If crystals of the cyanide are allowed to remain on the upper walls of the flask, they are not easily washed down and so are not hydrolyzed.
"Organic-Syntheses"
Conant, James Bryant
Experiments to be described under "The Poison" showed that the ether extract from the Soxhlet apparatus contained a substance which yielded rhamnose when hydrolyzed by dilute sulphuric acid.
"Some Constituents of the Poison Ivy Plant: (Rhus Toxicodendron)"
William Anderson Syme
To see whether the toxicodendrin could be hydrolyzed, the remainder was dissolved in alcohol and dilute sulphuric acid was added.
"Some Constituents of the Poison Ivy Plant: (Rhus Toxicodendron)"
William Anderson Syme