Can someone explain the molecular mechanism of how CaSO4.2H2o when heated to 200-300°C becomes anhydrite and when soaked in water attains only 1/2H2O molecule and become Hemihydrate. And the factors and conditions that influence in formation of alpha and beta hemihydrate and why it happens?
I am doing a Project on CaSO4 and the CaSO4 hemihydrate sample that I had processed has different setting time(solidifying time) on different days. Some days it sets by 5mins, some days by 20-25mins. Can someone guide me what might be the problem and why is it happening?
Hey there Jose James! Well, diving into the world of CaSO4 and its various forms is quite fascinating, isn't it? Let's break down the process and mechanisms involved in the formation of CaSO4 alpha and beta hemihydrate from CaSO4 dihydrate, as well as the setting time variations you're experiencing.
When CaSO4.2H2O, also known as gypsum or calcium sulfate dihydrate, is heated between 200-300°C, it loses water molecules to form anhydrite (CaSO4). The molecular mechanism involves the dehydration of gypsum, resulting in the removal of water molecules and the formation of anhydrite.
Now, when this anhydrite is soaked in water, it can rehydrate to form hemihydrate (CaSO4.0.5H2O). The factors influencing the formation of alpha and beta hemihydrate involve temperature, pressure, and the presence of impurities. These factors influence the crystal structure and hydration characteristics of the resulting hemihydrate.
As for the variations in setting time for your CaSO4 hemihydrate sample, this could be attributed to several factors. The quality and purity of your initial gypsum sample, ambient temperature and humidity during processing, and even variations in the mixing process can impact the setting time. It's essential to maintain consistent conditions for reproducibility.
Now, if you're experiencing significant fluctuations, consider checking the quality of your gypsum source, the accuracy of your processing equipment, and the storage conditions of your CaSO4 hemihydrate samples. Even subtle changes in these factors could contribute to the observed variations in setting time.
Feel free to delve deeper into these aspects, and let me know if you Jose James need more specific insights.
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