RESEARCH
Better Gas v i a Tritium Tritium traces gasoline distribution to cylinders i n auto engines, m a y point w a y to better carburetor design
HOT ROD? Gasoline containing a component tagged with hycLrogen-3 ( tritium ) is used in an instrumented test engine to determine composition of fuel in each cylinder. Incomplete vaporization leads to differences l>-etween cylinders
1 3 6 ACS NATIONAL MEETING Petroleum Chemistry Radioactive tracer studies of the fuel components which reach each cylinder of an automobile engine point to fuel savings, better engine performance, and lower octaine requirements. And tri tium-labeling is faster, much cheaper, and almost as accurate as carbon-14, says Dr. D . E. Cooper of Ethyl. Results of this research show how a fuel component with either very low or very high volatility will dispropor tionate with respect to the rest of the fuel. And once you have mapped this clisproportionation for an engine condi tion, you can then predict what will happen to an untested substance (such as a new additive) under similar con ditions. Other aspects of fuel behavior can be clarified this way, too. Dr. Cooper and his coworkers, R. L. Court ney and C. A. Hall, told the Division of Petroleum Chemistry. Among these other aspects: anti-knock performance, 50
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differences in the amount a n d kind of cylinder deposits, a n d e n g i n e power output or economy. ► The Technique. In earlier work, the Ethvl scientists iissed deuterium as a tagging element. This gave a good picture of how low and h i g h boiling components distribute» to the individual cylinders. However^ it c a n n o t be used to trace additives such as T E L . This is because even completely deuterateut T E L in the normal concentration that it is used in gasoline (about 0.l'< ) does not put enough deuterium i n t o the c o m bustion water to permit accurate results . Therefore, the Etliyl g r o u p changed to carbon-14. Since? this b e t a emittercan be accurately measured at e x tremely low isotope? ratios, the grourp was able to work out a v e r y precise method for tagging T E L and other hied components. However, low cost tritium ($2.00 .-' curie) from AEC, r>lus development o f efficient liquid scintillation counting; equipment, have made tritium t h e iso tope of choice for physical tracing o f hydrocarbon-containing compounds, a c
cording to Dr. Cooper. Some reasons. tritiated compounds are easier to make than C-'-labeled ones are. samples can be collected and purified more easih and more rapidh : a closely repro ducible count takes two minutes instead οϊ an hour. In a te>t« a synchronized sampling device collects a small puff ot combus tion gases troin each cylinder. T h e water \ apor is condensed and purified through charcoal. Beta particles are counted b\ the liquid scintillation tech nique. Relative concentrations are then determined. de\ iation in each cylinder calculated, and r e l a t h c iuel How estab lished. Using a modern Y-S engine, the E t h \ l workers studied three typical hy drocarbons ot \ cry different \olatilities —octadeeane, toluene*, and cyclopentane. In the first case, concentration in individual cylinders differed by from 8 to 2 3 ' * . or an average of 15.1'». For cyclopentane. the average deviation is 10.6' f a n d for toluene, 2.7'» . Dr. Cooper interprets these results this way: ie cylinders high in octadecane are rich cylinders and receive an excess ol the liquid feed which is en riched in this high-boiling material. Such a cylinder, however, receives only its normal share of vapor and thus ol the very volatile cyclopentane and its concentration of this hydrocarbon is therefore low. Having intermediate volatility, toluene distributes evenly. Using this technique, the Ethyl re search team has been able to show the gains in performance and economy re sulting from improved carburetor de signs. But even more important. Dr. Cooper adds, is the fact that a way exists to detect and measure such im provements when they are achieved.
Polyesters Made to Order Shell method forms poly esters of desired chain length and termination 1 3 8 ACS NATIONAL MEETING Paint Plastics, and Printing Ink Chemistry Shell Development has come u p with a new w a y to make polyesters to suit particular needs. It reacts monoanhydrides with terminal epoxides in the presence of a tertiary amine to give linear polyesters. Shell's Dr. R. F .
