The following safety precautions must be observed when handling desiccants: Always wear your lab coat and safety goggles, especially when handling powdery substances. Suitable gloves are essential when handling the most hazardous substances, namely sulphuric acid, phosphorous pentoxide, potassium hydroxide and magnesium perchlorate. Gloves are also recommended when handling calcium chloride, potassium carbonate, sodium carbonate, and copper sulfate. The use of the desiccants is similar for all substances: the porcelain bowl is filled with the desiccant. It is crucial to remove "wet" desiccant and replace it with fresh and "dry" one.