248 Apparatus and Processes. 



for the insertion into the cylinder of four valve cocks, each furnished 

 with a gallows screw. The cylinder is surmounted by a stuffing box, 

 through which a copper sliding rod, G, passes air tight- The brass 

 plate is turned and ground to fit a bell glass of about five inches in 

 diameter, and eight inches in height, which is pressed up when neces- 

 sary between the plate and the block by the screw D, supporting the 

 block. Within the space comprised by the bell glass, and on one 

 side of the centre of the plate, two stout brass wires are inserted, 

 one of them insulated by a collet of leathers, so as to admit of the 

 ignition, by a galvanic discharge, of a small arch of platina wire, which 

 terminates them. The sliding rod above-mentioned as occupying 

 the stuffing box, terminates below the plate in an elbow which sup- 

 ports a cap at right angles to the rod, at the same distance from the 

 rod as the platina wire, and on the opposite side of it, there is a brass 

 cover, H, for the cap, supported from the plate. The arrangement 

 is such that by a suitable movement in the sliding rod, made by 

 grasping it by the handle G, in which it terminates externally, the 

 cup may be made either to receive into its cavity the platina wire, or 

 to adjust itself to its cover H. 



The bell being removed, about sixty grains of potassium in pieces 

 not containing more than fifteen grains each, are to be introduced 

 into the cup, which is then to be adjusted to the cover, and the bell 

 secured. In the next place, by means of the flexible lead tubes, 



■ 



P, P, P, P, and the gallows screws attached to the valve cocks, es- 

 tablish a communication severally with an air pump, a self-regula- 

 ting reservoir of hydrogen, a barometer gage, and a jar over the mer- 

 curial cistern containing fluo-silicic acid gas. First by means of the 

 air pump exhaust the bell, and in order to wash out all remains of 

 atmospheric air, admit hydrogen from the reservoir. Again exhaust, 

 and again admit hydrogen. Lastly exhaust the bell of hydrogen 

 and admit the fluo-silicic acid gas. By means of the gage, the ex- 

 haustion is indicated and measured, and by the same means it will be 

 seen when the pressure of the gas within the bell, approaches that of 

 the atmosphere. When this takes place, the cocks being all closed, 

 by means of a calorimotor, the platina wire is to be ignited, and the 

 potassium brought into contact with it. 



A peculiar deep red combustion ensues, evolving copiously choco- 

 late colored fumes, which condensing into flocks of the same hue, 

 subside throughout the receiver, (excepting the color,) like snow in 

 miniature. On removing the bell after the potassium is consumed, 



