Author Institution: Department of Chemistry, The Ohio State University, Columbus 1

Caley, Earle R.

McBride, Harold D.

The Ohio Journal of Science

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CHEMICAL COMPOSITION OF ANTONINIANI OF TRAJANDECIUS, TREBONIANUS GALLUS, AND VALERIAN1EARLE R. CALEY AND HAROLD D. McBRIDEDepartment of Chemistry, The Ohio State University, Columbus 10The principal silver coin of the Roman republic and the early empire was thedenarius. In the time of the republic and during the reign of the first few emperorsthis coin consistently contained a very high proportion of silver. Gradual debase-ment began at about the time of Nero (54-68 A. D.) and subsequently increasedwith slow acceleration, until at the time of Caracalla (211-217 A. D.) the silvercontent was down to about 60 percent. This emperor introduced a silver coin ofnew denomination known as the antoninianus, which was equal to 1 ^ denarii inweight but contained about the same proportion of silver as the denarius. Theweight of silver ^ in this new coin was about equal to that in the denarius of themiddle of the first century A. D.However, the same forces which caused the debasement of the denariusapparently continued to operate, for the antoninianus in turn began to be debasedvery soon after it was first issued. As is shown in table 1, this debasement atTABLE 1Weight and Fineness of Antoniniani Issued Prior to About the Middle of the Third Century A. D.EmperorCaracallaElegabalusAlexander SeverusMaximinusGordian IIIPhilip ITrajan DeciusDate211-217218-222222-235235-238238-244244-249249-251AverageWeightgm.5.015.104.424.184.02Average SilverContent%58.942.8None issuedNone issued41.743.741.9gm.2.952.181.841.831.68first took the form of a marked decrease in fineness, which was followed by adecrease in weight, the total result being a considerable decrease in the weight ofsilver in the coin over the period covered by the table. The data on the averageweights shown in this table are those given by West (1941) and are derived fromthe weights of considerable numbers of coins. The data on the average finenessare based on relatively few coins and are largely derived from the results of fireassays first published by Rauch and republished by Bibra (1873). Apparentlythe proportion of silver in the antoninianus remained at almost a constant levelfrom the time of the initial decrease up to about 250 A. D., but it must havedropped very rapidly between about 250 A.D. and 270 A.D., for the results ofboth fire assays and chemical analyses show that the proportions of silver inantoniniani issued in 270 A.D. and later are almost always less than 5 percent.One purpose of the present investigation was to determine the exact time atwhich the second and final decline in the proportion of silver began to occur; theother was to make some careful chemical analyses of antoniniani since no really1 Paper presented at the Sixty-fifth Annual Meeting of the Ohio Academy of Science,Springfield, Ohio, April, 1956.THE OHIO JOURNAL OF SCIENCE 56(5): 285, September, 1956.286 EARLE R. CALEY AND HAROLD D. MCBRIDE Vol. LVIsatisfactory analyses have been available. It is true that Bibra (1869, 1873) madea number of analyses of such coins, but the procedures he used were in variousrespects defective. His most satisfactory analyses are shown in table 2. Thoseexcluded were made on corroded coins that contained" considerable silver chloride,for such analyses are very probably not representative of the composition of theoriginal coinage alloys. As with nearly all the chemical analyses of ancientalloys published by Bibra, the summations shown in the table total to exactly100 percent, either because some one component was determined by difference orbecause the analytical results were prorated to obtain this exact summation.Aside from the errors introduced by this undesirable practice, the correctness ofcertain of his determinations may be questioned in other grounds. For example,most of his results for nickel are probably much too high, as is indicated not onlyby the method of determination he employed but by the results of the presentinvestigation. However, it is likely that his results for silver are essentiallycorrect.TABLE 2 'Analyses of Antoniniani by BibraCoinNo.*123A5678Ag47.5221.4317.3119 14.6.015.024.894.22Au%0.371.53— -t r~Cu%50.3175.8681.83oc 4987.8892.2093.6488.07Sn%0.420.11t rft 880.770.420.505.17Pb%0.830.460.853.000.510.272.27Fe%0.550.300.01ft 1ft0.100.370.080.27Ni%tr0.31t r0 440.130.330.62t rZn%.,2.111.15t rSb%,.