Why water is so weird. Stockholm University's Lars Pettersson, and Stanford University's professor Anders Nilsson, a guest researcher at Stockholm, have developed a theory that may change the way we understand the microscopic construction of water. [Huang, et al., PNAS (2009), doi:10.1073/pnas.0904743106].
Pettersson and Nilsson's work challenges our hitherto understanding of the weird and wonderful properties of water.
Water is unique as a liquid in that it already has 67 known anomalies compared to normal liquids. For example, water has a higher density at 4C, an unusual thermal capacity and very high surface tension. Up until fairly recently there hasn't been a comprehensive explanation for these anomalies; however, Anders Nilsson and Lars Petterson published an article in 2004 that claimed to identify that water has a “dual structure”.
Pettersson and Nilsson's results have prompted considerable discussion amongst the scientific community as their theory goes against the prevailing theory of water. They posit that water has a dual structure where as most physicists believe water placed under certain extreme conditions may separate into two different structures but that it resumes a single structure under normal conditions.
Anders Nilsson says there are several aspects of their research that makes it pioneering. For instance, they have developed different forms of X-ray emission spectroscopy and X-ray experiments to get new and unique insight into the complexities of water. “We show that the established understanding of water as a continuous dispersion around primarily ice-like tetrahedral structures bound to four other molecules in a certain disarray doesn't fit with our experiment,” says Nilsson.
The researchers claim, instead, to have identified two peaks in the spectrum of emitted X-rays which suggests that there could be two separate structures in water. Despite attracting considerable attention from the scientific community, Pettersson and Nilsson's theory is still open to considerable debate but may well lead to a better understanding of how drugs and proteins interact with water molecules within the body, enabling researchers to develop more effective medicines. An increased understanding of the microscopic structure of water could also lead to the development of better membranes for water purification.
“One of the effects of global warming that is often overlooked is the shortage of drinking water in the future,” says Anders Nilsson. “New desalination and purification techniques are going to have enormous significance in guaranteeing pure water for the world's population. To develop these we need a solid understanding of water at a molecular level and how narrow pores in the water desalination membrane, affect the structure.” For Professor Pettersson striving to understand the physycial chemistry of water remains a challenge.