Assay of Salicylic Acid by Colourimetry

1. Aim

To complete the Year 3 syllabus practical assay of salicylic acid by colourimetry using an instructor-approved method or dataset. Actual analyte, measurements, and result must be entered in the student record.

2. Requirements

Instructor-approved sample and reference standard, validated method, instrument and calibration records, blank and controls, observation sheet, calculator or graphing aid, protective equipment, and chemical waste route. Confirm sample identity from its label and use the college method sheet for reagent quantities, concentrations, wavelengths, pH, and temperature. Acceptance criteria are to be recorded from the assigned current monograph or approved college method in the student record.

3. Theory

A salicylic-acid colour reaction can produce an absorbance signal under a validated reagent and wavelength. The actual method determines reaction conditions, interference controls, and calibration. A raw absorbance must be blank-corrected and compared with standards before an amount or percentage can be reported.

4. Procedure

Confirm sample identity, method version, hazards, instrument calibration, and required controls.
Record raw standards, blanks, sample readings, units, and any preparation or dilution factors.
Follow the verified laboratory method under instructor supervision, or analyze its supplied dataset.
Review the assay method, standard certificate, blank, calibration data, sample preparation and replicate readings. Interpolate within the accepted range and account for validated dilution.
Check the fit, control recovery, and measurement range before applying a formula.
Report the calculation with units, method limitations, and unresolved details recorded in the student record.

5. Observation and calculation

Student record field	Entry
Case or product	Record here
Method	Record here
Observation	Record here
Inference	Record here
Supervisor check	Record here
Outcome	Record here

Assumed values for calculation practice only: Assumed standard curve has slope 0.10 absorbance per mg/L and assumed blank-corrected sample absorbance is 0.50. Assumed concentration = 0.50 / 0.10 = 5 mg/L before dilution correction. These are invented values. Each invented input and output is assumed, not a reagent instruction or actual laboratory result.

6. Output or final result

Submit a labelled salicylic acid calibration, calculations where justified, and a conditional conclusion. Record the supervised outcome here.

Teaching-lab safety: Use instructor-supervised chemical handling and the approved disposal method. No assumed value here authorizes a preparation or analytical release decision.

This page is a supervised-activity guide; it does not report a completed case.

7. Sources

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