The environmental history of production, and its impact on the United Nations Minamata Convention on . Saul Guerrero, Invited Professor, Universidad Metropolitana, Caracas, Venezuela ([email protected])

Introduction The tragic consequence of the presence of mercury compounds in the waters of Minamata Bay (Japan) on the health of its local population in mid-20c, focused the world’s attention on the global dangers to humans of anthropogenic emissions of mercury and its compounds to the environment. By 2018, 91 countries had ratified the Minamata Convention (2013) sponsored by the United Nations, through its Environmental Program (UNEP). This is a multilateral agreement that seeks, among other aims, to control ‘the anthropogenic releases of mercury throughout its lifecycle’.1 An important part of the work undertaken by environmental scientists in support of this convention, has been the modelling of mercury emissions to the environment, as the sum of natural processes and anthropogenic emissions over time. Mercury is known to persist in the atmosphere for many months, thus contributing to its global dispersion. Historic anthropogenic mercury can be re-issued to the environment over multiple cycles spanning centuries, before it is taken out of circulation within deep ocean sediments or land sinks. The problem lies in that ‘the accumulated burden of legacy anthropogenic Hg [mercury] means that future deposition will increase even if primary anthropogenic emissions are held constant. Aggressive global Hg emission reductions will be necessary just to maintain oceanic Hg concentrations at present levels.’2 It is widely recognized that the main source of this legacy mercury up to the end of the 19c has been the historic of silver and , thus this topic provides a fertile ground for collaboration between historians and environmental scientists. Current scenarios Several studies have been published proposing ranges for historical anthropogenic mercury emissions from silver refining. The majority are based on two assumptions: 1) 60 to 65% was due to direct losses of volatile mercury to the air, the remainder as losses of liquid mercury to the ground or waterways 2) a conflation of historic silver refining with modern artisanal gold production practice, so that ratios of mercury ‘losses’ to refined metal are deemed to be the same for gold and silver.3 Some later models have not made explicit the distinction between historic production of silver using mercury, and the fraction that has been extracted by .4 Others

1 see http://www.mercuryconvention.org. 2 Helen M Amos et al., "Legacy Impacts of All‐time Anthropogenic Emissions on the Global Mercury Cycle," Global Biogeochemical Cycles 27, no. 2 (2013): 410. Legacy mercury is defined as ‘the re-emitted component of anthropogenic Hg’, Helen M. Amos et al., "Observational and Modeling Constraints on Global Anthropogenic Enrichment of Mercury," Environmental Science & Technology 49, no. 7 (2015): 4036. 3 J. Nriagu, "Legacy of Mercury Pollution," Nature 363 (1993): 589; "Mercury Pollution from the Past of Gold and Silver in the ," The Science of the Total Environment 149 (1994): 167-189 . 4 S. Strode, L. Jaeglé, and N.E. Selin, "Impact of Mercury Emissions from Historic Gold and : Global Modeling," Atmospheric Environment 43, no. 12 (2009): 2012-2017; David G Streets et al., "All-time releases of 2 have sidestepped the issue of exactly how much silver was produced using mercury, and based their projections on the estimated amount of mercury used to refine silver.5 In the following sections I will argue that the historical (and chemical) scenario was more complex than current models allow for, and though I will present working figures at an order of magnitude level, to highlight the need for a major review of current models, the more important aim at this stage is to identify those areas where further historical research is required. It will be of great importance for UNEP’s policy decisions on the control of future emissions of anthropogenic mercury, to have a firm knowledge of the historical record on all the processes related to mercury and its use in silver refining.6 Methodology The projections I present of mercury issued to the environment as a result of historic silver production take into account that: 1) only total consumption of mercury, or direct losses to the air of volatile mercury during the heating of the , the casting of silver bars, or the processing of cinnabar (mercury sulphide) to produce the required mercury, are reported in historical sources. The fraction of liquid mercury lost, or the amount of mercury consumed as calomel (mercurous chloride), have to be estimated, based on historical and chemical evidence, since they were never measured during actual operations 2) results are location and period specific, since recipes, processes and equipment went through major changes between the 16c and 19c 3) historical silver refining with mercury and modern artisanal gold refining practice are two quite different historical and technical processes, and there is no theoretical or empirical basis to justify extrapolating values between them 4) the fraction of silver produced by smelting has to be subtracted from total silver production data. Direct air emissions of volatile mercury Operational data measured in the 19c in , of direct losses of mercury to the air during the recycling of mercury from the amalgam, ranged from 0.06 to 0.6%.7 In the U.S.A. ‘when the

