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 ICJ 8921 
 
 Bureau of Mines Information Circular/1983 
 
 Methods for Determining Sources 
 of Mercury Vapor in the Workplace 
 
 By D. L. Neylan, H. C. Triantafillou, and S. L. Law 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 

Information Circular 8921 
 
 Methods for Determining Sources 
 of Mercury Vapor in the Workplace 
 
 By D. L. Neylan, H. C. Triantafillou, and S. L. Law 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 James G. Watt, Secretary 
 
 BUREAU OF MINES 
 Robert C. Horton, Director 
 
Mi 
 
 This publication has been cataloged as follows: 
 
 Neylan, D. L, (David L.) 
 
 Methods for determining sources c 
 
 (Information circular / United Sta 
 reau of Mines ; 8921) 
 
 Bibliography: p. 15 . , 
 
 Supt. of Docs, no.: I 28.27:8921. 
 
 1. Air pollution— Measurement. 2. 
 dustries — Environmental aspects. I. 
 II. Law, Stephen L. III. Title. IV. S< 
 States. Bureau of Mines) ; 8921. 
 
 f mercury vapor in the workplace. 
 :es Department of the Interior, Bu- 
 
 Mercury — Analysis. 3. Mineral in- 
 
 Triantafillou, H. C. (Heidi C). 
 
 ;ries: Information circular (United 
 
 622s [622\8] 82-600371 
 
 HNzytJ.U4 L 1 JJoo (Jvloi J 
 
Or 
 
 
 ft. 
 
 CONTENTS 
 
 Page 
 
 Abstract 1 
 
 Introduction 1 
 
 Chemical spot tests 2 
 
 Sensitivity 7 
 
 Reagent shelf life 7 
 
 Spot test techniques 8 
 
 Selected spot tests 9 
 
 Mercury vapor test papers 10 
 
 Portable mercury vapor detectors 11 
 
 Portable analytical Instruments 13 
 
 Conclusions 14 
 
 References 15 
 
 ILLUSTRATION 
 
 1. Gold-film analyzer for locating sources of mercury vapor 12 
 
 TABLES 
 
 1 . Reagents for mercury detection 2 
 
 2. Portable mercury vapor detection devices 11 
 
 3. Portable analytical instruments 13 
 
 *0 
 
UNIT 
 
 OF MEASURE ABBREVIATIONS 
 
 USED IN 
 
 THIS REPORT 
 
 cm 
 
 centimeter 
 
 mg/m 3 
 
 milligram per 
 cubic meter 
 
 g 
 
 gram 
 
 
 
 
 
 mm 
 
 millimeter 
 
 m3 
 
 cubic meter 
 
 
 
 
 
 nm 
 
 nanometer 
 
 mg 
 
 milligram 
 
 
 
 
 
 Mg 
 
 microgram 
 
 mL 
 
 milliliter 
 
 
 
 
 
 M L 
 
 microliter 
 
METHODS FOR DETERMINING SOURCES OF MERCURY VAPOR IN THE WORKPLACE 
 
 By D. L. Neylan, 1 H. C. Triantafillou, 2 and S. L. Law 3 
 
 ABSTRACT 
 
 The Bureau of Mines evaluated various methods for identifying sources 
 of mercury vapor in excess of the threshold limit value (TLV) of 0.05 mg 
 of mercury per cubic meter of air set by the American Council of Govern- 
 ment and Industrial Hygienists (ACGIH) for mines and mineral processing 
 plants. Chemical spot tests and portable devices for mercury determina- 
 tion were evaluated, based on information from published sources and 
 performance in laboratory tests. Among the parameters examined were 
 sensitivity, interferences, cost, ease of use, and other factors perti- 
 nent to field application. More than 50 methods were evaluated. 
 
 The investigators found that many readily available methods are suita- 
 ble for identifying sources of mercury vapor in mines and mineral pro- 
 cessing plants. The best method appears to be one that uses a commer- 
 cially available mercury test paper sensitive only to mercuric ions. 
 
 For some of the more promising chemical spot tests, this report in- 
 cludes step-by-step instructions for field application. 
 
 INTRODUCTION 
 
 In order to enable the mining and mineral processing industry to com- 
 ply with Federal regulations and to ensure workers' health, portable 
 methods are needed for the on-site identification of sources of mercury 
 vapor. In this report, many such methods are evaluated. 
 
 Although the TLV for mercury vapor in mines and mineral processing 
 plants is set by ACGIH, Part 30 of the Code of Federal Regulations as- 
 signs enforcement of this limit to the Mine Safety and Health Adminis- 
 tration (MSHA). At MSHA's request, the Bureau undertook the evaluation 
 of chemical spot tests and instrumental methods for mercury determina- 
 tion described in this report. A commercially available mercury test 
 paper evaluated by the Bureau as the best indicator for mercury is cur- 
 rently under study by MSHA for possible routine use in mine and mineral 
 processing plant inspections. 
 
 i Research chemist. 
 ^Chemist. 
 
 3 Research supervisor. 
 All authors are with the Bureau of Mines, Avondale Research Center, Avondale, Md. 
 
CHEMICAL SPOT TESTS 
 
 Spot tests are portable, provide on- 
 site results, and are less expensive than 
 other qualitative methods for determining 
 the presence of metal ions. Because spot 
 tests offer these advantages, the Bureau 
 evaluated more than 50 spot test reagents 
 to determine their suitability for iden- 
 tifying sources of mercury vapor in mines 
 and mineral processing plants. These re- 
 agents are listed in table 1. For each 
 reagent, the table lists the positive re- 
 sults observed when mercury is present, 
 sensitivities, and interferences. 
 
 Generally, chemical reagents will not 
 react directly with mercury or undis- 
 solved minerals containing mercury. 
 Therefore, dissolution of some of the 
 mercury-containing material with an ap- 
 propriate acid is usually the first step 
 in a chemical spot test. To achieve the 
 desired test reaction, it may also be 
 necessary to further adjust the dissolved 
 
 mercury to the mercuric or mercurous va- 
 lence state, adjust the acidity of the 
 mercury and acid solution, or take other 
 steps. The references in the last column 
 of table 1 provide the guidance needed to 
 perform spot tests using each of the 
 listed reagents, and for some of the re- 
 agents an additional source of informa- 
 tion is cited. 
 
