Hi everyone! So, something sort of weird happened in analytical lab and I was wanting some guidance. I was trying to determine the ethanol concentration in a 4 Loko, a red wine, and a beer through acid/base titration. I pipetted a little bit of a diluted alcohol sample into a small beaker and suspended it over a potassium dichromate solution made from sulfuric acid, water, and potassium dichromate. I left it for two days, then I took the sample out, squirted water down the sides of the flask and titrated the potassium dichromate solution with thiosulfate. The thiosulfate determined how much potassium dichromate did not react with ethanol (I had blanks that help me determine this). Well, one indicator I used was KI. Apparently, it is used to oxidize the chromium. Once it faded from a rust color back to the bright yellow it was prior to adding the KI, I then added starch which turned the solution dark blue and continued titrating. The end point was when the dark navy changed to a transparent blue color. Now, my issue here is this. The first time I did this, I got terrible results (5% ethanol for the wine, 9% for the 4 Loko, and 0% for the beer). I figured it was because of how much they were diluted so I did more samples with far smaller dilution factors. Well, for the first set of trials the color of the acid chromate layer was what it was supposed to be prior to titration: bright yellow. For the second set, it was either a weird blue/green or light blue. I figured that some of the suspended solution dripped down into the acid layer which it reacted with the starch in the beverage, but that doesn't make sense because the starch wouldn't react without KI being present. Maybe I'm confused, but if anyone can shed any light on what these colors mean, I would appreciate it. The colors for the titration, if correct, go like this: Highlighter yellow --add KI--> Rusty brown/red --titrated w/ thiosulfate----> back to yellow --add starch--> dark navy --titrated with thiosulfate--> light blue BUT, after the second trials incubated, the colors for most of the solutions ranged from light green to light blue rather than bright yellow. Maybe it was a fluke, but maybe there is some interaction in there I don't know about. The samples were only diluted with water and the acid dicrhomate solution that the alcohol samples were suspended over contained potassium dichromate, sulfuric acid, and water. Again, the colors were right for the first trials (even though my results were horrible), but were really weird for the second set of trials. The only differences were the dilution factors. Some of them, when I added KI, turned to a yellow-y color but then after two drops of thiosulfate, they were light blue. -____- confused! One other thing was that for the first trials, the dichromate solution was fresh and had just been made; however, the second trials were done maybe two weeks later using that same solution. It had been left in the hood over break. Not sure if this changes anything, but figured I'd throw that out there. Thanks!