 Hello, I am Sumitra Watana, Director of Office of Science for Land Development, OSRD, Land Development Department, Ministry of Agriculture and Cooperatives Thailand. Our Office has six fields of soil quality testing laboratories, which are soil chemistry, soil physics, soil mineralogy, plant analysis, fertilizer and soil environment, all for recommendations and improvement of soil fertility. Our services are for all stakeholders, farmers, researchers, private sector and university. It is a pleasure for our laboratory to host the choosing of this video to show you how to determine soil organic carbon using Warglitt and Black Titration Method. Organic carbon is one of the most important soil parameters. Determine its quantity in soils permits to derive many information, especially on soil fertility, soil biodiversity, soil erosion and soil buffer capacity for hazardous chemicals. In this video, we will show you how to quantify soil organic carbon using Warglitt Black Titration Method. This protocol allows you to determine oxidizable organic carbon content in soil, calculated from the amount of chromic iron formed during the reaction. Anyway, the method described here does not routinely apply correction for chloride, which will produce a positive interference directed. This standard operating procedure is based on the Warglitt and Black Comic Acid with Oxidation Method. Basically, oxidizable organic carbon in the soil is oxidized by 0.167 molar potassium dichromate solution in concentrated sulfuric acid. Temperature needed to induce substantial oxidation is rate by the heat of reaction. The dichromate reduced during the reaction with soil is proportional to oxidizable organic carbon present in the sample. The organic carbon can then be estimated by measuring the remaining unreduced dichromate by back titrating with ferrous sulfate or ammonium ferrous sulfate, using diphenyl or phenanodine ferrous complex as an indicator. Regarding this procedure, some points might be noted. Warglitt and Black found that on the average about 77% of the organic carbon was recovered by the heat of the erosion procedure. And a correction factor of 1.3 be used to account for unrecovered organic carbon. For soils with high organic carbon content, the Warglitt and Black method may underestimate the result due to the incomplete oxidation of the organic carbon in the sample. Therefore, in case of samples with very high carbon content, smaller sample weights should be used. This method is for the determination of organic carbon in soils. It is not applicable to soils containing significant amounts of carbonized materials. This method is subject to interferences by certain soil constituents that lead to false results in certain type of soils. Chloride, ferrous iron, and higher oxide of manganese have been shown to undergo oxidation, reduction, reactions in chromic acid mixtures, leading to incorrect values for organic carbon. In case of soils with high concentrations of such constituents, we recommend to add for ferric acid after the sample has been cooled in order to eliminate interferences from the ferric iron. Watch soil sample free of chloride before analyzing or precipitate the chloride as silver chloride by addition of silver sulphate to the digestion acid. Be aware that this procedure involves the use of parsadate chemicals. Please take note of following safety and hygiene measures. Refer to laboratory safety guidelines and material safety data sheets before proceeding. Be sure to wash hands and clean other export areas with mild soap and water after using all chemical reagents. All titrations and handling of chemicals to be undertaken in a firm hood. When handling any chemicals, remember to wear safety glasses, gloves, lab coats, remark for some specific elements. Potassium dichromate is an inorganic compound that emits toxic chromium fumes up on heating. It is a known human carcinogen and it is associated with an increased risk of developing lung cancer. Sanfering acid must be kept away from naked flames or heat. Remember to measure the concentration in the air regularly and to carry out operations in a firm hood with exalt or ventilation. Do not discharge the waste into the drain. Keep in mind never dilute by pouring water into the acid. Always add the acid to the water. Samples should be air dry and seep to less than 2 millimeter size. In order to perform the walk leg and black method using titration, you need balance with an appreciation of 0.001 gram for the preparation of reagents. Precision balance dependent on the weight of the sample 50 milliliters of burette with an appreciation of plus minus 0.02 milliliters for the tritransolution. Volumetric dispenser of 10 milliliters of known uncertainty to be used with the potassium dichromate solution and 20 milliliters to be used with concentrated sulfuric acid, 250 lmF, 1,000 milliliters of volumetric fast, 100 and 250 milliliters beakers, magnetic stirrer, film hood and burette stand. The reagents used for the titration method. DIO nice water or distilled water. It should have an electro conductivity less than 0.0015 desiccement per