Benzaldehyde
(ben zal' de hyde).
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C7H6O 106.12
Benzaldehyde     [100-52-7].
DEFINITION
Benzaldehyde contains NLT 98.0% and NMT 100.5% of C7H6O.
ASSAY
•  Procedure
Solution A:  Dissolve 34.7 g of hydroxylamine hydrochloride in 160 mL of water, and dilute with alcohol to 1000 mL.
Sample solution:  Transfer 1 mL of Benzaldehyde to a tared, glass-stoppered weighing bottle. Loosen the stopper, and transfer the weighing bottle and contents to a 250-mL conical flask containing 25 mL of Solution A. Rinse down the sides of the flask with 50 mL of Solution A. Allow to stand for 10 min, and add 1 mL of bromophenol blue TS.
Analysis:  Titrate the liberated hydrochloric acid with 1 N sodium hydroxide VS to a light green endpoint. Perform a blank determination (see Titrimetry, Residual Titrations 541). Each mL of 1 N sodium hydroxide is equivalent to 106.1 mg of C7H6O.
Acceptance criteria:  98.0%–100.5%
IMPURITIES
•  Limit of Hydrocyanic Acid
Sample solution:  Shake 0.5 mL of Benzaldehyde with 5 mL of water, add 0.5 mL of 1 N sodium hydroxide and 0.1 mL of ferrous sulfate TS, and warm the mixture gently.
Acceptance criteria:  Upon the addition of a slight excess of hydrochloric acid, no greenish-blue color or blue precipitate is produced within 15 min.
•  Limit of Nitrobenzene
Sample solution:  Dissolve 1 mL of Benzaldehyde in 20 mL of alcohol, and mix with 10 mL of water.
Analysis:  Add 1-g portions of zinc and 1-mL portions of 2 N sulfuric acid, as needed, to maintain a brisk evolution of hydrogen for 1 h. Filter, evaporate the liquid to 20 mL, and boil 10 mL of the concentrated liquid with 1 drop of potassium dichromate TS.
Acceptance criteria:  No purplish color is produced.
•  Chlorinated Compounds
Analysis:  Wind a strip of 20-mesh copper gauze 1.5-cm wide and 5-cm long around the end of a copper wire. Heat the gauze in the nonluminous flame of a Bunsen burner until it glows without coloring the flame green. Permit the gauze to cool, and heat several times until a thick coat of oxide has formed. With a medicine dropper, apply 2 drops of Benzaldehyde to the cooled gauze, ignite, and permit it to burn freely in the air. Again cool the gauze, add 2 more drops of Benzaldehyde, and burn as before. Repeat this process until a total of 6 drops have been added and ignited. Then hold the gauze in the outer edge of the Bunsen flame, adjusted to a height of 4 cm.
Acceptance criteria:  Not even a transient green color is imparted to the flame.
SPECIFIC TESTS
•  Specific Gravity 841: 1.041–1.046 at 25
•  Refractive Index 831: 1.544–1.546 at 20
ADDITIONAL REQUIREMENTS
•  Packaging and Storage: Preserve in well-filled, tight, light-resistant containers.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, M.S.
Scientific Liaison
1-301-816-8335
(EXC2010) Monographs - Excipients
USP35–NF30 Page 1708