[KKataoka]

I am in need of an IPA surface tension (g) v. temperature equation. I found this equation in Lange's (12th ed) pg 10-98 and 10-114:
g = a -bT
Where:
a = 22.9;
b = 0.0789; &
T = °C
However this equation implies a linear relationship between T and g. The surface tension graph I've seen for IPA does not indicate this.

Additionally, when this equation is applied to 20°C it gives 21.32 dyne/cm. My CRC (62nd ed, pg F-38) gives the surface tension @ 20°C as 21.7 dynes/cm.

Anyone else have either a more realistic equation or can point me to a source of temp v. g for IPA?

I'm attempting to set-up an Excel sheet for determining the max. pore dia. of filters per SAE ARP 901A. Which brings me to another issue:

The aforementioned SAE spec has an equation in which the density of IPA (in g/cm³) is multiply by the height of IPA over the filter (in inches) and this product is subtracted from a bubble point pressure (in inches of water) to give inches of water. The spec seems confused. It identifies "d" as "...test liquid density (specific gravity)". Which is it? The example equations use a density value in the equation. Leave it to an engineer to screw-up the units. My spreadsheet uses SpG not density (i.e., r IPA^T/r H₂O^T).

Thank you for your assistance and allowing me to rant-
-Keith Kataoka