Adapted from Experiment 48: Luminol, in Pavia, Lampman and Kriz, “Introduction to Organic Laboratory Techniques: A Contemporary Approach” (1976) Saunders
Changes to published procedure
As far as I remember the proportions are about the same as the original.
Since the experiment is beng done in the hood no special venting of the test tube is done.
Summary of Experiment
This is a two step synthesis that is done in a large test tube.
The reaction temperatures are above 200 degrees, so heating is done with a bunsen burner.
There are two filtration steps but the product does not have to be thoroughly dried for either of them. In fact the intermediate and the product are rather pastey.
Once a reasonable amount of gooey yellow precipitate has be made it is reacted with KOH to produce luminscence.
Positive
+ Its a nice end of the year experiment because there is not further analysis of the product beyond observing the chemiluminescence.
+ The techniques are somewhat advanced. Another reason I do this at the end of the 2nd semester.
+ It seems to work well even if the student's technique is somewhat poor.
+ Student usually find the usual properties of luminol intriguing.
Neutral
± It is best if the directions are followed carefully.
± An important thing to know is that some the luminol, DMSO, KOH solutions need to be vigorously shaken to produce a decent glow.
Negative
- It is somewhat dangerous. The combination of test tubes, thermometers, and Bunsen burners are challenging for some students.
- Since the product is not dried, wieghed, and analyzed for purity one is not really sure how well the experiment really did work.
Inquiry & Extension ideas
= More careful attention could be paid to characterizing the product.
= The luminscence can be modulated with dyes.
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