44(5 POTASSIUM. 



when the sticks are dissolved in water. To obtain hydrate of 

 potash free from carbonate, the sticks are dissolved in alcohol, 

 in which the foreign impurities are insoluble, and the alcoholic 

 solution is evaporated to dryness. 



The pure and fused hydrate of potash is a solid white mass of 

 a structure somewhat crystalline, of sp.gr. 1.706, fusible at a 

 heat under redness. It is a protohydrate, and cannot be de- 

 prived of its combined water by the most intense heat. It de- 

 stroys animal textures. It rapidly deliquesces in damp air, from 

 the absorption of moisture, is soluble in half its weight of 

 water, and also in alcohol. Mixed in powder with a small 

 quantity of water, it forms a second crystalline combination, 

 which is a terhydrate ; and its solution in water affords, at a 

 very low temperature, crystals in the forms of four-sided tables 

 and octohedrons, which are a pentahydrate, KO, HO + 4 HO. 



The solution of potash, or potash ley, has a slight but pecu- 

 liar odour, characteristic of caustic alkalies, which they ac- 

 quire from their action upon organic matter, derived from the 

 atmosphere or other sources. The skin and other animal sub- 

 stances are dissolved by this liquid. It is highly caustic, and 

 its taste intensely acrid. It has those properties which are 

 termed alkaline in an eminent degree. It neutralises the most 

 powerful acids, restores the iblue colour of reddened litmus, 

 changes the blue infusion of cabbage into green, but in a short 

 time altogether destroys these vegetable colours. It acts upon 

 fixed oils, and converts them into soaps, which are soluble in 

 water. It absorbs carbonic acid with great avidity from the 

 air, on which account it should be preserved in well stopt 

 bottles. 



The presence of free potash or soda, in solutions of their car- 

 bonates, may be discovered by nitrate of silver, the oxide of 

 which is precipitated of a brown colour by the caustic alkali, 

 while the white carbonate of silver only is precipitated by the 

 pure carbonated alkali. Potash, whether free, or in combination 

 with an acid as a soluble salt, may be detected and distinguished 

 from soda and all other substances, by means of certain acids, 

 &c., which form sparingly soluble compounds with that alkali. 

 A strong solution of tartaric acid produces a precipitate of bi- 

 tartrate of potash, in a liquid containing 1 per cent of any 

 potash salt. The precipitate is crystalline, and does not ap- 

 pear immediately, but is thrown down on stirring the liquid 



