For context, i'll describe the problem. I'm working in chromatography, and the first part of the work was to do TLC experiments to narrow mobile phase compositions for separation of valuable components of plant extracts through column chromatography. In these experiments, we found that there were impurities that could not be moved by ANY type of mobile phase. We tried several procedures, but none were effective, we just abandoned this problem because something else became evident.

I'm now writing the description of the events in my thesis, and I have a whole subsection with a structure of "we tried this, here is a picture, you can see it did not work", repeated something like 5 or 6 times. Those SHOULD have worked, but they didn't. Imagine having a car in which the engine chugs and does not start, you replace the whole engine, and then the car continues to not start.

I am therefore stuck in a situation in which I can only describe an additional two procedures as "throwing stuff at the wall and seeing what sticks". I am however pretty sure you can't actually write that on a thesis. How should I express this?

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    Not an answer to your question, but possibly worth mentioning: in thesis writing, do not devote space in proportion to effort invested. – ff524 Jul 26 '16 at 19:46
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    If you want to say "I tried doing A, B, and C, and I thought they might work because of X, Y, and Z respectively, but they didn't work and I don't know why," you can probably just say that. – user37208 Jul 26 '16 at 20:30
  • Difficult to answer without knowing its place in the thesis. How do these failed efforts relate to the overall contribution of the thesis? Usually I'd assume that a thesis focuses on a contribution/narrow topic and is not a chronological log of all you did. But if it is relevant for what you achieved (stepping stone to something that worked) I'd have no problem with a chapter describing what did not work. Although question remains — did it perhaps not work because you made errors in the implementation? (BTW, "should have worked but did not" is quite common, you're doing science. :-)) – Daniel Wessel Jul 27 '16 at 11:55
  • "Exploratory".. – Fomite Jul 27 '16 at 20:02
  • did you also try mixtures? => combinatorial screening of solvents – cbeleites unhappy with SX Jul 28 '16 at 12:39

It would be best to explain why such experiments were conducted along with supporting concepts that you would like to verify. It ought not to look like a random set of trials.

You may write something like this:

Concept X follows from [explanation of X]. This concept formed the hypothesis Y to justify the following experiments. ... Although the experimental results were negative, it would be of worth to note them here as to why they were so.

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In my field we call it "trial-and-error" approach. It's not the best thing to do from a scientific point of view, but some times it's just faster.

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  • So what would be a better thing to do from a scientific point of view then? For me, trial-and-error sounds like an inherently scientific approach. – lighthouse keeper Jul 27 '16 at 19:55
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    A better approach is to base the selection of the trial / trial parameters on some supporting theory. If the trial fails, then you need to find the error in your theory or the trial implementation and fix it before trying again. Of course some trials will fail, however, there is a difference between knowing why something failed (bad calculations, wrong assumptions, contaminated experiment, etc.) and fixing it before trying again, and just "throwing on the wall to see what sticks". – electrique Jul 27 '16 at 20:11

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