During the development of liquid chromatographic procedures in our laboratory, it was noted that mixtures of carbon tetrachloride (LC grade ; Burdick and Jackson, Muskegon, Mich ., U.S.A.) and 2-propanol (HPLC grade ; Fisher Scientific, Fair Lawn, N .J., U .S.A.) react severely and rapidly with stainless steel . Within a 24-h period after having run a step gradient, a dark green fluid was observed in the purge lines of the liquid chromatograph . This occurred even though the system was flushed with 2-propanol at the end of each daily series of runs . Carbon tetrachloride was never left in the instrument overnight . It seemed that once the reaction was initiated, flushing was not effective in removing carbon tetrachloride from the stainless-steel surfaces . Within a few days, all of the stainless-steel flow lines that had contacted the mixed mobile phase were plugged with corrosion . Some of the metal had a brown crust omit, and other parts had a pinkish crust which turned green when exposed to air . Since the solvents were mixed inside the mixing chamber of the liquid chromatograph, it would seem that light is not necessary for the corrosive reaction.
In order to observe these effects in a less costly manner, 1-in . lengths of 1/8-in . 316 stainless-steel rods (6 .4 g) were placed in 10%, 25%, 50%, 75% solutions of carbon tetrachloride in 2-propanol, and also in 100% carbon tetrachloride . No sign of a reaction was observed in pure carbon tetrachloride after 50 days . The tubes containing the stainless-steel samples are shown in Fig . , at 30 days .
A noticeable green color developed in the liquid phase at 50 and 75% carbon tetrachloride iii about two days . In three days a brownish crust had formed on the surface of the rods, and there was obvious gas evolution. Within five days, the liquid phase in the 75% sample separated into two phases, an upper dark green phase, and a lower yellow phase containing the dispersed crust .
The liquid phase in the 25 % sample began to develop a green color in about 8 days, and the 10 % sample took approximately 32 days . Once the green color began to develop the reaction took place rapidly with a crust forming in two days .
All of the samples in which corrosion was observed evolved a gas which was found to be acidic by placing moist pH test paper over the tube . The gas also gave a positive test with phosgene test paper', indicating that it was probably HCI, since phosgene test paper gives a positive response to HCI . Phosgene would not be stable in the presence of the large amounts of alcohol .