mercury to the atmosphere from human activities," Environmental science & technology 45, no. 24 (2011): 104585- 10491; David G Streets et al., "Total mercury released to the environment by human activities," Environmental Science & Technology 51, no. 11 (2017): 5969-5977. 5 Nicola Pirrone et al., "Global Mercury Emissions to the Atmosphere from Anthropogenic and Natural Sources," Atmospheric Chemistry and Physics 10, no. 13 (2010): 5951-5964; Julio A. Camargo, "Contribution of Spanish– American Silver Mines (1570–1820) to the Present High Mercury Concentrations in the Global Environment : A Review," Chemosphere 48 (2002): 51-57. 6 At present there is a debate within the field of environmental science whether the high level of legacy mercury predicted by some models is not consistent with global field measurements of mercury. See for example C.H. Lamborg et al., “Modern and Historic Atmospheric Mercury Fluxes in Both Hemispheres: Global and Regional Mercury Cycling Implications,” Global Biogeochemical Cycles 16, no. 4, 1104; Colin A. Cooke et al., "Over Three Millennia of Mercury Pollution in the Peruvian Andes," Proceedings of the National Academy of Sciences 106, no. 22 (2009): 8830-8834; Daniel R. Engstrom et al., "Atmospheric Hg Emissions from Preindustrial Gold and Silver Extraction in the Americas: A Reevaluation from Lake-Sediment Archives," Environmental Science & Technology 48, no. 12 (2014): 6533-6543; Yanxu Zhang et al., "Six Centuries of Changing Oceanic Mercury," Global Biogeochemical Cycles 28, no. 11 (2014):1251-1261. 7 Saint Clair Duport, De la production des métaux précieux au Mexique, considérée dans ses rapports avec la géologie, la métallurgie et l'économie politique (Paris: Firmin Didot Frères, 1843), 117 ; M.P. Laur, "De la metallurgie de 3 retorting is properly done the loss of quicksilver by distillation is merely nominal. At the about one half a pound of quicksilver is lost per 1,000 pounds of amalgam retorted [less than 0.1% of the mercury in the amalgam]’.8 The heating stage of the amalgam never removed all the mercury, for fear of compromising the long-term physical integrity of the vessels employed, so those percentages had to include the amount of residual mercury left with the silver. Other data indicate a 1 to 2% of weight loss (with respect to silver) during the final casting of silver bars, that was attributed to loss of residual mercury.9 I will apply the highest scenario of the historical data, of an average loss of 5% of volatile mercury, with respect to the weight of silver refined. The chemistry of silver refining with mercury ‘In the of amalgamation a very large amount of quicksilver is converted into calomel and lost’.10 I have argued at length elsewhere on the importance of recognizing the formation of calomel as a major by-product of the chemical reaction between mercury and silver chloride, the last of several chemical stages in the refining process that allowed metallic silver to be extracted from its chemical compounds (halides, sulphides) present in an . I have proposed a simple mathematical model that can explain the narrow range of historical values for the ratio of mercury consumed/silver refined in Hispanic America, on the basis of 85% of mercury consumed (not ‘lost’) by conversion to calomel, and 15% lost by physical pathways (liquid mercury to the soil, or to waterways, and direct volatile losses to the air), for with little native silver.11 Calomel is an insoluble solid, and would have been buried within millions of tons of fine mineral silt, either in landfills close to the refining units, or washed away in waterways close to refining centres. In the patio process it would have functioned as a chemical sink for anthropogenic mercury emissions from silver refining. The pan process utilized in the latter part of the 19c in the U.S.A. introduced a major change in the refining process. It incorporated a very large ratio of iron to mercury consumed (up to 15), compared to ratios of zero to less than unity in the patio process or its precursor in . In addition, the ore was subject to significant attrition in an iron vessel (the pan) and steam, or indirect heat, was applied to the slurry together with the addition of mercury.12 Iron was known since the 16c to l'argent au Mexique," Annales des Mines, 6th series, 20 (1871): 163, 176-177 ; Thomas Egleston, The of Silver, Gold, and Mercury in the (London; New York: J. Wiley & Sons, 1887), 306. 