206 Experiments for obtaining and preserving Potassium. 



ent and directed the experiment. The remainder in consequence of 

 his absence from the city, I was obliged to conduct without assist- 

 ance. 



Method of Preparing the Potassa. 



The crude jrotash of commerce and pure lime in proportions, by 

 weight of three of the former to one of the latter, are to be inti- 

 mately mixed and lixiviated by means of pure rain water in a cylin- 

 drical iron or wooden vessel.* The apparatus which we constantly 

 use in the Laboratory, is composed of a cylindrical copper vessel, 

 about eighteen inches high and eight inches, internal diameter, tinned 

 on the inside, and supplied with a small stop cock about half an inch 

 from the bottom, and tube dipping down into the receiver below, 

 which should have a narrow neck for the purpose of preventing, as 

 far as practicable, the access of air, which it would afford carbonic 

 acid to the alkali, and thus change it back to a carbonate. The best 

 receptacle for the alkaline solution, is a large narrow necked bot- 

 tle, the size of which must depend on the quantity to be lixiviated. 

 The solution is to be transferred to a clean iron kettle and rapidly 

 boiled to dryness ; when the heat is to be raised to low redness, and 

 the alkali kept in a state of fusion till the appearance of ebullition cea- 

 ses, and the whole remains perfectly quiescent. It is now ready to 

 pour into the retort, or it may be poured on a clean slab of marble, 

 and immediately broken up and transferred to stopped bottles for fu- 

 ture use. 



Apparatus, &fC.for the Experiment. 



The apparatus necessary for obtaining potassium, consists essential- 

 ly of a wind furnace with a good draught, a wrought iron retort capa- 

 ble of holding two or three quarts, and a large tube connected with 

 the retort by a screw, and of sufficient length to project through die 

 front of the furnace at least twelve inches. Charcoal is the only fuel 

 1 have been able to use with success. The retorts most economically 

 fitted up, especially for those who live in the vicinity of large cities, are 

 the common iron bottles in which quicksilver is imported. These 



* On account of its cheapness a wooden vessel is perhaps preferable. A small 

 cask about the size of a common butter firkin, with a small hole bored and stop cock 

 inserted, near the bottom, and dipping- down into the mouth of the bottle for receiving 

 the alkali, would Ibrm a very toleiable apparatus. 



