A strange factoid about a zinc supplement

Seeking to calculate the percent by mass of the active ingredient in a tablet of zinc mineral supplement, an interesting fact was discovered. The zinc supplement is manufactured by Jamieson Laboratories of Toronto; the label amount is 10 mg zinc.¹ These supplement tablets are utilized as analytical samples in an EDTA titration laboratory exercise for an introductory analytical chemistry course at Mohawk College.²

The zinc in the tablets is in the form of zinc gluconate. Wikipedia was consulted for the structure and molar mass of gluconic acid and hence of the gluconate anion.³ The article in Wikipedia is short, but an interesting statement and link caught my attention. A solution of zinc gluconate can be used by injection to necrotize the testicles of male dogs, rendering them neutered!!⁴

References

1. Jamieson Zinc 10 mg: http://www.jamiesonvitamins.com/2159.
2. Experiments for term 2 of the 2-year programs for health science, environmental, and biotechnology technicians: http://www.uclmail.net/users/dn.cash/experiments.html.
3. Gluconic acid: https://en.wikipedia.org/wiki/Gluconic_acid.
4. American Journal of Veterinary Research 2008: http://avmajournals.avma.org/doi/abs/10.2460/ajvr.69.1.140