pH lab outline and rubric.doc

Set 1 – calibrate pH meters
Care, use, and calibration of pH meters
pH e in several shapes, but all consist of an electrode pair and a readout device. The electrode pair is usually in a thin glass probe termed bination electrode. It is fragile. Contained in that probe is a saturated KCl solution and a reference electrode. Many electrodes have a vent hole near the top to vent H2 gas and allow refilling. Some electrodes have caps to fit over the end, which protects the electrode and holds in storage solution. Others must be stored in a separate container.
Storage: electrodes are stored with the end immersed in a mixture of saturated KCl and pH 7 solution, and the vent hole should be closed. Do not let the electrode, inside or out, get dried out.
Use: rinse off the outside of the electrode with dH2O. place electrode in the solution for which you seek to determine the pH. Turn on the meter and measure pH. When done, turn off the meter, remove the electrode, rinse it off, and return it to storage solution. If using a stir bar in your solution, make sure that it will not contact the electrode as they are fragile.
Calibration: Before use, you should calibrate the pH meter. Rinse off the electrode and place in standardized pH 7 solution. Turn on the meter. You may need to allow it to warm up some. Adjust the readout to 7.
On the digital meters, there is a screw on top which is