Why does liquid caustic soda, accounting for about 30% of the content in the storage tank, turn yellow when exposed to air?
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Why does liquid caustic soda, accounting for about 30% of the content in the storage tank, turn yellow when exposed to air? The temperature of the liquid caustic storage tank is around 60 degrees.
When liquid caustic is exposed to the air, it reacts with gases such as carbon dioxide, water vapor, and oxygen present in the air, producing various degradation products and oxidation products, which causes the color of the liquid caustic to turn yellow. High temperatures in the storage tank may accelerate the occurrence of this reaction, and poor quality of liquid alkali or prolonged exposure to air can also speed up the yellowing process. It is recommended to check the interior of the storage tank to ensure the quality and safety of the stored liquid caustic, and to avoid exposing it to air for extended periods of time. .
Anyone with a primary school education or above should know about chemical reactions.
A concentrated sodium hydroxide solution is a strong base that has the ability to absorb acidic gases; due to its high concentration, it also possesses a certain capacity to absorb water vapor from the air. However, sodium hydroxide absorbs carbon dioxide and moisture from the air, so it does not undergo any color change. If a color change occurs, it must be because there is something in the surrounding environment that can be absorbed by sodium hydroxide and form a yellow-colored substance. Additionally, the container in which this sodium hydroxide is stored may have its internal coating (if any) or the wall material dissolve or release colored substances as a result of the attack by the strong alkali. The poster should take some samples for analysis, and make a judgment by considering the storage conditions of sodium hydroxide as well as the characteristics of the containers. It’s better to have colleagues in your laboratory who have a solid foundation in chemistry and knowledge of analytical testing discuss and analyze it; such a question, lacking any contextual background or conditions, cannot be answered simply.
Okay, thank you! It is suspected that ferrous ions have been oxidized to ferric ions! In that case, the storage tank could be corroded during transportation and storage!