on the Nature of certain Bodies* 48 1 



furnished with stop cocks. These retorts were exhausted by 

 an excellent air pump, they were filled with hydrogen, ex- 

 hausted a second time, and then filled with ammonia from 

 an appropriate mercurial gas holder*. In this way the gas 

 was operated upon in a high degree of purity, which was 

 always ascertained ; and all the operations performed out of 

 the contact of mercury, water, or any substances that could 

 interfere with the results. 



I at first employed potassium procured by electricity ; but 

 I soon substituted for it the metal obtained by the action of 

 ignited iron upon potash, in the happy method discovered by 

 MM. Gay Lussac and Thenard, finding that it gave the 

 same results, and could be obtained of an uniform quality f, 

 and in infinitely larger quantities, and with much less labour 

 and expense. 



When ammonia is brought in contact with about twice its 

 weight of potassium at common temperatures, the metal 

 loses its lustre and becomes white, there is a slight diminu- 

 tion in the volume of the gas ; but no other effects are pro- 

 duced. The white crust examined proves to be potash, and 

 the ammonia is found to contain a small quantity of hydro- 

 gen, usually not more than equal in volume to the metal. 

 On heating the potassium in the gas, by means of a spirit 

 lamp applied to the bottom of the retort, the colour of the 

 crust is seen to change from white to a bright azure, and 

 this gradually passes through shades of bright blue and green 

 into dark olive. The crust and the metal then fuse together; 

 there is a considerable effervescence, and the cru3t passing 



* A representation of the instruments will be given in the next Number 

 of our Magazine. 



f When the potash used for procuring potassium in this operation was 

 very pure, and the iron turnings likewise very pure and clean, and the whole 

 apparatus free from ahy foreign matters, the metal produced differed very 

 little, in its properties, from that obtained by the Voltaic battery. Its lustre, 

 ductility, and inflammability were similar. Its point Of fusion and specific 

 gravity were, however, a little higher, it requiring nearly 130° of Fahren- 

 heit to render it perfectly fluid, and being to water as 7960 to 10000, at 60° 

 Fahrenheit. This I am inclined to attribute to its containing a minute pro- 

 portion of iron. 



Vol. 33. No. 134. June 1809- Hh off 



