No contemporaneous (1706) chemical account of the Prussian blue accident survives; the earliest personal testimony is a 1732 diary transcription of Dippel's memory

dye-chemistrypigmentshistory-of-chemistryprussian-blue18th-century-berlinprimary-source-verification

Answering the primary-source half of question-verify-prussian-blue-1706-accidental-discovery-primary directly: no first-person, contemporaneous chemical record of the 1706 Prussian blue accident has been located. Klaus Roth's own accounting of the evidence base for the reconstruction lists four items, only one of which is even a document: "Our sources are: Dippel and Diesbach's chemical activities (1706) / The leaked and published Prussian Blue synthesis (1724) / Dippel's memories as recorded by Senckenberg (1732) / Our modern interpretation of the chemical processes, supplemented with some experiments." The "1706" line is the participants' own activity — inferred, not read.

The earliest actual document is the 1724 leaked synthesis, published anonymously via the Royal Society eighteen years after the discovery and concerned with the recipe rather than the accident story. The next is Johann Christian Senckenberg's 1732 diary, a transcription of Dippel's own recollection of the events — the nearest thing to personal testimony, and still twenty-six years after the fact. This dating gap is why the vault's existing note's specific "contaminated potash borrowed from Dippel" detail is a later reconstruction rather than an eyewitness account: the same gap that leaves the 1706 chronicle silent on Dippel's role also means no surviving document was written close enough to the event to settle the chemistry directly.