EFFECT OF SHOCK ON CS, VAPOR Submitted by: Arcot Viswanathan, The New College, Madras 14, India Checked by: Willard D. Houston, Ravenna High School, Ravenna, Ohio PREPARATION
Provide 3 clean thick-walled glass tubes, 11/%X 20 in., one deflagrating spoon (brass) 6 in. long with the spoon bent a t right angle, heavy copper wire, high voltage spark source, connecting wires, CS2, cork, slightly moist mercury fulminate (see directions below under "Remarks"). The inside of the spoon and the connections are sand papered to ensure clean metallic surfaces.
carbon is formed on t,he walls over a length of 6 in. near the lower end and the rest of the tube is covered by a yellow deposit of sulfur. As the fuhninate is slightly moist, the explosion is not violent enough to damage the tuhe. With fulminate alone or vapor alone in t,he other tubes, sparking does not produce the long black and yellow patches similar to the above and the patches in the three tubes can he compared. REMARKS
DEMONSTRATION
The glass tubes are mounted at about 30" in ring stands. The stem of the spoon is pierced through the cork and the heavy copper wire is pierced through about in. from the stem. The wire should be bent down to dip into the spoon hut not touch it. The cork should be inserted into the lower end of the tuhe so the spoon is inside the tube. The assembly is tested to make sure a spark is produced in the spoon. Mercury fulminate (about half the size of a pea) is placed in the spoon. The glms tube is filled with CSz vapor by inserting into it a long strip of filter paper (25 in.) moistened with the liquid; the paper is withdrawn after 20-30 sec. The heavy. vauor . formed displaces the air almost completely. CAUTION. USE A SAFETY SHIELD. Pass a spark through the system. The fulminate explodes with a s h a.r ~renort. The shock wave nronaeat,ed through the vapor resolves the compound instantaneously into its elements. A shiny velvet deposit of A
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Preparation of Mercury Fulminate. 3 g of mercury is dissolved in 28 ml of concentrated nitric acid (density 1.42) kept in a large flask. The hot solution is allowed to cool somewhat and 43 ml of 90% ethanol is added in two or three port,ions. A violent reaction follows. After the reaction is over, the vessel ma..v be set aside. Needles of mercury fulminate are deposit,ed. The solid is filt,cred, washed with a little water, and airdried for a day. Complete drying is not desirable. I t is then preserved in a short specimen t,uhe t,ightly corked and stored away in a cardboard box in a cool and safe plncc. When the substance is slight,ly moist, there is no danger of spont,aneous explosion, but if it is visibly moist, it does not explode whcn subjected to sparking. NOTE: Ordinary caps such a.s are used in a cap pistol may he substit,uted for the fulminate. The explosion is not as violent, and a carbon deposit is not obtained; however, sulfur does settle out on the walls of the tube. Journal of Chemicnl Bdllcolion . Novamber 1968
Volume 45, Number I I , November 1968
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