Twaddell number

An arbitrary hydrometer scale usually used for liquids denser than water, 19th-20th century, mostly used in England, for example in the leather industry to check tanning solutions, and for sulfuric acid and milk. Abbr, °Tw.

To convert a Twaddell number to a scale in which the specific gravity of water = 1, multiply by 0.005, then add 1. For example, 20°Tw is equivalent to a specific gravity of 1.100. To convert specific gravity to a Twaddell number:

$A equation. degrees Twaddell equal the fraction whose numerator is the density of the solution and whose numerator is the density of distilled water, both at 60 degrees Fahrenheit, minus one, times 200$