Abstract
Zinc cyanide can be prepared by double decomposition reaction of sodium cyanide or potassium cyanide with zinc chloride. Before the preparation of zinc cyanide, it is necessary to remove the free alkali in the raw material sodium cyanide or potassium cyanide. Magnesium chloride is used to remove the free alkali in sodium cyanide or potassium cyanide. The concentration of cyanide ion in potassium cyanide solution under different conditions is measured. The results show that magnesium chloride can not only remove the original free alkali in potassium cyanide, but also promote the hydrolysis of potassium cyanide to produce new free alkali and react with it to form new precipitate. By analyzing the components of the precipitate, it is determined that the main components in the precipitation are Mg(OH)2 and MgCO3. The final conclusion: after the free alkali in cyanide is removed by magnesium chloride, the solution must be quickly put into the double decomposition reaction to reduce the further loss of cyanide ion; In the preparation of zinc cyanide, the adding order needs to be noted: the cyanide aqueous solution must be added into the zinc chloride solution to ensure the excess of zinc chloride.
Highlights
Zinc cyanide is a raw material needed in many chemical production
It can be concluded that magnesium chloride can remove the original free alkali in cyanide, and promote the hydrolysis of cyanide to produce new free alkali, and react with it to produce new precipitation, which explains the phenomenon of flocculent precipitation after the clarified filtrate is standing
When magnesium chloride is used to remove the free alkali in cyanide, the precipitate must be filtered as soon as possible to prevent the color deepening of the system, and the cyanide solution should be quickly put into the reaction to avoid further hydrolysis
Summary
Zinc cyanide is a raw material needed in many chemical production. Zinc cyanide, potassium cyanide or sodium cyanide solid can be used to replace hydrocyanic acid for chemical reaction in some chemical production [1,2,3], which can reduce the harm of hydrogen cyanide poisonous gas to human body and environmental pollution to a certain extent. The preparation process is shown in the following figure: Cyanide such as potassium cyanide and sodium cyanide are often used as raw materials for chemical experiments or industrial synthesis. They are soluble in water and ethanol, and are highly toxic dangerous chemicals. A small amount of alkali is often added to some industrial cyanide to reduce its hydrolysis degree These free alkali sometimes bring some troubles to its subsequent synthesis and chemical production. -Dissolve the solid potassium cyanide in water, and take a small amount of potassium cyanide aqueous solution as sample 1;
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