"Harold & Susan Vordos" wrote:

I'm no chemist, but my work with precious metals got me somewhat acquainted
with acids. One of the things you get when you buy the higher
concentrations isn't just that, you also pay for the level of purity.

Not true. Purity and concentration are independent variables. Both lab
grades and technical grades are available in a variety of
concentrations. Lab grades cost more than technical grades; higher
concentrations cost more than lower concentrations; and smaller
quantities cost more (on a $/volume basis) than larger quantities,
sometimes much more.

For example, VWR offers 0.5 L of reagent grade HNO3 for $49.35 (70%)
and $184.55 (90%). The 70% is also offered in a 2.5 L container for
$67.65, which is less than $20 more than the cost of the 0.5 L
container, or nearly a 73% discount! Go figure. VWR doesn't list any
technical grade HNO3.

Finding a source for small quantities of technical grade HNO3,
especially in the higher concentrations, can be problematic. If you
know of a good source, please share!

Bert