The 500mg PABA tablets metwurst had were determined to average 700mg each, and since metwurst is still several weeks away from aquiring equipment and consumables for TLC, he decided some bucket chemistry was in order.
35g of PABA tablets were added to 250mL 95% ethanol, and stirring was commenced.
When the pills were broken up entirely after about 30 minutes, the mixture was vacuum filtered yielding a clear yellow ethanolic solution of PABA and whatever component of the filler, if any, dissolved in the alcohol.
25mL conc. sulfuric was added and the mixture was refluxed for 75 minutes.
The resultant acidic yellow-brown mixture was taken to about pH 8 with sodium bicarbonate solution, which turned the mixture to a light beige color, and some precipitate was evident.
600mL of water was added causing immense precipitation.
This white precipitate was vacuum filtered and washed with water.
The mildly damp precipitate weighed 27.4g, and is still drying.
In the absence of any proper diagnostic equipment, and having read on the applications and dosage of benzocaine in medicine, a small amount (about two poppy seeds in size) was applied to the tip of the tongue. Mild anaesthesia of the tongue tip resulted, and from the taste, perhaps a tiny quantity of PABA is left. 100mg was smeared on a one inch square section of skin. Blunting of the pain response resulted within ten minutes, and lasted perceptibly for about 35 minutes.
Anaesthetic throat lozenges routinely contain 6.5mg of benzocaine.
If doing this, you might wish to test that you are not sensitive to benzocaine, as some people experience an irritation of the skin when benzocaine is applied. metwurst's only known chemical sensitivity is to a particular antibiotic agent, which might explain some of his nonchalance with regards to taste testing the product of this esterification.
This stuff obviously needs to be cleaned up properly, and metwurst would like to know how pure the product was to start with. More fun.