Fishtail Diagrams

Quick Start

The standard Fish Diagram is all about 50:50 oil-water mixtures because that's what academics do. But in general, we don't care about 50:50. More typically we might have 10% oil, and that needs far less surfactant to reach the "tail" where you get Type III complete dissolution of the oil/water.

This app is essentially the Fish app with the "tail" points surrounding it, showing where the Type III point is at different O:W ratios. Alternatively, you can just select one O:W ratio and view it like a traditional fish diagram, but at your selected ratio.

Again, this is an expert-level app, and one that provides lots of insights if you get used to it.

Fishtail Diagrams

T °C
ξ Å
As discussed in the previous section, the problem with the fish diagram is that it defaults to the generally useless 50:50 O:W system. Happily, HLD-NAC makes it easy to calculate the fish diagram at other O:W ratios. I term the plot (shown in red) the Fishtail diagram showing you at a glance where the fish's tail will be at other O:W ratios. What you have below is essentially the same as the previous fish diagram but with the option of setting an O:W ratio. To try this out, select the O:W option and slide the %Oil slider. The fish plot loses its general symmetry and the tail crossing moves to lower % surfactant, showing the obvious fact that you need less surfactant to get an homogeneous solution if you have less oil (for o/w) or less water for (w/o).

The positions of the fishtail points at different O:W ratios can be plotted. By deselecting the O:W option and returning to the default 50:50 fish plot, the red line with the individual data points shows the tail positions for different O:W ratios. By moving the mouse over the point, the O:W ratio is shown.

Below we'll discuss why this is so useful

The point of the fishtail plot is that it instantly tells you many things you should know about your emulsion system and which most of us don't know. You can choose to answer the questions using the whole fishtail plot or homing in on a specific O:W ratio.

  1. What is the best surfactant concentration for your application?
  2. Could you get a better result with a different surfactant in terms of MWt, ξ, A?
  3. At a given O:W ratio, given your current T, EACN, Cc and S, are you in the right zone of Type I (if you want o/w) or Type II (if you want w/o)?
  4. At a given O:W ratio, how close are you to the "tipping point" at the tail crossing?
  5. What might happen to your system if there are changes to any of the parameters?
  6. Is this system suitable for PIT? If the surfactant is not an ethoxylate then the answer is no.
  7. Is this system suitable for Phase Inversion Formulation (PIF)? See the PIF section for more.