Analysis method for chlor-alkali brine concentration
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Recently, the number of samples has increased significantly, resulting in an **increase in analysis time**. Seek a more convenient and rapid method for analyzing saltwater concentration. The method currently used is: 10 ml of saline solution is made up to 250 ml, and then 10 ml of this diluted saline solution is taken for titration with mercuric nitrate. Does anyone have any good suggestions to help me? I’ve been working overtime lately, but it’s not counted as overtime – I’m essentially working for free.
If a very precise detection is not required, density or conductivity can be used.
Some level of accuracy is still required; after all, this is a laboratory, not a manufacturing facility
Then you’ll need to purchase equipment; potentiometric titration can be used, and the instruments are available both imported and domestically produced. There are both manual and automatic options. But the manual version isn’t much faster.
Miss, could you provide the specific operating procedures?
Recently, in data comparisons using the densitometer method, the difference in chlor-alkali analysis at the branch office was around 50 g/L, while our side saw a difference of about 18 g/L. Moreover, this method can only be used for brackish water; the feed saltwater cannot be analyzed using a densitometer – Anton Paar’s densitometers are required for such analyses
It is recommended to give it a try; take about 300 ml of sample, using part of it for determining specific gravity and the other part for analysis. Use filter paper from a dry Erlenmeyer flask lid to weigh the empty weight on an analytical balance. Then remove the filter paper, add 1 or a few drops into the Erlenmeyer flask using a dropper – the number of drops can be determined through experimentation or by referring to common concentration ranges. Place the filter paper that was used earlier back in place, weigh again, and calculate the amount of sample. Remove the Erlenmeyer flask, add the amount of distilled water specified in the procedures, conduct the titration analysis as per the guidelines, and use the analysis results together with the specific gravity to calculate the concentration values typical for your company*. This eliminates the need for constant-volume dilution, mixing, and sampling again. During weighing with an analytical balance, the error caused by the evaporation of trace amounts of water is likely to be smaller than the errors resulting from repeated use of a pipette. Give it a try; I have done this before, and both precision and accuracy were very good. Gloves must be worn during weighing, and a large piece of dry filter paper should be placed next to the balance. Before each weighing, the Erlenmeyer flask must be placed on this filter paper to prevent water from remaining at its bottom and ending up on the balance’s weighing pan due to haste.
The method suggested by the original poster is already simple enough; do you really want it to be simpler? Then 0.5 mL of sample can be drawn, mixed with about 30 mL of water, and dropped directly. However, the precision is not as good as what you described regarding drawing air in after fixing the volume; P
This post was last edited by qugd on 2021-1-14 09:32. For experienced analytical technicians, performing a titration to determine saltwater concentration takes no more than 20 minutes, and this is while still ensuring accurate and reliable results, as the saltwater concentration does not change significantly on a daily basis. I think the titration method is probably the most accurate and fastest way. Other methods have certain reliability issues; as I mentioned in my previous post, if an extremely accurate measurement is not required, density or conductivity can be used. If possible, an automatic titrator or an online titrator can be used to accurately measure saline, but this requires some investment. But even with automated measuring instruments, for a volumetric analysis method like titration, the time required cannot be very short, as there is still time needed to clean the measurement cell and the electrodes; each sample takes no less than 10 minutes, and I would estimate it to take around 15 minutes. In fact, it’s not as fast as when done manually by an experienced operator – for example, using an automatic liquid feeder for the titrant can significantly reduce the time needed to add the titrant and to zero the instrument each time.
The error in conductivity density is still quite large, and it is also related to temperature; when the temperature drops, salt precipitates. It is recommended to speed up the accurate pipetting process and use rapid titration with silver nitrate. For now, there is no better solution, and even with automatic titration, cleaning and sample addition are still necessary, so the accuracy may not improve significantly.