Antiknock Antagonists H. K. LIVINGSTON Jackson Laboratory, E. I . d u Pont de Nemours & Co., Inc., Wilmington, Del. T h e antiknock efficiency of tetraethyllead and related compounds is decreased by antagonist which limit the utility of the antilcuoclrs and lead to economic waste, unless the nature of the antagonists is recognized and their concentrations in gasoline are reduced to the minimum. Furthermore, antagonism studies offer an indirect method for investigating the mechanism of antiknock action. Sulfur, phosphorus, or halogen compounds are antagonists for metallic antiknoclcs but have little effect on the octane number of fuels containing no antiknoclcs or nonmetallic antilcnocks. The antagonists for tetraethyllead (listed in order of harmfulness) are: phosphates, phosphites, silicates, silicanes, arsines, mercaptans (thiols), disulfides, sulfides, thiophenes, and organic halides. A mechanism of antiknock action based on these facts is proposed. The results show which compounds will have a harmful effect on the octane number of leaded gasolines and permit prediction of the economic advantage to be expected from their removal. The proposed mechanism provides a basis for further work leading to an ultimate understanding of the chemical processes involved in the lmocl
