many politically and socially sensitive topics. It could be argued that the author, in trying to make the book relevant to the local market, has strayed from chemistry as the central physical science and has made it part of political science. If publishers are going to hawk their wares in other countries, they have a responsibility to make the text a world rather than a parochial one. Colin H. L. Kennard Universitv of Queensland St. ~ucia,Queensland Australia
imum of 150 mA. It allowed a current of 225 mA when set a t 300 V-very definitely a potentially lethal hazard, ifone were both careless and sweaty. I have three suggestions. Don't use the apparatus suggested in this article. Buy a commercial chamber, or make one with square plastic boxes (3)for the chambers to which the bottom glass plate id sealed and with the electrodes positioned in the lids such that the circuit must be broken before one can contact either the electrode or the electrolyte. And finally, have the reviewer of this article personally grasp one electrode in each hand, preferably wetted with 0.1 M HCI, while the power supply is set for 300 V. Then throw the switch.
The Addition of Hydrogen Bromide to UnsymmetricalAlkenes
To the Editor: The article by Brown, Dronsfield, and Ellis [J. Chem. Educ. 1990,67,518] was valuable in pointing out the utility of HBr in acetic acid for the addition of HBr to alkenes. We tried it on a few simple alkenes and found it effective ila. all cases. As expected, cyclohexene produced bromocyclohexane. In our hands, however, the addition to l-hexene and to 3,3-dimethyl-l-butene proceeded in an anti-Markovnikov fashion with no rearrangement. In retrospect, we do not find these results surprising. Hilton M. Weiss Bard College Annandale-on-Hudson. NY 12504 lonophoresis ~ ~ ~ a r aPotentially tus Lethal Hazard
To the Editor: In reading Vitale and Labandera's recent article (1)on "Ionophoresis" in this Journal, I was shocked by the potentially hazardous apparatus suggested for this technique. I was also not persuaded by their statement, "Although this is a safe technique, all necessary precautions when handling these voltages must he taken." Among these precautions, I would suggest, is not using exposed electrodes stuck into beakers filled with acid between which is precariously balanced a glass plate and filter paper sandwich! Since I could find no hint in the paper of the currents to which students might be accidentally exposed during these experiments, I attempted to reproduce t h e ionophoretic conditions indicated as closely as possible, but using a Gelman Semimicro Chamber, which is totally enclosed when current is present and has fully insulated electrical leads that must be disconnected before the chamber can be opened. As expected the 0.01 M HCI electrolyte gave the lowest currents. With 1.5- x 25-cm paper and 300 V, I measured currents of 1.54.0 mA during the 15 min suggested to complete a run. A solution of 0.05 M KN03 gave 2.54.0 mA, but 0.1 M HC1 produced 12.5-24 mAduringsuch a run. Finally, as a plausible extensionof the technique, I substituted the readily available 2.5-cm wide chromatography paper one can buy on a roll. This paper gave 24-55 mA during a 300-V run with 0.1 M HCI, and the plates were quite hot by the end of 15 min, which might cause one to drop them if not warned. To put these currents in perspective, a handbook (2)states that 1mA is detectable, 8 mA causes shock and surprise, 15 mA causes mnscle tetany, and 75 mA can cause death. Thus, even the currents carried by the paper are potentially dangerous, but the real concern is the maximum currents possible if a student should become the conductor. Obviously the result will depend on what kind of resistance helshe represents, but I measured the current possible from my Heathkit power supply, whichis supposed to be regulated for a max172
Journal of Chemical Education
Terry L. Helser S.U.N.Y. at Oneonta Oneonta, NY 13820-4015 Citations
Comments on the Safety of the Methanol Cannon
To The Editor: We noted the letter by Alber and Chambers [Alber, A.; Chambers, J. J . Chem. Educ. 1990,67,7201 on the safe use of the methanol cannon. We have performed this demonstration numerous times without ever having encountered their difficulty. Of course, the nails should always be checked to see that they are firmly seated. If one pushes them through the solid wall of the bottle as opposed to predrilline the holes. the nails are held quite tightly. and after they r i s t a little on the inside they are ext~emelydifficult to remove. If one is trulv concerned. a dror, . of glue could be used on the juncture. we have used flexible translucent polyethylene and polypropylene plastic bottles from 50 mL up to 2 L without trouble. However, on three occasions we have had 5-gal. clear plastic distilled waterjugs fitted with long electrodes blow up on us (they were always behind safety shields). We have traced this to the narrow opening at the top of the jug and the fact that the clear plastic from which these jugs are made is more brittle and will craze or shatter after several uses. Cutting a >5 in. hole in the top of the jug, not using them more than three times, and covering the hole loosely with a plastic lid has solved this safety problem. We have developed two alternate ways to ignite the methanol cannon using spark lighters, which we believe are cheaper and easier to use than that described by Alber and Chambers. The Coleman Model R29-750 electronic lighter uses a C cell and a high voltage circuit to generate a spark that "iumm about 118in. This unit can be easilv disassembled to replace the wand with two 3-R lengths of insulated wires terminatillg in allieator dins. Just connect the clim to the nails and Gess thebutton:~his unit costs about $10. The rewiring job does require a bit of skill. Our preferred method is to use a two-wire piezoelectric replacement part for home gas grills that cost us $10 a t a store that sells tanked gas and supplies. The connectors a t the ends of the wires are simply replaced with alligator clips. The leads should he extended for safety. This unit easily throws a U4-in. spark. Rubin Battino John J. Fortman Wright State Unlverstty Dayton, OH 45435
