diff --git a/doc/supply_demand.rst b/doc/supply_demand.rst
index ddc2f2af..d90c1fb7 100644
--- a/doc/supply_demand.rst
+++ b/doc/supply_demand.rst
@@ -11,6 +11,8 @@ Test |H2O|
 
 This is a test
 
+\ce{(2Na+,SO4^2- ) + (Ba^2+, 2Cl- ) -> BaSO4 v + 2NaCl}
+
 .. |H2O| replace:: H\ :sub:`2`\ O
 .. |CH4| replace:: CH\ :sub:`4`
 .. |H2| replace:: H\ :sub:`2`