[ 53 ] 



XIII. On the Applicaiioyi of Potassittvi hi Endiometni Bu 



John Murray, F.L.S. M.W.S. c^r. 

 'X'HERE are several methods of examining the relative pro- 

 portionals of atmospheric air, and ascertaining its compara- 

 tive purity; as for instance. By a solution of green sulphate of 

 iron impregnated with nitrous gas, or more immediately by 

 passing up into a limited volume of the atmospheric air a gra- 

 duated quantity of the gas itself; — By burning phosphorus in a 

 given volume, or exploding an assignable quantity of hydrogen 

 with the confined atmosphere, by the electric spark; and it may 

 be fairly presumed that this last Is the one most to be depended 

 on. 



The electrical machine, however, is not always in order when 

 we want it, and the electrophorus is frequently difficultly ex- 

 cited amid the counter agency of an occasional humid atmo- 

 sphere, &c. The following is a new application of />o/c5sm7re 

 in eudiometry, and an elegant substitute for the electric spark, 

 whether from the electrical machine or electrophorus. 



Into the graduated detonating tube (provided with the usual 

 recoil spring, and affixed to the mercurial cistern) pass up the 

 assigned quantity of hydrogen ;— let a bubble of water follow, 

 so as to form a thin film on the surface of the mercury ; then 

 by means of delicate iron forceps bring the smallest chip of po- 

 tassium in contact through the mercury, — it immediately ex- 

 plodes, while the mercury ascends and determines the relative 

 purity. 



Thus also, by way of illustration, mix equal parts of hydro- 

 gen and chlorine in a small and strong cylinder over water, re- 

 taining a small portion of the water on inverting it. Throw 

 in the smallest ]5ortion of potassium : a violent explosion in- 

 stantly ensues, and the production of muriatic acid gas is com- 

 plete. 



In like manner, drop a minute chip of the metal into a cy- 

 linder filled with hydrogen, with a litde water at bottom, the 

 orifice being exposed to the atmosphere ; — an explosion ensues, 

 in a few seconds, and so soon as it mixes sufficiently with the 

 descending atmospheric air to form an explosive medium. 



Perhaps this may be deemed not an uninteresting applica- 

 tion of that wonderful substance called pofassiiaii, the discovery 

 of which we owe to the genius of Sir H. Davy. 

 London, 25th December, 1822. I am yours, &c. 

 __^ J. Murray. 



XIV. Tnic apparent Right Ascension of Dr. Maskeuynk's 

 3G Stars for everij Daij in the Year '\H2'S, at the time of 

 passing the Meridian of Grccnieich. Culailalcdfrom Biib- 

 sel's Tables of \H20. 



