Different hydrous compounds have specific dehydration temperatures, and most of them are accompanied by significant endothermic effects; The crystal water contained in soil particles can not directly participate in the physical action in soil, nor can it be directly absorbed by plants. When crystals crystallize out of solution, they combine with a certain number of water molecules. They are originally water linked with other compounds in the form of molecules, so they do not have the characteristics of water. Such crystals include hydrated iron oxide, cobalt chloride and copper sulfate crystals.
Extended data:
The water content of most compounds can be determined by its molecular formula. The unknown samples were determined by thermogravimetric analysis (TGA). During the heating process, the water in the sample is separated from the compound, and the free water connected with the compound by intermolecular force is evaporated first, and then the crystal water with stronger binding force is evaporated. According to the heating temperature and the mass of the substance, the mass of evaporated water can be obtained. Then, the amount of separated water is divided by the molar mass of water to obtain the number of water molecules bound to the salt.
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