2,4-Dinitrophenylhydrazine reagent— Add 4 mL of sulfuric acid to 0.8 g of 2,4-dinitrophenylhydrazine, then add 6 mL of water, dropwise, with swirling. When dissolution is essentially complete, add 20 mL of alcohol, mix, and filter. The filtrate is the 2,4-Dinitrophenylhydrazine reagent.

Procedure— Add 0.4 mL of Concentrate to 20 mL of 2,4-Dinitrophenylhydrazine reagent, mix by swirling, and allow to stand for 5 minutes. Collect the precipitate on a filter, and rinse thoroughly with alcohol. Dissolve the precipitate in 20 mL of hot ethylene dichloride, filter, and cool the filtrate in an ice bath until crystallization occurs. Collect the precipitate on a filter. Redissolve the precipitate by refluxing with 30 mL of acetone, filter, and cool the filtrate in an ice bath until crystallization occurs. Collect the precipitate on a filter: the 2,4-dinitrophenylhydrazone so obtained melts between 185 and 195, within a 3 range (see Melting Range or Temperature 741).

(Official January 1, 2007)

Hydroxylamine hydrochloride solution— Dissolve 35 g of hydroxylamine hydrochloride in 150 mL of water in a 1000-mL volumetric flask, add isopropyl alcohol to volume, and mix.

Triethanolamine solution— Transfer 65 mL of triethanolamine to a glass-stoppered, 1000-mL volumetric flask, add water to volume, and mix.

Procedure— To 500 mL of Hydroxylamine hydrochloride solution add 15 mL of a solution of bromophenol blue in alcohol (1 in 2500), and add Triethanolamine solution from a buret to obtain a neutralized solution that appears greenish blue by transmitted light. Transfer 65.0 mL of the neutralized solution to a glass-stoppered, 500-mL conical flask, add 50.0 mL of Triethanolamine solution, purge with nitrogen, and insert the stopper. Add about 1.2 g of Concentrate, accurately weighed, by means of a suitable weighing pipet, insert the stopper, and allow to stand for 60 minutes, swirling the flask occasionally. Titrate with 0.5 N sulfuric acid VS to a greenish blue endpoint, and perform a blank determination (see Residual Titrations under Titrimetry 541). Calculate the percentage, by weight, of C5H8O2 in the Glutaral Concentrate taken by the formula: in which N is the normality of the sulfuric acid; B and A are the volumes, in mL, of 0.5 N sulfuric acid VS consumed by the blank and specimen solution, respectively; 0.05006 is the mEq weight, in g per mEq, of glutaraldehyde; and W is the weight, in g, of Concentrate taken.