 Table 1 does not list all the reported 
 chemical methods for detecting mercury; 
 only those for which sensitivities could 
 be found are listed. Additional tests 
 are mentioned by Feigl (2^,4 Welcher (11- 
 14), and others. However, most, if not 
 all, of the tests in popular use are sum- 
 marized in table 1. 
 
 ^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this report. 
 
 TABLE 1. - Reagents for mercury detection 
 
 Reagent ' 
 
 Reaction indica- 
 tive of mercury 
 
 Sensitivity, 
 Ug Hg 
 
 Comments 
 
 Refer- 
 ences 2 
 
 ORGANIC REAGENTS 
 
 Acridine thiocyanate 3 . 
 
 Yellow needles .... 
 
 0.5 
 
 Yellow crystals also 
 formed by Bi, Cd, 
 U, Zn. 
 
 13 
 
 
 Dark precipitate. . 
 
 100 
 
 Reacts only with Hg + 
 ion. 
 
 11 
 
 
 Colorless needles. 
 
 .06 
 
 Precipitates also 
 formed by Ag, Ce, 
 Co, Cu, Fe, Pd, Zn. 
 
 12 
 
 
 Reddish-violet 
 color with Hg 2 2+ ; 
 bluish-gray ring 
 with Hg 2+ . 
 
 40 
 15 
 
 Also reacts with Ag, 
 Al, Mg, U. 
 
 14 
 
 
 
 20 
 
 Forms a violet-red 
 ring with Pb. 
 
 14 
 
 
 Crystals or 
 precipitate. 
 
 .5 
 
 Also reacts with As, 
 Bi, Cd, Ce, Cr, Cu, 
 Pb, Sn, Zn, and 
 others. 
 
 14 
 
 
 
 See footnotes at end of table. 
 
TABLE 1. - Reagents for mercury detection — Continued 
 
 Reagent 
 
 Reaction indica- 
 tive of mercury 
 
 Sensitivity, 
 US Hg 
 
 Comments 
 
 Refer- 
 ences 2 
 
 ORGANIC REAGENTS— Continued 
 
 
 Pink to red color. 
 
 .1 
 
 Also reacts with 
 Ag , Au , Cu , Os , Pd . 
 Ammonium chlorstan- 
 nate causes the 
 color. 
 
 14 
 
 
 
 2-Carboxyphenyl-5- 
 azo-8-hydroxyquino- 
 line. 
 
 Rose-violet 
 precipitate. 
 
 200 
 
 Also reacts with Ag, 
 As, Co, Cr, Cu, Ni, 
 Pd. 
 
 11 
 
 
 Bright yellow 
 precipitate. 
 
 10 
 
 Ag, Fe, Ti inter- 
 fere. No reaction 
 with mercury 
 chlorides. 
 
 2, 11 
 
 2 , 3-Diaminophenazine . . 
 
 Red precipitate... 
 
 10 
 
 Also reacts with Cu. 
 Fe and ammonia 
 interfere. 
 
 12 
 
 Diethylaminophenyl- 
 imi no camphor. 
 
 Rich pink or scar- 
 let color. 
 
 20 
 
 Color from Hg 2+ van- 
 ishes upon exposure 
 to ammonia; color 
 from Hg 2 2+ turns 
 black upon exposure 
 to ammonia. Also 
 reacts with Ag and 
 Bi. 
 
 13 
 
 p-Dimethylaminobenzal- 
 rhodanine. 
 
 Pved-violet color 
 or precipitate. 
 
 .33 
 
 In the presence of 
 chlorides, acetate 
 must be added. Al- 
 so reacts with Ag 
 and Cu. 
 
 13 
 
 Dimethylaminophenyl- 
 iminocamphor . 
 
 Rich pink or scar- 
 let color. 
 
 20 
 
 Color from Hg 2+ 
 vanishes and color 
 from Hg 2 2+ turns 
 black upon exposure 
 to ammonia. Also 
 reacts with Ag and 
 Bi. 
 
 13 
 
 Di-a-naphthylcarba- 
 zone. 
 
 Gray-violet color. 
 
 .05 
 
 Also reacts with Cd, 
 Cu, Fe, Mo. 
 
 13 
 
 Di-3-naphthylcarba- 
 zone. 
 
 
 .015 
 
 
 13 
 
 Di-( O-nit rophenyl ) 
 carbazone. 
 
 Gray-blue color... 
 
 .08 
 
 Also reacts with Cu, 
 Fe, Mo. 
 
 13 
 
 See footnotes at end of table. 
 
TABLE 1. - Reagents for mercury detection — Continued 
 
 Reagent 
 
 Reaction indica- 
 tive of mercury 
 
 Sensitivity, 
 yg Hg 
 
 Comments 
 
 Refer- 
 ences 2 
 
 ORGANIC REAGENTS— Continued 
 
 Di-(m-nitrophenyl) 
 carbazone. 
 
 Red-brown color... 
 
 .05 
 
 Also reacts with Cu, 
 Fe, Mo. 
 
 13 
 
 Di-(p-nitrophenyl) 
 carbazone. 
 
 
 .025 
 
 do 
 
 13 
 
 
 
 
 Violet or blue 
 precipitate. 
 
 1 
 
 Also reacts with Cd, 
 Cr, Cu, Mo. Chlo- 
 rides interfere. 
 
 2, 13 
 
 
 
 .05 
 
 Also reacts with Cd, 
 Co, Cr, Cu, Fe, Ni, 
 Pb, Zn. 
 
 2, 13 
 
 
 Yellow or brown 
 crystals. 
 
 400 
 
 Also reacts with Al, 
 Be, Co, Cr, Cu, Fe, 
 Ni, Zr. 
 
 14 
 
 
 
 .25 
 
 Reacts with many 
 metal ions. In 
 acid solution, Au, 
 Bi, Cu, Pt metals, 
 Sb, Sn are main 
 interf erents. 
 
 2, 13 
 
 
 
 
 Pink precipitate. . 
 
 10,000 
 
 Reacts only with 
 Hg 2 2+ . 
 
 14 
 
 
 
 Hexamethylenetetra- 
 mine. 5 
 
 Light yellow color 
 
 .035 
 
 Color results from 
 addition of iodide. 
 Also reacts with 
 Ca, Li, Mg, others. 
 
 13 
 
 
 Gray precipitate.. 
 
