819 



maintained by Messrs. Berthollet on the non-existence of oxygen in 

 ammonia, and on account of the inference deduced by Messrs. Gay- 

 Lussac and Thenard, from the action of potassium on ammonia, who 

 conclude that potassium is a compound of potash and hydrogen. 

 Mr. Davy consequently details a variety of processes in which he 

 examined all the circumstances and results of their mutual action. 



The potassium employed was procured by passing dry potash 

 through red-hot iron turnings in a gun-barrel, which appears to differ 

 from that obtained by electricity solely in containing a very small 

 portion of iron. 



A green glass retort, after the introduction of a piece of potassium, 

 is first exhausted, then filled with ammoniacal gas, and after two 

 subsequent exhaustions, finally filled again with the gas in an ex- 

 tremely pure state. The potassium thus exposed to ammonia at 

 common temperatures, loses its lustre and becomes white by a thin 

 crust of potash on its surface ; while the gas suffers a slight diminu- 

 tion, and then contains about -sVth of its bulk of hydrogen. 



When the potassium is heated by a spirit-lamp, the colour changes 

 from white to a bright azure, thence to bright blue, green, and olive, 

 which is the last state to which the whole of the potassium may be 

 brought by continuation of the heat. When sufficient ammonia is 

 present to insure the complete saturation of eight grains of potas- 

 sium, twelve cubic inches of ammoniacal gas disappear, and nearly 

 eight cubic inches of hydrogen are evolved. The French chemist 

 having stated this quantity to be exactly equal to that given out by 

 the action of an equal quantity of potassium on water, Mr. Davy has 

 made the comparison with great care, and finds the quantity of 

 hydrogen given out by its action upon water to be just 8^ cubic 

 inches. 



The olive-coloured compound formed is combustible, heavier than 

 water, and a conductor of electricity. It fuses at a low temperature, 

 and then begins to emit ammonia, till its quantity amounts to 4f- 

 inches out of 12 cubic inches that had disappeared. The residuum 

 is then no longer fluid, and begins to give off hydrogen and nitrogen, 

 till the former amounts to 4 inches and the latter to 1-iV, in propor- 

 tion exactly suited to the formation of ammonia. When this residuum 

 no longer yields any gas, even at a red heat, a quantity of ammonia 

 may still be formed from it by the addition of water, and amounting 

 to about four cubical inches, and along with these about -j^th of an 

 inch of hydrogen. The formation of ammonia in this case having 

 proved that a quantity of nitrogen was here combined with the po- 

 tassium, other experiments were instituted for the purpose of obtain- 

 ing it separate. By combustion in oxygen gas, a part of the nitrogen, 

 but not the whole, was obtained ; but by distillation with red oxide 

 of mercury, the product of nitrogen was greater. For the formation 

 of ammonia from this nitrogen, as much hydrogen is wanted as was 

 originally given out by the ammonia, in the first part of the action of 

 potassium upon it ; but unless oxygen, as well as hydrogen, be sup- 



