244 Apparatus for the Evolution of Cyanhydric or Prussic Acid. 



of water to cover the mouth of the flask, and that this is occupied 

 with the same liquid in part until it is displaced by the hydrogen. 



The preliminary arrangements being made, a mirror must be pla- 

 ced in a situation to receive the solar rays directly, and reflect them 

 upon the flask. The result is an explosion, from the effects of which 

 the spectators are protected by the wire gauze. 



It must be obvious that this experiment can only succeed, when 

 the sun is unobscured. 



It should be understood that the condensation arises altogether 

 from the absorption of the gas by the water. 



Art. X. — Apparatus for the Evolution of Cyanhydric or Prussic 

 Acid; by R. Hare, M. D. Prof, of Chem in the Univ. of Penn. 



Let a tube, three-fourths of an inch in bore, and about two feet in 

 length, be bent at right angles, at about six inches distance from one 

 end. Let the shorter portion be drawn out into a tapering form, 

 with a bore not exceeding a tenth of an inch in diameter. Upon the 

 larger orifice let a brass band be cemented, in which a female screw 

 has been cut, so that a stuffing box furnished with a corresponding 

 male screw, may be easily fastened air-tight to the band, or removed 

 when desirable. Through the stuffing box an iron rod passes, flat- 

 tened like an oar at the end, which is within the tube when the stuf- 

 fing box is in its place. There must likewise be a lateral aperture 

 in the band communicating with the cavity of the tube, and furnish- 

 ed with a gallows screw. The main body of the tube is to be situ- 

 ated nearly level, yet a little inclined towards the curvature, so that 

 the tapering extremity may descend nearly perpendicularly into a 



