What would be a good chemical blank to use for the Tollen's Test (Silver Mirror test)?
a test tube will work, a flask is neat (but more expensive). Pre-treat the glass with Tin(II) chloride stabilized with hydrochloric solution, you want the glass very clean so the silver adheres in a film.
thanks
To determine a suitable chemical blank for the Tollen's Test, let me first explain what the Tollen's Test is used for.
The Tollen's Test is an analytical technique used to distinguish between aldehydes and ketones using a silver mirror reaction. In this test, a silver mirror is formed on the inner surface of a glass tube or flask when an aldehyde is present. Ketones, on the other hand, do not produce a silver mirror and remain colorless.
Now, when selecting a chemical blank for the Tollen's Test, we want a substance that won't give a false-positive result by forming a silver mirror but will still allow us to observe any potential silver mirror formation in the presence of an aldehyde. A common choice for a chemical blank is an organic compound called acetone.
Here's how you can proceed to choose acetone as a chemical blank:
1. Obtain a small amount of acetone, preferably in a pure form. You can find acetone in hardware stores or chemical supply stores.
2. Prepare a control test tube or flask by adding a small amount of acetone to it. This will serve as your chemical blank.
3. Set up another test tube or flask containing your aldehyde solution (such as formaldehyde).
4. Perform the Tollen's Test procedure by adding Tollen's reagent (ammoniacal silver nitrate) to both the control flask (acetone) and the aldehyde flask.
5. Observe the results. If silver mirror formation occurs only in the aldehyde-containing flask and not in the control flask, then acetone is an appropriate chemical blank.
Remember, a chemical blank should not produce a silver mirror on its own but should allow for detection of silver mirror formation in the presence of an aldehyde.