Prewet Nucleation of Supercooled Water by Organic Chemicals Under Optimum Test Conditions.
NAVAL WEAPONS CENTER CHINA LAKE CALIF
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Over 140 organic compounds were examined for their activity in nucleating super-cooled water using a high degree of interfacial contact with drops that were 40 plus or minus 10 micro-liter in size. It was found that a single freeze caused a significant deactivation of most of the test materials. Despite a minute-wise time delay in nucleation, median temperatures of freezing showed an average relative standard deviation of only 0.16. Thirteen of the compounds gave test results better than or equivalent to those of silver iodide. There appears to be some agreement between molecular structure and ice-nucleation activity -- but not as much as would be liked. Many of the organic compounds would have limited lifetimes as cloud-seeding agents due to high vapor pressure, high water solubility, or formation of low activity hydration compounds. However, it is noted that short-lived ice nucleating materials will be essential to precise cloud seeding. Author
- Physical Chemistry