 10,000 
 
 Reaction is with 
 Hg 2 2+ ions. Also 
 reacts with Sb and 
 Sn. 
 
 14 
 
 Methylene blue iodide. 
 
 
 .021 
 
 Also reacts with Ag 
 and Sn. 
 
 14 
 
 ct-Naphthylamine 3 » 5 . . . . 
 
 Yellow precipitate 
 
 37 
 
 Also reacts with Cr, 
 Cu, Au, W, others. 
 
 12 
 
 o-Nitrosophenol 3 > 4 . . . . 
 
 Reddish-violet 
 solid. 
 
 .1 
 
 Reacts only with 
 Hg 2+ ; similar re- 
 sults with Cu 2+ , 
 Ni, Zn, Fe 2+ . 
 
 13 
 
 See footnotes at end of table. 
 
TABLE 1. - Reagents for mercury detection — Continued 
 
 Reagent 
 
 Reaction indica- 
 tive of mercury 
 
 Sensitivity, 
 Ug Hg 
 
 Comments 
 
 Refer- 
 ences 2 
 
 ORGANIC REAGENTS— Continued 
 
 Phenyl-5-azo-8- 
 hydroxy quinoline . 
 
 Violet precipitate 
 
 100 
 
 Also reacts with Cu, 
 Au, Mo, Ni, Pd, Zn. 
 
 11 
 
 Phenylhydrazinephenyl- 
 thiocarbazinate. 3 
 
 Reddish-purple 
 precipitate. 
 
 10 
 
 Excess reagent must 
 be avoided. Cr0 4 2- , 
 Mo0 4 2-, V0 3 ~ 
 interfere. 
 
 14 
 
 Phenylthiodantoic acid 
 
 Yellow precipitate 
 
 5 
 
 Similar results are 
 obtained with Cu, 
 Bi, Sb. 
 
 14 
 
 
 Grayish-black 
 precipitate. 
 
 20 
 
 Reaction is with 
 Hg 2 2+ ion. Sensi- 
 tivity of 20 yg is 
 for Hg 2 2+ ; sensi- 
 tivity for Hg 2+ is 
 1,000 yg. Also re- 
 acts with Ag, Cu + , 
 Au-5 + , Pd 2 + , Pt4 + . 
 
 14 
 
 
 Red precipitate... 
 
 20 
 
 Reacts in the pres- 
 ence of sodium 
 acetate. 
 
 13 
 
 
 
 
 
 20 
 
 Br", Cl~, I", CN~, 
 SCN" interfere. 
 Also reacts with 
 Cr, Fe, Sb, Sn. 
 
 11 
 
 
 Yellow precipitate 
 
 .15 
 
 Also reacts with Ba, 
 Cd, Cu, Fe, Ni, Ag, 
 and many others. 
 
 14 
 
 
 Red precipitate... 
 
 4,000 
 
 Forms a violet pre- 
 cipitate with Ag. 
 
 13 
 
 
 
 
 Colorless needles. 
 
 .32 
 
 Also reacts with Bi, 
 Cd, Co, Sn, and 
 others. 
 
 13 
 
 
 
 
 Dark red 
 precipitate. 
 
 1,000 
 
 Also reacts with Au, 
 Bi, Mo, Sb, W, and 
 others. 
 
 14 
 
 
 
 Sodium diethyldithio- 
 carbamate. 
 
 
 100 
 
 Reaction is with 
 Hg 2+ . Also reacts 
 with Cd, Co, Mn, 
 Pb, Sr, Zn. 
 
 14 
 
 See footnotes at end of table. 
 
TABLE 1, - Reagents for mercury detection — Continued 
 
 Reagent 1 
 
 Reaction indica- 
 t ive of mercury 
 
 Sensitivity, 
 Mg Hg 
 
 Comments 
 
 Refer- 
 ences 2 
 
 ORGANIC REAGENTS— Continued 
 
 
 Yellow precipitate 
 
 5 
 
 Reaction is with 
 Hg 2 2+ . Also reacts 
 with Ag, Pb, Tl, 
 N0 2 ~. 
 
 11 
 
 
 
 5-(p-Sulf ophenylazo)- 
 8-hydroxyquinoline . 
 
 Bright red 
 precipitate. 
 
 50 
 
 Cl~ interferes. Re- 
 acts also with Cu, 
 Ni, Pd. 
 
 11 
 
 
 Yellow-white 
 precipitate. 
 
 10,000 
 
 Reacts with many 
 ionic species. 
 
 12 
 
 
 
 Tetramethyl-p-phenyl- 
 enediamine (Wurster's 
 reagent) , 3 
 
 Violet precipitate 
 
 1 
 
 Also reacts with Ag, 
 Cu, Fe, Os. 
 
 12 
 
 
 Rose-colored 
 solution. 
 
 1 
 
 Also reacts with Cu, 
 Zn. 
 
 14 
 
 
 
 
 INORGANIC 
 
 REAGENTS 
 
 
 
 
 
 0.0001 
 
 Neutral solution 
 needed. Hg is 
 amalgamated with 
 Al using current 
 from a flashlight 
 battery; alumina 
 
 2 
 
 
 
 
 
 
 
 formed gives red 
 color with Alizarin. 
 
 
 
 Deep red to orange 
 color. 
 
 .003 
 
 Oxidants, Ag, Au, Mo, 
 Pd, Pt, W interfere. 
 
 2 
 
 Hydrogen sulfide and 
 formic acid. 3 
 
 Colored colloidal 
 suspension. , 
 
 10 
 
 Also reacts with As 
 and Pb. Colorimeter 
 used for detection. 
 
 12 
 
 Hypophosphite-tin-IV. . 
 
 Red or light pink 
 color. 
 
 .1 
 
 Cacotheline used to 
 form color with 
 tin-II. Ag, Os , 
 and noble metals 
 interfere. 
 
 2 
 
 
 Absence of blue 
 color in test 
 solution. 
 
 .14 
 
 Same reaction with 
 Ag. 
 
 14 
 
 
 
 .02 
 
 I 2 is dissolved in 
 equal amounts of 
 ethanol and toluene. 
 
 11 
 
 
 
 
 See footnotes at end of table. 
 
TABLE 1. - Reagents for mercury detection — Continued 
 
 Reagent 
 
 Reaction indica- 
 tive of mercury 
 
 Sensitivity, 
 pg Hg 
 
 Comments 
 
 Refer- 
 ences 2 
 
 
 INORGANIC REAGENTS- 
 
 -Continued 
 
 
 Potassium dichromate- 
 pyridine. 3 * 5 
 
 Orange crystals . . . 
 
