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Laboratory Glassware – A Primer, Part 2

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

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

Filtration Flasks are Erlenmeyer flasks with a spout for attaching a hose. That

Filtration Flask

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.

 

Continued in Part 3

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Laboratory Glassware – A Primer Part 1

There are dozens and dozens of different types of lab glassware available to anyone who wants to buy them. But all of these different types of glassware can get rather confusing to folks so we figured is was time for a little educational post about the many different kinds of glassware than scientists use:

We’ll start with the basics.

Griffin Beakers: These are one of themost common pieces of glassware out there. They are pretty much just glasses with graduations to show much they are holding (usually in ml). They should be made of borosilicate glass (which has many brand names: Pyrex, Bomex, etc). and can go in size from 5ml up to 10,000ml. They usually have a pouring spout and are capable of holding liquids or powders. Griffin beakers are used for mixing or heating chemicals or for staging chemical reactions.

Plastic versions of Griffin Beakers are available where breakage might be a concern, but plastic is completely unsuited to some chemical reactions and cannot be used for heating.

Erlenmeyer Flasks:

A flask is different from a beaker in that it has sloping or round sides rather than

the straight sides of a beaker. In the case of an Erlenmeyer Flask they slope in a

cone shape to close towards the top of the flask. There are many types of flasks and Erlenmeyer Flasks are the most common. The narrow top allows mixing with reduced chance of spillage, and the smaller mouth can be topped with a cork, or in some designs with special joints for attachment to other lab tubing.

Erlenmeyer flasks are used for stirring or shaking where their narrow mouth openings can reduce spillage. They can be used for reactions, heating and most other functions. Erlenmeyer flasks should be made of borosilicate glass for safety purposes, although plastic versions are available for non-heating, less caustic experiments. These plastic versions often have screw on lids for vigorous shaking/stirring. The plastic used should be the more durable Polypropylene.

Graduated Cylinders:

Graduated Cylinders are used for more accurate measurement of liquids. While Griffin Beakers and Erlenmeyer Flasks may have measurement markings printed on them, they are more for general reference than accurate measurement. To properly measure liquid in quantities larger than 1ml an appropriate size cylinder should be used. Reactions should rarely be done in cylinders, and heating/shaking/stirring should not be done in them. The chemicals should be poured into a beaker or flask to do that. Cylinders are usually made of borosilicate glass, with either a 1 piece glass base  or a  glass tube inserted into a plastic base. The plastic base can make the cylinder easier to clean, but can also be more vulnerable to spilled caustic chemicals.

Completely plastic graduated cylinders are also available for those who want less glass breakage and aren’t using reactive chemicals. The plastic used can be either polyproplyene, which is translucent and can be tricky to read the measurements, or PMP which is clear but can be more expensive and more brittle.

Since graduated cylinders are used for measuring chemical quantities they have markings on them to note quantity of liquid, etc.  These markings are usually ascending but in some cases they may be ‘Double Scale’ where the 1 set of markings counts up and the other counts down. A lot of graduated cylinders just have one set of markings, however.

Most graduated cylinders sold are considered to be class ‘B’ quality. These are accurate for most purposes. More precise measurements  should use Class ‘A’ cylinders which usually has tolerances of about 0.5% for more accurate chemical measurement. These high tolerances come at fairly steep price, however.

Continue to Part 2!  More flasks and specialty glassware!

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