In 1848, Sir William Burnett (1779-1861), Surgeon and Director-General of the Royal Navy’s Medical Department, developed, patented, and marketed zinc chloride (zincane or ZnCl2) as a disinfecting agent (Anon., G. T. Bettany, C. Penn). This compound had been synthesized in 1812 by John Davy, M.D. (1790-1868), brother of the chemist, Sir Humphry Davy (1778-1829) (H. Davy 214; J. Davy, "An Account," 185-6, 201). Burnett was granted a patent for its manufacture on the ground that the compound had routinely demonstrated its worth as a preservative of timber, canvas, cordage, cotton, wool and other articles, all of which were subject to rot, mildew, and insect damage ("Sir William Burnett’s Disinfecting Fluid"). The chloride solution was, foremost, a deodorizer of sick-rooms, clothing, linen, drains, cesspools, bilge-water, stables, ship’s-holds, kennels, sewers, and other locations; and, because it preserved, anatomical specimens, it was widely employed in natural history museums and for anatomical instruction ("Reports & Testimonials," 1-13; Bryson 61).
Sir William Burnett. Henry Cousin’s engraving of the painting by Martin Archer Shee.
Courtesy Wellcome Library, London. Click on image to enlarge it.
When compared empirically to similar agents, ZnCl2 seemed to have extraordinary properties. Without reliable disinfectants and deodorizers, many thought zinc chloride to be a panacea, shipboard testimonials even describing it as "magical" in the way it eliminated bilge odors, seemed to attenuate outbreaks in cramped areas below deck and to resolve cutaneous infections ("Reports & Testimonials,"" 12, 67). It took more than 50 years of experimentation, however, for medical scientists to determine that the chloride’s disinfectant and antiseptic properties were overrated: it was found, not only to be a source of accidental poisoning, but to have negligible antiseptic properties. These caveats notwithstanding, it remained in the Victorian pharmacopoeia for use as an escharotic paste against breast and skin cancers throughout the Victorian period.
Practicing medicine before the germ theory and antiseptic system had been firmly established, Burnett had only a limited understanding of disease etiology. In a letter of 20 May 1848, while Director-General of the Medical Department of the Navy, he addressed the Secretary of the Admiralty on how ZnCl2 could destroy "personal Miasmata" and interrupt the spread of contagious disease ("Reports & Testimonials," 30). Burnett assumed, incorrectly, that chloride’s ability to neutralize noxious gases meant that it had eradicated the source of disease (30). Equating the odor with the pathogen was a logical inference since the regnant theory was that contagious disease was communicated via polluted air (M. Susser & E. Susser 668-69). A variant of the gas theory of disease held that ammonia, a compound of nitrogen and hydrogen (NH3), and a constituent of swamp gas and decomposing matter, was itself a pathogenic agent. The precise nature of the "æriform substance" or disease-causing agent remained nebulous ("miasma," OED. II, 1786). The German chemist, Justus Liebig (1803-1873), was convinced that ammonia was responsible for infectious disease since it was a component of putrescent gas and was detectable where "diseased patients lie" (Liebig 408-09).
Even though Liebig realized that certain chemical agents were toxic, he did not proscribe the use of zinc chloride because it seemed to be effective and safe (409). Dr. Robley Dunglison (1798-1869), author of the encyclopedic, General Therapeutics and Materia Medica (1846), endorsed it, unequivocally, as a means of sterilizing the "morbific properties" of effluvia (370). While Dunglison tentatively embraced the miasmatic theory, he also acknowledged that the medical community was "entirely unaware of the precise character of the tertium quid [ i.e., unclassified substance]" (370). On the other hand, Burnett was more confident: "there is every reason to believe" that these odors were both "the direct source" and cause of disease; the chloride was therefore considered to be a disinfectant ("Reports & Testimonials," 31). Since "a specific contagion" had never been isolated, Burnett envisioned the disease-causing agent as being either molecular or particulate; thus, for a time, Liebig’s ammonia hypothesis was considered plausible (32).
Testimonials which Burnett published reveal that zinc chloride’s effects impressed naval personnel and physicians alike. Among Royal Navy surgeons, the empirical consensus portrayed zincane as a multi-purpose product: a deodorizer and disinfectant of bilge-water and ship’s-holds, an inhibitor of dry rot, and, according to the testimony of anatomists, a cadaver preservative (Anon.; "Dry Rot," 315; "Reports & Testimonials," 11-14; K. M. Gregersen). The testimonials reveal occasional patterns of inductive inference that warranted investigation into the cause-effect relation between the chloride, putrefaction, and human disease. Observations compiled on board stricken ships and in hospital wards led highly-regarded Royal Navy surgeons to suspect that a cause-and-effect relation between the ZnCl2 and contagious disease existed. Several reports are reviewed below.
