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The top half of the page is taken up with notes on chemistry in relation to colour:
Potash added to a solution of Iron a brown | precipitate falls – Carbonat of Potash solution | a yellow oxide. which soon become a beautiful | orange oxide
Muriatic solution of Iron is a | permanent yellowish green color
Without establishing their origin, Joyce Townsend describes these notes as concerning the ‘production of unidentifiable early pigments’.1
This is one of fourteen pages of notes on varnishes and colours resulting from chemical reactions between folio 62 verso (D09974) and folio 55 recto (D09959), working from the back of the sketchbook as now foliated. Among his potted transcriptions from these passages, Thornbury noted: ‘the following scrap, I think from Beckmann:– “Potash added to a solution of iron, a brown precipitate falls, carbonate of potash separates, and yellow oxide, which soon becomes a beautiful yellow [sic] oxide.”’.2 (For Beckmann see under folio 58 verso; D09966). As discussed in the sketchbook’s Introduction,3 most are taken from William Nicholson’s 1808 Dictionary of Practical and Theoretical Chemistry, here from the unpaginated entry on ‘Iron’:
If potash be added to the nitric solution of iron, a brown precipitate falls down; of which a small quantity is redissolved by the alkali. Carbonat of potash separates a yellowish oxide, which soon becomes of a beautiful orange red colour. ...
The muriatic solution of iron is of a yellowish green colour, and is much more permanent than the solutions of that metal in the sulphuric or nitric acid