POTASSIUM. 119 



Potassium sulphate exists in small quantities in plants, and in 

 nearly all animal tissues and fluids, more abundantly in urine. 



Potassium hydrogen sulphate, bisulphate or add sulphate of potas 

 sium, may be obtained by the action of one molecule of potassium 

 chloride upon one molecule of sulphuric acid : 



KCl + H 2 S0 4 = HCl + KHSO 4 . 



Potassium sulphite, Potassii sulphis, K 2 S0 3 2H 2 = 194. Ob- 

 tained by the decomposition of potassium carbonate by sulphur- 

 ous acid : 



K 2 C0 3 + H 2 S0 3 = H 2 + C0 2 + K 2 S0 3 . 



Potassa sulphurata, U. S. P. (Sulphurated potassa, Sulphuret of 

 potash). A mixture of potassium sulphide and hyposulphite. It 

 is made by heating a mixture of sulphur and potassium carbon- 

 ate in a covered crucible, and pouring the fused mass on a 

 marble slab : 



3K 2 CO 3 + 8S = K 2 S 2 3 + 2K 2 S 3 + 3CO 2 . 



The freshly prepared substance has a liver-brown color, turn- 

 ing gradually to. greenish-yellow; it is very apt to absorb oxygen, 

 both the sulphide and hyposulphite becoming oxidized, and 

 finally converted into sulphates. 



Potassium hypophosphite, Potassii hypophosphis, KH 2 P0 2 = 104, 



may be obtained by decomposing a solution of calcium hypo- 

 phosphite by potassium carbonate : 



Ca2PH 2 O 2 + K 2 CO 3 = 2NaPH 2 O 2 + CaCO 3 . 



Potassium iodide, Potassii iodidum, KI = 165.6 (Iodide of potas- 

 sium], is made by the addition of iodine to a solution of potas- 

 sium hydrate until the dark brown color no longer disappears : 



6KHO + 61 = 5KI + KIO 3 + 3H 2 O. 



'Iodide and iodate of potassium are formed, and may be sep- 

 arated by crystallization. A better method, however, is to boil 

 the liquid containing both salts to dryness, and to heat the mass 

 after having been mixed with some charcoal, in a crucible, when 

 the iodate is converted into iodide : 



KIO 3 + 3C = KI + 3CO. 



