Kerosene jet fuel typically has 50 pS m-1 conductivity. Often a static dissipator additive (aka. as a conductivity improver) is used to increase the electrical conductivity so as to prevent ignition from an electrical discharge during aircraft refuelling. Some specifications require a conductivity as high as 600 pS m-1 in which case the static dissipator additive has to raise the conductivity by up an order of magnitude. The limit on the amount of static dissipator additive is 3 milligrams per litre of fuel. This is because amounts any higher would interfere with fuel tank level measurements by capacitance. A widely used static dissipator additive is Stadis 450, manufactured by Octel, the active ingredient of which is dinonylnaphthylsulfonic acid (DINNSA). Pour point depressant additives, being non-ionic, do not affect the capacitance.
Tables of values for the refractive indices of liquids give values of typically 1.448 for the refractive index of kerosene. We saw in our discussion of the refractive index of gasolines in the previous chapter that when a gasoline is contaminated with kerosene the refractive index can provide a measure of the degree of contamination. This idea was taken further when gasoline-kerosene blends in the composition range pure gasoline to pure kerosene were examined for refractive index. Up to a kerosene content of 5% balance gasoline, the refractive index is indistinguishable from that for the neat gasoline which is 1.418. With greater amounts of kerosene there is a rise to 1.425 at 30% kerosene and to 1.440 at 100% kerosene. We note in passing that the kinematic viscosity of the blends studied in rises from 1.0 to 2.2 cSt across the composition range.