Colloidal fuel is an

emulsion An emulsion is a mixture of two or more liquids that are normally Miscibility, 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 colloi ...

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 Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

kerosene Kerosene, or paraffin, is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from the Greek (''kērós'') meaning " ...

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 (bunker fuel), marine f ...

. 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 (, ) or Scythica (, ) was a geographic region defined in the ancient Graeco-Roman world that encompassed the Pontic steppe. It was inhabited by Scythians, an ancient Eastern Iranian equestrian nomadic people. Etymology The names ...

'' 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