Over a two-year period, Dr. John Allen supported the idea that zinc chloride had medical benefits. In correspondence of 30 September 1847, he reported to Burnett on a several-month-long hospital trial of nitrate of silver (AgN3) and ZnCl2 at the Royal Naval Hospital at Haslar, both compounds having been used for skin infections since 1819. Dr. Allan’s patients also benefited. Ulcers, syphilitic sores, and erysipelas infections of patients whose rooms had been fumigated and whose lesions had been topically treated were reported as having improved significantly. To some a cure-all, zinc chloride had been routinely applied as a disinfectant lotion and injected into gonorrhea patients ("Reports & Testimonials," 23). In a letter of 7 October, Dr. Allan described the outcome of testing the topical efficacy of AgNO3 against ZnCl2: those to whom the chloride had been administered had the better results, while silver nitrate’s severe toxicity and corrosiveness outweighed its disinfectant properties. In 1848, Dr. Allan contributed a medical report to Burnett’s compendium of letters. Written on the H.M.S. Juno, from 1 October 1848 to 4 February 1849, the correspondence attributed the cures of 111 of 114 cases of infectious disease, along with the suppression of outbreaks, to zinc chloride, employed as a disinfectant in the holds. Consistent with miasmatic theory, Allan attributed the improvement in health to "the deodorizing and disinfecting properties of this agent" ("Reports & Testimonials," 41).
Thomas Stratton, M.D., Royal Navy Surgeon, summarized what was known about zinc chloride up to 1848. He listed its proven benefits as: (1) an "antiseptic" useful for the preservation of dead bodies in anatomy classes or in mortuary science (the term "antiseptic" is used because the chloride reduced the danger of septic disease from a cut during dissection); (2) as a deodorizer of putrefying organic substances; and (3) as a disinfectant in hospital wards (Stratton 6). Where typhus and dysentery were present, the hospital wards became malodorous. To eliminate the odor and presumably the infectious agent as well, flannel cloths soaked with diluted chloride were circulated (1:40, zincane-to-water per fluid ounce); this was done two or three times daily to fumigate the rooms; the solution was also sprinkled on the floors and poured into lavatory receptacles overnight; in addition, dysentery patients were sponged down with the fluid. The odor would disappear by the next morning, suggesting that the unknown source of infection had been destroyed with 1:40 strength (zincane to water) of Burnett’ solution per fluid ounce.
Laboratory testing of disinfectants and antiseptics, and efforts to distinguish agents such as zinc chloride from mere deodorizers, intensified in the mid-1880s. The consensus was that, for an agent to qualify as "a true disinfectant," it had to destroy "all living micro-organisms and their spores," and not merely check their growth (Koch 494-95). In 1885, United States Army physician and bacteriologist, Dr. George M. Sternberg (1838-1915) and colleagues defined a disinfectant as a substance that prevents "the extension of infectious diseases by destroying the specific infectious material which gives rise to them"; and he stressed the important distinction between these substances and deodorizers, chemical agents that destroy or mask bad odors (Sternberg, et al. 3). In 1886, after assessing the disinfectant properties of zinc chloride in watery solution, the physician and microbiologist, Robert Koch (1843-1910), on the basis of three experimental findings, reported that the chloride was "practically worthless" (508). His experiments yielded unexpected results: 1.0% of watery solution could thin out, but not destroy, a colony of Micrococcus prodigiosus over a 48-hour period; a 5.0% watery solution of the chloride was entirely ineffective against anthrax spores; and a 0.5% failed to retard anthrax spores from developing in blood serum (508). Koch concluded that the three principal disinfectants (carbolic acid, sulfuric acid and zinc chloride) proved unreliable (Crace-Calvert 687; Koch 508).
In 1905, the results of large-scale experiments of the chloride as an antimicrobial diminished its long-held reputation as a panacea. Dr. Thomas B. McClintic (1873-1912), formerly Assistant Surgeon of the U.S. Public Health and Marine-Hospital service, explains the sanitarian fallacy that deodorization necessarily destroyed pathogenic microbes. "A substance," he writes, "may have practically no germicidal properties, but if it has the power to mask or destroy odors arising from matter undergoing decay many persons will class it as a disinfectant" (McClintic 5). The error of equating chemical deodorization with disinfection, moreover, often produced "unfortunate consequences in handling and disposing of infected material" (McClintic 5). Extensive investigations had demonstrated that zinc chloride was, indeed, a "deodorant" that combined with hydrogen sulfide, ammonia, and other putrefactive gases, to form odorless compounds (11). Its deodorizing property, McClintic points out, "is more or less responsible for its historical reputation as a disinfectant" (11).
As for zinc chloride’s antiseptic powers, laboratory experiments revealed that, at best, it was a low-level antimicrobial. Against mold, a 1:40 chloride-to-water proportion unremarkably inhibited growth for 14 days. Although it inhibited bacterial growth in sewage in the 1:500-to-1:200 diluent range, it was classed as an unreliable antimicrobial. Several experiments supported this conclusion: 60-minute exposure to a 5.0% solution did not kill B. coli communis, whereas 10-minute exposure to a 25% solution did; Staphylococcus pyogenes aureas was destroyed by a 25% solution in 30 minutes; and anthrax spores were virtually impervious to it, having survived in a 50% solution of ZnCl2 for 40 days (McClintic 24). On the basis of these results, McClintic called zinc chloride "feeble." Despite McClintic’s 1905 devaluation of zinc chloride’s antimicrobial properties, the paste compound remained popular in allopathic practice throughout the late-Victorian period for the treatment of breast and cutaneous cancers.
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Last modified 19 January 2017