Bin Chemiker der kein Physiker ist, ist gar nichts.
A chemist who is not a physicist is nothing at all.

At the moment I am occupied by an investigation with Kirchoff which does not allow us to sleep. Kirchoff has made a totally unexpected discovery, inasmuch as he has found out the cause for the dark lines in the solar spectrum and can produce these lines artificially intensified both in the solar spectrum and in the continuous spectrum of a flame, their position being identical with that of Fraunhofer’s lines. Hence the path is opened for the determination of the chemical composition of the Sun and the fixed stars.

At the moment I am occupied by an investigation with Kirchoff which does not allow us to sleep. Kirchoff has made a totally unexpected discovery, inasmuch as he has found out the cause for the dark lines in the solar spectrum and can produce these lines artificially intensified both in the solar spectrum and in the continuous spectrum of a flame, their position being identical with that of Fraunhofer’s lines. Hence the path is opened for the determination of the chemical composition of the Sun and the fixed stars.

Working is beautiful and rewarding, but acquisition of wealth for its own sake is disgusting.
A comment Bunsen often told his students.

You can find that sort of regularity in Stock Exchange quotations.
[Expressing his lack of confidence in reported regularities in the periodic classification of elements.]

Describing Robert Bunsen:
As an investigator he was great, as a teacher he was greater, as a man and friend he was greatest.

First I would like to wash Bunsen, and then I would like to kiss him because he is such a charming man.
Remark by the wife of Emil Fischer, upon meeting Bunsen for the first time, perhaps noticing a lasting chemical odour from his work.

Before an experiment can be performed, it must be planned—the question to nature must be formulated before being posed. Before the result of a measurement can be used, it must be interpreted—nature's answer must be understood properly. These two tasks are those of the theorist, who finds himself always more and more dependent on the tools of abstract mathematics. Of course, this does not mean that the experimenter does not also engage in theoretical deliberations. The foremost classical example of a major achievement produced by such a division of labor is the creation of spectrum analysis by the joint efforts of Robert Bunsen, the experimenter, and Gustav Kirchoff, the theorist. Since then, spectrum analysis has been continually developing and bearing ever richer fruit.