adj.of or relating to a process in which the substance that causes a chemical reaction is itself the product of that reaction Kraus 1994However, more recent investigations have shown that under such conditions the “vinegar syndrome” (the formation of acetic acid) causes the onset of autocatalytic degradation in about 40 years and that the free acidity will double about every 5 years thereafter.Shahani 1995, 7Acidic compounds produced as a result of the aging of acidic paper are retained by a paper matrix that is isolated from free interaction with the environment. As the concentration of these acidic species increases with aging time, the rate of acid hydrolysis of cellulose accelerates. This process is autocatalytic, that is, it feeds upon itself. An alkaline buffer incorporated in paper, or even in contact with an alkaline paper stabilizes acidic paper by neutralizing the acidic degradation products. ¶ The fact that acidic degradation products are produced in the accelerated aging of acidic paper in a humid environment, was clearly established at NBS in the seventies (Parks, 1971-1972). However, these data did not point to the accumulation of these acids within a paper mass, such as a book, and the subsequent autocatalytic nature of the degradative process.Peters 1996A study of the environmental factors in the mechanism of acid migration has revealed the risk of autocatalytic degradation in microclimates. High relative humidity was found to contribute to the transport and deposition of degradative volatiles present in the chambers. The alarming reality is that this is not necessarily a contact based phenomenon. Neutral pH paper decreased in pH to the same degree, whether it was in physical contact with an acidic newsprint or just exposed to the chamber environment where volatiles from the newsprint were present.Leggio, Berthon, and Webb 2000Acetic acid generated on deacetylation gradually diffuses to the surface of the film. Initially, the free acid is generated slowly, the rate of reaction being governed primarily by temperature and relative humidity. However, after the autocatalytic point has been reached, the levels of free acid rapidly increase as the presence of free acetic acid catalyses further deactylation and the reaction rate is influenced mainly by the presence of the acidity.Oxborrow-Cowan 2002, 105The acetate stock of the 1930s to 1950s was far more unstable than nitrate and so is more likely to show decay. Acetate decay is autocatalytic, ie the fumes given off feed the deterioration process.Selle 2003, 3Once acetate film reaches the autocatylitic [sic] point, the decaying film begins to “feed on itself,” and the rate of decomposition becomes very rapid. The more advanced the deterioration becomes, the more the reaction rate is influenced by the amount of acid present.Capell 2010, 240As the acetate in the negative begins to break down, it produces acetic acid. This autocatalytic process progresses slowly at first and then accelerates as more acid accumulates in the negative.Heckman 2010, 501Unhappily, primary decomposition produces “volatile nitrogen oxide products,” which catalyze secondary reactions in both the photographic base and emulsion. These reactions in turn produce more nitrogen oxides, creating an autocatalytic reaction loop. Initially, secondary decomposition, like primary decomposition, is a relatively slow reaction. It increases at an exponential rate, however, and enters a very fast stage.
Notes
Since the chemical agent initiating an autocatalytic reaction reproduces itself via the reaction itself, autocatalysis is a process that increases in speed over time, requiring quick action (such as storage of affected microfilm, motion picture film, or photographic negatives in extremely cold conditions) to retard or stop it.