 
 .075 
 
 Both Hg 2 2+ and Hg2+ 
 cause the reaction. 
 
 13 
 
 Potassium iodide- 
 glycerol. 
 
 Black precipitate. 
 
 
 50 
 
 Ag, Pb, Tl also 
 precipitate with 
 iodide, but are 
 avoided in the 
 test. 
 
 11 
 
 Stannous chloride- 
 aniline. 3 
 
 Brown, gray, 
 or black 
 precipitate. 
 
 
 1 
 
 Aniline is used to 
 provide proper al- 
 kalinity and avoid 
 Sb interference. 
 Ag may interfere. 
 
 2 
 
 1 A11 reagents should be considered hazardous. Before use, properties such as tox- 
 icity, carcinogenicity, explosibility , etc. , should be determined by consulting such 
 references as "Cancer Causing Chemicals" by N. I. Sax (Van Nostrand-Reinhold, New 
 York, 1981, 466 pp.), "Dangerous Properties of Industrial Materials" by N. I. Sax 
 (Van Nostrand-Reinhold, New York, 5th ed. , 1979, 1258 pp.), "Handbook of Reactive 
 Chemical Hazards" by L. Bretherick (CRC Press, Inc., Boca Raton, Fla. , 1975, 976 
 pp.), and "The Merck Index" (Merck and Co., Inc., Rahway, N.J. , 9th ed. , 1976, 1313 
 pp.). For the reagents listed above, no listed hazards were found except as other- 
 wise noted. 
 
 2 For each reagent, these references generally give the chemical symbol, molecular 
 weight, alternate nomenclature, and guidance for performing spot tests; for the less 
 common organic compounds, preparation procedures are also given. 
 
 3 Has toxic properties ranging from irritant to highly poisonous. 
 
 4 Explosive or flammable. 
 
 ^Possible or known carcinogen. 
 
 SENSITIVITY 
 
 The sensitivities of the spot test 
 reagents listed in table 1 range from 
 0.0001 to 10,000 yg. If the mercury to 
 be determined is in a form that dis- 
 solves slowly in acid, the more sensi- 
 tive reagents are recommended because 
 they minimize the time needed to obtain 
 a positive test. However, if a reagent 
 is to be used to locate fine droplets 
 of a mercury spill, and low levels of 
 mercury or mercury compounds with low 
 solubility are not of interest, it may 
 be better to use one of the less sensi- 
 tive reagents that will test positive 
 only for relatively high levels of dis- 
 solved mercury. For example, a reagent 
 sensitive to mercury at the 10,000-yg 
 level will detect — though perhaps with a 
 weak color change — a droplet of mercury 
 
 (density 13.6 g/cm 3 ) that is only 0.0007 
 cm 3 in volume. 
 
 For locating sources of mercury vapor 
 in the workplace, test reagents of inter- 
 mediate sensitivities are recommended. 
 Their use avoids positive results for 
 trace amounts of mercury but produces 
 strong color changes for readily soluble 
 forms of mercury at part-per-million lev- 
 els of concentration. 
 
 REAGENT SHELF LIFE 
 
 Several of the reagents listed in 
 table 1 need to be prepared fresh daily 
 because they deteriorate rapidly upon 
 exposure to actinic light (ultraviolet 
 radiation capable of initiating photo- 
 chemical reactions) or oxidation by 
 air. These reagents would not generally 
 
be considered for field applications. 
 In laboratory testing of various re- 
 agents, it was found that chronotropic 
 acid, Wurster's reagent (tetramethyl-p- 
 phenylenediamine) , and dithizone contin- 
 ued to give positive results for over 4 
 weeks after preparation if stored in low- 
 actinic-glass (colored glass that absorbs 
 actinic light) containers and kept out of 
 direct sunlight. When stored in clear 
 glass containers, all three were ineffec- 
 tive within 4 days of preparation. Dith- 
 izone changed to an ineffective yellow 
 solution after only 1 day of exposure to 
 sunlight. By comparison, symdiphenyl 
 carbazide showed no effect from exposure 
 to the direct sunlight. As a rule of 
 thumb, all reagents should be prepared 
 fresh, kept away from heat, and stored 
 or carried in light-opaque, tightly stop- 
 pered containers. Proper safety contain- 
 ers should be used for the few reagents 
 that require flammable organic solvents 
 of high vapor pressure. 
 
 SPOT TEST TECHNIQUES 
 
 Chapters 1 and 2 of Feigl's text on 
 spot tests (2) give a thorough overview 
 of various techniques used in conduct- 
 ing spot tests. Some general guidelines 
 are given in this section for the tests 
 selected by the Bureau for mercury 
 detection. 
 
 As mentioned in the previous section, 
 low-actinic containers should be used for 
 the organic reagents to retard deteriora- 
 tion. In the field, it is recommended 
 that amber polyethylene dropping bottles 
 with screw-cap tops be used. Even so, 
 many of the organic reagents need to be 
 prepared fresh for reliable results. 
 Low-actinic containers are not needed for 
 the 1:1 nitric acid used to dissolve the 
 mercury for each test, but the container 
 should be acid resistant. A Teflon^ 
 fluorinated ethylene propylene (FEP) 
 dropping bottle or a drop dispensing 
 bottle with a screw-cap top is useful for 
 this purpose. 
 
 ^Reference to specific trade names is 
 made for identification only and does not 
 imply endorsement by the Bureau of Mines. 
 
 It is important that the tip of the 
 eyedropper pipet used to deliver the rea- 
 gents remain free from contamination. 
 The tip of the pipet should not be 
 touched against the receiving surface. 
 The pipet tip should be no more than 1 or 
 2 cm above the place where the drop is to 
 be delivered to assure accurate delivery 
 and avoid splashing, but the drops should 
 be allowed to fall freely. Not only does 
 this technique avoid contamination, but 
 the size of the drops remains fairly uni- 
 form, thereby allowing a semiquantitative 
 comparison of mercury in the samples 
 based on color intensities. 
 
