Why didn't KSCN react when cobalt dichloride solution was added? Adding KSCN solid will produce a blue-purple solution.

That's right. When cobalt dichloride solution is added to KSCN solution, if the concentration of the two is not large enough, the amount of cobalt thiocyanate complex ions generated by the reaction is very small, which is difficult to observe. If the solution is concentrated, it is ok.

The best method is to test cobalt ions with very concentrated KSCN solution, and then add ether or amyl alcohol after mixing. Because the solubility and stability of cobalt thiocyanate complex ion in organic phase are much greater than that of water, the blue-purple color of cobalt thiocyanate complex ion can be clearly seen in ether or amyl alcohol solution.

Blood red flocculent complex is produced after addition; It is also used to prepare thiocyanate (thiocyanate) solution, and to determine iron ions, copper, silver, urine test, tungsten chromogenic agent and titanium indicator by volumetric method; Can be used as refrigerant and photographic thickener.

Extended data:

KSCN is unstable in chemical properties at room temperature, deliquescent easily in air, and absorbs a lot of heat to cool down. The chemical properties are stable at -29.5 ~ 6.8℃, and semi-crystal can be obtained at low temperature. It turns blue when heated to about 430℃ and colorless when cooled.

Using ammonium thiocyanate conversion method, carbon disulfide and ammonia water were synthesized under pressure to generate ammonium thiocyanate, which was a by-product ammonium bisulfate. Then ammonium bisulfate was decomposed into hydrogen sulfide by desulfurization and evaporation, and then potassium thiocyanate was slowly added at the liquid temperature of 105℃. A large amount of carbon dioxide and ammonia will be produced during the reaction.

Ammonia can be recovered, the reaction solution is filtered, evaporated under reduced pressure, cooled and crystallized, and centrifugally separated to obtain industrial potassium thiocyanate.

Cobalt chloride crystal is stable at room temperature, loses crystallization water and turns blue when heated, and turns red in humid air. When heated or added with concentrated hydrochloric acid, chloride or organic solvent, its aqueous solution will turn blue.

Crystallization at 30 ~ 45℃, weathering and turbidity, heating at 45 ~ 50℃ for 4 hours to be tetrahydrate, and heating to 1 10℃ to be anhydrous. Its toxicity is extremely weak.

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