Reagent ChemicalsNinth Edition

ACS SpecificationsOfficial from January 1, 20002000 American Chemical Society

Reagent: Formaldehyde Solution

Formaldehyde Solution(with stabilizer)

HCHO Formula Wt 30.03

CAS Number 50000

NOTE. This reagent contains 1015% of methanol as a stabilizer.

REQUIREMENTSAssay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36.538.0% HCHO

MAXIMUM ALLOWABLEColor (APHA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Residue after ignition . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.005%Titrable acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.006 meq/gChloride (Cl). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppmSulfate (SO4). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.002%Heavy metals (as Pb) . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppmIron (Fe) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 ppm

TESTSNOTE. The assay procedure specified herein is intended to deter-mine both formaldehyde and its paraformaldehyde polymerizationproduct that may form upon standing. A different procedure (see,for example, Reagent Chemicals, 5th edition) should be used if onlythe formaldehyde content is desired.

ASSAY. (By bisulfite addition and acidbase titrimetry). Transfer a glass-stop-pered weighing vial containing 2.0 g of sample, accurately weighed, to 100 mL ofsodium sulfite solution in a 500-mL conical flask. Avoid getting any of the sampleon the wall of the flask. Add 50 mL of 1 N sodium hydroxide and 0.15 mL of thy-molphthalein indicator, and then titrate to a colorless end point with 1 N sulfuricacid. Correct for a reagent blank and any significant quantity of acid (asHCOOH) in the sample. One milliliter of 1 N sodium hydroxide corresponds to0.03003 g of HCHO.

COLOR (APHA). (Page 19).

RESIDUE AFTER IGNITION. (Page 16). Evaporate 20.0 g (20 mL) to dryness ina tared dish on a hot plate (100 C), add 0.05 mL of sulfuric acid to the residue,and ignite gently to volatilize the excess sulfuric acid. Finally, ignite at 800 25 Cfor 15 min.

TITRABLE ACID. To 10 mL in a flask containing 20 mL of water, add 0.15 mL ofbromthymol blue indicator solution, and titrate with 0.1 N sodium hydroxide.Not more than 0.60 mL of 0.1 N sodium hydroxide should be required.

CHLORIDE. (Page 27). Dilute 2.0 mL with 20 mL of water.

SULFATE. (Page 33, Method 1). Use 2.5 g (2.5 mL).

HEAVY METALS. (Page 28, Method 1). To 4.0 mL add about 10 mg of sodiumcarbonate, evaporate to dryness, and heat gently to volatilize any organic matter.Dissolve the residue in about 20 mL of water and dilute with water to 25 mL.

IRON. (Page 30, Method 2). Dilute 2.0 mL with water to 15 mL. Adjust the pHto 5 with ammonium hydroxide after addition of the 1,10-phenanthroline reagentsolution.