ANSI IT4.152-2001 pdf download Processing Chemicals – Specifications for Formaldehyde 37% Solution with Stabilizer
6 Sampling
See ISO 1 0349-1 .
7 Test methods
7.1 Assay
7.1.1 Specification
Minimum content of formaldehyde shall be 37.0% (m/m).
7.1.2 Reagents
7.1.2.1 Sodium hydroxide, NaOH (DANGER: <>), standard volumetric solution of 1 mol/l (40 g/l) 2)
7.1.2.2 Hydrogen peroxide solution, H 2 O 2 , 3% solution
Add 1 0 ml of 30% hydrogen peroxide solution (DANGER: <>,<>) to 90 ml of water. Mix thoroughly.
7.1.2.3 Sulfuric acid, H 2 SO 4 , standard volumetric solution of 0.5 mol/l (49.04 g/l) 2)
7.1.2.4 Ethanol, CH 3 CH 2 OH (DANGER: ,), 95%
7.1.2.5 Bromthymol blue indicator
Dissolve 0.1 0 g of bromthymol blue in 50 ml of 95% ethanol (7.1 .2.4) (,). Dilute with 50 ml of water.
7.1.3 Procedure Place approximately 3 ml of a test portion of the the formaldehyde sample (<>,) into a tared glass- stoppered weighing bottle having a small diameter, and weigh to the nearest 0.001 g. Quantitatively transfer the contents of the weighing bottle into a 250-ml Erlenmeyer flask containing 1 0 ml of distilled water and mix thoroughly. Pipette 50 ml of 1 mol/l sodium hydroxide solution (7.1 .2.1 ) (<>) followed immediately, but slowly, by 50 ml of freshly prepared 3% hydrogen peroxide solution (7.1 .2.2). Place a watch glass over the flask, and heat the mixture on a steam bath for 5 min with occasional swirling. Cool, let stand for 30 min, and titrate to a blue-green color with 0.5 mol/l sulfuric acid solution (7.1 .2.3) using 3 drops of bromthymol blue indicator (7.1 .2.5).
7.1.4 Expression of results
The assay, expressed as a percentage by mass, for formaldehyde solution is given by 3.003 (50c 2 – c 1 V 1 ) / m,
where
c 1 is the actual concentration, expressed in moles per liter, of the sulfuric acid solution (7.1 .2.3);
V 1 is the volume, in milliliters, of the sulfuric acid solution (7.1 .2.3) used to reach the titration endpoint;
c 2 is the actual concentration, expressed in moles per liter, of the sodium hydroxide solution (7.1 .2.1 );
m is the mass, in grams, of the test portion;
3.003 is the conversion factor obtained from the mass of formaldehyde equivalent to 1 mole of sodium hydroxide (i.e., 30.03) x the conversion for milliliters to liters (i.e., 0.001 ) x 1 00 (for percentage).
7.2 Heavy metals content (as Pb)
7.2.1 Specification
Maximum content of heavy metals shall be 0.001 % (m/m).
7.2.2 Procedure
NOTE – The standard for the iron test (7.3) is prepared in the same way as the heavy metals standard.