Studied by 16 people
Keep the balance clean
Always zero the balance before weighing.
Use a beaker or weighing boat instead of placing any kind of substances directly on the balance pan.
Recheck to confirm that the balance is still zeroed after use.
Laboratory thermometers are not to be shaken.
Immerse bulb of the thermometer in the substance, for which you are to measure the temperature, allow the mercury to stabilize and read thermometer.
Study the calibrations.
Do not use it to stir.
Kindly inform the instructor if thermometer breaks.
To obtain a solid, unscrew the cap of remove the cork or stopper.
Rotate and tilt the bottle at the same time to dispense the solid slowly to a weighing boat or a clean dry container.
Do not take reagent bottles to your working tables.
Do not take more than what is required.
Never return unused solids to the reagent bottle.
When heating liquids in test tubes, always point the open end of the test tube away from yourself and anyone.
When heating liquids in beakers, stir the liquid while carefully heating to avoid bumping. Note: Uneven boiling can cause dangerous spattering of large quantities of hot liquid.
Evaporation should be carried out in small porcelain casserole.
It should be heated over a small flame.
In evaporating to dryness, remove the casserole from the flame while there is still a drop or two of liquid left.
The heat from the vessel is usually enough to complete the drying.
If additional heat is required, warm the casserole gently to avoid dry heating the reside.
Each drop of reagent added should be mixed with the solution before the next drop is added.
Observe the effect of each drop of reagent as it is added and mixed into the solution.
When a test tube is less than half full, mixing can usually be accompanied by shaking or flicking the tube. • Shaking a closed tube with or finger results in thorough mixing of the contents, but danger of contamination from the cork or injury to the finger, making this technique impractical.
To determine the acidity of a solution, indicators or indicator papers are used.
Place the indicator paper on a watch glass and then drop or two of the solution.
Use a clean nichrome wire loop.
The wire loop must be cleaned by dipping it in HCl or HNO3 followed by rinsing with distilled water or deionized water.
The loop must be cleaned between tests.
The clean loop is dipped in wither a powder or solution of an ionic salt, exposed to the blue part of the flame and the resulting color is observed.
Hydrogen sulfide is the most useful reagent in qualitative analysis.
In acidic solution, it is the group reagent for the copper-arsenic group of ions.
In basic solution, it is the group reagent for iron-aluminum group of ions.
Thioacetamide is recommended as the source of hydrogen sulfide in the laboratory.
Note: Group 1 to 5 cations and anions will be discussed or used in anachem.
The separation of a solid from a liquid can be accompanied either by centrifugation or by filtration.
Centrifugation is more rapid and leaves the solid in a test tube were it may be treated with the next reagent.
Filtration leaves the precipitate spread over a circle of paper from which it must be transferred to some vessel.
Wash the precipitate with a jet of distilled water or wash solution from a capillary syringe.
Begin the washing at the upper edge of the paper.
If possible, loosen the precipitate, from the paper with the jet and work it toward the apex.
If the precipitate is soluble in the first reagent, it may be dissolved by dropping the reagent over the precipitate on the filter.
Puncturing a small hole through the apex with a pointed glass rood and then washing the precipitate into the receiving vessel with a fine stream of water from a wash bottle.
You may remove the filter paper from the funnel, unfolding and holding the paper in inclined position over a casserole and washing the precipitate in the receiving vessel.
If the precipitate is in appreciable quantity and is allowed to dry, the bulk of it may be scraped from the paper with a spatula and the small amount retained on the paper may be washed off.
If the amount of the precipitate is small, tear off and discard those portions of the filter paper that are free of precipitate and place the remaining paper carrying the precipitate in a reagent that dissolves it.
place one beaker or bottle on a table.
place the rod inside the bottle and place it 90 degree. in the video, the rod is placed at the middle of the bottle.
Pour the liquid from the other bottle to the rod.
watch as the rod guides the liquid safely to the other bottle.
