What is one key step in the procedure for using a nephelometer?

The correct answer involves the calibration of the nephelometer using a standard solution. Calibration is a vital step in any analytical procedure, including the use of a nephelometer, because it ensures that the instrument provides accurate and reliable measurements. A nephelometer works by measuring the intensity of light scattered by particles in a solution, which is essential in assessing concentrations of substances in various fluids.

In this context, using a standard solution allows the operator to establish a reference point, making it possible to compare the intensity of scattered light from unknown samples against that standard. This step is crucial for quantifying the concentration of analytes accurately, as it helps to account for variations in instrument performance and environmental factors.

The other actions listed, such as inserting a sample into a heating chamber, are not relevant to the operation of a nephelometer, which is designed to measure light scattering rather than temperature. Watching a video and taking notes, while potentially useful for learning the procedure, does not contribute to the analytical process itself. Measuring absorbance at different wavelengths relates more closely to spectrophotometry than to nephelometry, which focuses specifically on light scattering rather than absorbance. Thus, calibrating with a standard solution is an essential first step in ensuring the reliability of