These are designed to be exceptionally high precision

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: rolling the flask also controls the buret, and reads the volumes on the buret. Once the endpoint is reached, read the final volume in the buret. The volume added to the flask is this volume minus the initial volume. You need not refill the buret after each run; if you still have enough liquid in the buret for a second run (which should have the same volume as the first run), you can just use the liquid that is already in the buret. Only refill the buret if necessary (and remember; do NOT refill the buret in the buret clamp!). If you underestimate the volume in the buret, do not try to “save” the run by letting the liquid run below 50 mL in the buret, or by adding liquid mid-titration. These are designed to be exceptionally high precision Dakota State University Page 45 of 232 Basic Laboratory Procedures General Chemistry I and II Lab Manual experiments; either of these techniques will introduce undue error into your calculations. Just refill the buret, and do another run. Cleaning laboratory Equipment: Finally, we come to the general process of cleaning laboratory equipment. This is critical; contaminants can have a profound influence on an experiment, and since equipment is shared, you will want to be sure the glassware is clean from the other groups. Heck, you don’t know what they did! So how does one go about cleaning laboratory glassware? Easy; you make your lab partner do it. But what if YOU are the lab partner? OK, well, it’s really not that bad. The first thing you will want to recognize, however, is the simple fact that glassware is easiest to clean before the gunk has the opportunity to dry into it. However, the same basic rules apply even if it is old. Begin by rinsing very well with tap water (surprised?). You will find an assortment of brushes near each sink; rinse out as much of the bulk of the contaminants as possible. Then, still using tap water, add Alconox. Alconox is a white cleaning agent at each sink; it is a detergent made BY chemists FOR chemists. This is good stuff; it’s like Lava soap with an attitude. Use the brush to clean the glassware thoroughly; if you are cleaning something that cannot be cleaned with a brush (like a pipette); dissolve a little Alconox in a beaker of water and run it through as best you can. After cleaning with Alconox, rinse the glassware VERY THOROUGHLY with TAP water to get rid of all of the excess soap. If you are not happy with how clean it is, repeat the step with Alconox. Finally, rinse it THREE TIMES with SMALL amounts of distilled water (in the large carboys near each sink). Do NOT allow the distilled water to run the entire time during the rinsing process; open the spicket just long enough to allow a small volume (maybe 5 mL) out, and close it again. Rinse thoroughly and repeat two more times. It does take time to make distilled water, so if we run out during a lab, there is nothing I can do about it. If you are working with something like a pipette, run distilled water through it using a wash bottle. If the glassware is clean, the water shoul...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online