Determination of sodium hydroxide and sodium carbonate in industrial sodium hydroxide

There are many methods for measuring sodium hydroxide and sodium carbonate in industrial sodium hydroxide. I will give you two methods here. Please compare method one.: (1) Overview of the method Use methyl orange as an indicator, titrate with hydrochloric acid standard solution, measure the total alkali content of sodium hydroxide and sodium carbonate (in NaOH%), and then subtract the amount of sodium carbonate (in NaOH%), which is the mass fraction of sodium hydroxide. (2) Instruments and reagents (1) Magnetic stirrer. (2) C02-free distilled water or water of corresponding purity. (3) Methyl orange (HGB 3089) indicator solution 0.5g/L. (4) Hydrochloric acid (GB 622) standard solution c (HCl) = 1 mol/L. (3) Operation steps 1. Preparation of sample solution Use a weighing bottle of known mass, quickly weigh (38±1)g solid sodium hydroxide sample or 50g sodium hydroxide aqueous solution sample, weigh accurately to 0.01g, place it in a stoppered Erlenmeyer flask, dissolve it with water that does not contain carbon dioxide, cool it, move all the solution into a 1000ml volumetric flask, dilute to the mark, and shake well. 2. Titration: Take 50.0ml of the sample solution and pour it into a 250ml Erlenmeyer flask. Add 2 to 3 drops of methyl orange indicator solution (0.5g/L). Under stirring with a magnetic stirrer, titrate with hydrochloric acid standard solution until the solution changes from yellow to orange as the end point. (4) Calculation 1. The mass fraction of the total alkali content of sodium hydroxide and sodium carbonate mol/L ； V——volume of hydrochloric acid standard titrant, ml ； m——mass of sample, g ； 0.040——millimolar mass of sodium hydroxide, g/mmol. 2. The mass fraction X2 of sodium hydroxide content is calculated according to formula (2) X2=X1-1.818X3 (2) where ； X3——Sodium carbonate content (calculated as C02%), measured according to GB 7698, % ； 1.818——Coefficient for converting carbon dioxide into sodium hydroxide. Method two: 1.1.1.2 Method principle 1.1.1.2 .1 Determination principle of sodium hydroxide content: First add barium chloride to the sample solution to convert sodium carbonate into barium carbonate precipitate, then use phenolphthalein as the indicator and titrate with hydrochloric acid standard solution to the end point. 1.1.1.2 .2 Determination principle of sodium carbonate content: The sample solution uses bromocresol green-methyl red mixed indicator as the indicator, titrates with hydrochloric acid standard solution to the end point, measures the sum of sodium hydroxide and sodium carbonate, and then subtracts the sodium hydroxide content, the sodium carbonate content can be measured. 1.1.1.3 Sampling volume: 50±1g. 1.1.1.4 Constant volume: 1000ml。 1.1.1.5 Dosage during analysis: 50ml。

There are other methods, such as the potentiometric method. Determination of sodium hydroxide and sodium carbonate in industrial sodium hydroxide by potentiometric titration Yao Xiaohong1 Zhang Di2 Liu Li2 Wang Xin2 Zhang Xiangying2 (1 Safety and Environmental Protection Department of Ethylene Plant of PetroChina Dushanzi Petrochemical Company 2 Central Laboratory of Ethylene Plant of PetroChina Dushanzi Petrochemical Company Dushanzi 833600) Abstract At present, when measuring the content of sodium hydroxide and sodium carbonate in industrial sodium hydroxide according to GB/T4348.1-2000, chemical titration is used. However, with the development of analytical technology, the use of potentiometric titration is an inevitable trend. The prerequisite for using potentiometric titration instead of chemical titration is that the accuracy and precision of the potentiometric titration meet the requirements of the national standard. A large number of samples were measured using a Swiss Metrohm 682 potentiometric titrator. The data showed that the accuracy and precision of the potentiometric titration method can meet the requirements of the national standard. Keywords Potentiometric titration ； chemical titration ； sodium hydroxide ； sodium carbonate ； Precision ； Accuracy CLC classification number O657.15

You can refer to* * Standard GB4348, what is mentioned above is quite detailed.

You must add less standard solution for your end-point operation.