Testing for Methonal Purity Using a Hydrometer
There is a method of testing moisture content of methanol. The main method is to ensure to test for the specific gravity of the substance (methanol). Make sure to see if the methanol to water content is 95% or lower, if it is, this is too much water content and can be problematic.
Specific gravity is the ratio of the substance density to the density of water. If the liquid is lighter than water, it should have less than a 1.0 specific gravity, beyond 1.0, it'll be heavier than water.
Density also plays a role in all of this, since temperature variations do affect the density of the liquid. In fact, temperature can effect both specific gravity and density, so it would be important to conduct this test at a specific temperature.
A hydrometer can measure the specific gravity of methanol. When the lower portion or “bulb" is placed in the solution, the specific gravity is based on how much of that bulb sits underneath or above the surface of the methanol.
For instance, the specific gravity of pure methanol at 20 degrees C is .7913, but let's say there is water intrusion in the methanol solution reaching the maximum specific gravity of 1.0000 at the same temperature. Then, with a specific gravity of .8957 which is halfway between .7913 and 1.000. This translate that the solution consists of half methanol and half water.
From this, a formula for calculating methanol purity is as follows:
Methanol Purity = ( 1 – Specific Gravity) / .2087