Similar we can make a strong moonshine by using the azeotrope when distilling ethanol, :lol:
We can concentrate a dilute solution of nitric acid by evaporation up to its azeotropic mixture of about 68%, without loss of very much nitric acid, as long as we do not heat it to too high of a temperature at that concentration, as the boiling point of nitric acid changes with its concentration, evaporation of water from solution can occur well below the boiling point of nitric acid at that concentration.
Evaporation of the dilute nitric acid will vapor off mostly water (temperature kept below boiling point of nitric acid at that concentration) this will raise the concentration of the acid, and the procedure can continue to the azeotropic solution of 68% nitric is reached
I have tried to explain this in several posts, and gave boiling points and densities for different concentrations of nitric acid.
Those posts will have more detail than I will post here.
20% HNO3 boiling point 104 deg C
30% HNO3 boiling point 107 deg C
50% HNO3 boiling point 114 deg C
68% HNO3 boiling point 120 deg C
Notice how the boiling point raises as it gets more concentrated.
If we kept heating after azeotrope the fume would just vapor off 68% nitric acid until the pot was dry, we cannot concentrate past the azeotropic mixture.
For evaporation concentrating nitric acid keep the temperatures below boiling points for that concentration of acid, as water will vapor off well below the boiling point of nitric acid, too strong of heat will just boil off acid wasting it.
From this we see we can concentrate the 10% HNO3 to 68% HNO3. by heating around 80 deg C until concentrated, we can test concentration by the reaction with copper, or by using density measurements as the density changes with concentration.
The dilute nitric will also concentrate when heated and reacting with metals, so a dilute nitric can be heated to dissolve silver, it would also waste less nitric acid as NOx gas if not heated to hot, although it may take a little more time, as the silver would react with dilute solution and the nitric acid would be concentrating as the water vapors are evaporated from heated solution, dilute solutions also can keep the NOx gas in solution as nitric acid dissolve more silver, than with what might have been wasted as gas if we were using a more concentrated acid on the silver.