TWO TESTS FOR THE DETECTION OF VOLATILE ORGANIC ACIDS AND FORMALDEHYDE
JINPING ZHANG, DAVID THICKETT, & LORNA GREEN
Results from the iodide-iodate and chromotropic acid tests correlated well with those from the Oddy test with lead for the particular materials tested. The chromotropic acid test is more sensitive than the Oddy test to formaldehyde. Consequently, using this test may cause rejection of some materials that could have been used safely. However, this test is more acceptable than a test that may be less sensitive and result in unsuitable materials being used.
The iodide-iodate test is specific to volatile organic acids, and the chromotropic acid test is specific to formaldehyde. The major causes of lead corrosion in museums are considered to be volatile organic acids and formaldehydes. However, other species—such as phenol or ammonia, which can be present in some adhesives—have been reported as being corrosive to lead (Evans 1937; Oddy 1975). These species will not be detected by the iodide-iodate test or chromotropic acid test, but they would cause corrosion of lead in the Oddy test.
TABLE 4 RESULTS OF COMPARATIVE TESTS WITH A RANGE OF MATERIALS
Although the two tests have an advantage over the Oddy test because they take less than 2 hours to complete, they do not replace the Oddy test with lead, which detects the presence of any vapor corrosive toward lead.