 Direct testing on surfaces in a mill or 
 mine is generally not possible nor desir- 
 able. A portion of the dust or material 
 to be tested should be scraped from the 
 surface with a spatula and placed on a 
 filter paper or in a white glazed spot 
 plate, a watch glass, or a micro test 
 tube for attack by the 1:1 nitric acid. 
 The acid is diluted with distilled water, 
 generally by a factor of 3, before it is 
 combined with the color-producing rea- 
 gent. If the mercury is dissolved in a 
 container other than filter paper, some 
 of the liquid is then transferred to a 
 white filter paper using an eyedropper 
 pipet. If cotton is placed in the tip of 
 the pipet, it will separate the liquid 
 from the solids for a more interference- 
 free observation of the color change. 
 However, this separation is not usually 
 necessary because the solution containing 
 the dissolved mercury will diffuse away 
 from the solids through the capillaries 
 of the paper. The color-producing rea- 
 gent is added to the solvent -moistened 
 portion of the paper around the solids 
 whether the solids are treated with the 
 nitric acid directly on the paper or are 
 transferred to the paper along with the 
 solvent from a separate dissolution 
 vessel. 
 
 The capillary action and adsorptive 
 effects of filter paper make it the 
 preferred substrate for spot reactions. 
 Color reactions that appear to be rel- 
 atively insensitive when diluted with 
 the solvent in a spot plate or test tube 
 may have excellent sensitivities on an 
 
appropriate filter paper. This is be- 
 cause the colored, soluble, or insoluble 
 reaction products of the test are held 
 near the site of their production by the 
 capillaries of the paper and are more 
 readily seen because of the white back- 
 ground of the paper. Precipitation and 
 filtration take place in the plane of the 
 paper, resulting in a local enrichment 
 and improved visibility of the colored 
 reaction product. 
 
 When the mercury is dissolved from the 
 sample directly on the filter paper, as 
 recommended for some procedures, an acid- 
 hardened paper such as Whatman 50 or 
 Schleicher and Schuell 576 is recommend- 
 ed. These papers have a slow filtering 
 speed, resulting in increased acid con- 
 tact with the sample; they are acid- 
 resistant; and they retain very fine 
 precipitates on their smooth, white, 
 lint -free surfaces for easy observation. 
 
 SELECTED SPOT TESTS 
 
 From the spot tests for mercuric ions 
 listed in table 1, the Bureau selected 
 the four tests described below as repre- 
 sentative of those applicable to conven- 
 ient field testing for sources of mercury 
 vapor in the workplace. These tests were 
 selected because of their simplicity, 
 sensitivities, minimal interferences, and 
 strong positive color changes in the 
 presence of mercury. 
 
 The sample size for each test is ap- 
 proximately half of a 3- by 10-mm spatula 
 spoonful. The mercuric ions for each 
 test are obtained by dissolution of mer- 
 cury metal or compounds from the sample 
 using 1:1 nitric acid prepared by adding 
 50 mL of reagent-grade concentrated ni- 
 tric acid to 50 mL of distilled water. 
 All chemicals should be reagent grade and 
 prepared with distilled water. Once pre- 
 pared, the reagents should be tested with 
 a blank 1:1 nitric acid sample for mer- 
 cury contamination. 
 
 Cuprous Iodide Test 
 
 Reagents 
 
 1. Potassium iodide-sodium sulfite 
 solution: 5 g KI and 20 g Na 2 S0 3 *7H 2 in 
 100 mL water. 
 
 2. Copper sulfate solution: 5 g CuS0 4 
 •5H 2 in 100 mL IN hydrochloric acid 
 (83 mL reagent-grade concentrated hydro- 
 chloric acid diluted to 1 L with dis- 
 tilled water). 
 
 Reagent Paper 
 
 The filter paper is impregnated with 
 the reactive reagents in the laboratory, 
 minimizing the chemicals needed in the 
 field. This is done by soaking an ab- 
 sorbent filter paper (e.g., Schleicher 
 and Schuell 598 or Whatman 1) in the po- 
 tassium iodide-sodium sulfite solution 
 and then in the copper sulfate solution. 
 The excess reagents are rinsed from the 
 papers , and the papers are allowed to 
 dry prior to their use in the field. The 
 papers should last for several weeks if 
 kept dry and if long exposure to direct 
 sunlight or oxidizing environments is 
 avoided. 
 
 Field Procedure 
 
 1. Add 1 or 2 drops of 1:1 nitric acid 
 to the sample in a spot plate and let 
 stand for 1 min. 
 
 2. Add 3 times as many drops of dis- 
 tilled water to dilute the acid. 
 
 3. Remove a portion of the liquid with 
 an eyedropper pipet, and place a drop on 
 the reagent paper. A red or orange color 
 indicates the presence of mercury. 
 
 Diphenylcarbazide Test 
 Reagents 
 
 1. Diphenylcarbazide solution: 2 g 
 diphenylcarbazide in 10 mL acetic acid 
 and 10 mL ethanol. (Use low-actinic bot- 
 tles. The solution is reddish-orange 
 while effective.) 
 
 2. Sodium pyrophosphate solution: 3 g 
 Na 4 P 2 7 '10H 2 in 100 mL water. 
 
 3. 3 pet hydrogen peroxide solution if 
 chromates may be present. 
 
 Field Procedure 
 
 1. Add 1 or 2 drops of 1:1 nitric acid 
 to the sample on a filter paper and let 
 stand for 1 min. 
 
10 
 
 2. Add 3 times as many drops of dis- 
 tilled water to dilute the acid. 
 
 3. Add 2 drops of sodium pyrophosphate 
 solution to eliminate interferences. If 
 chromates are present, a drop of 3 pet 
 hydrogen peroxide may also need to be 
 added. 
 
 4. Add 1 drop of diphenylcarbazide 
 solution at the edge of the solids. A 
 violet or blue fleck indicates the pres- 
 ence of mercury. 
 
 Chromotropic Acid Test 
 
 limit of 25 mg Hg 2+ per liter is ob- 
 tained. Bureau tests with nitric acid 
 solutions of Zn, Pb, Cu, Bi, and Cd did 
 not produce a color change, This ob- 
 servation is in agreement with the man- 
 ufacturer's claims that there are no 
 interferences for this paper. MSHA has 
 selected this test paper for field 
 evaluation. 
 
