Equations
When it comes to math and chemistry equations and formulas, the visual positioning of the numbers and symbols convey meaning. This visually-conveyed info needs to be made available to all users, including those using assistive technology.
Images or screenshots of equations can be given alt text describing the formula, though this almost always falls short of conveying the information properly.
In order to make these equations accessible you will need to become familiar with MathML and or LaTeX.
Mathematical Equations, LaTeX, and MathML
Mathematical equations are highly semantic and providing unambiguous alternative text for images of math equations e.g., in a PDF document, can be challenging. For example, even a simple equation “a plus b over c” is too ambiguous for a user to know if the numerator of the fraction is “a plus b” combined or if the numerator of the fraction includes only “b”. While it is possible to write unambiguous alternative text e.g., “quantity a plus b, divided by c”, it is easier and more accessible to all users when mathematical equations are written or coded with Mathematical Markup Language (MathML).
The best approach for creating accessible mathematical equations will depend heavily on the level of mathematics being taught, the future profession of the students and the instructor’s experience with LaTeX.
For example, instructors teaching beginning math or math courses for non-majors will want to consider using built-in equation editors that will automatically convert equations into MathML, e.g., the equation editors within Microsoft Word or D2L. This allows students to view equations in tools and software that they are already familiar with.
For upper-division math courses or courses for math majors, mathematical documents are generally written in LaTeX using a processor such as Overleaf. Exporting these documents to HTML will generally produce an accessible file. The step-by-step conversion may depend on the overall formatting and packages of your original LaTeX file.
Although many formatting elements are unnecessary for someone only using a screen reader to interact with the document, that formatting can still be beneficial for vision-based usage. In all, you may need to experiment with conversion methods that balance the preservation of the original look of the document with the accessibility of the document.
Chemical Formulas, Equations and Structures
Many chemical formulas can be written with basic text and use of super and subscripts, for example C8H10N4O2.
Chemical formulas containing combinations of brackets and/or parenthesis will benefit from using equation editors (such as the one built into Microsoft Word) to allow screen readers to navigate and identify subcomponents within the chemical formula.
Simplified Molecular Input Line Entry System (SMILES) notation in combination with two-dimensional chemical structure images provides users with both a standardized, text-based description of the structure and the option to explore the chemical structure using online visualizer software.
Alternative text or long descriptions should be provided for three-dimensional chemical structures, for example to describe the chirality of molecules.