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Solve the preparation problem of chrome black T indicator
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Larry Walden
Solve the preparation problem of chrome black T indicator
Yes, the chrome black T in the national standard does not require adding triethanolamine, but I have a method of adding triethanolamine when searching on the website. I wonder whether this method of preparing indicators can also serve as a shield, killing two birds with one stone?
Yes, the chrome black T in the national standard does not require adding triethanolamine, but I have a method of adding triethanolamine when searching on the website. I wonder whether this method of preparing indicators can also serve as a shield, killing two birds with one stone?More
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Triethanolamine is the complexing agent, except for iron and aluminum plasma. Check the book to see the introduction of triethanolamine as a concealing agent
Triethanolamine is the complexing agent, except for iron and aluminum plasma. Check the book to see the introduction of triethanolamine as a concealing agentMore
2g hydroxylamine hydrochloride strong reducing agent is basically enough to keep chrome black T from air deterioration and oxidation for a period of time. After all, indicators will not be configured in large quantities. It is generally best to use it up within a week. Some articles wrote that EBT aqueous solution (pH< 6.3) was added with triethanolamine to prevent polymerization deterioration; In alkaline solution, hydroxylamine hydrochloride or ascorbic acid is added to prevent oxidation fading; EBT+NaCl (1 ∶ 100) - solid (long-term use). If you are really afraid of fast deterioration, it is better to use solid indicators.
2g hydroxylamine hydrochloride strong reducing agent is basically enough to keep chrome black T from air deterioration and oxidation for a period of time. After all, indicators will not be configured in large quantities. It is generally best to use it up within a week. Some articles wrote that EBT aqueous solution (pH< 6.3) was added with triethanolamine to prevent polymerization deterioration; In alkaline solution, hydroxylamine hydrochloride or ascorbic acid is added to prevent oxidation fading; EBT+NaCl (1 ∶ 100) - solid (long-term use). If you are really afraid of fast deterioration, it is better to use solid indicators.More
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http://bbs.hcbbs.com/thread-586940-1-1.html Here is a post for your reference.
http://bbs.hcbbs.com/thread-586940-1-1.html Here is a post for your reference.More
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The stability of chrome black T solution is not very good, and it is easy to be oxidized and polymerized to form dimers. Therefore, in general, if it is used for a long time, it is better to prepare it by dry method or before use. When preparing chrome black T solution, adding a small amount of triethanolamine can prevent its polymerization, adding a small amount of hydroxylamine hydrochloride or ascorbic acid can prevent its oxidation, and the added reagents will not affect the hardness measurement. The purpose of triethanolamine added to each black T is different from that of triethanolamine added to the sample. This is the structural formula of chrome black T, which is easy to be oxidized. It can be seen from the azo bond and phenolic hydroxyl, but I can't see the polymerization characteristics from the structure. But by adding alcohol amine to prevent its polymerization, it can be judged that amine can absorb excess positive charges, and the steric resistance of the three ethoxyls is large. I judge this mechanism by myself, but I don't know whether it is right or not.
The stability of chrome black T solution is not very good, and it is easy to be oxidized and polymerized to form dimers. Therefore, in general, if it is used for a long time, it is better to prepare it by dry method or before use. When preparing chrome black T solution, adding a small amount of triethanolamine can prevent its polymerization, adding a small amount of hydroxylamine hydrochloride or ascorbic acid can prevent its oxidation, and the added reagents will not affect the hardness measurement. The purpose of triethanolamine added to each black T is different from that of triethanolamine added to the sample. This is the structural formula of chrome black T, which is easy to be oxidized. It can be seen from the azo bond and phenolic hydroxyl, but I can't see the polymerization characteristics from the structure. But by adding alcohol amine to prevent its polymerization, it can be judged that amine can absorb excess positive charges, and the steric resistance of the three ethoxyls is large. I judge this mechanism by myself, but I don't know whether it is right or not.More
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