I chromic acid and sulfuric acid can be titrated and analyzed by what chemistry

1.Coarsening (CRO3 H2SO4).

CRO3 accurately pipette 2ml of cylinder liquid into a 100ml volumetric flask, set the volume, shake well, take 100ml of this solution in a 250ml Erlenmeyer flask, add 50ml of pure water, add 2g of potassium iodide, 12N H2SO4 ml, titrate with standard sodium thiosulfate solution, drop until light yellow, add 2-3ml of 1% starch indicator, and continue to drop until the blue disappears and is terminated.

cro3（g/l）=168nv

H2SO4 took 10ml of solution from the above 100ml volumetric flask in a 250ml beaker, added 100ml of pure water, and titrated to pH = that is, the end point with a standard sodium hydroxide solution with pH meter.

h2so4（g/l）= cro3)

CR3+ take 10ml of solution from the above 100ml volumetric flask in a 250ml beaker, add 100ml of pure water, add 2g of Na2O2, boil for 10-15 minutes, cool, add 12N H2SO4, add potassium iodide 2g, titrate with standard sodium thiosulfate solution, drop until light yellow, add 2-3ml of 1% starch indicator, and continue to drop until the blue disappears.

Cr3 + (G L) = 87 N (V total Cr-V CRO3) V total Cr = total volume of chromic acid titrated in this titration (ml).

V CRO3 = titration volume (ml) of CRO3 done in the previous step

Sorry, I haven't done anything about it.

Sulfuric acid can be titrated with barium hydroxide to form a white barium sulfate precipitate.

Generally, redox is used by the reverse drip method.

Measure six late chromium, and according to the electrode potential.

It can be found that hexavalent chromium only has its strong oxidizing properties under acidic conditions.

Secondly, hexavalent chromium has different forms when the acidity is different.

The most acidic is CR207

Neutral or alkaline is. cro4

This also creates a deviation in the dosing, so the acid needs to be added.

In this way, the specific experiments actually done in the laboratory, the dosage of the agent must be controlled.

First of all, in order to save the principle of medicine.

Then it can be avoided.

Side effects are possible, though almost impossible.

Again: it is always more convenient to drop 1 drop of solution than to pour as many reagents as you pour.

As for side reactions, let's give an example (whatever you like).

We know the electrode equation for the oxidation reaction of dichromate.

and hydrogen ions. Concentrations are positively correlated.

The more hydrogen ions, the higher the potential).

Then, although I didn't calculate the verification myself.

In the unlikely event that the concentration of hydrogen ions is so high that its potential is higher than the reduction potential of oxygen in water... Isn't that just oxidizing the oxygen out? (I didn't calculate, just a random example, just to prove the term side reaction).

Such as sedation, so the laboratory requires the reagent to be used.

Thinking back to the various experiments done before, the indicator should also be in moderation, and everything should be in moderation) So the amount of this acid, as long as the appropriate amount, is also good, and this appropriate amount is prescribed.

Is it titrated with ferrous iron?

If it is titrated with ferrous iron, it is similar to the determination of iron content in iron ore, the purpose of adding sulfuric acid is to adjust the acidity, and the purpose of adding phosphoric acid is to make Fe3+ form a complex of phosphate, so as to reduce the interference of ferroelectric power to change the bending position of electricity, eliminate purification and remove iron ion yellow.

Make sure there are no interfering ions.

Remove 2 ml of the reagent to be measured with a pipette and place it in a 250 ml beaker.

Add 50 ml of distilled water and adjust the pH to 10 with 10% NaOH solution (the color will change at this point).

Add to the above solution.

Boil the 30% H2O2 for 30 for 40 minutes (completely remove the excess amount of 30% H2O2).

After cooling, adjust the volume of the solution to 100ml with distilled water.

Prepare the solution with 35% hydrochloric acid to be acidic (the color changes from yellow to orange), add 1g of KI to the above solution, and calibrate it with Na2S2O3 5H2O until the color of the solution changes to light yellow.

Add 1% starch solution to continue calibration (preferably until the cyan color of the solution disappears) cr(3+)vol%=

v(na2s2o3•5h2o)xxf

When testing sulfate ions, in order to exclude the interference of other ions (such as carbonate ions, sulfite ions, silver ions, etc.), excessive hydrochloric acid acidification should be added first.

CO3 2- +2H+ = CO2 +H2OSO3 2- +2H+ = SO2 +H2OAG+ +3Cl- = AGCL3 plus barium chloride, if a white precipitate is produced, it can indicate that the presence of sulfate ions BA2+ +SO2- = BASO4 in the original solution can only be acidified with hydrochloric acid, not nitric acid, should be whether it is dilute nitric acid or concentrated nitric acid has oxidation, it can oxidize sulfite ions (SO3 2-) to sulfate ions (SO4 2-).

Hydrochloric acid is added, no bubbles are produced, and BA ions are added to produce precipitation.

Add dilute hydrochloric acid first, if there are no bubbles, add barium chloride to see if there is a precipitation.

This is the traditional way.

Add nitric acid and then add barium nitrate.