The Colorful (and Dangerous?) History of Show Globes
Many hypotheses swirl around the origins of the pharmacist’s show globe, (see this amazing online exhibit from the Waring Historical Library), but by the late 19th century, these spherical glass containers functioned more as traditional signage. Just as barber poles, the colorful globes alerted people walking by about the goods and services inside. According to American Druggist and Pharmaceutical Record, “bold, indeed, and reckless would be the druggist who should discard the colored show globe, and not one of you can name druggists who can tell why they have them except for the single reason that others do.” 
Indeed, a great number of pharmacy journals instructed shop keepers about how to best arrange their front windows to draw business from the street. The centerpiece of these windows remained the show globe — typically filled with bright colored liquids, arranged with a light source and a mirror. At night this set up resulted in a beautiful tinted glow apparently coming from the orbs. During the day, some pharmacists found such designs too dangerous, as sunlight shining off the cut glass and beveled mirrors occasionally set nearby products ablaze [2, 3].
If you’ve ever seen a show globe, maybe while strolling through a museum or antique store, you might have wondered at the concoctions once held inside. Museums today use inert dyes in water to create bright, clear colors meant to fill the large globes. In the 19th century, chemists mixed solutions in a of variety shades by following published formulae . This meant the liquids could react with external factors like light and heat – possibly resulting in faded colors, chemical precipitates, or even explosions .
Show Globe Chemistry!
What were these formulae like? The Era Formulary (1893) contains over 50 ways to create a rainbow of show globes and provides a glimpse at the mix of ingredients on hand inside 19th century pharmacies. Let’s look at the chemistry behind some of these colorful reactions.
Bichromate of potash, or potassium bichromate (K2Cr2O7) was used to make a number of warm-toned shades . When dissolved in water, the molecule dissociates and establishes an equilibrium of Cr2O7-2 (orange) + H2O to 2CrO4– (yellow) + 2H+, which maintains an intermediate golden hue. Adding the sulfuric acid shifts the equilibrium by adding more H+ ions, resulting in a greater number of Cr2O7-2 ions and a deeper orange color. (Check out these videos from Chem Toddler for more information)
The above formula calls for dissolving both copper and nickel coins (obviously when U.S. currency was still mostly composed of those metals). When dissolving the coins in a strong acid, the copper and nickel ions coordinate with the nitrate groups of the acid and nitrogen dioxide, a poisonous brown gas, is released. Although the nickel and copper nitrate mixture is at first a dark brownish green, diluting the solution completely changes the configuration ions and results in a new color. Copper nitrate alone would result in a blue liquid; nickel nitrate would be deep green. When mixed together, these compounds create more of an emerald shade. (To see the color change, watch this video from the Royal Society of Chemistry)
This last formula used a similar process of dissolving cobalt in nitric acid to form cobalt nitrate, but the addition of ammonia and alum (KAlSO4) without information about concentrations makes guessing at the final outcome a little more challenging. After doing some calculations and brushing up on my chemistry, one possible explanation would be that blood red appearance is due to the production of two isomers with some fairly unruly chemical formulae and ever worse names: [Co(NH3)5NO3]SO4, which produce red-violet ions and [Co(NH3)5SO4]NO3, which produce red ions. Together these isomers create a deep ruby hue.
Whether sitting in a bright window or kept safely in the shade, the colors created by such formulae were still prone to fading and required periodic refreshing. Although the meanings of the colors are still debated, their creation and maintenance testified to the skill of the chemists working inside.
About the Author:
Catherine Osborn, BA, BS, is a graduate student in Medical Anthropology at Case Western Reserve University, the Editorial Associate at Culture, Medicine and Psychiatry, as well as a Research Assistant at the Dittrick Museum of Medical History. She enjoys pursuing historical tangents and proving she can find almost any source online.
 “Old Fogey Ways of Druggists.” 1885. American Druggist and Pharmaceutical Record vol. 27. America Druggist Publishing Company.
 “Jersey Jettings.” 1898. The Druggists’ Circular and Chemical Gazette vol 43. Oil, Paint and Drug Publishing Company, Incorporated.
 “Fires from Show Bottles.” 1888. The Druggists’ Circular and Chemical Gazette vol 32. Oil, Paint and Drug Publishing Company, Incorporated.
 “Show Globe Colors.” 1893. The Era Formulary: 5000 Formulas for Druggists. D.O. Haynes and Company.
 Fink, Leon C. 1892. “One Thousand Practical Hints for Dispensing Pharmacists.” The Bulletin of Pharmacy vol. 6: 101-107.