146 On the Formation of Ammonia> $c. [1S25. 



ash, a portion of that alkali was prepared from potassium ; and 

 as the experiment made with it includes all the precautions 

 taken to exclude nitrogen, I will describe it rather minutely, 

 as illustrative of the way in which the other numerous experi- 

 ments were made. A piece of new glass tube, about half an 

 inch in diameter, was first wiped clean, and then heated red- 

 hot, a current of air passing at the same time through it ; about 

 six inches in length was drawn off at the blowpipe lamp, arid 

 sealed at one extremity. Some distilled water was put into a 

 new glass retort, and heated by a lamp ; when about one-half 

 had distilled over, the beak of the retort was introduced into 

 the tube before-mentioned, and a small portion of water (about 

 fifty grains) condensed into it. A solid compact piece of potas- 

 sium was then chosen, and having been wiped with a linen 

 cloth, was laid on a clean glass plate, the exterior to a con- 

 siderable depth removed by a sharp lancet, and portions taken 

 from the interior by metallic forceps, and dropped successively 

 into the tube containing the water before-mentioned. Of course 

 the water was decomposed, and the tube filled with hydrogen ; 

 and when a sufficient quantity of solution of potash had been 

 thus formed, the tube was heated in a lamp, and drawn out to 

 a capillary opening, about two inches from the closed extremity 

 (fig. 2, plate I). The tube now formed almost a close vessel ; and 

 being heated, as the water became vapour, it passed off at the 

 minute aperture, and ultimately a portion of pure fused hydrate 

 of potassa remained in the bottom of the tube. The aperture 

 of the tube was now closed, and the whole set aside to cool. 



A piece of new glass tube was selected about 0*3 of an inch 

 in diameter; it was heated to dull redness, and air passed 

 through it : about 10 inches of it was then cut off, and being 

 softened near to one end by heat, it was drawn out at that part 

 until of small diameter (a, fig. 3, plate I) : that part was then 

 fixed into a cap, by which it could afterwards be attached to a 

 receiver containing hydrogen. The tube containing the potas- 

 sium potash being now broken in an agate mortar, a piece or 

 two of the potash were introduced by metallic forceps into the 

 tube at the open end, so as to pass on to the contracted part ; 

 a roll of zinc-foil, about one grain in weight, cleaned with all 

 the precautions already described, was afterwards introduced, 

 and then more of the potash. The tube was then bent near 



