Chlorine for Cars

For three uninterrupted hours, the little blue Chevrolet Vega cruised steadily around the Michigan International Speedway southwest of Detroit at a constant 50 m.p.h. That performance fell far short of setting any endurance or speed records. But when the car finally pulled into the pits, the joy at trackside was unconfined. Toasts were drunk and the engineer who had prepared the Vega for its run was doused with beer. The small knot of men had every reason to celebrate. Their little car had just traveled some 150 miles at a respectable highway speed, although under its hood there was nothing more than a 40-horsepower electric motor.

For years, the principal obstacle in the way of practical electric-powered highway vehicles has been the power supply. Familiar lead-acid storage batteries, while adequate as a supplemental source of electricity in conventional cars, suffer from what engineers call a "low energy density"; they need frequent recharging and deliver relatively little energy for their size and weight. Enough of them to power an electric car would weigh as much as an entire conventional automobile. Furthermore, there is little room for improvement; lead-acid batteries have already been developed close to their theoretical peak. Other batteries using different materials--nickel and cadmium, zinc and silver, or sodium and sulfur--have greater energy density, but they have not yet proved practical either, largely because of high costs.

Looking for alternatives. Chemist Philip C. Symons, director of the Udylite Co.'s energy development lab, turned to a combination of inexpensive and readily available substances: zinc and chlorine. Other experimenters--notably General Motors' Allison Division --have also built batteries using chlorine and are confident that such batteries, when refined, will have an energy density high enough to make them practical for powering electric automobiles. But chlorine has two serious drawbacks. It is a poisonous gas that could endanger the occupants of a car if it seeped into the passenger compartment and under ordinary conditions it occupies a very large volume, making it difficult to store. To overcome the problems of free chlorine, Symons devised a system using a solid called chlorine hydrate (C112*8H2O) a loosely bound combination of chlorine and water molecules that looks like gold-tinted ice and is safe and easily handled.

When Symons' battery is in use, the heat produced by its electrochemical reactions breaks the chlorine hydrate apart into its separate components. The freed chlorine is released directly into the battery's electrolytic solution, where it helps sustain the electricity-producing chemical reactions. Because the chlorine remains dissolved, it is no more of a threat to driver or passengers than the acid in an ordinary battery.

The Udylite system is hardly ready for the road. Together with its supporting gear, the Vega's experimental battery alone weighed some 2,000 lbs., almost as much as the full weight of a conventional Vega. But now that the troublesome chlorine is under control, the weight problem seems relatively minor. Symons foresees the day when zinc chloride batteries will be small enough and powerful enough to push small two-to four-passenger cars--if not at turnpike speeds, at least fast enough and far enough to meet the less strenuous demands of city and suburban driving.

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