8 C. King, S.F. Emmons, and G.F. Becker, Statistics and Technology of the Precious Metals (Washington: US Government Printing Office, 1885), 267. 9 John Percy, Metallurgy. The Art of Extracting Metals from their Ores. Silver and Gold (London: J. Murray, 1880), 630; Manuel Eissler, The Metallurgy of Silver (London: Crosby Lockwood, 1889), 85. Henry F. Collins, The Metallurgy of & Silver (London: Griffin & Co., 1899), 137, 139. At the Mint, ‘in silver bullion issuing from the mines, the disagreements between dry and humid assays … gave us notice that mercury must be looked for. It is indeed surprising that a metal so volatile should not be utterly driven off by the heat required to melt silver, and yet we have found it to remain after more than one melting… it is present as a residuum from the amalgamating process … [we found] a presence of one-half thousandth to three thousandths of mercury—usually one or two [0.05 to 0.3%]’, as reported in W.E. DuBois, ‘Silver containing Mercury’, in Report to the Director of the Mint (Philadelphia: US Government Printing Office, 1875), 97. 10 King, Emmons, and Becker, Statistics Precious Metals, 265. 11 Saul Guerrero, Silver by Fire, Silver by Mercury. A Chemical History of Silver Refining in and Mexico, 16th to 19th Centuries (Boston: Brill, 2017), 123-143. 12 Eissler, Metallurgy of Silver, 161. In comparison, the iron to mercury ratio used in Potosí in 1602 was less than unity. Guerrero, Silver by Fire, Silver by Mercury, 229. 4 decrease the consumption of mercury, though it did not increase the yield of silver (it does not act on silver sulphides). The former can be explained by a direct reduction of silver chloride by iron, thus decreasing the conversion of mercury into calomel, and a possible parallel reduction of calomel to mercury.13 In the case of the pan process, consumption of mercury has been reported in the range of 1 to 2 lbs of mercury per ton of ore. One published range of silver content of these ores lies between US$35 to US$50 per ton.14 This implies a range of mercury to silver ratios between 0.6 and 1.2, about half of those reported for the patio process, that reflect the large presence of iron in the recipe. Therefore I assume that for the lower ratio (0.6), physical losses dominate the consumption of mercury, and for the higher ratio (1.2) I apply the same breakdown of mercury consumption as for the patio process. Anachronism in science Historic silver refining, with its specific chemistry, industrial scale of operations and innovative equipment and infrastructure, is quite distinct from the rudimentary practices and atomized scale of multiple individual modern artisanal gold refiners, who use mercury to carry out purely physical separations. In the case of gold, there are no chemical reactions involved between mercury and gold in the ores, so any consumption is due to physical losses. These in turn depend on the operational practice of the period, the skill of the refiner, and the sophistication of the equipment used. A comparison of processes will reveal a major regression in operational practice with regards to the handling of mercury, so that modern artisanal practices with gold are much more primitive than the historical refining of silver using mercury. If the chemical context is added, there is no basis to the extrapolation of empirical ratios of mercury to refined artisanal gold, as observed in modern times, to the case study of historical silver refining. Anachronism is always a concern in any historical analysis but is not usually an issue in the sciences.15 However, its occurrence within environmental models can unfortunately invalidate otherwise carefully structured calculations. Mercury emissions from the processing of cinnabar The other major source of anthropogenic mercury, as a result of historic silver refining, is the loss of mercury during the conversion of cinnabar ore to liquid mercury. Up to mid 19c there were three main sources of mercury in the world, two in Europe and one in the Americas: Almadén in southern Spain, Idria in modern day Slovenia, and in modern day Peru. In the second half of the 19c these would be joined by the mercury mines of the U.S.A., mainly in California (New Almaden, New Idria and others). The technology of the process and the control of mercury

