You have inherited an old cabinet containing reagent bottles. As buying reagents is becoming difficult these days, you want to keep as many reagents as possible, but to do so you have to know the content of the bottles. Unfortunately, many of the labels are either stained or have fallen off. You are limited with tests that you can do, but you do have some lab glass, reagents and an old pH meter.
Label on one of the bottles is hand written and badly stained and the only readable information is that it contains a 98% solution (with an exclamation mark after 98%, probably to mark the substance as dangerous) of something with molar mass of 98. Content of the bottle is a clear, syrupy liquid. After transferring 1 mL of the liquid to the beaker mass of the beaker increased by 1.8 g, suggesting density around 1.8 g/mL. After adding 100 mL of water pH of the solution was around 1.50, so apparently it is a strong acid. Titration of 10 mL of the diluted solution with 0.10 M NaOH against phenolphthalein required 37 mL of the titrant, which suggests acid is diprotic. Putting a drop of the concentrated acid into solution of the calcium chloride yields a white precipitate. It all suggests it is a sulfuric acid... but can you be sure?