 Field Procedure 
 
 1. Add 1 or 2 drops of 1:1 nitric acid 
 to the sample in a spot plate and let 
 stand for 1 min. 
 
 Reagent 
 
 1. Chromotropic acid solution: 5 g 
 sodium salt of chromotropic acid in 100 
 mL distilled water. (Use low-actinic 
 bottle.) 
 
 Field Procedure 
 
 1. Add 1 or 2 drops of 1:1 nitric acid 
 to the sample on a filter paper and let 
 stand for 1 min. 
 
 2. Add 3 times as many drops of dis- 
 tilled water to dilute the acid. 
 
 3. Add 1 drop of chromotropic acid 
 solution at the edge of the solids. A 
 bright yellow color indicates the pres- 
 ence of mercury. 
 
 Commercial Test Paper 
 
 Description and Characteristics 
 
 A commercially available test paper 
 sensitive only to Hg 2+ ions is manufac- 
 tured by Machery, Nagel and Co., Duren, 
 West Germany, and is available in the 
 United States from Gallard Schlesinger 
 Chemical Mfg. Corp., Carle Place, N.Y. 
 The cost is under $10 for 200 strips mea- 
 suring 20 by 70 mm. No information is 
 given by the manufacturer about the ac- 
 tive ingredient in the paper. In the 
 presence of Hg 2+ ions, the grayish-brown 
 paper turns white. If a capillary or 
 micropipet is used to apply 10 to 20 yL 
 of solution to the paper, a sensitivity 
 
 2. Add 3 times as many drops 
 tilled water to dilute the acid. 
 
 of dis- 
 
 3« Touch a strip of the test paper to 
 the liquid or use a capillary tube to 
 touch the liquid to the paper. A white 
 discoloration of the paper indicates the 
 presence of mercury. 
 
 MERCURY VAPOR TEST PAPERS 
 
 Two test papers applicable for the 
 direct detection of mercury vapor — as 
 opposed to mercury ions, which are 
 needed for reaction with most of the 
 reagents listed in table 1 — can be pre- 
 pared in the laboratory. Filter paper 
 impregnated with a 1 pet solution of 
 palladium chloride and then dried pro- 
 vides a sensitive test for traces of 
 mercury vapor in air (2) . When mercury 
 vapor comes in contact with the paper, 
 the light brown color turns light gray to 
 deep black. The stain can be made more 
 visible by briefly holding the paper over 
 concentrated ammonia. The formation 
 of tetrammine palladium (II) chloride 
 [Pd(NH 3 ) 4 Cl 2 ] changes the light brown 
 paper to white, and the gray metallic 
 palladium formed by the mercury vapor 
 is easily seen against the white back- 
 ground. The most sensitive tests are 
 obtained when the paper is completely 
 dry. 
 
 A selenium sulfide test paper for mer- 
 cury vapor can be prepared by bathing 
 filter paper in a water solution of 
 selenious acid, exposing the paper to 
 
11 
 
 hydrogen sulfide, then washing and dry- 
 ing it (2). Black mercuric selenide and 
 mercuric sulfide are formed when the 
 selenium sulfide is exposed to mercury 
 vapor. 
 
 Both mercury vapor test papers must be 
 exposed to vapor for several hours if 
 
 used as a passive monitor (J7) in order to 
 detect the 0.05 mg/m 3 TLV for mercury. 
 Pumping the air across the test paper 
 will shorten the time required for a pos- 
 itive test, and the degree of darkening 
 of the selenium sulfide paper is propor- 
 tional to the square root of the velocity 
 of the air (7). 
 
 PORTABLE MERCURY VAPOR DETECTORS 
 
 Several portable, commercially avail- 
 able devices for mercury vapor detec- 
 tion are compared in table 2 for relia- 
 ble measurement range, cost, and mode of 
 mercury detection. Mercury vapor absorp- 
 tion of ultraviolet light at the 253.7- 
 nm wavelength is the means of measuring 
 relative concentrations for the Bach- 
 arach and Beckman instruments. Organic 
 
 vapors, dust, or other components of the 
 air that absorb ultraviolet light at the 
 specified wavelength will give false in- 
 dications of mercury, but generally this 
 is not a problem. Background correction 
 for broadband absorption could be added 
 to the instrumentation, although this 
 would add to the expense, bulk, and 
 weight of the instrument. 
 
 TABLE 2. - Portable mercury vapor detection devices 
 
 Vendor 
 
 Model 
 
 Detection principle 
 
 Reliable 
 measurement 
 range , ' 
 mg Hg/m 3 
 
 Approx- 
 imate 
 cost 
 
 (1982) 
 
 Bacharach Instrument Co. , 
 Pittsburgh, Pa. 15238. 
 
 MV-2 
 
 Hg vapor absorption of UV 
 light. 
 
 0.01 - 0.2 
 
 $1,800 
 
 Beckman Instruments, 
 Inc. , Fullerton, Calif. 
 92634. 
 
 K-23 
 
 
 .005- 1 
 
 2,200 
 
 Bendix Corp. , Largo, Fla. 
 33543. 
 
 Tube 40 
 
 Absorption of Hg in a tube 
 causes cupric iodide color 
 change to orange. 
 
 .05 -13 
 
 200 
 
 Jerome Instrument Co. , 
 Concord, N.H. 03301. 
 
 401 
 
 Absorption of Hg by Au film 
 increases electrical 
 resistance. 
 
 .01- .5 
 
 3,000 
 
 Mine Safety Appliances, 
 Pittsburgh, Pa. 15235. 
 
 C-210 
 
 Absorption of Hg by iodine- 
 impregnated charcoal; Hg 
 determined by laboratory 
 analysis. 
 
 .01- .3 
 
 400 
 
 National Draeger, Inc. , 
 Pittsburgh, Pa. 15235. 
 
 Mercury 
 
 Absorption of Hg in a tube 
 causes cupric iodide color 
 change to orange. 
 
 .1- 2 
 
 400 
 
 3M Co., St. Paul, Minn. 
 55101. 
 
 23600 
 
 Absorption of Hg by an Au 
 film which is sent to man- 
 ufacturer for analysis. 
 
 .005- .20 
 
 ( 3 ) 
 
 1 Actual detection limits 
 able measurement. 
 
 2 Personnel mercury vapor 
 3 $160 for 5 film badges. 
 
 are generally lower than the lowest values given for reli- 
 monitor (film badge). 
 
