What's the difference between inconvertible and unexchangeable?

Inconvertible

Definition:

(a.) Not convertible; not capable of being transmuted, changed into, or exchanged for, something else; as, one metal is inconvertible into another; bank notes are sometimes inconvertible into specie.

Example Sentences:

(1) The apparatus can be used to mix small volumes (about 50 mul) of equilibrium mixtures of enzyme-substrate and enzyme-product complexes with a quenching solution, ideally to inactivate the enzyme more rapidly than such complexes can be inconverted.
(2) Furthermore, DAB was oxidized in the presence of polyunsaturated fatty acids inconvertible to prostaglandins (linoleic and linolenic acid) as well as in the presence of H2O2--in the latter case reaction possessed identical features with that induced by fatty acids.
(3) Chicken liver, which contains an inconvertible dehydrogenase form, also showed high activity in sinusoidal cells.