Potassium of Rhodanate 0,1 N.

Potassium of Rhodanate 0,1 N.

The colourless crystals of monoklinny system blurring in humid air. Square of 1,886 ^g/cm3. T. square of 173,2 °C. At 430 °C the preparation gets blue coloring, when cooling becomes colourless again. At 500 °C decays. The reactant is well soluble in water (68,5% at 20 °C) with strong cooling of solution (when mixing 150 g from 100 ml of water temperature falls from 10,8 °C to - 23,7 °C); let's well dissolve also in ethyl alcohol. At crystallization of solutions of potassium sulphocyanate at low temperature _{the KNCS·0,5H2O crystalline hydrate} steady in the range of - 29,5 ÷ 6,8 °C turns out.
Preparation Potassium sulphocyanate can be received at interaction of ammonium rhodanide with potassium hydroxide: _NH4NCS + KOH = KNCS + _Nh3b + _H2O In hot (70 °C) solution of 500 g _NH4NCS (h and. ) in 250 ml of water flow (under draft) when hashing solution of 368 g of KOH (p. ) in 400 ml of water. Mix is heated at 80 - 85 °C to full removal _{of NH3} (test of solution when heating with KOH should not allocate _NH3 found on smell). Upon termination of reaction solution is filtered via the double folded filter. The filtrate is boiled out before film formation of crystals and cooled. The dropped - out crystals suck away on Buchner filter and dry at 30 - 40 °C. Exit of 400 - 440 g (62 - 70% ) of the preparation corresponding to reactant of qualification of h and. From mother solution evaporation and crystallization it is possible to receive 100 - 140 more g of salt. If as raw materials the technical product _{of NH4NCS} containing considerable impurity of sulfates, then technique of preparation of KNCS a bit different apply. To 50 ml of water add _Ba(OH)2 before full sedimentation _{of SO42 -} to the solution of 175 g _NH4NCS heated to 80 °C. To solution allow to be defended and filter. The filtrate is heated to 80 °C and added in the small portions _{of K2CO3}(p. ) before alkalescent reaction to phenolphthalein. Then reactionary solution is boiled by 10 - 12 h before removal _{of NH3}, bring 2 g of active coal and boil out until density of solution does not become equal 1,45 (at 110 °C). Solution is filtered and cooled. The dropped - out crystals suck away on Buchner filter and dry at 30 - 40 °C. Exit of 100 g (47% ). Using mother solution, it is possible to raise preparation exit considerably.