Slagging deposits, analysis

A.D. were found in old mines, and sizable slag deposits suggest at least some level of lead exploitation during Roman times (2). By the careful selection of Roman lead artifacts likely to have been manufactured in Carthage, and the use of lead isotope analysis, it may be possible to confirm the use of Tunisian lead ores during the Roman period. In this preliminary study, analysis of 22 curse tablets by electron microprobe analysis (EMPA) and six tablets by thermal ionization mass spectrometry (TIMS) suggest that these artifacts might be used to better understand Roman lead use and trade. 

A quartz tube with diameter of 100 mm permits direct observation of the process with normal coal. The cyclone furnace produces steady combustion at gas temperature of 700 C but can also be extended to a temperature level of more than lOOO C. Combustion of salt coals is difficult to observe because the alkalines vaporize from the fuel and condense on the colder quartz tube wall to form an opaque layer. This problem is partially overcome by inserting a probe which measures gas and wall temperature and allows the slagging process to be determined as a function of temperature by weighing the deposit. Measurement of deposit hardness supplies additional information on the character of the clinker formed. The cyclone separator behind the reactor allows an analysis of structural changes which occur in the finest grain. The test results obtained indicate the cyclone reactor can be improved by automation (for easier operation) and by standardization to result in a piece of equipment capable of evaluating slagging tendencies. 

With weld metal deposits it is important to remove all slag from specimens before analysis in order to avoid spuriously large hydrogen figures. This should be carried out by a brisk wire brushing treatment while the specimen is still cold. Samples should then be degreased with acetone and petroleum ether, and dried under vacuum or in a stream of dry gas. 

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