Effect of Weathering on the Vapor-Locking Tendency of Gasolines 300021

WEATHERING of gasoline occurs in fuel tanks, carbureter float-bowls and vacuum tanks of automotive equipment, the extent being dependent upon conditions of temperature and pressure. If there is sufficient fuel loss due to weathering, the vapor-locking tendency of the gasoline is reduced.
Experiments were made in laboratory equipment to determine the amount of loss and the decrease in vapor-locking tendency of a number of gasolines under various conditions. The factors varied were temperature, pressure, time and the size of opening to the gasoline container. In general it was found that there is very little loss until the vapor pressure of the gas-free gasoline exceeds the external pressure. When the vapor pressure of the gasoline exceeds the external pressure, loss occurs until the vapor pressure becomes equal to the external pressure if sufficient time is allowed for the vapors to escape through the opening.
In most of the experiments A.S.T.M. distillations were made on the gasolines before loss had occurred and on the residues after weathering. It was found that the A.S.T.M. temperature of the original gasoline, at a percentage evaporated corresponding to 10 plus the loss by weathering, was equal to the 10-per cent point of the residue. Since, with most gasolines, the vapor-locking tendency is determined by the 10-per cent point, a knowledge of the weathering loss permits an evaluation of the change in vapor-locking tendency on weathering. The loss may be computed from the temperature of weathering and the external pressure.


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