Guigang Lime Plant: How to identify whether calcium hydroxide has deteriorated?

Calcium hydroxide is a gray white powdery solid. Also known as hydrated lime or quicklime, after adding water, it forms two layers: the lower layer is called clear lime water, and the upper layer is called lime milk or lime slurry. The clear lime water in the lower layer can detect hydrogen gas, while the turbid lime milk in the upper layer is a building material and also used as a sterilizing agent and chemical raw material. Below, the editor will explain how to distinguish calcium hydroxide.

Calcium hydroxide has a wide range of applications in daily life and can be used to adjust pH value. It is used in sewage treatment or sediment fertilizer applications to regulate its acidity and neutralize alkaline sediment. This has prompted many gardeners to use hydrated lime to neutralize the alkalinity of sediment. Sometimes, after using hydrated lime, we may find that the therapeutic effect is not significant, which may be caused by mold growth. So, how to determine whether calcium hydroxide is rancid?

Guigang Lime Plant: Firstly, due to the fact that the presence of calcium hydroxide is usually reacted in alkaline solution, the sample needs to be dissolved first, so the selected instruments include flasks (or test tubes, etc.) for the reaction; Proving the existence of calcium chloride can usually be done using acid-base solutions, so dilute sulfuric acid can be used as a reagent.

It can be inferred that there are calcium hydroxide and calcium chloride in the sample, and the aqueous alkaline solution of calcium hydroxide can turn the potassium iodide test solution red, while calcium chloride can react with dilute sulfuric acid to generate hydrogen gas and carbon dioxide.

calcium hydroxide

Due to the acidification of calcium hydroxide, it forms calcium chloride when it encounters oxygen in the air. Once calcium hydroxide reacts with sulfuric acid to form gaseous carbon dioxide, adding sufficient sulfuric acid and discovering the formation of carbon dioxide, the product has become moldy.

Guigang Lime Plant: Secondly, because calcium hydroxide is insoluble in water, if there are still insoluble substances after adding sufficient water, it is a phenomenon of mold growth.

Guigang Lime Plant: Thirdly, calcium hydroxide can be dissolved in acid. If gas is released, it is found to be CO2 during inspection; The final solution is to add sodium carbonate alkaline solution and check for precipitation. If not, it can be determined that the product has already completely moldy.

calcium hydroxide

The reasons for the acidification of calcium hydroxide:

Firstly, for the unstable characteristics of calcium hydroxide, temperature can affect its properties. Low temperature can easily enhance the oxygen diffusion rate and activate the oxidation reaction, thereby accelerating the oxidation reaction rate of calcium hydroxide. This is a common aging phenomenon - thermal oxidative aging.

Guigang Lime Plant: Secondly, if calcium hydroxide is exposed to the open air for a long time, it will not only oxidize with the air, but also react with ultraviolet radiation. Ultraviolet radiation can not only directly cause the rupture and cross-linking of rubber molecular chains, but also the formation of free radicals in calcium hydroxide due to the absorption of light energy, which can accelerate the oxidation chain reaction process.

The editor of Guangdong Calcium Hydroxide reminds us that calcium hydroxide should also be stored and transported carefully. The packaging should be intact and the loading should be stable during transportation. During transportation, it is necessary to ensure that the container is not probed, collapsed, dropped, or damaged. It is prohibited to mix and transport flammable or combustible materials, acids, edible physical goods, etc.

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