Laboratory operations with formalin in open vessels should be carried out in a fume hood. Because repeated exposure to formaldehyde can lead to a formaldehyde allergy, it is well to avoid skin contact with aqueous solutions by appropriate use of neoprene, butyl rubber, or polyvinyl chloride gloves. Splash-proof goggles must be worn to avoid any possibility of splashing formaldehyde in the eyes. The current threshold limit value for formaldehyde is 1 ppm. Perchloric Acid Perchloric acid is a water white liquid, with no odor.
Perchloric acid can be dangerously reactive.
Contact with combustible material at elevated temperatures may cause fire or explosion. Perchloric acid should only be used in a fume hood specially designed for that purpose. The Aldrich catalog or Merck Index also notes the toxic character of many chemicals.