Envco – Environmental Equipment

The Purpald Method

Purpald® developed by Aldrich Chemical Co. Purpald® is subject to fewer interferences than Shiffs’ reagent or chromotropic acid procedures. A purplecolored complex is formed when Purpald in alkaline solution reacts with formaldehyde. Results are expressed as ppm (mg/L) CH2O.

Shelf-life of the Purpald Reagent: six months. We recommend stocking quantities that will be used within five months. Refrigeration will dramatically extend the shelf-life of these products.

The Acid Titrimetric Method

CHEMetrics offers a titrimetric method for formaldehyde, which uses sulfuric acid and sodium sulfite. The end point indicator, thymolphthalein, provides a sharp color change from colorless to bright blue. Results are expressed as percent (%) formaldehyde.

Ordering Information:

Analyte: FORMALDEHYDE
Method: PURPALD METHOD.
Type: CHEMet

K-4605 Formaldehyde 0-1 and 1-5 ppm

Analyte: FORMALDEHYDE
Method: PURPALD METHOD.
Type: VACUettes

K-4605D Formaldehyde 0-30 and 30-150 ppm
K-4605A Formaldehyde 0-60 and 60-300 ppm
K-4605B Formaldehyde 0-120 and 120-600 ppm
K-4605C Formaldehyde 0-1200 and 1200-6000 ppm

Analyte: FORMALDEHYDE
Method: CERIC SULFATE TITRANT WITH FERROIN AS THE INDICATOR
Type: Titret

K-4250 Formaldehyde 0.5% to 5.0%

Kits come in a plastic case and contains everything needed to perform 30 tests (except distilled water): Refill, Low and High Range Comparators, Activator Solutions, 25 mL sample cup, instructions, and MSDS.