The purple antifreeze was Zerone, which was methanol (wood alcohol) and would evaporate over time and needed to be frequently checked and replenished. Zerex is ethylene glycol, like today's antifreezes. Both are toxic, but especially so the Zerone.
Some people used kerosene as antifreeze, which works but is flammable. Some used sugar water, or salt water, which is death on CoBra engines.
Seller: Squirrel Haven's Antiques and Collectibles (www.TIAS.com/stores/squirrel)
Title of item: ADVERTISING, ZERONE & ZEREX, 1947
Item #: ADV29
To see it, go to: http://www.tias.com/13/PictPage/1922560654.html
ADVERTISING SHEET FOR ZERONE AND ZEREX ANTIFREEZE BY DUPONT DATED OCT. 27, 1947. WONDER IF IT HAS CHANGED MUCH. IT IS ON THE BACK SIDE OF THE LIFE MAGAZINE WITH THE U.S. AMBASSADOR TO BRITAIN, LEWIS W. DOUGLAS.IT IS 13 1/2 INCHES BY 10 1/4 INCHES.