meter. Potassium dichromate standard 0.167 molar. This is a 49.04 gram of traceable or equivalent analytical grade of potassium dichromate. Previously dry at 105 Celsius for two hours and cool in the desiccator to room temperature. Sulfuric acid concentrated. Not less than 96 percent. Indicator. Frenantoline, ferrous complex at 0.025 molar is used at an indicator in our laboratory. Dissolve 1.485 gram of frenantoline monohydrate and 0.695 gram of ferrous sulfate hetahydrate in DIO nice or distilled water. They dilute the solution to a volume of 100 milliliters. For the titrant, you can use either ferrous sulfate or ferrous ammonium sulfate at 0.5 molar. Ferrous sulfate solution 0.5 molar. Dissolve 140 gram ferrous sulfate hetahydrate in DIO nice or distilled water. Add 15 milliliters of concentrated sulfuric acid. Cool the solution. Then dilute it to a volume of 1000 milliliters with DIO nice or distilled water. Finally, standardize this reagent daily by titrating it against 10 mils of 0.167 molar potassium dichromate. Ferrous ammonium sulfate 0.5 molar. Dissolve 196 gram of ferrous ammonium sulfate in 700 milliliters of distilled water. Add 20 milliliters of concentrated sulfuric acid. Cool the solution. Dilute it to a volume of 1000 milliliters with distilled water. Then standardize this reagent daily by titrating it against 10 milliliters of 0.167 molar potassium dichromate. After preparing necessary reagents, now we are ready to start our procedure using the titration method. Weigh 1 gram of air dye soy into a 250 milliliters aluminium fast or beaker. Add 10 milliliters of 0.167 molar potassium dichromate and swirl the fast gently to disappear the soy into the solution. Then with care, rapidly add 20 milliliters concentrated sulfuric acid directing the stream into the suspension. Immediately swirl the fast gently until the soy and reagent are mixed. Then move vigorously for a total of 1 minute. To minimize heat loss, allow the fast to stand for 30 minutes in a film hood. Then add 100 milliliters of water into the fast. It proceeds the titration by manual method. Add 3 to 4 drops of the financial indicator and titrate the solution with 0.5 molar ferrous sulphate solution. Add the end point is approached. Proceed the furrow in titration when using financial indicator. The solution takes on a greenish cache and then changed to a dark green. At this point, add the ferrous sulphate peptide hydrate drop by drop until the color changes sharply from blue to red. Maroon color in reflected light against a white back cloud. Determine one to three pranks in the same manner but without soy to standard diet potassium dichromate. In case you proceed by manual potentiometric titration. First, set an expand scale pH meter with a platinum electrode and caramel reference electrode to read the potential difference in millivolt. Insert the electrodes and temperature compensator in the solution and stir with a magnetic stirrer. Tall form vehicles can be used as an alternative to conical fast, giving more room for the electrode, temperature compensator and billet. Pop a titration curve by recording a value of major potential difference in mineral and millilitre titrant 0.5 normal ferrous sulphate added from a billet. The end point is then found on the point of infractions on the curve approximately 750 millivolt. Titration are simply discontinued when this point is reached and the corresponding titrant consumption is then matured. During the titration, if over 8 millilitre of the 10 millilitre of dichromate has been reduced, the determination must be repeated with a smaller amount of soy sample. Form the display equation. We can access that 1 millilitre of one normal dichromate solution is equivalent to 3 milligram of carbon. After the reaction, the excess of dichromate is titrated with 0.5 molar ferrous sulphate or 0.5 ammonium ferrous sulphate at the display equation shows. For accuracy, we participate in an inter-laboratory proficiency test at least once a year. The PTCs ago should be less than 2. If not, identify root cause, develop corrective and preventive actions and address the problem. Perform replicate analysis of the certified reference material. Compare results of own laboratory with results of other laboratories as provided in the performance analysis report or certified reference material certificate. The old laboratory result is considered accurate when it falls within the reported 95% confidence. For the precision, perform replicate analysis of 10% of samples in a test batch. Calculate the percent relative standard deviation using the display equation to determine if the precision of replicate analysis is within specification. Compare results with the target precision for the analyte concentration as indicated at the display table, which shows expected precision as a function of analyte concentration. Analyze at least one duplicate of the shake samples or internal reference material in every batch analysis. Plot the result in the control shot. Monitor for the results that are outside of the specific limits. Identify the root causes and develop the corrective and preventive actions.