—-—ft (V)trL"* Attributions and NotesNo. 1. Philip I, 244-249 A.D. Bibra, 1873, p. 37.No. 2. Valerian, 254-260 A.D. Bibra, 1873, p. 37.Nos. 3 and 4. Posthumus, 259-267 A.D. Bibra, 1869, pp. 64-65. No. 4 also containeda trace of arsenic.Nos. 5, 6 and 7, Gallienus, 260-268 A.D. Bibra, 1869, pp. 64-65. No. 5 contained atrace of cobalt, and Nos. 6 and 7 each a trace of sulfur.No. 8. Claudius Gothicus, 268-270 A.D. Bibra, 1869, pp. 56-57. This coin also containeda trace of sulfur.The figures for percentages of silver shown in tables 1 and 2 indicate clearlythat the second marked decline in the fineness of the antoninianus must havebegun sometime in the decade beginning with 249 A.D. However, because ofthe lack of chemical analyses of antoniniani of this period, the exact determinationof this time has not been possible up to now. Therefore, twelve coins representa-tive of the antoniniani issued by the principal rulers of this period were carefullyanalyzed. These coins, which were obtained by purchase, were in very good tovery fine condition and could be accurately attributed to the rulers who issuedthem. By the method of analysis employed, which was essentially that outlinedin a previous publication (Caley, 1950), all the principal components and all theusual minor components of the coinage alloys were accurately determined. Theresults are shown in table 3. Numbers la to 4a inclusive were coins of TrajanDecius (249-251 A.D.); numbers lb to 4b inclusive were coins of TrebonianusGallus (251-254 A.D.); and numbers lc to 4c inclusive were coins of Valerian(254-260 A.D.). Each of the individual percentage figures for the componentsof these coins shown in the table is the average of two closely agreeing determina-No. 5 COMPOSITION OF ROMAN COINS 287tions, and consequently each average percentage figure is based on eightdeterminations.The sharp decline in the proportion of silver in the antoninianus in the periodfrom 249 A.D. to 260 A.D. is clearly evident from both the individual and averagefigures shown in table 3. On the basis of these average figures this decline amountsto approximately 50 percent. However, by reason of the rather wide range of theindividual figures for the coins of each emperor, it is obvious that a great manymore analyses of coins of these emperors need to be made before exact averagefigures can be obtained and an exact figure given for the percentage decline in theproportion of silver. These rather wide variations in the proportion of silver inthe coins of each emperor may be due merely to accidental variations in compositionbecause of lack of proper control in minting, but this does not seem an adequateexplanation since the fineness of Roman coins in general was controlled moderatelywell. A more likely explanation is that the proportion of silver in the coins notonly decreased from reign to reign but also within each reign. In other words,TABLE 3Results of AnalysesCoinNo.la2a3a4aAv.l b2b3b4bAv.lc2c3c4cAv.Ag%42.2139.5338.3321.5235.4036.8035.2829.9623.7631.4524.4417.3215.1014.9217.95Au%0.330.300.270.710.400.170.480.220.190.270.240.160.150.140.17Cu%56.1859.0259.0074.9362.2861.3161.8365.9473.8765.7473.4479.8780.8783.6079.45Sn%0.110.431.401.450.850.651.252.630.741.320.781.632.740.181.33Pb%0.430.480.641.050.650.500.801.070.720.770.750.911.020.550.81Fe%0.080.160.110.050.100.100.050.030.100.070.080.070.130.310.15Ni%0.080.040.040.040.050.030.060.050.060.050.070.060.060.050.06Zn%0.110.090.110.510.210.050.080.090.490.180.080.050.040.090.07Total%99.53100.0599.90100.2699.9499.6199.8399.9999.9399.8599.88100.07100.1199.8499.99coins of higher fineness were issued earlier and those of lower fineness later in agiven reign. However, the usual minor variations in fineness due to lack ofvery close control probably occurred also. If this explanation for the rather widevariations in the proportion of silver is substantially correct, chemical analysiswould appear to offer a means of dating antoniniani of the emperors of this periodmore closely than is now possible from the inscriptions alone. Contrary to whatseems to be indicated by the data of table 1, the second marked decline in theproportion of silver in the antoninianus had its beginning with the reign of TrajanDecius. Hence, with a possible error of a year one way or the other, the dateof the beginning of this decline was 250 A.D.The percentages of gold shown in table 3 are somewhat higher than might beexpected in ancient silver coins of such low finenes. Though gold is nearly alwayspresent in ancient