pH meter curves are apparent in titrations set up in chemistry labs.
Data from a pH meter generate a titration curve. The curves are composed of flat or gently sloping buffer regions punctuated by steep clifflike parts. Polyprotic acids such as sulfuric (H2SO4) and phosphoric (H3PO4) have multiple steep "cliffs" or "steps" in a complete titration curve. Illustrations in the University of Lethbridge and UMASS references are helpful to understanding curve characteristics.
Flat Buffer Regions
At the y-axis, a titration curve starts at low pH. Solution pH rises gently with base addition. The curve is almost flat and gently sloping. This is the "buffer region." A pH meter with sufficiently low sensitivity may register the same values across a range of added basic solution.
Steep Curve Portion
Sudden increase in pH is the sign that titration reached a steep clifflike "step." Acid/base indicators typically signal a transition, depending on the exact pH values involved. After the sudden increase, pH values (now much higher) plateau into another buffer region.
Polyprotic Acid
Polyprotic acids are responsible for multiple steep and buffer zones. Adding basic solution shows more bufferlike behavior. At multiple base concentrations, there are several (up to three) steep pH climbs. These multiple steep "steps" on the curve correspond to different acidic hydrogen protons in a polyprotic acid.
Tags: multiple steep, titration curve, basic solution, buffer region, flat gently, flat gently sloping, gently sloping