# Estimating parameters to Falkenhagen equation for viscosity of solutes

In this answer to a question about viscosity of water in the presence of solutes, the Falkenhagen relation is given:

$$\frac{\eta_s}{\eta_0}=1+A\sqrt{c}$$ where $\eta_s$ is the solution viscosity, $\eta_0$ the solvent viscosity, $A$ a constant that depends on the electrostatic forces on the ions, and $c$ the concentration of the solute.

Now, in what order of magnitude would I assume A? Can one make general statements which group of solutes will be around which order of magnitude, like "expect A to be around $10^{-8}$ for single atom salts and $10^{-5}$ for long chained organics" (numbers plucked out of thin air) or similiar?

p.s. The relation is quoted from a paywalled paper that I can't access.

Turns out the book (not paper) is on Google books (hopefully the link works, otherwise go to books.google.com and search "VISCOSITIES OF SOLUTIONS AND MIXTURES").

It says for salt (NaCl), the values for the three-parameter equation, $$\frac{\eta_S}{\eta_0} = 1+A\sqrt{c}+BC + Cc^2,$$ are given by $$A=0.0062 \quad B=0.0793 \quad C=0.0080$$ Unfortunately, the one-parameter values are not given in that book (at least from my perusal), but I imagine you might be able to approximate it by comparing estimations with the above three-parameter values.

PS: Sorry about not responding to that comment, seems I totally missed that in my feed. Hopefully this answer makes up for that!

Dissolve an extremely high MW hydrophilic polymer to obtain high viscosities (Polyox, vegetable gums, derivatized cellulose). Dissolve an interactive copolymer (maleic anhydride-alt-styrene and two equivalents of base, hair gels). Superabsorbent polymers, super slurpers. Elegant low molecular-mass organic gelators (LMOGs) form reversible networks that build remarkable viscosities at remarkably low concentrations, 1% or less. 2,3-Bis-n-decyloxyanthracene for alcohol, and

http://pubs.acs.org/doi/abs/10.1021/cr0302049?journalCode=chreay
Chem. Rev. 104(3), pp 1201–1218 (2004), review
http://pubs.acs.org/doi/abs/10.1021/la404258v
DOI: 10.1021/la404258v

• This does not appear to answer the question, which is about estimating parameters to the Falkenhagen equation. – Kyle Kanos Feb 10 '14 at 22:15
• "Which dissolved substances have a huge impact on the viscosity of water?" – Uncle Al Feb 11 '14 at 0:40
• "Now, in what order of magnitude would I assume A?" Your comment merely points out that there is an inconsistency between the title and question (that has now been rectified). – Kyle Kanos Feb 11 '14 at 1:26