. "Preferred second hydrogen-containing compounds are substituted or unsubstituted methane and substituted or unsubstituted, branched or straight chain, saturated or unsaturated aliphatic hydrocarbons, particularly those having from 2 to about 5 carbon atoms, such as methane, methyl methacrylate, ethane, ethylene, propane, propylene, butane, butylene, pentane, 2-methyl butane, etc." . . .