13 For the reduction of silver chloride by iron, see Percy, Metallurgy, 94; Eissler, Metallurgy of Silver, 97. The claim for the direct reduction of calomel by iron during the pan process seems to arise from a single source which I have not been able to consult, Clarence King et al., "United States Geological Exploration of the Fortieth Parallel ", ed. U.S. Geological Survey (Washington, D.C.: Government Printing Office, 1870). While the spontaneous reaction is in theory possible (personal communication from Benjamin Scharifker, Universidad Metropolitana, Venezuela), there is no modern corroboration on its extent during the pan refining process. 14 John Arthur Phillips, The Mining and Metallurgy of Gold and Silver (London: E. and F.N. Spon, 1867), 405. Eissler, Metallurgy of Silver, 95. 15 Anachronism is defined as the ‘neglect … of chronological relation’ in The New Encyclopaedia Britannica, 15th edition, Micropaedia Vol. I (Chicago: The Encyclopaedia Britannica, 1992), 364; ‘representation of … something as happening in other than the chronological, proper, or historical order’ in the American Heritage Dictionary of the English Language, 3rd Edition (Boston, New York: Houghton Mifflin Co., 1992), 65. 5 losses to the air varied substantially according to period and location, from the primitive xabecas of early Almadén production to the Spirek furnaces of late 19c Europe. Just as a working figure I have applied a loss factor of 10% of mercury produced for the second half of the 19c, and 20% for all previous historical periods.16 Finally, I assume a simple scenario whereby in colonial times all the mercury consumed in New Spain came from Almadén and Idria, and all the mercury consumed in Upper Peru was furnished by Huancavelica. For the 19c, I assume all mercury consumed in the U.S.A. was supplied from California, which also exported approximately 7 Gg to Mexico and 2 Gg to South America between 1850 and 1890.17 The remaining estimated requirements of Mexico and /Peru I source from Almadén and Idria, and ignore minor production from Huancavelica.18 Historical data sets and mercury to silver ratios Two primary historical data sets are required, the fraction of the total silver produced that was refined using mercury (ignoring for now minor contributions from lixiviation processes), and second, the corresponding amount of mercury used to refine silver, by historical period and location. Neither of the two are at present available concurrently for the whole period where legacy mercury could have been generated (16c to 19c). For many periods one set of primary data is used to project the other, based on assumptions as to the mercury to silver ratio. The deemed mercury to silver ratio for South America and Mexico will be 1.9, consistent with what is known for the patio process. For the U.S.A. I apply a range from 0.6 to 1.2, as explained above.

