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Purity is mentioned often when we talk about specialty gases and HiQ®. But what is purity? How can one define it?
The minimum purity of a gas refers to the specified impurities that characterize the pure gas. The specific limits for the impurities are not exceeded. In the case of gases without details on impurities, the specification of their purity is to be seen as a typical value.
The maybe simplest and most accurate definition of purity is:
“Purity is the absence of impurity in a substance.”
Impurity can be defined as a material or substance in the finished product that differs from the chemical composition of the requested material or compound. BUT: 100% purity cannot be achieved due to the manufacturing process.
Purity classification is normally written in two ways:
1. As a quality code, where the number before the dot represents the
number of nines and the last number indicates the last decimal (e.g.
Grade 5.5 = 99.9995% or Grade 6.0 = 99.9999%)
2. As a percentage, e.g. >99.9995%
Helium 4.7 means 99.997 % purity
Argon 6.0 means 99.9999 % purity