silver coins, the ratio of the percentage of gold to percentageof silver does not usually exceed about 0.005, and is very often less. But in theseantoniniani as a whole this ratio is about 0.010. The actual ratios for each ofthe coins, as well as the several average ratios, are shown in table 4. The ratiofor number 4a is unusually high and has not been included in computing the288 EARLE R. CALEY AND HAROLD D. MCBRIDE Vol. LVIaverages since it is clearly atypical. If it were included, the overall average ratiowould be 0.011 instead of the 0.009 shown in the table. Since there is a generaltendency for the ratio of gold to silver to increase as the percentage of silverdecreases and the percentage of copper increases, some of the gold in the coinagealloys was evidently introduced along with the copper or copper alloys that wereused for debasement. A possible source of such gold could have been smallproportions of gilded bronze or copper in scrap metal used for debasing the coinagealloys. Whether an unusually high ratio of gold to silver, such as was found forthese coins, is characteristic of late Roman silver coins in general cannot be knownuntil many additional careful analyses of such coins have been made.TABLE 4Ratios of Gold to Silver and of Nickel to Copperin the Coins AnalyzedCoinNo.la2a3a4aAv.l b2b3b4bAv.lc2c3c4cAv.Gen. Av.% Au% Ag0.0080.0080.007[0.033]0.0080.0050.0140.0070.0080.0090.0100.0090.0100.0090.0100.009% Ni% Cu0.00140.00070.00070.00050.00080.00050.00100.00080.00080.00080.00100.00080.00070.00060.00080.0008As may be seen from the data in table 3, copper was the principal metal usedfor debasing the coins. The percentages of tin, lead, and zinc are generally toolow and the ratios of these to the percentages of copper too small to indicate thatbrass or bronze in the form of coins or in any other form was used exclusivelyfor this debasement. Brass or bronze in small proportion may have been used,but the indications of the data are that impure copper was the principal materialused for debasement. Probably this was added in the form of scrap metal or oldworn coins from previous reigns, since the use of new metal for this purpose atthis period seems unlikely.The relationship that the percentages of nickel bear to the percentages ofcopper appears to be the only one among the percentages of the base metals that isin any way regular or systematic. As may be seen from table 4, the average ratioof these percentages for the coins of each emperor is the same. This indicates thatthe nickel is associated only with the copper in these coinage alloys. In alllikelihood it was contained in the ores from which the copper was smelted. Theactual percentages of nickel are very different from those found by Bibra (table 2)in his analyses of coins of this class.In table 5 are listed the weights of the coins that were analyzed and their actualsilver content in grams as computed from these weights and the correspondingNo. 5 COMPOSITION OF ROMAN COINS 289percentages of silver. It will be seen that the average weight of the coins of eachof the three emperors is substantially the same. On the basis of proportion ofsilver the intrinsic value of these antoniniani for this period was reduced a littleless than 50 percent (actually 49.4%) and on the basis of silver content by weighta little more than 50 percent (actually 51.7%). Evidently the intent was todecrease their value solely by decreasing the proportion of silver and not bydecreasing their weight.TABLE 5Weight and Silver Content of Coins AnalyzedEmperorand DateTrajan Decius249-251 A.D.Trebonianus Gallus251-254 A.D.Valerian254-260 A.D.Av. =Av. =Av. =Weightgm.3.643.613.463.123.463.863.343.182.793.293.853.483.422.683.36Silver Content%39.542.238.321.535.423.836.835.330.031.514.924.417.315.117.9gm.1.441.521.330.671.240.921.231.120.841.030.570.850.590.400.601869.REFERENCESDie Bronzen und Kupferlegirungen der alten and altesten Volker.Bibra, E. von.Erlangen.. 1873. Ueber alte Eisen- and Silber-Funde. Nurnberg and Leipzig.Caley, E. R. 1950. Notes on the chemical composition of Parthian coins with special referenceto the drachms of Orodes I. Ohio Jour. Sci. 50: 107-120.West, L. C. 1941. Gold and silver coin standards in the Roman Empire. New York.

Chemical Composition of Antoniniani of Trajan Decius, Trebonianus Gallus, and Valerian

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Chemical Composition of Antoniniani of Trajan Decius, Trebonianus Gallus, and Valerian

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