Water reacting with strong chemicals

The Hazards of Water booklet [1] reviews the risks of mixing of strong acids and water. In part, it states that a basic chemistry lab maxim should always be observed POUR ACID IN WATER—NEVER POUR WATER INTO ACID. It should even be more important when applied to the large quantities of acids in refineries and chemical plants. Serious overheating or dangerous eruptions of acid can occur if you add water or water solutions to strong acids. The dilution of some strong acids by water makes the acid more corrosive. 

Some operators who have been asked to wash out and prepare vessels for inspection or repairs understand these problems. Energetic reactions are likely with strong sulfuric acid, some salts like calcium chloride, and some alkalis. A violent eruption of steam and dilute caustic soda occurred when a preparing 73-percent caustic soda storage tank for maintenance. This incident appeared in the British Loss Prevention Bulletin about a decade ago. [6] 

Observant operators discovered a small caustic soda seeping leak at the bottom of a 20 ft. (6 m) in diameter storage/tank car shipping tank in a somewhat congested tank farm. The tank was oozing 73-percent caustic soda at 250° F (121° C). Maintenance was promptly scheduled but the tank had to be emptied and cleaned. 

The Shipping Department loaded one less rail tank car than the operations foreman anticipated. Much more caustic soda remained in the tank than the operations supervisor expected when he wrote the tank clearing instructions. There were perhaps 90 tons of 73-percent caustic soda remaining when operational supervision believed only a small heel would be left. 

Operations followed the instructions in the log book and started adding hot water to the vessel. It took about 11 hours to increase the tank level by 11 ft. (3.4 m) with hot water. The operator completed adding the prescribed amount of water early in the morning or about 5 45 A.M. About 15 minutes later, the operator opened up compressed air valve to the lance to roll or mix the contents within the tank as the Log Book instructions directed. The caustic soda was about 250° F (121° C) (well above the boiling point of water) and mixing of water and strong caustic soda solutions is strongly exothermic. 

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CHEMICAL PROPERTIES stable under ordinary conditions of use and storage hazardous polymerization will not occur substance is a strong base that is soluble in water reacts with strong oxidants FP (68°C, 154°F) LFL/UFL (unknown) AT (unknown). 

CHEMICAL PROPERTIES combustible solid gives off water of crystallization at 215°F and begins to sublime anhydrous form sublimes best at 157°C (315°F) decomposes into carbon dioxide, carbon monoxide, formic acid, and water reacts with strong alkalies, strong oxidizing materials, chlorites, and hypochlorites forms highly insoluble calcium oxalate FP (NA) LFL/UFL (NA) AT (NA) HF (-821.7 kJ/mol crystal at 25°C). 

Chemical/Physical. The hydrolysis half-lives of atrazine in aqueous buffered solutions at 25 °C and pH values of 1, 2, 3, 4, 11, 12 and 13 were reported to be 3.3, 14, 58, 240, 100, 12.5, and 1.5 d, respectively (Armstrong et al., 1967). Atrazine does not hydrolyze in uncatalyzed solutions, even under elevated temperatures. The estimated half-life of atrazine in neutral, uncatalyzed water at pH 6.97 and 25 °C is 1,800 yr. Under acidic conditions, hydrolysis proceeds via mono- and diprotonated forms (Plust et al., 1981). Atrazine is stable in slightly acidic or basic media, but is hydrolyzed to hydroxy derivatives by alkalies and strong mineral acids (Windholz et al., 1983). Atrazine reacts with strong mineral acids forming hydroxyatrazine (Montgomery and Freed, 1964). 

Chemical/Physical. Reacts with strong acids forming water-soluble salts. Also reacts with potassium permanganate forming tetraphenyl hydrazine (Zbozinek, 1984). In water, diphenylamine reacted with OH radicals at a rate of 4.9 x lO /M-h at 25 °C (Armbrust, 2000). 

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