Having worked in science professionally, I can tell you that a lot of ‘science how to books’ are exactly the same.
I remember reading in separate treatises how you could only precipitate DNA out of solution using ethanol if temperature was reduced to -70C, -20C or 4C and the times at that cold temperature varied betwen 5 minutes and overnight!
My experience was that if you were working with more than 20 microgrammes, you’d get it all precipitated within 5 minutes! If it was more than 200 microgrammes, all done in 5 seconds!! And that was true in both cases at room temperature. It was only if you were working with tiny amounts of material that you needed extended times below zero……
The quantitative aspects of precipitation from solution was something remarkably free from undergraduate practical lessons, despite it being one of the most widely used techniques in professional science, be that chemistry, biochemistry or molecular biology.
Strange that…….