Potassium permanganate molecular weight = 158.026, equivalent = 31.605. The aqueous solution of potassium permanganate is affected by the reducing substances and impurities in the water, and the brown water-containing manganese dioxide precipitate can be resolved by direct sunlight to change the concentration. When preparing its standard solution, it must be contained in a brown bottle to prevent direct sunlight. After preparation, it should be placed for a period of time. After the reducing substance in the water is completely acted, the precipitate is filtered out. Then, after calibration, it can be basically stable and not easy to change. standard solution.
Preparation method: Take 3.2 g of potassium permanganate per 1 liter of 0.1N solution and place it in a 1 liter beaker. After adding 500-800 ml of boiling water to dissolve, place it in the dark for a week, and then use a siphon to transfer the upper clear solution to the brown bottle Medium (or filtered with glass wool) to save for calibration.
If there are many types and concentration types, in order to reduce the storage time and simplify the procedures, 48 ​​to 50 grams of potassium permanganate can be taken for every 1 liter, which is made into a concentrated solution of about 1.5N according to the above method. Then take this according to the calculated amount The concentrated solution is diluted with boiled distilled water to prepare a solution with the required concentration (such as 0.1N for 67ml), so that the resulting solution can be calibrated after only 2 to 3 days. The concentrated solution can also be used to correct the diluted solution use.
Calibration method:
1) Sodium oxalate method: It is accurately weighed that it is dried for 2 hours at 110 ° C and cooled to room temperature in a desiccator. The guaranteed reagent sodium oxalate is 0.1340 g (that is, equivalent to 20 mg equivalent) in a 250 ml Erlenmeyer flask, add 30 ml of water and sulfuric acid (1: 4) Dissolve 10ml, heat to 70 ~ 80 ℃, titrate with potassium permanganate to be calibrated until the solution is slightly rose-red, and the end point can be maintained for 30 seconds. At the same time, make a blank.
Calculation: m
C (1 / 5KMnO4) = ----------------
(V1-V2) * 0.06700
C --------- KMnO4 concentration
V1 ———— Consumption of potassium permanganate solution ml
V2 ———— Consumption of potassium permanganate solution in blank ml
m——Quality of sodium oxalate (g)
0.06700——The quality of sodium oxalate in grams equivalent to the standard solution of 0.1 mol / L potassium permanganate.
2) Iodometry: Add 250ml of potassium iodide (10%) solution and 10ml of sulfuric acid (1: 4) to a 250ml Erlenmeyer flask, then use a burette to accurately measure the desired height
20ml of potassium manganate solution. Then titrate with 0.1N sodium thiosulfate standard solution, when the solution is light yellow, add 5ml of starch (0.2%) solution, and then continue titration until the blue color disappears as the end point.
Female sunglasses, according to the women's fashion collocation, highlight the indispensable ornaments, this kind of sunglasses have a variety of materials, the most commonly used in three kinds of metal, acetate, plastic. Each type of material is different and the style is different. It is also a kind of glasses that can block the sun's light in the strong light protection of the eyes of the products can block ultraviolet and infrared, while the color of the external environment does not change, only light intensity changes, play the protection of the eye.
Sunglasses For Women,Custom Sun Glasses,Lady With Sunglasses,Sunglasses For Female
China Guangdong Shenzhen city Omelle glasses Co., Ltd. , https://www.omelleoptical.com