The pH of a product may be a poor predictor of caustic injury. The titratable acid reserve (for an acid) and the titratable alkali reserve (for an alkali) may give more information about the caustic nature of the product.
Task: to neutralize 100 mL of a 1% solution of the product to pH 7
For an acid, 0.1 M sodium hydroxide is used.
For an alkali, 0.1 M hydrochloric acid is used.
Three separate neutralizations are performed, and the number of mL of acid or base is recorded.
The TAR is the mean of the volumes from the 3 neutralization procedures.
Interpretation:
• A low TAR (around 1) is associated with a low risk of caustic burn.
• A high TAR (around 10) is associated with a high risk of a caustic burn.
Limitations:
• Boldt and Carroll found that the TAR was not predictive of esophageal perforation.
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