The global production of silver according to refining process, 1493 to 1895 Europe Up to the end of the 15c, Europe accounted for most of the global production of silver, and the only refining process used was smelting from ores that also contained lead or .19 Refining

16 Operational losses as low as 5% have been measured in Italian mercury production for late 19c, as reported in Vincente Spirek, "The Quickilver in Italy " in The Mineral Industry, ed. Richard P. Rothwell (New York and London: The Scientific Publishing Co., 1898), 570. 17 David J. St. Clair, 2016. "New Almaden and California Quicksilver in the 19th Century World Economy." Paper presented at From Underground to End-Users: Global Monetary History in Scientific Context, San Francisco, May 16, 2016, Table 3 and Table 5. The data does not cover the period 1890 to 1895, when another 6 Gg of mercury were produced according to S.M. Cargill, D.H. Root, and E.H. Bailey, "Resource Estimation from Historical Data: Mercury, A Test Case," Mathematical Geology 12, no. 5 (1980): 495. Though Nriagu reports that imports of mercury to the U.S.A. from 1870 to 1893 averaged 0.075 Gg per year, he does not provide the source of his data. Nriagu, “Mercury Pollution”: 177. Since California in that period was exporting an important part of its production, at times over half (see St. Clair cited above), the role of imports, and their final use, needs to be clarified. For now I have not included imports of mercury to the U.S.A., since according to Nriagu they represented around 5% of total California production from 1850 to 1900. 1 Gg = 1,000 tons. 18 José R. Deustua, "Mercury (not always rising) and the social economy of nineteenth-century Peru," Economía 33, no. 66 (2010): 128-153. 19 Adolf Soetbeer, Edelmetall-produktion und werthverhältniss zwischen gold und silber seit der entdeckung Amerika's bis zur gegenwart (Gotha J. Perthes, 1879); J.U. Nef, "Silver Production in , 1450-1618," The Journal of Political Economy (1941): 575-591; Ian Blanchard, Mining, Metallurgy and Minting in the Middle Ages. Continuing Afro-American Supremacy 1250-1450. Vol. 3 (Munich: Franz Steiner Verlag Stuttgart, 2005). 6 of silver ores with mercury had been patented by two Venetian refiners in 1507, but would always remain a method of little relevance in Europe.20 Smelting of ores would predominate, even if mercury was used at a few locations (for example Freiberg in Germany and Hiendelaencina in Spain). Thus, for the current exercise all the silver produced in Europe will not be considered as a relevant source of pre-20c anthropogenic mercury. Russia From 1816 to 1895, a total production of 1.8 Gg has been reported.21 In the absence of information on refining methods, I assume that this production was based on smelting. Japan Silver production from Japanese mines is claimed, as ‘a bold conjecture’, to have reached yearly averages of 0.2 Gg/y, in the order of magnitude of the output from Potosí, at the beginning of the 17c.22 In Japan, major silver ore deposits were of the same nature as those found in the New World (silver sulphide ores), and would have responded equally well to the use of mercury for refining them, thus lowering the environmental impact of having to source charcoal and lead for smelting. The absence of major mercury sources may explain why smelting was the only method reported as used, even though Jesuits provided information on the use of mercury for refining such lead- free ores.23 Thus Japan is also excluded as a source of legacy mercury. The Hispanic New World, 16c to early 19c The widespread use of mercury to extract silver from silver sulphide ores would take place only on the American continent, first in New Spain and then in Upper Peru. The colonial sources of data on silver production and mercury sales in New Spain have been used in a previous study to estimate the overall split between smelting and the use of mercury, in the period from the 16c to the first decade of the 19c. These indicate that on average approximately two-thirds of total silver was refined with mercury, and one-third via smelting, based on primary tax records of silver registered and mercury sold.24 For Upper Peru I have no such detailed breakdown of silver production by refining process, though total production figures have been published. I will assume that in Upper Peru mercury was used to refine 80% of all its silver. Other colonial silver sources in the New World contributed to less than 1% of the total silver produced, so will be ignored.25

20 Raffaello Vergani, "La métallurgie des non-ferreux dans la république du Venise (XVe-XVIIIe siècles)," in Mines et métallurgie, ed. Paul Benoit (Villeurbanne: Programme Rhône-Alpes recherches en sciences humaines, 1994), 209. 21 Depeyrot, Imperialism and Gold Standard (1870-1900). Transfers of Precious Metals and Globalisation. II, Documents and Studies on 19th c. Monetary History (Wetteren: MONETA, 2015), 132-134. 22 Atsushi Kobata, "The Production and Uses of Gold and Silver in Sixteenth- and Seventeenth-Century Japan," The Economic History Review 18, no. 2 (1965): 248. 23 See discussion in Guerrero, Silver by Fire, Silver by Mercury, 144-146. 24 Based on ibid., 335. 25 John Jay TePaske and Kendall W. Brown, A New World of Gold and Silver (Leiden, Netherlands; Boston: Brill, 2010), 78, 113. 7

Mexico and Peru/Bolivia, 19c In the case of Mexico, limited official data from the last years of the nineteenth century point to 80% of its silver refined by mercury. Since I have no primary data on mercury consumption, I will use the historical mercury to silver ratio observed in New Spain (1.9) to estimate a total amount of mercury used to refine silver. For Peru/Bolivia I will also assume that 80% of total silver production was refined using mercury, with a mercury to silver ratio of 1.9.26 The United States of America The first information in government data on silver production classified by refining process appears for the year 1885, when it is reported that nearly 50% (by weight) of silver produced in Utah was smelted, 95% in , and 41% in Montana.27 In 1892 smelting accounted for 54% of the total silver produced that year in the U.S.A.28 Though refining by mercury had dominated production in the boom years of Nevada, from 1880 onwards the decline in the output from Nevada was overtaken by the increase in production from smelting regions such as Colorado. By 1885 the author of the Census report on production in the United States confirms that ‘smelting [is] acquiring a relatively more important place that it formerly held’.29 Because the nature of the silver ore deposits being mined in each State could and did vary over time, the extrapolation of the ratio of smelting to mercury refining from the data of a single year can lead to major distortions. For the present exercise I carried out a preliminary tracking of production, subject to a future detailed revision, in those counties with a known smelting output, for the following States where smelting played an important role in silver production: Colorado, , Montana, Nevada and Utah.30 Order-of-magnitude mercury emissions from the refining of silver ores, 16c to 19c Table I summarizes an order of magnitude of the three main types of mercury issued in the Americas to the environment from the silver refining stage, from the end of the 16c to the end of the 19c. The year 1895 has been chosen as the end date, since by that time the cyanide process was displacing the use of mercury, and the estimation of production according to refining methods becomes even more uncertain. In the absence of a complete set of data from primary sources regarding the amount and sources of mercury destined for silver refining, most of the data in Table II is derived from the estimates of silver produced using mercury. It then projects an order of magnitude of direct emissions of

