Acid-free paper. Suppose you want to recycle some random paper for archival purposes, but don’t know if it is acid-free paper or not. How do you check for acid contents in paper? There are “acid pens” that you can use to draw across the paper and check if it is acidic or not. However, this is not viable for checking if there is ligin in the paper that will degrade and make it become acidic over time.
Also, beware if you do buy “acid-free paper,” as it may actually be acidic.
Testing ligin contents requires more complex chemicals, but among the different ways, one is fairly easy: Aniline sulfate.
20180629/DuckDuckGo how to test if paper is actually acid free
20180629/https://practicalarchivist.blogspot.com/2007/12/when-acid-free-isnt-actually-acid-free.html
20180629/https://web.archive.org/web/*/https://practicalarchivist.com/ermadenefollowsmyadvice/
20180629/https://web.archive.org/web/20160316201642/http://practicalarchivist.com/ermadenefollowsmyadvice/
20180629/DuckDuckGo how to test paper for ligin
20180629/http://cool.conservation-us.org/byorg/abbey/an/an17/an17-1/an17-112.html
20180629/https://en.wikipedia.org/wiki/Lignin