Why are volumetric flasks not put into the drying oven?

Answer 1

Because your teacher will probably have a fit. In the old days, you could put volumetric flasks into a drying oven, but you couldn't take volumetric flasks out of a drying oven... the heat would warp the glass slightly and introduce error into the calibration mark, so the flasks would not actually be volumetric anymore. However, borosilicate glass (Pyrex and the like) is much less heat-sensitive, and studies have shown that there's no discernable change in the capacity of borosilicate flasks even after repeated exposure to temperatures considerably higher than those normally found in a drying oven. So, aside from the aforementioned fit, there's no real reason not to do it as long as you're using borosilicate glass flasks.

Answer 2

Volumetric flasks are not put into the drying oven because the heat can cause the glass to expand unevenly, leading to inaccurate volume measurements due to distortion. It can also damage the calibration marks on the flask. It's recommended to air dry volumetric flasks instead to ensure accuracy and longevity.