# What does the number 4-88 mean in “Polyvinylalcohol 4-88”?

Polyvinylalcohol is sold in different forms, one of those is 4-88.

What does that number mean?

The value $$\bf{4-88}$$ can be described as follows:

$$\bf{4}$$: This represents the viscosity (in $$\pu{mPa s}$$) of a $$4\%$$ solution in water at $$\pu{20 ^\circ C}$$. This value is somewhat proportional to the molecular weight of the polymer chain.

$$\bf{88}$$: This represents the percentage of moles of acetate ester that were hydrolyzed, since polyvinyl alcohol is manufactured by hydrolysis of polyvinyl acetate. This means that it is an indicator of its purity.

Source: you can check the catalogue at Sigma-Aldrich (Mowiol is a brand name for PVA) and see how those numbers correlate to those parameters.