For example draw a little of the reagent up into the

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Unformatted text preview: d form a smooth sheath as it runs off of the sides. If there are any spots where a “bubble” forms, you might want to re-clean the glassware. At this point, decide if you need to dry the glassware or not. If you are washing it for next week, it will dry without spots after the distilled water rinse. If you are going to put water based solutions into it, you might not have to dry it. If it is a qualitative lab and the exact concentration of the reagent is not so important, you can pour the reagent directly into the wet container. If, on the other hand, it is a quantitative lab, you might want to repeat the rinse cycle with even smaller volumes (say about 1 mL portions) of the reagent you will use. For example, draw a little of the reagent up into the pipette, wet the entire inside of the pipette, and repeat three times, discarding each wash. On the other hand, if you are working with something like and organic solvent, you will want to dry the container with paper towels before proceeding. One of the easiest way to dry a test tube is to begin with a paper towel twisted small enough to fit inside. This in and of itself may not sound terribly insightful; however, once you put the paper towel inside the test tube, twist the paper towel in the opposite direction of the twist Dakota State University Page 46 of 232 Basic Laboratory Procedures General Chemistry I and II Lab Manual you used on the paper towel itself. This will force the paper towel to open up, and, therefore expand, to dry the test tube. Dakota State University Page 47 of 232 Experiment 1: Density of a Liquid and a Solid General Chemistry I and II Lab Manual Experiment 1: Density of a Liquid and a Solid Purpose (1) To practice the procedures commonly used in a laboratory (2) To learn how to use some of the common laboratory devices (3) To distinguish between chemical and physical properties Pearly Having characteristics of pearls Background: See “Basic Laboratory Procedures”: pipette, graduated cylinder, balance Introduction In just about any lab manual you look at, you will notice that the first experiment is something like the determination of the density of various objects. The reason for this is quite simple to understand: the author wants you to learn how to use some of the basic pieces of the lab while performing an experiment that is relatively safe. In time, you will be performing experiments that do, out of necessity, have inherent dangers, but before you do, you want to be comfortable with your own laboratory skills through practice. That is really what this experiment is all about. You will be performing a series of relatively simple procedures, but as you do, keep in mind that these are skills and tools you will need in future experiments, so be sure to get any questions that arise answered, and be sure to take many notes and observations for yourself for future reference, especially potential problems and thing to watch out for when there techniques show up again. Remember to refer back to laboratory procedures for any techniqu...
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