The translation of Chymia philosophica by Jakub Barner is the second publication in Polish historiography of a printed source work on early modern chemistry (alchemy) written by a Polish citizen, well known and influencial across Europe (the first such translation comprised the treatises of Michael Sendivogius). This admirable initiative of unquestionable value to Polish historians of science resulted in an elegantly published volume, with an extensive introduction and useful appendices. The language of the translation is pleasant to read, retaining the spirit of the original by means of a moderate use of archaisms and generally accurate selection of proper terminology. A closer comparison of some fragments of the translation reveals, however, that it omits essential words, phrases and even entire sentences. The translation itself is occassionally incorrect as well, completely changing the meaning of the author’s text and distorting his intentions, thereby undermining the reliability of the Polish translation as a whole. In the factual layer, identifying both chemical substances and (especially) the names of the authors cited by Barner often appear to be doubtful or problematic. Apart from numerous obvious mistakes, as well as leaving many surnames unidentified even when it was very difficult, the translators and/or editors of the Polish text created some non-existent authors as a result of errors produced while copying their surnames from the original text or due to unfounded assumptions that some chemical or botanical terms are names of chemical authors. There is also no consistency in the spelling of surnames (usually left in the Latin form, sometimes spelled with wrong inflection, but also modernised). In the biographical introduction there are also numerous factual errors and some bizarre mistranslations. Not only did its author fail to correct invalid information of earlier biographers of Barner, relying only on the most obvious and accessible publications, but also perpetuated these "historiographical myths" and even created new ones. Neither did he consult any sources apart from some other of Barner‘s published books. Writing from the positivist perspective and on the basis of outdated literature, he also sustained the categorical distinction between alchemy and chemistry, already rejected in contemporary historiography, thus presenting the role and position of Barner in the history of science not quite adequately. If one adds to that the very numerous "typos” throughout the book, it may be regarded as a negative example of poor source editing in almost every respect, even though it makes a pleasant reading.