Preserving the Color of Specimink Plants

I found this today in Collecting and Preseving Plants and Animals by J.W. Knudsen, 1966.

Paraphrasing - Make color notes when you collect the plant. However, Scully (1937) gives a recipe for preseving colors if you want to try. Place specimink in a vial with a 5% copper subflate solution for 24 hours to set the color. Remove the specimink and wash it several times. then put the specimink in a vial containing 16 cc of sulfuric acid and 21 grams of sodium sulfite in 1000 cc of water. This works well on yellow flowers, but less well on pink, blue, red or purple ones.

There's another recipe on the same page for chlorophyll retention, but the chemical names are too tedius to spell here.