What is Deuterium Oxide?

Deuterium Oxide

Deuterium oxide (CAS 7789-20-0; heavy water; 2H20; D20) is a form of water in which both hydrogen atoms are the deuterium isotope as opposed to the protium isotopes (light hydrogen). Deuterium is a stable isotope.  Isowater has developed a proprietary process to produce deuterium oxide reliably and economically at a variety of concentrations ranging from 70% to greater than 99.995%.

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Deuterium Oxide Origins

Most of the deuterium (heavy hydrogen) that can be found on earth is believed to be formed about 10 minutes after the Big Bang, along with other very light isotopes presently found in the universe. More recently, 2.5 billion years ago, most of the deuterium atoms on the earth were incorporated into water molecules. The small fraction of natural hydrogen the Deuterium isotope made-up (only 0.015% of all hydrogen isotopes), was now found most commonly in the form of HDO molecules. Since then, deuterium has continued to be most commonly found in this form, and eventually was discovered by scientists as heavy water in 1931.

American chemist Harold C. Urey working with his associates Ferdinand G. Brickwedde and George M. Murphy discovered Deuterium in 1931. For this discovery he was awarded the Nobel Prize for Chemistry in 1934. Since the initial discovery of deuterium, many variants and formats of the substance have been created and discovered, such as deuterium oxide.

Isowater’s Founder and CEO Andrew T.B. Stuart’s grandfather Alexander T. Stuart implemented a water electrolysis facility in San Carlos California, which later became a deuterium enrichment site for the US Government in the 1930’s.

Pure heavy water, D2O, is the oxide of the heavy stable isotope of hydrogen, deuterium, denoted by the symbols 2H or D. Physically and chemically it is almost identical to ordinary “light” water, H2O, however, its density is 10% higher. It is this higher density which gives the compound its nickname, “heavy water.”

Deuterium Oxide Uses

All of the applications of deuterium oxide are due to the traits which the isotope has, giving it the ability to be useful in such a variety of applications. Around the world, Deuterium oxide is used in a variety of applications, from a moderator of neutrons in nuclear power plants to an isotopic tracer in studies of chemical and biochemical processes. Initially, Deuterium was used for analytical procedures in chemistry and physics, however, its use very quickly expanded to studies in possible cancer therapy techniques, experimental nuclear physics, and many more areas.

Physical Properties of Deuterium Oxide

The physical properties of water and deuterium oxide (heavy water) differ in several ways. For example, heavy water is less dissociated than light water at a given temperature. As well, the true concentration of D+ ions is less than H+ ions would be for a light water sample at the same temperature. The same is true when comparing OD− vs. OH− ions. For heavy water Kw D2O (25.0 °C) = 1.35 × 10−15, and [D+ ] must equal [OD− ] for neutral water. Thus pKw D2O = p[OD−] + p[D+] = 7.44 + 7.44 = 14.87 (25.0 °C), and the p[D+] of neutral heavy water at 25.0 °C is 7.44.

The pD of heavy water is generally measured using pH electrodes giving a pH (apparent) value, or pHa, and at various temperatures a true acidic pD can be estimated from the directly pH meter measured pHa, such that pD+ = pHa (apparent reading from pH meter) + 0.41. The electrode correction for alkaline conditions is 0.456 for heavy water. The alkaline correction is then pD+ = PHa(apparent reading from pH meter) + 0.456. These corrections are slightly different from the differences in p[D+] and p[OD-] of 0.44 from the corresponding ones in heavy water.

Heavy Water Deuterium Oxide

Heavy water is 10.6% denser than ordinary water, and heavy water’s physically different properties can be seen without equipment if a frozen sample is dropped into normal water, as it will sink. If the water is ice-cold the higher melting temperature of heavy ice can also be observed: it melts at 3.7 °C, and thus does not melt in ice-cold normal water.