Some would say that dry water is an oxymoron but it is not. Water can put on a silica disguise and disappear--at least on the surface.

Since it was patented in 1968, dry water has attracted a surprisingly small amount of published research until recently.
The inventors of dry water describe it in their patent as "having the appearance and behavior of a dry fluffy powder but composed by weight predominantly of aqueous liquid" which could be extended to salts and acids for pharmaceuticals and cosmetics¹. Efforts to understand how dry water stores gases and jumpstarts chemical reactions are currently underway.

Dry water gained renewed attention in August 2010 when scientists reported its varied uses at the 240^th ACS National Meeting in Boston. With the consistency of powdered sugar, dry water can contain a higher percent of water than seawater. Research show that it may have implications for reducing global warming and saving energy.²

When hydrophobic silica particles spontaneously surround individual liquid water droplets in air to form an inverse foam caused by chemical phase switching (liquid-solid), the result is dry water.³  To generate dry water, hydrogenated or oxygenated silica (CAS Registry Number (RN): 7631-86-9) must be treated with hydrophobic (water-fearing) hydrocarbon groups. The resulting hydrophobic silica is mixed with liquid water in a closed container to yield a fine, white powder. The final product has a weight equal to that of both the silica and the liquid water, indicating that the liquid did not evaporate but is stored inside the surrounding dry hydrophobic silica particles.²

To apply a desired matte finish to skin while avoiding oil-based emulsions, a recent Revlon patent uses dry water in a color-changing cosmetic application.⁴ This "smart" color consists of active organic and inorganic pigments stored in dry water that respond to water or lipids on skin, mechanical stress of application, or temperature and pH changes.

Dry water has potential use in chemical reactions to save energy.⁵ In a simple experiment, maleic acid was converted to succinic acid in just 30 seconds of spinning. The succinic acid was contained within the dry water. When performed outside of dry water, the same reaction would have required mechanical mixing or stirring with a magnetic bar.

Even efforts to reduce global warming may benefit from dry water, which can increase methane gas (CAS RN: 74-82-8) uptake following gas hydrate formation⁶ Since dry water eventually loses its ability to take up the natural gas, it needs the help of gelling agents, which have good kinetics, are easily handled, and have good gas storage capacity.⁷ The dry gel approach could be applied to recovering natural gas hydrates from the ocean floor by displacing the trapped methane with CO₂ (CAS RN: 124-38-9).

Contributed by
Kathryn J. Kitzmiller, Ph.D.

1. Schutte, D. Schmitz, F. Brunner, H. Predominantly Aqueous Compositions in a Fluffy Powdery Form Approximating Powdered Solids Behavior and Process for Forming Same. U.S. Patent 3,393,155, 1968.
    
2. Carter, B. O.; Weaver, J. V.; Adams, D. J.; Cooper, A. I.; Wang, W.; Spiller, D. G. Dry Water: Can We Still Make Waves? Abstracts of Papers, 240^th National Meeting of the American Chemical Society, Boston, MA, United States, Aug 22-26, 2010; American Chemical Society: Washington, DC, 2010; INOR-709. 
    
3. Binks, B. P. and Murakami, R. Phase Inversion of Particle-Stabilized Materials from Foams to Dry Water. Nat. Mater. 2006, 5, 865-869.
    
4. Zamyatin, T. Sandewicz, K. M. Russ, J. G. Jabush, S. K. Dry Water Cosmetic Compositions That Change Color Upon Application. U.S. Patent 20070218024, 2007.
    
5. Carter, B. O.; Adams, D. J.; Cooper, A. I. Pausing a Stir: Heterogeneous Catalysis in "Dry Water". Green Chem. 2010, 12, 783-785.
    
6. Wang, W.; Bray, C. L.; Adams, D. J.; Cooper, A. I. Methane Storage in Dry Water Gas Hydrates. J. Am. Chem. Soc. 2008, 130, 11608-11609.
    
7. Carter, B. O.; Wang, W.; Adams, D. J.; Cooper, A. I. Gas Storage in "Dry Water" and "Dry Gel" Clathrates. Langmuir 2009, 26 (5), 3186-3193.