Friend had dried cactus tissue, after the mistake of failing to add water to cactus CAOH at the appropriate time, and is going to re-add the water.  Thinking additional CAOH may be needed after the aborted limonene soak, he is wondering what PH he should aim for with the cactus-CAOH-water mixture, prior to adding the limonene.  Thinking to add water, and slowly add CAOH until proper PH is reached, but not sure what that should be.  Thanks wise ones!