We’ve put together helpful videos and many simple formulations to supplement your class material.
Tech Tips – Common Lab Solutions and Their Uses
Benedict’s Solution, Qualitative. This solution is used to test for the presence of reducing (simple) sugars such as glucose or fructose. Boil 5 mL of Benedict’s solution with unknown sample for five minutes. If simple sugars are present, solution will be reduced and the color will change from blue to orange. Note: Table Sugar (sucrose) is not a simple sugar and will not give a positive test with Benedict’s solution.
Biuret Solution. This solution is commonly used to detect the presence of proteins. It reacts with any molecule in which two carbonyl groups (CONH₂) are joined directly together, or through a single carbon or nitrogen atom, e.g., proteins.
Bromothymol Blue (0.4% Solution). This is a pH indicator solution that is used in titration and in monitoring the pH of reactions. The visual transition interval is from pH 6.0 (yellow) to pH 7.6 (blue).
Ethyl Alcohol, denatured. This alcohol is used as a dehydrating agent for tissues in concentrations of 50% – 100%. It is also used in a 10% solution as a narcotizing reagent for freshwater invertebrates
Glycerin. This chemical is used in a 50% aqueous solution with a 1% thymol as a slide mounting media. It is also used in a solution with gelatin for mounting fats. It is also used in labs to synthesizing polymers and preservatives.
Hydrochloric Acid. This is a common laboratory acid used as a titrant and general reagent. 1 Normal (1Molar) solution contained 86 mL concentrated acid (36%) in one liter of water.
Hydrogen Peroxide, 30%. This is a very strong oxidizing agent used in bleaching and decolorizing of textiles, wood, hair, etc. Also used in plasticizers, rocket fuel, and as a disinfectant.
Iodine Solution, This is an aqueous solution of 1.8% iodine and 2% potassium iodide which is used in modified Gram’s stain for bacteria.
Limewater. This is a 0.02 Molar solution (1.5g/liter) which is used to detect carbon dioxide.
Phenolphthalein, 1% Solution. This is a pH indicator solution that is used in titrations and in monitoring the pH of reactions. The visual transition interval is from pH 8.0 (clear) to pH 10.0 (red).
Silver Nitrate Solution. This chemical is used as reagent in the detection of chloride, a cellular stain for Golgi bodies, a protein stain used on electrophoresis gels, and as an antiseptic.
Sulfuric Acid. This is a common laboratory acid used as a titrant and general reagent. 2 Normal (1 Molar) solution contains 55 mL concentrated acid (97%) in one liter of water.
Sulfuric Acid is poured on a mixture of sucrose and sodium carbonate. The resultant reaction produces a large amount of black foam as well as steam and smoke.
A small amount of potassium permanganate is placed in a petri dish. A few drops of glycerin are added and after a few seconds a puff of smoke and violet flames are produced.
Make your own foam and explain how when two viscous liquids are mixed together, they initiate a reaction producing a light weight polyurethane foam which expands 30 times the original volume of the two liquids.
Explain and view chemiluminescence. Observe how luminol is converted to an excited state in the presence of an oxidizer such as hydrogen peroxide. As the excited state molecule decays or returns to the ground state energy is produced as light.
A large quantity of foam is produced when detergent and potassium iodide are added to hydrogen peroxide.
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