176 POTASSIUM HYDRATE 



fats, it forms soaps ; mixed with acids, it forms neutral, 

 soluble, crystallisable salts. It softens and dissolves soft 

 animal and vegetable tissues. Although little used in 

 medicine, it is of much importance in chemistry and phar- 

 macy. When boiled until a drop removed on a stirrer 

 becomes hard on cooling, and poured into pencil-like moulds, 

 there are formed the grey or white deliquescent, hard, 

 crystalline sticks of caustic potash. This agent may be 

 taken as the representative of the caustic alkalies other 

 members of the group being sodium and lithium hydrates 

 and in a less degree the carbonates and bicarbonates of 

 these metals. All these act by virtue of their OH (hydroxyl) 

 ion produced on dissociation in solution, and not by reason 

 of the metal ion. Thus KOH = K OH and the degree of 

 dissociation determines the severity of the action. With 

 the bicarbonate KHCO 3 = KOH + C0 2 and the KOH again 

 becomes K OH. The carbonates and bicarbonates, how- 

 ever, dissociate less readily than the hydroxides and hence 

 are milder and less caustic in action. (See Salt Action.) 



ACTIONS AND USES. Full doses of potassium hydrate are 

 actively dehydrating, irritant, and corrosive. Medicinal 

 doses are antacid and diuretic. Externally, potassium 

 hydrate, whether in substance or in concentrated solution, 

 is a penetrating caustic. The corrosive and caustic action 

 is due to the power caustic potash has of dissolving albumin, 

 and to its great affinity for water. 



Toxic EFFECTS. Large doses, when swallowed, soften, 

 corrode, and inflame the oesophagus and stomach, some- 

 times so severely as to cause perforation ; while great 

 depression, and often collapse, accompanies the local lesions. { 

 Hertwig records that two drachms, dissolved in six ounces \ 

 of water, killed a horse, with symptoms of colic, in thirty- 

 two hours. Orfila gave a dog thirty- two grains, which 

 caused violent vomiting, restlessness, and death in three i 

 days. Post-mortem discovered the mucous coat of the 

 oesophagus and stomach red and black from extravasation 

 of blood, with a perforation measuring three-quarters of an 

 inch near the pylorus, surrounded by a hard thickened 

 margin (Christison). The blood is dark-coloured and gener- 

 ally fluid, owing to the solvent action of the alkali. Smaller 