12 
 
 The Jerome instrument (fig. 1) works on 
 the principle that the electrical conduc- 
 tivity of a gold film changes as it forms 
 an amalgam with mercury vapor from the 
 air (b_, 8). Interference by dust, organ- 
 ic vapors, or other air components is 
 avoided unless a vapor that is reactive 
 with gold, e.g., chlorine, is present. 
 The 3M Co.'s personnel film badge moni- 
 tors also work on the principle of mer- 
 cury collection by gold, but the mercury 
 is measured in the lab using electrical 
 resistivity ( 5_) . 
 
 The remaining three mercury vapor de- 
 tection systems listed in table 2 — sold 
 by Bendix Corp., Mine Safety Appliances, 
 and National Draeger, Inc. — use the 
 chemical reaction of mercury with iodine 
 
 to detect the vapor. In the Bendix 
 and National Draeger absorption tubes, 
 the red to orange color of the cupro- 
 tetraiodomercuriate is the indicator of 
 the presence of mercury vapor. The Mine 
 Safety Appliances system uses iodine im- 
 pregnated charcoal to trap the mercury, 
 which must then be chemically eluted from 
 the charcoal and determined in the labo- 
 ratory. Although the lower limit of the 
 reliable measurement range of the Nation- 
 al Draeger tube is 0.1 mg/m 3 , the actual 
 detection limit — the level at which the 
 characteristic red coloring begins to ap- 
 pear — is below the 0.05 mg/m 3 TLV set by 
 ACGIH. A comparative study of personal 
 mercury sampling devices has been report- 
 ed by McCammon (4). 
 
 FIGURE 1. - Gold-film analyzer for locating sources of mercury vapor. 
 
13 
 
 For the purpose of on-site location of 
 mercury vapor sources , the need to return 
 to the laboratory for mercury determina- 
 tion would eliminate from consideration 
 the 3M Co. and Mine Safety Appliances 
 detectors. The absorption tubes sold by 
 Bendix and by National Draeger show a 
 cumulative mercury level, with the red 
 color advancing through the tube with 
 continued exposure to mercury vapor, and 
 therefore lack the ability to show 
 
 fluctuations in mercury vapor concen- 
 trations from one minute to the next 
 as the device is moved from place to 
 place. The most useful devices for the 
 intended purpose are the more expensive 
 battery-powered ultraviolet and gold- 
 film-resistivity instruments. Each in- 
 strument has a survey mode that contin- 
 uously samples the air, denoting areas of 
 high mercury concentration near sources 
 of mercury vapor contamination. 
 
 PORTABLE ANALYTICAL INSTRUMENTS 
 
 The portable analytical instruments 
 listed in table 3 have the capability, 
 except for the Perkin-Elmer (formerly 
 Coleman) model MAS-50A, of determining 
 other elements in addition to mercury. 
 The MAS-50A is designed specifically for 
 the cold-vapor atomic-absorption deter- 
 mination of mercury ( 1_) . 
 
 Samples must be taken from the area 
 being surveyed before instrumental 
 analysis can be performed using the MAS- 
 50A. This is true also for the Graphic 
 Controls ion-selective electrode and 
 the Hach Chemical ultraviolet spectro- 
 photometer. In each case the mercury 
 must be dissolved from the sample and 
 chemically treated. When the cold-vapor 
 
 atomic-absorption method is used, the 
 mercuric ion is reduced to the metallic 
 state and then vaporized so that mercury 
 can be determined by atomic absorption 
 at the 253.7-nm wavelength. The ion- 
 selective electrode method uses a sens- 
 ing component for the direct determina- 
 tion of mercuric ion activity, or the 
 mercuric ion may be determined indirectly 
 by titration with iodide until an excess 
 of iodide is detected by an iodide- 
 selective electrode (10). However, ac- 
 curate determination of mercury using 
 the ion-selective electrode may be diffi- 
 cult because of interferences from 
 chloride, bromide, iodide, cyanide, 
 thiocyanates, sulfide, and silver. The 
 ultraviolet spectrophotometric method is 
 
 TABLE 3. - Portable analytical instruments 
 
 Vendor 
 
 Model 
 
 Type of instrument 
 
 Approximate 
 cost (1982) 
 
 Columbia Scientific, 
 Austin, Tex. 78766. 
 
 700 
 
 
 $8,000 
 
 Graphic Controls 
 Corp. , Buffalo, 
 N.Y. 14240. 
 
 PHI 96100 
 
 Ion-selective electrode. . 
 
 300 
 
 Hach Chemical Co. , 
 Loveland, Colo. 
 80537. 
 
 DR/2 
 
 
 750 
 
 Panametrics, Inc., 
 Waltham, Mass. 
 02154. 
 
 Panalyzer 
 4000 
 
 
 6,400 
 
 Perkin-Elmer Corp. , 
 Oakbrook, 111. 
 60521. 
 
 MAS-50A 
 
 Cold-vapor atomic absorp- 
 tion analyzer. 
 
 2,400 
 
14 
 
 indirect: Dithizone is used as the ac- 
 tive ingredient to complex the mercuric 
 ions, and the complex is then extracted 
 into chloroform (3). The mercury concen- 
 tration is determined at the point where 
 an excess of dithizone gives an absorb- 
 ance at the 610-nm wavelength. (For an 
 indication of the many interferences that 
 are possible when dithizone is used, see 
 table 1). The usefulness of any of 
 these three techniques (cold-vapor atom- 
 ic absorption, ion-selective electrode, 
 and ultraviolet spectrophotometric) for 
 on-site location of mercury vapor sources 
 is greatly restricted by the need to col- 
 lect samples and chemically treat the 
 samples to obtain results. 
 
 The utility of fluorescent X-ray spec- 
 trography for determining trace concen- 
 trations of heavy metals in various 
 matrixes is well documented. The devel- 
 opment of portable X-ray instrumentation 
 has extended this application to in situ 
 determinations of trace elements in ore 
 samples (9). Mercury concentrations of 
 0.7 pet Hg in a 1-g sample can be deter- 
 mined. Sensitivity is a function of the 
 detector resolution and the activity 
 of the radioisotope used for sample 
 excitation. 
 
 The type of detector used in a portable 
 X-ray analyzer greatly affects both cost 
 and sensitivity. Scintillation detectors 
 and proportional counters have long been 
 used to detect X-rays in analytical in- 
 struments. The two devices listed in ta- 
 ble 3 use sealed proportional counters. 
 They are rugged, inexpensive, and provide 
 moderate sensitivity in portable devices 
 
 when coupled with balanced filters to 
 discriminate the X-rays of interest from 
 a complex spectral background. Only one 
 element is determined for each set of 
 balanced filters. 
 
