Which size syringe should a pharmacy technician use to draw 4.2 mL of potassium chloride?

When selecting a syringe size to draw up a specific volume, it's important to choose one that allows for accurate measurement while also accommodating the volume needed. In this case, drawing 4.2 mL of potassium chloride is the focus.

Using a 10 mL syringe for a volume of 4.2 mL would not be ideal, as larger syringes can lead to decreased precision in measuring smaller amounts due to the increased volume of the barrel. However, using a 5 mL syringe is more suitable, as it contains enough space to comfortably hold the 4.2 mL without needing to utilize a syringe that is too large. The 5 mL size would also allow for a more precise measurement of the liquid.

Using syringes that are too small, like the 1 mL or 3 mL options, would not be appropriate either, as they either do not provide enough volume to draw 4.2 mL or would require multiple draws, which increases the possibility of error and introduces unnecessary complexity in the process. Therefore, a 5 mL syringe is the correct choice, as it aligns well with the volume requirement and promotes accuracy in measurement.