Dielectric constant of water I need the dielectric constant of water from $10^{-2}$ Hz to $10^4$ Hz. As stupid as it may seem, I cannot find much info. I've googled for days. All I can find is close to GHz. And the only info close to Hz, ($100$ Hz) shows a great variation. A relative dielectric constant at $100$ Hz of about $4000$. So, I cannot interpolate back in frequency (I put a link to the paper at the end). Does anyone have any info about where I could find this data? I know that for constant current and about $20$ C the constant is $80.1$. What about at $50$ Hz?
I need the complex dielectric constant to test a program. Any lead would be really appreciated. 
http://arxiv.org/abs/1010.4089
 A: Sometimes "absence of evidence" leads to "safe to extrapolate" .  My bet is that the dielectric value is, to more precision than you could use, constant from 0 to 1 MHz.  I notice the wikipedia entry under permittivity suggests at least 0 to 1kHz. 
However, your search-fu may be wanting, grasshopper.  I found this calculator:
http://www.random-science-tools.com/electronics/water_dielectric.htm
and this paper:
http://arxiv.org/pdf/1010.4089.pdf
A: There is some data in http://www.nist.gov/data/PDFfiles/jpcrd487.pdf (J. Phys. Chem. Ref. Data, vol. 24, No. 1, 1995, p. 33) See, e.g., Table 2 there. Looks like dielectric permittivity of water is about 78.
A: EDIT#2:


*

*I'm now made aware that you need wavelengths that are much larger
than those presented here(a bit of an oops from reading this question quickly). This approach is still valid, but what you
need cannot be obtained from these data. I'm going to leave this here however to collect downvotes and if anyone needs $\epsilon_r$ as it depends on $10^{7}$ to $10^{16}$ Hz


You could find the imaginary(absorption) and real parts of the complex refractive index of water 
$$\bar{n} = n + i \kappa$$
and relate to the relative permitivitty where
$$\epsilon_r = n^2 - \kappa^2$$
at a given frequency. Some information on the frequency dependent absorption and refractive index are certainly available. 
EDIT: See www.philiplaven.com/p20.html -- Figure 6: Complex refractive
   index of water at different wavelengths.

so it is clear the data exists. This is from D. Segelstein, "The Complex Refractive Index of Water", M.S. Thesis, University of Missouri, Kansas City (1981). You can download the data at this page. From this data, you can construct the relative dielectric permitivitty using the formula above.
