Older printings of the 4th edition of Friendly Chemistry contained some errors.  As errors are identified, they are immediately corrected and the new version is sent to our printing service.  You very likely have a version with very few mistakes, however, if you find what you feel is incorrect, please check through the list below first.  If you don't find your item listed here, please contact us for assistance.  We continually update this list and thank our users for helping us improve our products.