LEAD-FREE

The picture we see now is that of new lead-free fuels having lower aromatics content but containing a variety of oxygenates. It is thus likely that the additives entering into the composition of gasoline will be also modified. 

Isomeri2ation of straight-chain hydrocarbons is of particular importance for lead-free gasoline. Addition of high octane aromatic hydrocarbons or olefins is questionable based on environmental considerations (77). An efficient octane enhancing additive is methyl tert-huty ether (MTBE). 

The term babbitt iacludes high tin ahoys (substantiahy lead-free) containing >80 wt % tin, and high lead ahoys containing >70 wt % lead and <12 wt % tin. Both have the characteristic stmcture of hard compounds ia a soft matrix, and although they contain the same or similar types of compounds, they differ ia composition and properties of the matrix. 

Strontium. Strontium 2-ethyIhexanoate [2457-02-5] is a candidate to replace lead in lead-free paints. It functions well under adverse weather conditions and promotes through drying. Outdoor performance of low pigmented coatings like stains may be effected negatively by using strontium instead of zirconium. 

The use of propane as a motor vehicle fuel has been highly developed in some countries, particularly in the USA, Holland and Italy. It is, of course, an entirely lead-free fuel. Very high efficiencies can be obtained using a gaseous fuel in spark-ignition engines since intimate mixing of the fuel and air is much more easily achieved than with a liquid fuel. This results in a much cleaner exhaust, with considerable reductions in CO and hydrocarbons. 

Catalysts can be poisoned, or inactivated. A common cause of such poisoning is the adsorption of a molecule so tightly to the catalyst that it seals the surface of the catalyst against further reaction. Some heavy metals, especially lead, are very potent poisons for heterogeneous catalysts, which is why lead-free gasoline must be used in engines fitted with catalytic converters. The elimination of... 

Alloy samples weighing either 100 or 25 g. were prepared by melting weighed amounts of lead and thallium together. The c. p. granular test lead, free from silver, gold and bismuth (Fisher Scientific Company), was indicated by spectroscopic examination to contain approximately 0-005 % iron, 0-001 % thallium and 0-001 % copper. The thallium used was supplied by the Varlacoid Company. Spectroscopic examination showed the presence of approximately 0-01 % lead, 0-005 % iron, and 0-001 % copper. 

Because of these damaging effects, most uses of lead that involve direct exposure for humans are being phased out. Unleaded gasoline and lead-free paints have replaced two former major commercial uses of lead. Lead has proved to be Indispensable, however, in the lead storage battery, which now provides the major use of this metal. Although leakage from damaged batteries is still a potential hazard, contemporary batteries are manufactured in such a way that human exposure to battery contents is minimized. 

Catalysts were expensive, however, so the petroleum industry did not solve the problem of cheap, lead-free, knock-free gasoline until the 1970s, after General Motors adopted the catalytic converter. Lead compounds inactivate the catalysts, and sophisticated catalytic cracking techniques had to be developed to replace the fuel additive. Ironically, an even more difficult job was finding a substitute for the protective coating that tetraethyl lead formed on exhaust valve seats not even newly developed, extremely hard materials prevent wear and tear on them as well as tetraethyl lead did. 

During the media blitz that followed, Patterson urged the public to buy Chicken of the Sea tuna because the Van Camp Sea Food Company s molded steel cans were lead-free. With characteristic bluntness, Patterson lambasted a host of government laboratories from the Environmental Protection Agency and its Bureau of Foods to the National Marine Fisheries Service and the Food and Drug Administration (FDA). Asked if any other laboratories agreed with his findings, Patterson declared loftily that scientific questions are not determined by majority vote. 

Patterson suffered the first of many severe asthmatic attacks after collecting acidic gas samples from a Hawaiian volcano in 1983. The steroids he took for the asthma exacerbated his inherited osteoporosis, and his frame shrank nine inches to five foot seven. He applied twice for funds to create a line of lead-free rats to study biological processes in uncontaminated mammals. After both applications were rejected, he frequently became depressed. 

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