Liquid Oxygen (LOx, LOX or Lox in the aerospace industry) is the liquid form of oxygen. It has a pale blue color and is strongly paramagnetic. Liquid oxygen has a density of 1140 kg/m³ and is moderately cryogenic (freezing point: −219 °C, boiling point: −183 °C). Oxygen is found naturally in the air. For industrial applications it is obtained from air by fractional distillation. Liquid oxygen is a powerful oxidising agent; organic materials will burn rapidly and energetically in liquid oxygen, hence LOx is a common liquid oxidizer for rocket applications usually in combination with liquid hydrogen or kerosene. It was used in early rockets like the V2, Redstone, R-7 Semyorka and Atlas boosters. LOX is useful in this role because it creates a high specific impulse. LOx was also used in some early ICBMs although more modern ICBMs do not use LOX because its cryogenic properties and need for regular replenishment to replace boiloff makeing it harder to maintain and launch quickly.