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Determination of borax content in Liaobin of five borax borax factory

Release date:2017-11-22 Author: Click:


Five borax manufacturer, Liao Bin explains borax content determination:

Take this product about 0.4g, precision weigh, add water 25ml dissolve, add 0.05% methyl orange solution 1 drops, titrate with hydrochloric acid titration solution (0.1mol/L) to orange red, boil for 2 minutes, cool, if the solution is yellow, continue titrating until the solution is orange red, plus neutral glycerin (taking glycerin 80ml, adding water 20ml and phenolphthalein indicator 1 drops, oxidizing with hydrogen. Sodium titration solution (0.1mol/L) titrated to pink) 8 drops of 80ml and phenolphthalein indicator solution, titrated to pink with sodium hydroxide titrant (0.1mol/L). Every 1ml sodium hydroxide titration solution (0.1mol/L) is equivalent to Na2B4O7.10H2O of 9.534mg.

Method name

Determination of borax borax by neutralization titration

Application scope

In this method, the content of borax (Na2B4O7? 10H2O) was determined by neutralization titration.

This method is suitable for the determination of borax.

Method principle

Take a proper amount of the trial products, add 0.05% drops of methyl orange solution with 1 drops of methyl orange solution, titrate to orange red with hydrochloric acid titration solution (0.1mol/L), boil for 2 minutes, cool, if the solution is orange yellow, continue titrating to orange red in solution, plus neutral glycerol and phenolphthalein indicator, titrated with sodium hydroxide titrant (0.1mol/L) to pink. Color. Every 1mL sodium hydroxide titration solution (0.1mol/L) is equivalent to 9.534mg Na2B4O7. 10H2O, calculated.


1. water (New boiling is placed to room temperature)

2. 0.05% methyl orange solution

3. neutral glycerol

4. hydrochloric acid titrant (0.1mol/L)

5. methyl red brominated cresol green mixture indicator

6. datum anhydrous sodium carbonate

7. sodium hydroxide titrant (0.1mol/L)

8. phenolphthalein solution

9. basic potassium phthalate hydrogen potassium hydroxide

Sample preparation

1. 0.05% methyl orange solution

Take methyl orange 0.05g, add water 100mL to dissolve, get.

2. neutral glycerol

Take 80mL glycerol, 20mL of water and 1 drops of phenolphthalein solution, sodium hydroxide titration solution (0.1mol/L) titration to pink.

3. hydrochloric acid titrant (0.1mol/L)

Preparation: take hydrochloric acid 9.0mL, add water amount to make 1000mL, shake well, get 0.1mol/L hydrochloric acid titration solution.

Demarcation: the base free sodium carbonate, which is dry to constant weight at 270~300 C, is about 0.15g, precise and fixed, adding water 50mL to dissolve, plus methyl red brominocresol green mixed indicator, 10 drops, when titrated to the solution from green to purple red, boil for 2 minutes, cool to room temperature, then continue titrating to solution from green to dark purple. Each 1mL hydrochloric acid titration solution (0.1mol/L) is equivalent to 5.30mg of anhydrous sodium carbonate. The concentration of the solution is calculated according to the consumption of the liquid and the dosage of anhydrous sodium carbonate.

4. methyl red brominated cresol green mixture indicator

Take 0.1% methyl red ethanol solution 20mL, add 0.2% bromo cresol green ethanol solution 30mL, shake well.

5. sodium hydroxide titrant (0.1mol/L)

Preparation: take appropriate amount of sodium hydroxide, add water to shake it and dissolve it into saturated solution. After cooling, put it in polyethylene plastic bottle for several days. Take the clarified sodium hydroxide saturated solution 5.6mL, add the new boiling cold water to make 1000mL, shake well.

Demarcation: the base phthalate two formic acid, which is dried to constant weight at 105 C, is about 0.6g, and it is niced accurately, adding new boiling cold water 50mL, shaking to make it as possible as possible, adding 2 drops of phenolphthalein indicator, titrating with this solution, when near the end, the potassium hydroxide of phthalate should be dissolved completely, titrated to solution pink. Each 1mL sodium hydroxide titrant (0.1mol/L) is equivalent to 20.42mg of potassium hydrogen phthalate two. The concentration of the solution is calculated according to the consumption of the liquid and the amount of potassium hydrogen two phthalate.

Storage: in the polyethylene plastic bottle, sealed and preserved; there are 2 holes in the plug, 1 tubes are inserted in the hole, the 1 pipes are connected with the Soda Lime tube, and the 1 pipes are used for the absorption of the liquid.

6. phenolphthalein solution

Take 1g 100mL to add phenolphthalein, ethanol solution.

Operation steps

Note 1: the weight of the "precision weighing" system should be accurate to 1/1000 of the weighed weight, and the accuracy of "precision taking" should be in accordance with the requirements of the national standard for the precision of the volume of the liquid pipette.

Note 2: "moisture determination" by drying, take the test product 2~5g, flat in the dry to constant weight of the flat bottle, thickness not more than 5mm, loose supply test products not more than 10mm, precision called, open the bottle cap at 100~105 C drying 5 hours, cover the bottle cap, displaced the dryer, cold for 30 minutes, precision weight, and then on the weight, and then on the top The temperature was dried for 1 hours, cooling, weighing, and weighing two times continuously until the difference was not more than 5mg. The water content (%) of the tested product was calculated according to the weight lost.

Process process

1. Pressure alkali solution: the pretreated boron and magnesium mineral powder is mixed with sodium hydroxide solution, and the sodium borate solution is decomposed with temperature and pressure, and then the borax is obtained by carbonization treatment.

2MgO.B2O3+2NaOH+H2O - 2NaBO2+2Mg (OH) 2

4 NaBO2+CO2 - Na2B4O7+Na2CO3

2, carbon alkali method: the pretreatment of boron magnesium ore powder and sodium carbonate solution mixed heating, through carbon dioxide pressure rise after reaction borax.

2 (2MgO.B2O3) +Na2CO3+2CO2+xH2O to Na2B4O7+4MgO.3CO2. xH2O

3, soda solution (salt brine): salt brine after treatment with borax paste, soda mixed cooking is borax.

CaB4O7+ Na2CO3 to Na2B4O7+ CaCO3

4H3BO3+ Na2CO3 to Na2B4O7+6H2O+CO2

4, soda alkali solution (sodium borite): soda ash and sodium bicarbonate decomposed pretreated sodium borosilicate, adding caustic starch to settle and crystallize borax.

2 (NaO.2CaO.5B2O3.16H2O) + Na2CO3+ NaHCO3 > 5Na2B4O7+4CaCO3+CO2+34H2O

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