Potassium hydroxide solutions freezing point

Caustic Potash Solution — (I) Chemical Designations — Synonyms Potassium Hydroxide Solution Lye Otemical Formula KOH—H O (ii) Observable Characteristics — Physical State (as normally shipped) Liquid Cobr Colorless Odor None (iii) Physical and Chemical Properties — Physical State at 15 X and 1 atm. Liquid Molecular Weight Not pertinent Boiling Point at 1 atm. >266, > 130, >403 Freezing Point Not pertinent Critical Temperature Not pertinent Critical Pressure Not pertinent Specific Gravity 1.45 - 1.50 at 20° C (liquid) Vapor (Gas) Density Not pertinent Ratio of Specific Heats of Vapor (Gas) Not pertinent Latent Heat... 

Potassium hydroxide is the principal electrolyte of choice for the above batteries because of its compatibiUty with the various electrodes, good conductivity, and low freezing point temperature. Potassium hydroxide is a white crystalline substance having a mol wt = 56.10 density = 2.044 g/mL, and mp = 360° C (see Potassium compounds). It is hygroscopic and very soluble in water. The most conductive aqueous solution at 25 °C is at 27% KOH, but the conductivity characteristics are relatively flat over a broad range of concentrations. 

Potassium Metarsenite, KAs02, is obtained in an impure form when potassium carbonate and the above diarsenite are boiled together in aqueous solution for several hours.1 A syrupy mass is obtained. That the metarsenite should exist has been shown 2 by results obtained in measuring the effect of the progressive neutralisation of arsenious acid by potassium hydroxide on the freezing point of aqueous solutions. 

This theory of electrolytic dissociation, or the ionic theory, attracted little attention until 1887 when vanT IIoff s classical paper on the theory of solutions was published. The latter author had shown that the ideal gas law equation, with osmotic pressure in place of gas pressure, was applicable to dilute solutions of non-electrolytes, but that electrolytic solutions showed considerable deviations. For example, the osmotic effect, as measured by depression of the freezing point or in other ways, of hydrochloric acid, alkali chlorides and hydroxides was nearly twice as great as the value to be expected from the gas law equation in some cases, e.g., barium hydroxide, and potassium sulfate and oxalate, the discrepancy was even greater. No explanation of these facts was offered by vanT Iloff, but he introduced an empirical factor i into the gas law equation for electrolytic solutions, thus... 

Electrolyte. The electrolyte used for reserve zinc/silver oxide cells is an aqueous solution of potassium hydroxide. High and medium discharge rate cells use a 31% by weight electrolyte solution because this composition has the lowest freezing point and is close to the minimum resistance which occurs at 28 wt. %. Low-rate cells may use a 40-45% solution since lower rates of hydrolysis of cellulosic separators occur with the higher KOH concentrations. 

The electrolyte used in secondary silver cells is generally an aqueous solution (35 to 45% concentration) of potassium hydroxide (KOH). Lower concentrations of electrolyte provide lower resistivity and thus a higher voltage output under load as weU as a lower freezing point. Concentrations below 45% KOH, however, are more corrosive to the ceUulosic separators typically used in silver-based batteries and are not used for extended wet-hfe applications. Table 33.3 depicts the critical parameters of various KOH solutions. Various additives such as zinc oxide, lithium hydroxide, potassium fluoride, potassium borate, tin, and lead have been used to reduce the solubility of the zinc electrode. " ... 

---