- single line bond (dash)
= double line bond
≡ triple line bond
quadruple line bond
equilibrium arrow (harpoons)
dot locator for use
A chemical formula contains the elements and number of atoms of each element used to make up a particular compound. Elements are expressed as their respective symbols from the periodic table. In a molecular or empirical formula, the elements are written together without spaces. The number of atoms for each element appears in the subscript position.
Follow UEB rules for use of capital indicators for single letters, words, or passage. Use of capital terminators should be avoided within natural subunits. Contractions should not be used in letter combinations that represent chemical elements.
H subscript 2 O
NaHCO subscript 3
Capital passage mode may be used for a long sequence of element symbols where no lower-case letters are used.
open parenthesis CH subscript 3 close parenthesis subscript 3 COOC open parenthesis CH subscript 3 close parenthesis subscript 3
Grade 1 passage mode may be used in a chemical equation where multiple grade 1 symbol indicators would otherwise be required.
N subscript 2 plus 3 H subscript 2 right arrow 2 NH subscript 3
Structural formulas are written in a spatial layout. Symbols used to draw lines with braille cells can be found in Section 16 of The Rules of Unified English Braille (Line Mode, Guide Dots). Complex formulas may be best done as graphic representations.
Grade 1 passage mode is used with formulas displayed as spatial layouts. The “dot locator for use” symbol is required with the grade 1 passage indicator and terminator because they are standing alone. Dot locator for use is formed with three cells, dot five in the first cell, dot five in the second cell, and dots one, two, three, four, five, six in the third cell.
CH subscript 3 OH
H – C – OH
Both Grade 1 passage and capital passage indicators are used in Example 6.
C subscript 3 H subscript 6
H – C – C = C – H
| | |
H H H
A chemical equation that does not fit entirely on one line should be divided before a sign of comparison or sign of operation.
Fe subscript 2 open parenthesis S O subscript 4 close parenthesis subscript 3 plus 6 KOH equilibrium arrow 3 K subscript 2 S O subscript 4 plus 2 Fe open parenthesis OH close parenthesis subscript 3
2 C subscript 2 H subscript 2 plus 5 O subscript 2 equilibrium arrow 4 C O subscript 2 plus 2 H subscript 2 O