More than 220,000 members of the union of engineers and workers of South Africa (NUMSA) will drop their tools on July 1, after the failure of talks to avert a strike, their leaders said Sunday. The secretary general of South Africa's largest union, Irvin Jim, said members of NUMSA also manifest at the headquarters of Eskom electricity on July 2 as part of their mobilization for a wage increase of 12 percent, nearly twice that of inflation. Eskom, which produces nearly all electricity in Africa's most developed economy, is considered an essential service making it illegal for workers to go on strike. South Africa is still reeling after a five-month strike platinum mine ended last week with a wage agreement…