Breyfogle Kimberly L, Dostal Christopher
Department of Anthropology, Texas A&M University, College Station, Texas United States.
ACS Omega. 2025 Aug 19;10(34):38686-38695. doi: 10.1021/acsomega.5c03779. eCollection 2025 Sep 2.
Following their defeat in the Texas Revolution of 1836, the Mexican Army disabled and buried cannons used in the defense of the Alamo. Rediscovered in 1852, 13 of these cannons have since journeyed through private collections and public exhibits before arriving at the Alamo. Among them is a bronze 4-pounder cannon, thought to have seen action during the battle itself. In 2017, the gun was conserved using electrolytic reduction with sodium hydroxide. White powder later appeared around the breech, identified as thermonatrite (NaCO·HO), trona (NaH-(CO)·2HO), and spertiniite (Cu-(OH)). The precipitate is likely the side effect of conservation treatment, and the cannon was retreated and boiled in deionized water in an attempt to remove all carbonates. This was ineffective, and an experiment was conducted to determine and effective way to neutralize the carbonates. Formic and citric acids were found to have the least negative effects on the experimental ingots, while phosphoric, acetic, and sulfuric acids were ruled out as too problematic. Formic acid was the most effective at preventing recurring precipitation, and was chosen for application to the artifact. It successfully kept the precipitate at bay for three months before reapplication was required, which was expected based on the experiment. Time to reapplication is expected to lengthen as the carbonate reacts with the formic acid and is removed.
1836年得克萨斯革命失败后，墨西哥军队拆解并掩埋了阿拉莫防御战中使用的大炮。1852年这些大炮被重新发现，其中13门此后辗转于私人收藏和公共展览，最终抵达阿拉莫。其中一门青铜4磅炮，据信在战斗中参与了作战。2017年，这门炮采用氢氧化钠电解还原法进行了修复。后来炮尾周围出现了白色粉末，经鉴定为天然碱（Na₂CO₃·H₂O）、天然苏打（Na₃H(CO₃)₂·2H₂O）和水羟铜矿（Cu₂(OH)₂CO₃）。这种沉淀物可能是修复处理的副作用，于是对这门炮进行了再次处理，并在去离子水中煮沸，试图去除所有碳酸盐。但这没有效果，于是进行了一项实验，以确定中和碳酸盐的有效方法。结果发现甲酸和柠檬酸对实验铸块的负面影响最小，而磷酸、乙酸和硫酸因问题太多被排除。甲酸在防止再次沉淀方面最有效，因此被选择用于该文物。它成功地抑制沉淀物三个月，之后才需要再次处理，这与实验预期相符。随着碳酸盐与甲酸反应并被去除，预计再次处理的时间会延长。
