Colloidal fuel is an

emulsion An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...

of powdered

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

kerosene Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning "wax", and was regi ...

fuel oil Fuel oil is any of various fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil, marine fuel oil (MFO), bun ...

. It was used in World War I aboard ships as kerosene supplies ran low. Development continued after the war, and in 1932 the Cunard liner ''

Scythia Scythia (Scythian: ; Old Persian: ; Ancient Greek: ; Latin: ) or Scythica (Ancient Greek: ; Latin: ), also known as Pontic Scythia, was a kingdom created by the Scythians during the 6th to 3rd centuries BC in the Pontic–Caspian steppe. His ...

'' made a round-trip transatlantic voyage partly powered by colloidal fuel containing 40% coal. Advantages over oil included cost and energy density. Colloidal fuel is denser than water, which allows it to be stored under water.

References

Fuels {{energy-stub