Why is the concentration of sodium thiosulfate relatively high?

The balance weighs 158g of sodium thiosulfate and dissolves it in water, and the volume is fixed to 1L.

I don't think you need to calibrate this solution.

The reason why the sodium thiosulfate listed on the Internet needs to be calibrated is because the sodium thiosulfate on the Internet is basically titrated by iodine titration, and the concentration needs to be relatively accurate.

The purpose of using sodium thiosulfate is only to react with the residual chlorine in the water, and the dosage must be excessive, and there is no need for precise sodium thiosulfate concentration.

In addition, the general concentration of sodium thiosulfate on the Internet is low, and the concentration of 1mol l seems to be difficult to judge when calibrating.

1N Na2S2O3 preparation: take 2 grams of anhydrous sodium carbonate, 260 grams of AR 6 1Na2S2O3 and boil cold distilled water to dissolve into 1000ml. Calibration:

Accurately suck the prepared 1N Na2S2O310ml into a 100ml volumetric flask, dilute it with water to the scale and shake well, pour it into a 25ml burette, take another 5ml potassium iodate in an iodine measuring flask, add about 30ml of water, add 30% ki 7ml, 6N HCl 10ml, shake slightly, place in a dark place for 10 minutes, titrate with the above Na2S2O3, and use starch as an indicator. Calculation: CNA2S2O3 = ML(NA2S2O3) NA2S2O3 Preparation:

Put 50ml of the calibrated 1N Na2S2O3 standard solution in a 1000ml volumetric flask with a burette, dilute it to the scale with water, and shake well. The actual operation is so on.

If the concentration is high, just add more water, haha.

Weigh grams of sodium thiosulfate plus grams of anhydrous sodium carbonate and dilute to one liter!

dissolved in boiled and cooled distilled water) for the precipitation of free iodine content

You will deduct the excess you are now calibrating from the preparation process in the future. Do the math. This is generally the case. It's up to you to tune it yourself.

Generally, it takes half a month to mark after preparation.

The reaction of sodium thiosulfate with sulfuric acid is: Na2S2O3 + H2SO4 = Na2SO4 + S + SO2 + H2O.

1. Due to sodium thiosulfate.

It is easy to be oxidized by air and decomposed, so it is unstable, and it is not a reference material, so it cannot be directly prepared into a standard solution, but needs to be calibrated.

2. The reference substance must meet the following conditions:

1) The lead composition of the cavity is consistent with the chemical wood chain formula.

2) The purity of the reagent is high enough (above).

3) The reagent is stable, easy to store and weigh accurately.