purity; degree of purity
Refers to the proportion of a pure substance in a material, often used in chemistry, metallurgy, and food contexts.
The purity of this gold is 99.9%.
High-purity silicon is used in semiconductors.
This gold has a high degree of purity.
I used alcohol with a purity of 99%.
We refined it repeatedly to increase its purity.
濃度 means the concentration of a substance in a mixture, while 純度 measures how pure (undiluted) that substance itself is.
Compound of 純 (pure) and 度 (degree). The kanji combination directly conveys 'degree of purity'.