Molarity vs Normality in labeling sulfuric acid
Who labels concentrated sulfuric acid as 18N?  36N sounds right to me and Sigma-Aldrich:


  Concentration: The commercial reagent contains 93-98% H2SO4, the balance being water. Its effective concentration is 18 M (36N).


https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma-Aldrich/Product_Information_Sheet/258105pis.pdf

IUPAC discourages use of normality because it is ambiguous.  The number of equivalents can be ambiguous depending upon the purpose (equivalents of protons, equivalents of electrons, etc.).  

See the following IUPAC document: http://old.iupac.org/publications/analytical_compendium/Cha06sec3.pdf