Potassium

Potassamide, discovered in 1811, is obtained as an olive green or brown mass by gently heating the metal in ammonia gas, or as a white, waxy, crystalline mass when the metal is heated in a silver boat. It decomposes in moist air, or with water, giving caustic potash and ammonia, in the latter case with con siderable evolution of heat. For the nitrite, see NITROGEN ; for the nitrate, see SALTPETRE ; and for the cyanide, see PRUSSIC ACID ; for other salts see the articles wherein the corresponding acid receives treatment.

Analysis, etc.

All volatile potassium compounds impart a violet coloration to the Bunsen flame, which is masked, however, if sodium be present. The emission spectrum shows two lines, Ka, a double line towards the infra-red, and KO in the violet. The chief insoluble salts are the perchlorate, hydrogen tartrate and chloroplatinate (platinichloride) ; and the difference in solubility between the potassium and ammonium salts of "eikonogen" en ables a separation to be effected, most other salts of these two radicals being similarly soluble. The atomic weight was deter mined by Stas, Richards and Stahler.

Pharmacology.

Numerous salts and preparations of potas sium are used in medicine; viz., Potassii Carbonis (salt of tartar), dose 5 to 20 gr., from which are made (a) Potassii Bicarbonas, dose 5 to 3o gr.; (b) Potassa Caustica, a powerful caustic not used internally. From caustic potash are made: (I) Potassii Permanganas, dose 1 to 3 gr., used in preparing Liquor Potassii Permanganatis, a I% solution, dose 2 to 4 dr., (2) Potassii lodidum, dose 5 to 20 gr., from which are made the Linarnentum Potassii lodidi cum Sapone, strength I in io, and the Unguentum Potassii lodidi, strength I in 1o. (3) Potassii Bromidum, dose 5 to 3o gr. (4) Liquor Potassae, strength 27 gr. of caustic potash to the oz. Potassii Citras, dose Io to 4o gr. Potassii Acetas, dose io to 6o gr. Potassii Chloras, dose 5 to 15 gr., from which is made a lozenge, Troclziscus Potassii Chloratis, each con taining 3 gr. Potassii Tartras Acidus (cream of tartar), dose 20 to 6o gr., which has a subpreparation Potassii Tartras, dose 3o to 6o gr. Potassii Nitras (saltpetre), dose 5 to 20 gr. Potassii Sulphas, dose io to 4o gr. Potassii Bichromas, dose to gr.

Toxicology.—Poisoning by caustic potash may take place or poisoning by pearl ash containing caustic potash. A caustic taste in the mouth is quickly followed by burning abdominal pain, vomiting and diarrhoea, with a feeble pulse and a cold clammy skin. The treatment is washing out the stomach or giving emetics

followed by vinegar or lemon juice and later oil and white of egg.

Therapeutics.—Externally : Caustic potash is a most powerful irritant and caustic ; it is used with lime in making Vienna paste, which is occasionally used to destroy morbid growths. Liquor potassae is also used in certain skin diseases. The permanganate of potash is an irritant if used pure. Its principal action is as an antiseptic and disinfectant. If wet it oxidizes the products of decomposition. It is used in the dressing of foul ulcers. The 1% solution is an antidote for snake-bite.

Internally : Dilute solutions of potash, like other alkalis, are used to neutralize the poisonous effects of strong acids. In the stomach potassium salts neutralize the gastric acid, and hence small doses are useful in hyperchlorhydria. Potassium salts are strongly diuretic, acting directly on the renal epithelium. They are quickly excreted in the urine, rendering it alkaline and thus more able to hold uric acid in solution. They also hinder the formation of uric acid calculi. The acetate and the citrate are valuable mild diuretics in Bright's disease and in feverish condi tions, and by increasing the amount of urine diminish the patho logical fluids in pleuritic effusion, ascites, etc. In tubal nephritis they aid the excretion of fatty casts. The tartrate and acid tar trate are also diuretic in their action and, as well as the sulphate, are valuable hydragogue saline purgatives. Potassium nitrate is chiefly used to make nitre paper, which on burning emits fumes useful in the treatment of the asthmatic paroxysm. Lozenges of potassium chlorate are used in stomatitis, tonsilitis and pharyngi tis; it can also be used in a gargle, io gr. tor fl.oz. of water. Its therapeutic action is said to be due to nascent oxygen given off, so it is local in its action. In large doses it is a dangerous poison, converting the oxyhaemoglobin of the blood into methae moglobin. Internally the permanganate is a valuable antidote in opium poisoning. The action of potassium bromide and potas sium iodide has been treated under bromine and iodine (q.v.). All potassium salts if taken in large doses are cardiac depressants; they also depress the nervous system, especially the brain and spinal cord. Like all alkalis if given in quantities they increase metabolism.