Questions about the analysis results of hydrochloric acid
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The hydrochloric acid produced by our factory has recently encountered problems in process analysis.* * The standard is to add 3 drops of indicator to see the end point and calculate the content. But why do we need to add 4-5 drops of excessive indicator to our acid to see the blue color of the end point? Please help analyze the reason.
1. It may be that the free chlorine content in the acid is too high, which may damage the indicator. 2. Check whether there is any problem with the preparation of the indicator. 3. Use the reagent hydrochloric acid as a blank for comparison. 4. Test the free chlorine in the acid.
Correct answer. :P: The bromocresol green indicator used in handshake is also a redox indicator, and its oxidation state is colorless. If the free chlorine in the product is too high, the phenomenon mentioned by the original poster will occur. Among the standards for hydrochloric acid, there is an item for testing oxidizing substances. This post was last edited by xwtsq on 2009-2-4 16:49 ]
I agree with the third floor's point of view. It may be that the sample contains free chlorine, which has strong oxidizing properties and destroys the indicator. Therefore, you need to add more to see the end point. I personally think that adding 2 to 3 more drops will not have much impact on the result.
The reason why the indicator is passivated. This is normal. I don’t know how precise your analysis is.
I agree with the third floor, it is possible that the sample contains free chlorine and the indicator is passivated.
What I would like to ask you is that there is an analytical problem with the finished hydrochloric acid produced by our factory.* * The standard is that you must add three drops of indicator and then analyze the hydrochloric acid content. But why do I need to add an excessive amount of indicator (4-5 drops) to my hydrochloric acid to see the blue color at the midpoint? Please help me analyze the reason. Thank you.
I have seen this topic before. Free chlorine leads to indicator passivation. Friends who can use the reagent hydrochloric acid for comparison tests. If you have posted on the same topic, I suggest you check it out. It is best not to post again. See you.: http://bbs.hcbbs.com/thread-382452-1-3.html This post was last edited by lifanwang on 2009-2-12 13:10 ]
Oh, thank you, old scalper who opened up wasteland. I would also like to ask. I have asked our laboratory to test the oxide content in acid many times, but why can it be measured when the oxide content is high?* * The standard analysis shows the content. Sometimes when the oxide content is low, more indicators need to be added. Thank you for your help.
To solve your problem two questions need to be clarified: 1. Is it hydrochloric acid or subacid? 2. What are the so-called oxides they measured? Let’s clarify these two issues and let’s discuss them together, okay?
Is the indicator wrong? You can do a blank experiment to control it.