Equiligraph Home Page


What is here and where to find it.

We, as scientists, engineers and technicians have forgotten or misplaced some very effective  general analysis tools.

There are many graphical methods of analysis developed to solve complex problems. The concept is to find a general solution to a set of coupled equations. The resulting equations are then simplified by casting the equations and solutions in terms of appropriate parameters, so that a graph can be made which can be easily used to solve a specific problem. 

This is similar using a compiled computer language - it splits the task into two parts: some of the work is done up-front, which permits the work to be done faster at a later date.

The beauty of this approach is that the details of the mathematical solution to the coupled equations does not have to be remembered in order to find a solution for a given set of parameters.

Keywords: chemistry, sourdough, acid, base, equilibrium, equiligraph, Buffer Capacity,  alpha, End point, Equivalence point, pH, pKa, pKb, pK1,Composition, graphic solution.

Equiligraph Basics:

This page explains the basic use of the equiligraph for monoprotoic acids and bases

  1. *what data are needed.

  2. *How the graph changes as the inputs change.

  3. *How to solve for:

    > pH of  solutions made of pure acid

    > pH of solutions made from pure monobasic salts.

    > pH of titration equivalence points  acid -> base and base -> acid

    > pH  of buffer solutions of known composition

    > Composition of buffers for a desired pH

Creating an Equiligraph:

This page shows how to draw an equiligraph on a piece of paper.

A spreadsheet template for monoprotic acids and bases can be downloaded as an Excel file (.xls) or as an OpenOffice file (.ods).

Titration App:

This page introduces the Equiligraph app, Titration 1.0,  for iPhone and iPad.

This app has 4 pages:

  1. *An Equiligraph, with graphic and numeric results

  2. *A graph of buffer capacity versus pH

  3. *A titration curve

  4. *An extensive help menu

Polyprotic acids and bases:

This page explains how to interpret equiligraphs for polyprotic acids and bases, using sulfuric acid as an exampleof a diprotic acid.

The concept of graphing solution alkalinity is explained

Sourdough Bread:

This is an example applying the equiligraph to the solution of a real world problem. The sourdough bread process is typical of the industrial, engineering or research problems.

There are more variables than can be readiliy identified and there is an established process and well defined bill of materials.

The process works - most of the time, but there are cases where it does not work well. This example looks at why the process fails when the sourdough starter ages. Most cookbooks suggest throwing the starter away if it has sat unused for more than a week.

This is a very long page, but it shows the versatility and power of the equiligraph, as well as showing how to recover a ‘dead’ sourdough starter!


This page explains the parameterization of the coupled equations of state for ionic equilibria which forms the foundation of the equiligraph.

The equiligraph is an analytical tool that predates computers, however it is still useful today. 

Apps for phones and tablets have been written so that the power of the equiligraph can be in your hand, available to you when you need it.

These equiligraph apps are productivity tools.

Use one to dry-lab your next experiment! It will save you lots of time.

DIY Chemistry Hero Kit:

This page shows you how to make a set of 5 equligraphs which will help you solve most problems you will encounter in the chemistry laboratory, including the effect of dissolved carbon dioxide and dissolved ammonia gas on the concentration of dissolved species and the pH.

This kit is needed for the Soluble Gasses page.

Soluble Gasses:

This page demonstrates how to use the Chemistry Hero Kit to predict the pH and concentration of dissolved gasses as a function of solution pH, which goes well beyond the simple Henry’s law calculation for DI water. The example uses ammonia gas, NH3, and carbon dioxide gas, CO2.

The worked example shows how to estimate the equilibrium concentration of ammonium carbonate for any level of CO2 and NH3. Results from two different types of graphic analysis are compared with the numeric calculations from rigorous physics based models.

Quick Links;


Tutorials / Interpretation:

Equiligraph Basics

Polyprotic acids and bases

Creating an Equiligraph

DIY Chemistry Hero Kit

Worked examples:

Sourdough Bread

Soluble Gasses

Physics / Theory:


Contact me:


Software / Apps:

Titration:    Apple AppStore

    Equiligraph, buffer capacity and titration curve.


**  Not yet available!

    A calculator showing CaCO3 solubility as a function of atmospheric CO2


****  Not yet available1

    Equiligraph showing solubility as function of pH


My goal is to re-introduce the equiligraph as a useful tool. In this site I provide background information on the equiligraph:

  1. *How to draw you own equiligraph on paper or with a spreadsheet.

  2. *How to interpret the graph

  3. *The the relationship between the fundamental physics and the tool.

    > Basic use to solve acid -base equilibria.

    > Intermediate use to solve problems with polyprotic acids and bases.

    > Intermediate use to solve pH dependent solubility problems

    > Intermediate use to solve gas - dissolved gas - ion interactions

    > Advanced use to solve problems involving complex-ion formation

  1. *Examples of real world technical problems which show application to real world problems

  2. *Description of phone and tablet apps developed so you can have these powerful tools in your pocket, ready to go!