Continued from Laboratory Glassware – Part 1
There are a few more flask designs to cover:
Round Bottom Flasks
Round bottom flasks are most often used for heating or chemical reactions. Their curved bottoms mean that there are no corners for materials to get stuck in, nor hot spots or weak points to form. Round bottom flasks are often part of systems and so while many have 1 neck, others designs may have 2 necks or 3 necks! These necks often have glass joints for joining to adapters and tubes.
Since they are used for heating or must join with other glass lab systems round bottom flasks are almost exclusively made of borosilicate glass. The big disadvantage of round bottom flasks is that they can’t stand up on a table on their own. They require a lab system to support them or use of a flask stand.
Flat Bottom Flasks
Flat bottom flasks are round flasks, usually 1-neck, that are used for heating in distillation or other reagent reactions. They are not as durable as round bottom flasks but don’t have the sharp and vulnerable corners of an Erlenmeyer Flask.Their flat bottoms do allow them to stand up on a hot plate, shelf, or table.
Volumetric flasks are use to make compounds to a decent degree of accuracy (the accuracy depends on Class ‘A’ or ‘B’ quality). To ‘operate’ a volumetric flask you put the correct mass of a compound (powder, concentrated liquid, etc) required to make a 1 molar, 2 molar, etc. mixture and then add water to the line marked on the long neck. The long neck and stopper (every Volumetric flask should come with some kind of stopper) allow for vigorous shaking to make the mixture. Volumetric flasks can be made of glass or plastic since they are not used for reactions or heating. Plastic is less expensive but more prone to staining, and it is also not as accurate.
Filtration Flasks are Erlenmeyer flasks with a spout for attaching a hose. That
hose runs to a vacuum pump that pulls the air out of the flask. When this happens a special funnel system (sometimes just filter paper) sitting on top of the flask. The pump pulls the liquid and smaller particles through the paper and into the flask. The larger particles get left behind on the filter. Filtering flasks need a lot of strength so they are built out of glass and have much thicker walls than their regular Erlenmeyer flask counterparts.