (3.2 mm) in diameter are formed manually as indicated in the standard INV E-126 in section 8.2.1.