26 I have used the 19c silver production data for Bolivia and Peru as reported from various sources in Georges Depeyrot, Transfers of Precious Metals, 54,55,119-122. For Mexico’s production in the 19c see ibid. 107,108 for the period 1831-1895, and also Guerrero, Silver by Fire, Silver by Mercury, 318-320 for other data. 27 King, Emmons, and Becker, Statistics Precious Metals, 316,335,340. 28 Report of the Director of the Mint upon the Production of Precious Metals in the United States during the Calendar year 1892, ed. U.S. Mint (Washington: Government Printing Office,1893), 17. 29 Statistics Precious Metals, xii. 30 Data on yearly production, from 1851 to 1895, from Report of the Director of the Mint upon the Production of Precious Metals in the United States during the Calendar Year 1900, ed. U.S. Mint (Washington: Government Printing Offfice, 1901), 322. These reports were used to approximately track the production by certain counties between 1865 to 1895. 8 volatile mercury to the air, as a consequence of the heating of cinnabar ores to produce mercury destined for silver refining. Losses of liquid mercury during transit are not included. I will defer a cross-check between this initial order-of-magnitude estimate and reports on global mercury production until I complete a similar exercise for the estimation of anthropogenic emissions from historic gold refining within the same historical period.31 Legacy mercury from historical silver refining. The main conclusions are as follows: 1. The main source of direct emissions to the air of mercury took place during the production of mercury required for silver production, from cinnabar. 26 Gg are projected from 1590 to 1850, and 8 Gg in the second half of the 19c. 2. Approximately 11 Gg of direct volatile emissions of mercury from silver refining and cinnabar processing are projected between 1850 and 1895, divided evenly between sites in Europe and in the Americas. The majority of total direct air emissions of mercury from cinnabar processing and silver refining would have taken place prior to 1850 (29 Gg), also evenly distributed between Europe and the Americas. It is one of the rare examples, if not a unique one, in the environmental history of the Early Modern Period where for more than two centuries the European core suffered an equivalent level of direct volatile emissions of a heavy metal as the colonial periphery, during production of a colonial commodity. 3. All the available historical evidence points to very low values of measured direct losses of volatile mercury from the refining stage of silver production. 3 Gg of direct volatile mercury emissions from silver refining are projected between 1590 and 1850, and 3 Gg in the second half of the 19c. Overall 6 Gg, compared to 34 Gg from cinnabar processing over the whole period. I have not come across any historical reports of measurements of direct losses to the air of 60 to 85% of mercury consumed during the refining of silver ores. 4. The mercury content in calomel constitutes the main anthropogenic emission from the refining stage with mercury of historic silver production using the patio process The balance between calomel production and liquid losses at very low mercury to silver ratios requires further research into the pan process used in the U.S.A. For both refining processes direct losses of volatile mercury to the air were not a major source of legacy mercury. The preliminary results presented in this paper highlight the pitfalls that need to be avoided in the accounting of historic mercury emissions from all activities related to silver refining. Further research is required on the global accounting of silver production according to refining method, and on mercury production destined for silver production, along the lines set out in the presentation by Dennis Flynn (“Inventory Demand and Global Silver Quantification”). Primary historical operational information on the loss of mercury during the processing of cinnabar is also necessary to establish credible ranges of direct losses of mercury to the air. As observed in Tables I and II, the production of mercury from cinnabar plays as significant a role in the level of legacy mercury as the refining stage of silver, so more details are needed on how the evolution in the industrial

