i 



NATURE AND EFFECTS OF POTASH. 119 



caustic, and dissolves in alcohol or water. Having a strong affinity 

 for water, it liquefies on exposure to the air. It is used in surgery, 

 by the name of lapis causticus ; it is also much used in chemistry and 

 in the arts. It is the basis of common soft soaps, though not thus 

 used in a pure state. It forms numerous salts with acids ; but free, it 

 gives a green color to the infusion of red cabbage, or the syrup of vio- 

 lets, reddens tumeric, and colors blue litmus reddened by an acid. It 

 has 1 atom of potash to 1 of water, 48 to 9 by weight, and 84 to 15 

 per cent, in quantity. 



The physiological effects are its immediate destruction of parts of 

 living plants ; on animals it is an energetic caustic poison, and most 

 frequently perforates the stomach. Injected into the jugular vein of 

 a do?, it coagulates the blood, and causes speedy death ; but, mixed 

 with blood out of the body, it does not coagulate it, but actually pre- 

 vents coagulation. On man it neutralizes any free acid, or the phos- 

 phate of lime of the bones, where it is applied, and combines with the 

 fibrin and albumen of the flesh, forming fibrate and albuminate of pot- 

 ash ; also with gelatine, and thus acts as in forming soap. It is in- 

 jurious to the stomach, by saturating the free acids, which are essen- 

 tial to digestion. If insufficient to exert action on the tissues, it is 

 absorbed, and alters the qualities of the secreted fluids, particularly of 

 the urine, so that it is a powerful diuretic ; if continued, it acts like 

 mercury, as a resolvent, and the ultimate effects are pernicious, pro- 

 ducing scurvy, &c. In water, it is applied for an issue, by washing 

 a linseed oil poultice with a hole in the middle. For the bite of poison- 

 ous animals, serpents or mad dogs, it is used with advantage; and also 

 as a wash for ulcers, for destroying warts, to modify the quality of 

 urine, &c. The alkalies, in fine, are used in numerous cases. The 

 antidotes are acids or oil, both forming salts with this or other alkalies, 

 and diminishing their causticity. 



The decomposition of potash was effected in 1807, by Sir H. Davy, 

 with a galvanic battery. A piece of solid hydrate placed between 2 

 platina plates was connected with the ends of a battery of 200 double 

 plates, 4 inches square, when it soon underwent fusion, oxygen sepa- 

 rating to the positive surface and metalic globules to the negative. 

 This metal (potassium) is the basis of potash. It may be obtained 

 by heating potash to a whiteness in a gun-barrel in cotact with iron 

 turnings, the air being excluded, the potassium is liberated and col- 

 lects in the cold end of the tube. It is immediately placed in naptha 

 to prevent combustion by exposure to the air. 300 grains have been 

 obtained from 24 oz. of crude tartar by a different process. Potassium 

 is the lightest solid known ; it is lighter than water, has a color like 

 silver, fuses at 150, and takes fire and burns rapidly on cold water by- 

 combining with its oxygen, and also in chlorine gas. It forms several 

 different compounds. Potash is a protoxide of potassium, and the 



