I have seen MANY posts over the last 6-7 years stating that the DS18B30 is the one to get if you want accuracy. The DS18B20 is pay-for-what-you-get cheap.
PS -- I tried to remember the degrees C increase in boiling point per mole of salt added to a liter of water but that was a long time ago so I looked it up. While the entire subject is loaded with conditions the basic idea of common minerals in water can be ballparked.
For saltwater, the boiling point is raised, and the melting point is lowered. By how much depends on how much salt there is. I’ll assume the salt is sodium chloride, NaCl (table salt). The melting point is lowered by 1.85 degrees Celsius if 29.2 grams of salt are dissolved in each Kg of water (called a "0.5 molal solution" of salt. The Na and Cl dissociate right away when dissolved, and so for a 0.5 molal solution of salt, there is a 1.0 molal concentration of ions). The boiling point is raised by 0.5 degrees Celsius for water with 29.2 grams of salt dissolved in each kg of water.
An ounce of salt per a liter of water is nothing like what comes out of my tap. I get trace minerals, some lead, mining tailing leachings and used fracking chemicals in my city water.