31 Since gold was at times the co-product of silver refining with mercury, any estimate of the historical consumption of mercury for gold refining must avoid the error of double counting. 9 infrastructure affected the historical levels of mercury emissions over time. The ultimate aim of this line of research is to provide better data, solidly grounded in historical evidence, to environmental scientists, and ultimately UNEP, for their models on the modern environmental impact of anthropogenic mercury. Beyond the field of history, more information is also needed on the chemical reactions taking place during the pan process, along the lines of the laboratory study undertaken for the patio process.32 The calomel life-cycle in the environment has to be established, to see if it functioned as a long- term chemical sink for anthropogenic mercury, or simply delayed a new cycle of release of legacy mercury. The fate of liquid mercury spilled or leaked to the ground around refining sites and cinnabar processing facilities becomes more relevant, both on the basis of historical anecdotal reports, and because of its order of magnitude in these projections. An inventory of the historical evolution in the heights of chimneys where volatile mercury was vented during the processing of cinnabar is also needed, to determine the ground deposition footprint around these sources of anthropogenic mercury, and their influence on its ultimate global dispersal.

Acknowledgements The author wishes to acknowledge financial assistance provided by Patrick Manning, University of Pittsburgh, and the Pacific World History Institute (Dennis O. Flynn, Director) that made possible attendance at the World Economic History Congress, Boston, 2018. The author at present is an independent scholar. Part of this research was carried out while he was Visiting Professor at the Universidad Metropolitana, Caracas, Venezuela (calendar year 2017).

32 D.A. Johnson and K. Whittle, "The Chemistry of the Hispanic-American Amalgamation Process," J. Chem. Soc., Dalton Trans., no. 23 (1999). 10

1590-1850 1850-1895 1590-1895 silver Hg emissions silver Hg emissions silver Hg emissions Hg Hg Hg in in total by Hg consumed liquid to air total by Hg consumed liquid to air total by Hg consumed in calomel liquid to air calomel calomel New Spain 56 39 73 60 11 2 31 25 47 40 6 1 88 64 120 100 17 3 Mexico USA 0 0 0 0 0 0 33 22 13 to 26 <22 <12 1 33 22 13 to 26 < 22 < 12 1

North 56 39 73 60 11 2 64 47 60 to 73 < 62 < 18 2 121 86 133 to 146 < 122 < 29 4 America

Peru 38 30 58 49 7 2 6 5 9 8 1 0 44 35 67 57 8 2 Bolivia

South 38 30 58 49 7 2 6 5 9 8 1 0 44 35 67 57 8 2 America

Total 94 69 131 109 18 3 70 52 69 to 82 < 70 < 19 3 164 121 200 to 213 < 179 < 37 6

Table I. Order of magnitude for global mercury emissions, 16c to 19c, in Gg, as a result of silver production, refining stage. Due to rounding off to whole numbers only, values may not add up as expected. For the methodology applied see text.

1590-1850 1850-1895 1590-1895

Hg consumed Hg produced Hg volatile loss Hg consumed Hg produced Hg volatile loss Hg consumed Hg volatile loss Hg produced for during silver for silver from cinnabar during silver for silver from cinnabar during silver from cinnabar silver refining refining refining process refining refining process refining process

New Spain 73 0 0 47 0 0 120 0 0 Mexico

USA 0 0 0 13 to 26 22 to 35 3 13 to 26 22 to 35 3

North 73 0 0 60 to 73 22 to 35 3 133 to 146 22 to 35 3 America

Peru 58 58 12 9 0 0 67 58 12 Bolivia

South 58 58 12 9 0 0 67 58 12 America

Almaden/I 0 73 15 0 47 5 0 120 20 dria

Europe 0 73 15 0 47 5 0 120 20

Total 131 131 26 69 to 82 69 to 82 8 200 to 213 200 to 213 34

Table II. Estimated legacy Hg from processing of cinnabar ore to supply the needs of the silver refining industry, in Gg. Due to rounding off to whole numbers only, values may not add up as expected. For the methodology applied see text.