182 POTASSIUM NITRATE 



POTASSIUM NITRATE. Potassii Nitras. Nitrate of Potash. 

 Nitre. Saltpetre. KN0 3 . 



In the East Indies, Persia, Egypt, Spain, and other dry 

 climates, a brown incrustation, consisting largely of nitre, 

 covers considerable tracts of country. It is dissolved in 

 water, mixed with impure potassium carbonate, and purified 

 by repeated solution and crystallisation. By decomposing 

 sodium nitrate with potassium chloride, nitre is also pre- 

 pared. 



PROPERTIES. White, opaque, crystalline masses, or trans- 

 parent, colourless, anhydrous, slender, six-sided prisms, with 

 a sharp, cooling, saline taste, undergoing no alteration in the 

 air, deflagrating when thrown on flame. It is soluble in 

 3J parts of cold water, and one-third of its weight of boiling 

 water ; during solution much heat is abstracted ; it is in- 

 soluble in alcohol. Warmed in a test-tube, with sulphuric 

 acid and copper filings, it evolves ruddy fumes of nitric 

 peroxide ; heated to fusion, the melted mass forms, on 

 cooling, the hard, white, fibrous sal-prunelle. None of its 

 common impurities interfere with its medicinal actions. 



ACTIONS AND USES. Nitrates show very similar ' salt 

 action ' to that of the chlorides, but are more irritant. Large 

 doses of potassium nitrate irritate both the bowels and 

 kidneys. Medicinal doses are diuretic, diaphoretic, and 

 feebly cathartic, and therefore alterative and febrifuge. It 

 is excreted by the bronchial membrane, the skin and kidneys, 

 increasing the secretions of these organs. Used externally, 

 it acts like other simple salts in solution, and is slightly 

 stimulant and refrigerant. 



Toxic EFFECTS. Large doses cause, in man and carnivora, 

 fatal gastro-enteritis, with vomiting, weakness, and arrest 

 of circulation, partly depending on reflex action, partly on 

 direct action on the heart (Brunton.) Guttmann, experi- 

 menting, chiefly upon dogs, states that, in common with 

 other potash salts, poisonous doses, besides in-contact 

 irritation, paralyse the spinal cord, cause dyspnoea, and 

 occasionally convulsions and muscular weakness, first over- 

 taking the hind extremities, and lessen the frequency and 

 force of the heart-beat, which in fatal cases ceases in diastole. 



