1 Scope
This standard is applicable to the determination of alkali concentration in alkaline solutions.
Summary of Method 2
Using phenolphthalein as an indicator, titrate the sample with a known concentration of hydrochloric acid standard solution, and calculate the alkaline concentration of the sample based on the volume of hydrochloric acid standard solution consumed.
3 reagents
Hydrochloric acid: analytical pure, prepared as a standard solution with C (HCl)=0.1mol/L;
Phenolphthalein indicator: prepared into an ethanol solution with a concentration of 10g/L.
4 Instruments
4.1 Cone flask: 150ml.
4.2 burette: 25ml.
4.3 Pipette: 5ml.
5 Experimental Steps
Use a pipette to transfer a certain volume of alkaline sample V (5% alkaline: 5ml, 10% alkaline: 3ml, 30% alkaline: 1ml) into a conical flask containing about 10ml of distilled water. Rinse the flask wall with distilled water until the volume of the sample inside is about 50-60ml. Then add 2-3 drops of phenolphthalein indicator and titrate the sample in the conical flask with a 0.1mol/L hydrochloric acid standard solution until the red color disappears, which is the endpoint of titration. Record the volume V1 of hydrochloric acid standard solution consumed.
6 Precautions
6.1 The sample is alkaline solution, and precautions should be taken to prevent burns from the sample;
During the analysis process, hydrochloric acid should be used to prevent acid burns.
In the calculation formula of 7 results
The concentration of C1 hydrochloric acid standard solution, mol/L
The volume of hydrochloric acid standard solution consumed during V1 titration, ml。
V sample volume, mL
8 Reports
Take the arithmetic mean of the two analysis results as the sample result.
