Nine acids with real relative strengths, bases that neutralise by quantity, and a pH axis that runs the whole way from fuming nitric to soda water. Gold now has something to be afraid of.
Every acid is ranked by its real pKa, so strength behaves like strength. Lower is stronger:
HI(aq) − 10.0 — hydroiodic
HBr(aq) − 9.0 — hydrobromic
HCl(aq) − 6.0 — hydrochloric
H₂SO₄ − 3.0 — sulfuric
HNO₃ − 1.4 — nitric
H₃PO₄ − 2.15 — phosphoric
HF(aq) − 3.17 — hydrofluoric
H₂CO₃ − 6.35 — carbonic
H₂S(aq) − 7.00 — hydrosulfuric
Concentration is a real axis. Acids dissolve the way salt does and spread by diffusion. Corrosion rate follows proton activity directly, so a 5% pour eats iron roughly six times slower than a 100% one — and dilute hydrochloric still outruns saturated carbonic by thirty times. Weak is weak.
Paint any solution, at any strength. A new Solutions section in the codex places brine, acids and dissolved salts ready-made. Pick one and use Shift + [ or ] to set concentration — hold to ramp.
Hydrofluoric finally does its trick. Feeble on the pH scale, and it walks straight through glass — and now quartz, at a quarter of the rate. Reinforce the vessel and it holds. Your sulfuric sits in the same beaker doing nothing at all.
Any metal oxide is a base. Drop calcium into water, or burn it in oxygen. Neutralisation works by quantity, drives pH past 7 into genuinely alkaline, and releases real heat — quicklime in hydrochloric will boil the water it lands in.
The salt decides whether you can see it. Products follow textbook solubility. Sulfuric on lime buries itself in gypsum; hydrochloric on the same lime stays perfectly clear. Drop acid on a carbonate and it fizzes CO₂.
Limestone, from nothing but air and lime. Burn carbon for CO₂, bubble it through water holding a calcium base, and calcium carbonate clouds out of solution. Same compound as chalk, marble and every seashell.
Nitric acid eats copper. Ordinary acid attack is protons pulling a metal apart, and copper, silver and gold sit below hydrogen where that cannot reach — pennies survive hydrochloric no matter how concentrated. Nitrate oxidises the metal directly instead, so nitric takes copper, silver and mercury, with brown NO₂ fuming off the surface.
Aqua regia. Get nitrate and chloride into the same water and you have the one thing that dissolves gold and platinum. The nitric oxidises the gold; the chloride holds it in solution. Neither acid can do it alone. Paint each below full strength so there is room in the water for the other.
Compounds survive a restart. Saves now record what each compound actually is, so reloading no longer hands you the wrong material or forgets the discovery.
The codex tells you what things are. Common names added to many formulae, and a "Did you know" note where there is one worth reading.
Deleting a save is a three-second hold. It sat one stray click away from the row you meant to load.
Faster. Simulation time down roughly a third on busy scenes.