v5.6

• generalization of the formula method concept, new methods chemist and chemfig (chemformula module)
• use tocbasic for the list of reactions if available (reactions module)
• fix reaction environments to obey \thereaction (reactions module)
• add cleveref and fancyref support (reactions module)
• add cleveref and fancyref support (scheme module)
• \DeclareChemTranslation and \DeclareChemTranslations
• moved translations from lang module to the corresponding modules they belong to

v5.5

new module polymers

v5.4

• \NewChemEqConstant and family, new option eq-constant (acid-base module)
• added \ignorespacesafterend to environments (reactions module)
• fixed erroneous definition of \NewChemMacroset (base module)
• new option explicit-zero-sign (redox module)

v5.3

• removed options german and ngerman (lang module)
• remove deprecated pre-v5 macros (several modules)
• new option atom-number-space (spectroscopy module)
• add \chemprime and ' shorthand (nomenclature module)
• new option space (particles module)
• TikZ decoration wave (tikz module)

v5.2

• warn if compatibility version requested is higher than the current version number
• enable to specify a minimal compatibility version for a module
• add info message to all module
• add values newest and latest to the compatibility option
• check for mhchem and chemformula and choose the formula method accordingly (chemformula module)
• fixes in the module hook mechanism
• fix in \chemmacros_if_module_loaded:n
• new internal module errorcheck

v5.1

• add option method? to chemformula` module
• make module scheme compatible with floatrow
• add module hooks before and after

Introducing modules

• the former chemmacros.sty is now chemmacros4.sty and can be loaded through the compatibility option
• chemmacros is now organized in separate modules which either are preloaded or can be loaded by the user with \usechemmodule
• various changes, see http://www.mychemistry.eu/2015/06/chemmacros-development/ and the manual section 3.4. Upgrading from version < 5.0 for details