Diluted Hydrochloric Acid
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
1 DEFINITION
Diluted Hydrochloric Acid contains, in each 100 mL, NLT 9.5 g and NMT 10.5 g of hydrochloric acid (HCI).
Diluted Hydrochloric Acid may be prepared as follows.
| Hydrochloric Acid | 226 mL |
| Purified Water, a sufficient quantity to make | 1000 mL |
Mix the ingredients.
2 IDENTIFICATION
A. IDENTIFICATION TESTS-GENERAL, Chloride (191)
3 ASSAY
3.1 PROCEDURE
Sample: 10.0 mL
Blank: 20 mL of water
Titrimetric system
(See Titrimetry (541).)
Mode: Direct titration
Titrant: 1 N sodium hydroxide VS
Endpoint detection: Visual
Analysis: Transfer the Sample to a conical flask, and add about 20 mL of water. Add 3 drops of methyl red TS. Titrate with Titrant. Perform a blank determination.
Calculate the amount of hydrochloric acid (HCI) in the portion of sample taken:
Result = (VS/VB) × N × F
VS = Titrant volume consumed by the Sample (mL)
VB = Titrant volume consumed by the Blank (mL)
N = actual normality of the Titrant (mEq/mL)
F = equivalency factor, 3.646 x 10-2 g/mEq
Acceptance criteria: 9.5-10.5 g of HCI in each 100 mL
4 IMPURITIES
4.1 RESIDUE ON IGNITION (281)
Sample: 20 mL
Analysis: To the Sample add 2 drops of sulfuric acid, evaporate to dryness, and ignite.
Acceptance criteria: NMT 2 mg
4.2 FREE BROMINE OR CHLORINE
Sample: 10 mL
Analysis: To the Sample add 1 mL of potassium iodide TS and 1 mL of chloroform, and agitate the mixture.
Acceptance criteria: The chloroform remains free from any violet coloration for at least 1 min.
4.3 SULFATE
Sample solution: Mix 3 mL of Diluted Hydrochloric Acid and 5 mL of water.
Analysis: To the Sample solution add 5 drops of barium chloride TS.
Acceptance criteria: Neither turbidity nor precipitate appears within 1 h.
4.4 SULFITE
Analysis: Complete the test for Sulfate, then add to the liquid 2 drops of 0.1 N iodine.
Acceptance criteria: Neither turbidity nor decolorization of the iodine occurs.
5 ADDITIONAL REQUIREMENTS
PACKAGING AND STORAGE: Preserve in tight containers.
