Tollen's reagent

[rosaliemb]

Does anyone use this? it is a test for Aldehydes. Or is it not allowed anymore for safety reasons?
I remember using it years back, and it was not all that satisfactory. And now our new chemistry teacher wants to try it.
Rosalie (another one)

[Labbie]

Taken from page 250 CSIS Tollens reagent year 11-12 ONLY.
Toxic if ingested. Corrosive to skin. Use eye & Skin protection when splashes can occur. Explosion hazard if the solution is eaporated to dryness. Prepare the reagent as equired: any excess should be, diluted with water, acidified and disposed of immediately into a silver waste bottle. Which is acidified with hydrocholoric acid.

Disposal: waste solution sof this chemical may be disposed of down the sink (*to Sewer*) End of quote.

[NTrivedi]

My reply is late however I hope it might be useful and relevant for some.

I find it is easier to organise the tollen's reagent preparation by year-11/12 teacher/student in laboratory as follows-

Prepare and supply dropper bottles of
1. 0.1 M Silver nitrate solution
2. 2 M sodium hydroxide solution
3. 2 M Ammonium hydroxide solution

and a container with dilute 0.1M Hydrochloric acid (to neutralise the tollen's reagent waste) for collecting waste from tollen's test.

Following is the method and instruction for teacher/stduent
Make sure to wear safety glasses during the experiment
Method for preparing Tollen's Reagent
1. Place 5 ml of Silver nitrate soultion (from the dropper bottle) in to a test tube.
2. Add 2 drops of 2 M NaOH solution (from the dropper bottle).
3. Shake the solution in the test tube.
4. Add 2 M Ammonia solution (from the dropper bottle) drop by drop until the precipitates just re-dissolves.


After the Tollen's test is complete make sure to transfer the waste contents of tollen's reagent in a container provided (contaning diluted hydrochloric acid.)

Following important safety information is from other source which I cannot remember.

Caution:
TOLLEN'S REAGENT SHOULD BE PREPARED IN SMALL QUANTITIES ONLY.
TOLLLEN'S REAGENT SHOULD NEVER BE MADE UP IN ADVANCE.

IT SHOULD NEVER BE STORED.

DO NOT SAVE THE USED SILVER SOLUTION IN A SILVER RESIDUE CONTAINER.
Silver nitrate will stain hands and clothing. Avoid skin contact with the solution.Safety

After the test has been performed, the resulting mixture should be acidified with dilute acid before disposal.
These precautions are to prevent the formation of the highly explosive silver azide.

I hope you might find it useful.

NT

[rosaliemb]

Thanks NT,
I'll keep your advice in case the another new chemistry teacher wants to use it. And I'm sure useful for others.

Winge. With turnover of teachers we seem to suffer here, I never know what prac they might want to do or need to resurect ones done years ago.

Rosalie (another one)