Science Play And Research Kit: DIY Titration Lab Ware

You often see demonstrations of titration using an expensive glass burette, but you can build titration lab ware using a disposable serological pipette, a solder sucker bulb, and a ring stand or support stand. For this build I’m using my erector set support stand (I sometimes call it my Bunsen burner stand). Titration is the process of determining the unknown concentration of a solution by adding a known amount of a solution with a known concentration. For example, in an acid-base titration, you can determine the unknown concentration of an acid in a solution by adding a base solution of known concentration. If you are designing your own Science Play and Research Kit, you could provide a bottle of NaOH (sodium hydroxide, or lye) at 0.1 M to 0.4 M solution and phenolphthalein solution for your indicator. There are a number of web pages that demonstrate this process that you can reference. To demonstrate how phenolphthalein solution reacts to acids and bases, you can use ordinary household ammonia and white vinegar.

Parts needed:

Goggles (to protect your eyes from splashes)

Disposable gloves (vinyl, latex, or nitrile)

Protective clothing (lab coat, or clothes that you would wear when using ammonia for cleaning)

Ring stand (I used my Erector set ring stand)

Burette clamp (I used a magnetic chip clip modified with an Erector set two hole right angle—it is attached to the stand with a computer case thumbscrew and Erector set lock nut)

Serological pipette (5 ml or 25 ml)

Solder sucker bulb (if you prefer, you can use a pipette pump or pipette bulb)

4 250 ml beakers

Eyedropper

Distilled or deionized water (or you can use tap water since all that is being demonstrated is the phenolphthalein color change)

Household ammonia

White Vinegar

Phenolphthalein solution

Wear protective clothing, goggles, and gloves. Pour 150 ml of water (for this experiment, ordinary tap water will do) in the beaker. Use the eye dropper to add four drops of phenolphthalein solution to the beaker. Add 50 ml of ammonia to the second beaker and 50 ml of vinegar to a third beaker. The fourth beaker contains distilled or deionized water to rinse the Mohr pipette.

Remove the tip from the solder sucker bulb and attach the bulb to the top of the pipette (the cylinder with the cotton plug). Attach the pipette to the ring stand.

Erector set ring stand (ring detached), chip clip burette clamp, 5 ml Mohr pipette with solder sucker bulb attached, beaker. The white pill-like object is the solder sucker tip removed from the bulb.

I find it easier to use the 25 ml pipette. With the 5 ml pipette, you have to be careful not to squeeze the bulb too hard and draw too much liquid into the pipette. You only need small amounts of ammonia or vinegar to demonstrate the phenolphthalein solution color change. Nonetheless, it’s an excellent opportunity to practice using the lab ware for titration experiments you may wish to design for your kit.

Draw a small amount of ammonia into the pipette then set the beaker of ammonia aside and slowly add the ammonia to the beaker with the 150 ml of water and phenolphthalein solution (swirl the liquid in the beaker if needed). With the 25 ml pipette I counted 13 drops per milliliter; you shouldn't have to use a full milliliter to turn the phenolphthalein magenta. Squeeze the remaining ammonia out of the pipette back into the beaker of ammonia. Rinse the pipette with the distilled water.

Next, draw a small amount of vinegar into the pipette. Then set the beaker of vinegar aside. Slowly add the vinegar to the beaker with the 150 ml of water, ammonia, and phenolphthalein solution, drop by drop, until the liquid becomes colorless again (swirl the liquid in the beaker if needed).

Rinse the pipette with distilled water. This is a simple demonstration of how to use the home made titration lab ware and how phenolphthalein solution reacts in the presence of acids and bases. Dispose of the vinegar, ammonia, and your experiment solution as you normally would dispose of household ammonia and vinegar according to the requirements of your local area.

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NOTES:

Disposable pipettes courtesy of TransGlobal Scientific Inc. www.transglobalsci.com

Science Play and Research Kit press release

Science Play and Research Kit competition web site

Solder sucker:

Source