Historical clue formulations

• They have pH's below 7 — 2026-01-07
• Complements to salts and fats in the kitchen — 2025-03-13
• One side of a chemistry scale — 2023-12-02
• They're far from basic — 2023-01-21
• Low-pH liquids — 2022-12-12
• Lemon juice and vinegar, for two — 2022-08-02
• They turn litmus paper red — 2021-03-31
• Lemon juice and vinegar, e.g. — 2020-11-17
• They're not basic — 2020-08-29
• Counterparts of tannins, in wine tasting — 2018-06-01
• Vinegar and lime juice — 2017-12-02
• One end of the pH scale — 2017-09-22
• Eating things — 2017-04-21
• They turn litmus paper red — 2016-08-09
• Vinegar and others — 2015-12-04
• Lemon juice and coffee, on the pH scale — 2015-06-22
• Etching supplies — 2014-11-20
• One side of the pH scale — 2014-08-10
• Fatty ___ — 2013-09-04
• Tums targets — 2013-06-17
• They're not basic things — 2013-03-16
• See 27-Across — 2010-09-23
• They turn litmus paper red — 2010-08-31
• Aminos, e.g. — 2009-11-15
• Gastric juices, e.g. — 2008-03-04
• Stomach contents — 2007-12-27
• Causes of breakdowns — 2006-09-07
• Etching fluids — 2006-04-20
• Tums' targets — 2005-10-05
• Citric and others — 2003-09-29
• Corrosive liquids — 2003-05-27
• They have pH's of less than 7 — 2002-10-07
• HCl and others — 2002-02-27
• Chem lab collection — 2001-10-13
• H2SO4 and such — 2001-06-19
• Litmus reddeners — 2000-11-29
• Niacin and vitamin C — 1999-10-08
• Tummy troublers — 1999-09-09
• They have low pH's — 1997-06-27
• Stomach ___ — 1997-06-26
• Fatty ___ — 1997-03-16
• Litmus reddeners — 1997-02-20
• Litmus reddeners — 1997-02-08
• These can be citric — 1996-12-25
• Niacin and others — 1995-07-30
• Base neutralizers — 1995-03-17
• Substances with low pH — 1995-02-16
• Stomach _____ — 1994-12-17