I also agree with the already suggested "accidental" impurities but there is a subtle difference:

- accidental may be known. It wasn't intended but you know what and how juchnit wad and ** can control ** the effects snd outcome.

- random (in my understanding) is closer to your text. A totally uncontrolled, random additions.

Both terms are well represented in Google technical results, so take your pick.

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Note added at 3 hrs (2012-02-25 23:44:16 GMT)
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Sorry for the mix up. "juchnit wad" was supposed to be "much it was".

Random impurity I guess :-)

makes sense, the obvious is correct most times.
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