Soil organic matter is an important source of various nutrients in the soil, especially nitrogen and phosphorus. It also contains humic acids and other substances that stimulate plant growth. Because it has colloidal properties, it can adsorb more cations, thus making the soil fertility and buffering. It can also loosen the soil and form structures that can improve the physical properties of the soil. It is also an essential carbon source and energy source for soil microorganisms. Therefore, in addition to the low-lying land, in general, the amount of soil organic matter is an important indicator of the level of soil fertility.
Instruments, Equipment and Reagents
1. Instruments and equipment Hard test tubes, oil bath digestion devices (including oil baths and wire cages), adjustable temperature furnaces, stopwatches, and automatic temperature control regulators.
2. Reagents
(1) 0.800 0mol·L-1 Potassium Dichromate Standard Solution: Dissolve 39.2245 g of potassium dichromate (K2Cr207, analytical grade) dried at 130°C in water to a volume of 1000 mL.
(2) 0.2mol·L-1FeS04 solution: Weigh 56.0g of ferrous sulfate (FeS04·7H20, chemically pure) into water, add 5mL of concentrated sulfuric acid, and dilute to 1L.
(3) Indicator 1 O-Phenanthroline Indicator: Weigh out 1.485 g of o-phenanthroline (Analytical Pure) and FeS04.7H 200.695 g, and dissolve in 100 mL of water.
22-Carboxydiphenylamine (o-phenylanthranilicacid, also known as o-phenylaminobenzoic acid, C13H11O12N) Indicator: Weigh 0.25
G reagent in a small mortar and pestle research, and then poured into a small 100mL beaker, add 0.1mol · L-1NaOH solution 12mL, and use a small amount of water to rinse the residual reagent in the mortar in a 100mL beaker, the beaker on a water bath heating Allow it to dissolve, dilute to 250 mL after cooling, place clear or filter, and use its serum.
Method and procedure
1. Sample Preparation Weigh 0.1 to 1g (accurate to 0.0001g) of 0.14mm (100 mesh) sieve air-dried soil samples, place 6-8 dry hard test tubes, and accurately add 0.8000 with a pipette. mol·L-1 Potassium dichromate standard solution 5mL (If the soil contains chloride, it needs to be added first (Ag2S040.1g), add concentrated H2S04 by syringe
Shake 5mL thoroughly and cover the neck with a small funnel.
2. Measurement
1 Place 8 to 10 test tubes (with 1-2 blank tubes per cage) in a wire cage, place a paraffin oil bath at a temperature of 185 to 190°C, and control the electric furnace so that the temperature inside the oil bath It is always maintained at 170～180°C. When the liquid in the test tube boils, start timing and boil 5
Min, remove the test tube, and wipe the external oil of the test tube after it is cold.
2 After cooling, inject the test substance into a 250 mL conical flask, wash the inside of the test tube and the small funnel with water, so that the total volume of the solution in the flask reaches 60 to 70.
In mL, keep the sulfuric acid concentration in the mixture at 2 to 3 mol·L-1, then add 12 to 15 drops of 2-carboxydiphenylamine indicator, and the solution is brownish red. With the standard 0.2mol·L-1 ferrous sulfate titration, during the titration constantly shake the flask, until the color of the solution turns from reddish purple to dark green (grey blue-green), which is the end of the titration. Such as with o-orpine porphyrin indicator, plus 2 to 3 drops of the indicator, the process of discoloration by the orange-blue-green-brick red is the end. Record Pml4 titration ml (y).
Simultaneously with the determination of each batch of samples, 2 to 3 blank tests were performed, ie, 0.5 g of powdered silica was used in place of the soil samples, and the other procedures were the same as those for the samples. Record the number of milliliters (Vo) of FeS04 titration, and take the average value.
3. Calculation
Where: c - the concentration of potassium dichromate standard solution, mol · L-1
Vo - blank titration with FeS04 volume, mL;
3.0 - 1/4 carbon atom molar mass, g · mol-1
1.1 - oxidation correction factor;
m - dry soil quality, g;
k - Convert dry soil into coefficient of dry soil.
Soil organic matter (g・kg-1) = Soil organic carbon (kg-1) Х 1.742
Where: 1.724 is the average conversion coefficient of soil organic carbon exchanged into soil organic matter.
Precautions 1 Those with an organic matter quality higher than 50g・kg-1, weighing 0.1g soil sample, containing 20-30g・kg-1 organic matter, 0.3g soil sample, weighing less than 20g・kg-1 g above.
2 The presence of chloride in the soil can lead to high results. Because chloride can also be oxidized by potassium dichromate, the determination of organic matter in saline soil must be prevented by chloride interference. A small amount of chlorine can be added with a small amount of Ag2SO4 to precipitate the chloride. The addition of Ag2SO4 not only precipitates chloride, but also promotes the decomposition of organic matter. The amount of Ag2SO4 can not be too much, about 0.1g, otherwise it will precipitate Ag2Cr2O7, affecting the titration.
3 It is necessary to start the boiling on the surface of the solution in the tube before calculating the time. Master boiling standards as consistent as possible, and then continue to cook 5min, cooking time has a greater impact on the analysis results, it should be as accurate as possible.
4 The color of the boiled solution should generally be yellow or slightly greenish. If the color is green, the amount of potassium dichromate is insufficient. If the amount of ferrous sulfate consumed is less than 1/3 of the blank amount during titration, there is a possibility of incomplete oxidation, and redoing should be discarded.
Related soil organic matter (nutrient) measuring instruments please see: http://?xtkeyword=Soil nutrient&page=1
About Other Silicone Products:
Are you still looking for other interesting silicone products?Look at this category,there are many different styles silicone products,and it can use for many places.Such as Silicone Label,it's a decoration tag for your bag or clothes,and Custom Bookmark,you can customize your own design bookmark.And there are other products for cigaratte,they are Silicone Cigaratte Pack Cover and Ashtray Silicone.Other silicone producuts you can visit:Silicone Label,Pencil Case Silicone,Silicone Zipper Puller.
Product introduction:
1.Product name:Silicone Label,Silicone Cigaratte Pack Cover,Ashtray Silicone,Pencil Case Silicone,Silicone Zipper Puller,Custom Bookmark
2.Place of origin:Guangdong China
3.Color:any pantone color
4.Effect:Any effect according to customer's requirement
5.MOQ:500pcs.
7.Design:Customized/stock
8.Certification:FDA,LFGB,SGS,ROHS,etc.
9.Usage:Use in daily life
10.Other Silicone Products photos for reference.
Other Silicone Products
Silicone Label,Silicone Cigaratte Pack Cover,Ashtray Silicone,Pencil Case Silicone,Silicone Zipper Puller,Custom Bookmark
Dongguan OK Silicone Gift Co., Ltd. , https://www.dgsiliconepettags.com