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Posted
does anyone know wot the advantages are of a volumetric flask over a measuring cylinder and any diavantages?
 
Posts: 7 | Location: home | Registered: 10-20-05Reply With QuoteEdit or Delete MessageReport This Post
Diamond
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The disadvantage of graduated cylinders is that they aren't very accurate - you can only measure approximate volumes with them. With volumetric flasks, you can measure very accurate volumes.

The main advantage of graduated cylinders is you can measure a range of volumes with them by filling them up to different graduations (markings). Any particular volumetric flask can only measure one volume, so you would need one for each volume you wanted to measure.

Another advantage of graduated cylinders is that they are less expensive - it takes less effort to make a graduated cylinder where the volumes only have to be approximate than it does to calibrate a volumetric flask so that the volume is accurate.
 
Posts: 5891 | Location: Indiana | Registered: 06-13-02Reply With QuoteEdit or Delete MessageReport This Post
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As a survivor of many chemistry labs in my student days, I know what a graduated cylinder is -- they always made a big deal about accurately reading volumes based on interpreting the curved meniscus at the air/fluid interface. But I must confess ignorance about volumetric flasks -- what do they look like?
 
Posts: 1957 | Location: U.S. | Registered: 06-03-02Reply With QuoteEdit or Delete MessageReport This Post
Diamond
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Volumetric flasks are measured in the same fashion as graduated cylinders, but there is only one line and therefore only one volume. They are broad at the bottom so that they can hold a lot of solution without being too tall, but they are narrow at the top so that the volume can be measured more accurately (so that the meniscus can be better matched to the line).

 
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Much obliged, methos. Smile
 
Posts: 1957 | Location: U.S. | Registered: 06-03-02Reply With QuoteEdit or Delete MessageReport This Post
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Note too that Graduated cylinders come in 2 versions of calibration 'TC' to contain and
'TD' to deliver.

Volumetric flasks are most often TC.
For accurate work you'll need to allow your solute solvent come to thermal equilibrium before adding the last few drops of your solvent.. The Calibration is based on aqueous solutions as well.

One last hint from a person still stinging from lessons learned from a good instructor..

Don't store your solutions in vol' flasks.
 
Posts: 211 | Location: Vadnais Heights MN. | Registered: 06-15-02Reply With QuoteEdit or Delete MessageReport This Post
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