EDTA？ The main instruments used to measure ash dosage by titration are burette and burette clamp, titration stand, pot-bellied pipetting bottle, conical bottle, beaker, volumetric bottle, enamel cup, steel bar, measuring cylinder, jar, tray balance, stopwatch, watch mirror, mortar, soil sample sieve, ear washing ball, precision test paper, polyethylene bucket (4 pieces), brush and decontamination powder.
2. Preparation of test solution
Preparation of (1)0. 1 m o l/？ m3？ Disodium ethylenediamine tetraacetate (EDTA? Standard solution: EDTA? 37.226g, dissolved in lukewarm distilled water without carbon dioxide, completely dissolved, cooled to room temperature, and constant volume to 1000mL.
(2) Prepare 10% ammonium chloride solution: mix 500g? Put ammonium chloride in a 10L polyethylene barrel, add 4500mL distilled water, and shake well to make ammonium chloride completely dissolved.
(3) 1.8% preparation? Sodium hydroxide solution (containing triethanolamine): 100g? The balance of the rack is 18g? Sodium hydroxide (analytically pure), put it into a beaker of 1000mL, add 1000mL distilled water to completely dissolve it, cool it to room temperature and add 2mL. Triethanolamine (analytically pure) is stirred evenly and stored in a plastic bucket.
(4) Preparation of calcium red indicator: 0.2g of calcium reagent sodium hydroxide is mixed with 20g of potassium sulfate which has been dried in a drying oven at 65438 005℃ for 65438 0 hours in advance, put into a mortar and ground into fine powder, and stored in a brown jar.
3, prepare the standard curve
(1) sampling: take lime and aggregate used in the construction site, dry them, and then pass through a 2.0 or 2.5 mm sieve to determine their water content.
(2) calculation of mixture composition: calculation formula: dry material mass = wet material mass /( 1+ water content)
Calculation steps:
Dry mixture mass = 300g /( 1+ optimal water content)
Dry soil mass = dry mixture mass /( 1+ lime dosage)
Dry lime quality = dry mixture quality-dry soil quality = dry soil quality ×( 1+ dry soil water content)
Wet lime quality = dry lime quality × (air-dried moisture content 1+ lime)
Water addition of calcareous soil = 300g-wet soil mass-wet lime mass.
(3) Prepare five kinds of samples: prepare two standard samples with lime content of 0%, 2%, 4%, 6% and 8% and put them in enamel cups.
(4) Add 600 ml 10% ammonium chloride solution into the enamel cup containing the sample, stir it with a steel bar for 3 minutes, leave it for 4 minutes, move the supernatant into a 300 ml beaker, shake it evenly, and cover the watch mirror to be measured.
(5) Absorb the upper suspension 1 0 m L with a pipette and put it in a 200mL conical flask, and take 50ml 1.8% with a measuring cylinder? Put the solution of sodium hydroxide (containing triethanolamine) into the conical flask, and the P H value is 12.5~ 13. Then add calcium red indicator, titrate with EDTA disodium standard solution to pure blue, and record the consumption of EDTA disodium.
Similarly, several other samples were tested and their respective consumption of E, D, T and A disodium was recorded.
(6) Taking the average consumption of disodium EDTA as the ordinate and the lime consumption (%) as the abscissa, the relationship curve between them is a smooth curve.
4, test steps
Take a representative lime-soil mixture, weigh 300 g, put it in an enamel cup, disperse and agglomerate with a stirring rod, add 600ml 10% ammonium chloride solution, and then carry out the test according to the above steps (4), (5) and (6). According to the number of milliliters of disodium edetate consumed, the amount of lime in the mixture is determined by the prepared standard curve.
5. Records and reports
Records should be made during the test, and a test report should be made according to the records, which should include test times, average results, standard deviation, deviation coefficient, etc.
Extended data
Use of EDTA
1, EDTA is widely used, and can be used as bleaching fixing agent, dyeing assistant, fiber treatment assistant, cosmetic additive, blood anticoagulant, detergent, stabilizer and polymerization initiator of synthetic rubber in color photographic materials processing. EDTA is the representative substance of chelating agent. It can form stable water-soluble complexes with alkali metals, rare earth elements and transition metals.
In addition to sodium salts, there are ammonium salts and various salts, such as iron, magnesium, calcium, copper, manganese, zinc, cobalt and aluminum. In addition, EDTA can also be used to quickly discharge harmful radioactive metals from the human body and play a detoxification role. It is also a water treatment agent. EDTA is also an important indicator, but it can be used to titrate metals such as nickel and copper. Only when it is used with ammonia water can it play the role of indicator.
2. It is often used to soften the water quality of boilers. Prevent scaling.
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