Cement foaming agent, also known as foaming concrete foaming agent, refers to an admixture that can reduce the surface tension of liquid and generate a large amount of uniform and stable foam for the production of foamed concrete. Foaming agent is a kind of substance that can make its aqueous...
The Property and Synthesis Method of Calcium Hydride
What is calcium hydride?
Calcium hydride is an inorganic substance with a chemical formula of CaH2 and a molecular weight of 42.10. Grayish-white crystal or lump, easily deliquescent, used as reducing agent, desiccant, chemical analysis reagent, etc. ; it is also a colorless orthorhombic crystal; industrial products are gray, orthorhombic or powder. Sensitive to moisture. It does not react with dry air, nitrogen, or chlorine at room temperature, but can react with the above gases at high temperatures to generate calcium oxide, calcium nitride, and calcium chloride, respectively. When it meets with water, it decomposes and releases hydrogen at the same time. It can also react with ethanol to produce hydrogen and calcium ethoxide. The reduction effect on metal oxides is stronger than sodium hydride or lithium hydride.
Synthesis method of calcium hydride
1. Put refined calcium with a purity of about 99.5% into the iron plate and place it in the center of the quartz reaction tube. Use rubber plugs at both ends of the quartz reaction tube to install the inlet pipe and the outlet pipe respectively, and pass through the inlet pipe to purify hydrogen, and the outlet pipe passes through The mineral oil bubbler is connected to the fume hood. The reaction tube is heated with an electric furnace. After the purified hydrogen, a large amount of hydrogen was introduced to replace the air in the reaction system at the beginning, and then heated with an electric furnace. The reaction started at about 200degC and was further heated to 250-300degC, and hydrogen was introduced at a flow rate of 0.6 ml/min. The reaction can be completed in about 2 hours. The calcium hydride produced is a porous off-white crystalline powder. The purity of the calcium hydride is about 99%.
2. Alkaline earth metal and pure electrolytic hydrogen hydrogenation can produce alkaline earth metal hydride. The hydrogenation device for preparing CaH2 is the same as the device for preparing alkali metal hydride. In order to purify metallic calcium, it is necessary to perform vacuum distillation repeatedly, and then scrape off the oxide layer on the calcium surface in an operation box filled with argon gas, and cut it into small pieces as much as possible. Under the condition of isolating air, the surface is smooth and clean. Small metal calcium is packed in a boat made of electrolytic iron, and the boat is packed into a quartz tube. The heated part of the quartz tube is covered with a thin-walled tube made of electrolytic iron to prevent the quartz tube from being corroded by calcium vapor. Pure hydrogen is introduced, the calcium is heated to 400-500degC, the hydrogenation reaction starts, and then the temperature is raised to 1000degC, after the reaction is completed, it is cooled to room temperature to obtain calcium hydride.
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