...
- Clean the countertop around the balance and the balance pans with isopropyl alcohol. Put sheets of white paper on all the working surfaces.
- Arrange all supplies on the white paper: tweezers, scoopula, and a sheet of 6x6 weigh paper.
- Ensure the following items are available and labeled for each sample.
- 1 bottle of pre-weighed flux
- 1 new, empty, acid-washed vial for the remaining ignited powder
- Pre-label the bottles before weighing (one label each on the cap and the bottle).
- Make two weigh boats. Cut a rectangular strip from your piece of weigh paper and fold up the two long sides. Put one on the 'Tare' Side and the other on the sample side. You will need to make a new boat for each sample. The tare boat will remain there for all of your samples.
- Close the door of the balance and tare for 100 counts.
- Remove a crucible of ignited powder from the desiccator. If the powder has hardened from the furnace then transfer the sample from the crucible to a clean agate mortar and grind until it is a loose fine powder. If your sample is fine proceed to the next step.
- Keep your boat in the weigh pan and with your scoopula measure out 100 gramsmilligrams. Be careful not to spill your sample onto the pan. If you do remove your sample boat and with a small brush wipe away the loose powder.
- Close the door and weigh the sample, putting more sample on or off until you achieve a reproducible weight that is within ±0.00050 g of 0 (half a milligram).
- When the sample weight is as close to 100 mg as you can get it (i.e., 0.0995–0.1005 g), open the labeled bottle with the pre-weighed flux and carefully pick up the paper with the sample powder on it and transfer all of the powder into the bottle containing the flux. Snap the paper a few times with a flick of your index finger to make sure everything goes in.
- Homogenize the sample/flux mixture by holding the vial slightly off of vertical and rotating it. Tap it from time to time on the bench top as you rotate it to clear any powder from the sides of the vial. Avoid getting the sample/flux powder stuck around the cap.
...