 The alternative approach is to use a 
 device similar to the "X-site" alloy- 
 sorting instrumentation marketed by Kevex 
 Inc. This system uses a solid-state 
 semiconductor detector (lithium-drifted 
 silicon) , and simultaneous multielement 
 determinations are therefore possible. 
 The probe head containing the detector is 
 portable, but the required power supply 
 and the computer hardware are not. The 
 silicon detector gives the system greater 
 flexibility for resolving complex spectra 
 than a proportional counter has, but the 
 detector requires constant liquid nitro- 
 gen cooling and costs much more than a 
 proportional counter. 
 
 The only commercially available porta- 
 ble X-ray analyzer with a solid-state de- 
 tector is a gold analyzer marketed by 
 Ortec Inc. It has a germanium detector, 
 requires liquid nitrogen cooling, and 
 costs about $60,000. Its sensitivity for 
 gold is less than 0.1 pet Au in ore sam- 
 ples, and its sensitivity for mercury is 
 probably comparable, because gold and 
 mercury X-rays have similar energies. 
 The germanium detector is able to detect 
 higher energy X-rays than the proportion- 
 al counter, and fewer interferences exist 
 for the K-alpha X-rays of mercury; there- 
 fore, consistently lower detection limits 
 for mercury in different types of samples 
 would be expected. 
 
 CONCLUSIONS 
 
 Of the more than 50 reagents for mer- 
 cury identification spot tests that were 
 examined, many could be applied for the 
 identification of sources of mercury 
 vapor in mines and mineral processing 
 plants. Poor shelf life, nonselectivity , 
 and lack of sensitivity would eliminate 
 some from consideration. At least two 
 spot tests that react to mercury vapor 
 are available; the others require the 
 presence of mercury ions for positive 
 test results. One commercially available 
 
 mercury test paper, sensitive only to 
 mercuric ions, appears to best meet the 
 need for locating sources of mercury 
 vapor in the workplace. 
 
 Portable mercury vapor detectors that 
 could be used for real-time surveying in 
 a mine or mill range in cost from $1,800 
 to $3,000. Less expensive vapor detec- 
 tion devices require laboratory backup or 
 cannot provide the flexibility needed to 
 pinpoint a mercury vapor source. 
 
15 
 
 Portable analytical instrumentation is 
 also limited for field use by the need 
 for sample collection, dissolution, and 
 chemical treatment in every case except 
 for the X-ray analyzers. However, the 
 portable X-ray analyzers are the most ex- 
 pensive of all the detection systems ex- 
 amined, ranging from $6,000 to $8,000 or 
 more. 
 
 Methods of identifying sources of mer- 
 cury vapor in mines and mineral process- 
 ing plants are readily available with no 
 need for further research and develop- 
 ment. The inexpensive, commercially 
 available mercury test paper mentioned 
 above appears to have no interferences 
 and requires minimal skills to obtain re- 
 liable results. 
 
 REFERENCES 
 
 1. Dumarey, R. , R. Heindryckx, R. 
 Dams, and J. Hoste. Determination of 
 Volatile Mercury Compounds in Air With 
 the Coleman MAS-50 Mercury Analyzer Sys- 
 tem. Anal. Chim. Acta, v. 107, 1979, 
 pp. 159-167. 
 
 2. Feigl, F. Spot Tests. Elsevier 
 Pub. Co., New York, v. 1, 1954, 518 pp. 
 
 3. Kolthoff, I. M. , and P. J. Elving, 
 eds. Treatise on Analytical Chemistry. 
 John Wiley & Sons, Inc., New York, part 
 II, v. 3, 1961, 380 pp. 
 
 4. McCammon, C. S., Jr., S. L. Ed- 
 wards, R. D. Hull, and W. J. Woodfin. A 
 Comparison of Four Personal Sampling 
 Methods for the Determination of Mercury 
 Vapor. J. Am. Ind. Hyg. Assoc, v. 41, 
 1980, pp. 528-531. 
 
 5. McCammon, C. S., Jr., and J. W. 
 Woodfin. An Evaluation of a Passive Mon- 
 itor for Mercury Vapor. J. Am. Ind. Hyg. 
 Assoc, v. 38, 1977, pp. 378-386. 
 
 6. McNerney, J. J., and P. R. Buseck. 
 Geochemical Exploration Using Mercury Va- 
 por. Econ. Geol. Bull. Soc Econ. Geol. , 
 v. 68, 1973, pp. 1313-1320. 
 
 7. Nordlander, B. W. Selenium Sul- 
 fide — A New Detector for Mercury Vapor. 
 Ind. Eng. Chem. , v. 19, 1927, pp. 518- 
 521. 
 
 8. Ohkawa, T., H. Uemoyama, and M. 
 Kondo. (Mercury Analysis in Ambient Air 
 by Means of Thin Gold Resistors.) Eisei 
 Kagaku, v. 22, 1976, pp. 11-19. 
 
 9. Rhodes, J. R. , C. S. Barrett, 
 D. E. Leyden, J. B. Newkirk, P. K. 
 Predecki, and C. D. Ruud, eds. Advances 
 in X-Ray Analysis. Plenum Press, New 
 York, v. 23, 1980, 390 pp. 
 
 10. Sekerka, I., and J. F. Lechner. 
 Behavior of Ion Selective Electrodes 
 Based on Silver or Mercuric Sulfide Sel- 
 enide and Telluride. Anal. Lett., v. 9, 
 1976, pp. 1099-1110. 
 
 11. Welcher, F. J. Organic Analytical 
 Reagents. D. Van Nostrand Co., Inc., New 
 York, v. 1, 1947, 442 pp. 
 
 12. . Organic Analytical Rea- 
 gents. D. Van Nostrand Co., Inc., New 
 York, v. 2, 1947, 530 pp. 
 
 13. . Organic Analytical Rea- 
 gents. D. Van Nostrand Co., Inc., New 
 York, v. 3, 1947, 581 pp. 
 
 14. . Organic Analytical Rea- 
 gents. D. Van Nostrand Co., Inc., New 
 
 York, v. 4, 1948, 624 pp. 
 
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