What would be an incorrect practice when measuring precise amounts on a scale?

Relying solely on visual approximation is considered an incorrect practice when measuring precise amounts on a scale because precision in measurement requires the use of a scale’s calibrated readings. Visual approximation can lead to significant errors, especially when dealing with small quantities where even slight deviations can lead to inaccuracies that impact results and outcomes.

In laboratory and pharmaceutical settings, utilizing the scale's exact measurements is crucial to ensure the proper formulation of medications and other substances. Accurate readings help in maintaining the efficacy and safety of the products being created, which is particularly vital in fields where precise dosing is necessary.

The other practices mentioned, such as using fine tweezers to place materials on the scale, measuring with gloves to prevent contamination, and calibrating the scale before each use, are all designed to enhance accuracy and maintain the integrity of the measurement process, thus supporting the overall objective of achieving precise and reliable results.