When pouring a sample for laboratory analysis involving acid and water, how should the sample be handled?

Pouring acid into water is the appropriate handling procedure because it ensures safer mixing of the two substances. When acid is added to water, it dilutes more gradually and minimizes the risk of a violent reaction or splashing. This is particularly important because many acids are exothermic when mixed with water, meaning they release heat, which can cause the mixture to splash if added improperly.

In contrast, pouring water into acid can cause the water to suddenly vaporize into steam due to the heat generated, potentially leading to splattering or an explosion of acid droplets. This can result in severe chemical burns or injuries. Mixing them beforehand is generally not recommended because the interaction can be quite vigorous and produce dangerous fumes or heat that could pose a risk to the individual handling the materials. Moreover, using only water leaves out essential analytical procedures that require the acid for proper testing. Therefore, the safest and most effective practice in a laboratory setting is to pour acid into water.