Julius Jeffreys, late of the Hon. East India Company's Medical Establishment."
The inner surfaces of a flue built of siliceous bricks appeared to be deeply eroded by the passage over it of steam at a very high tem- perature, and fragments of siliceous materials laid in the course of the current were partially consumed. A siliceous crust was de- posited on several vessels of stone ware, coated with a micaceous glaze, placed in the upper part of the furnace, and this crust was re-dissolved when the vessels were removed to a hotter situation in the same furnace. The author notices the experiments of Dr. Turner and others, which failed in showing the solubility of silica by steam, in consequence, as he conceives, of the heat having not been sufficiently great to effect the solution.
June 4, 1840.
The MARQUIS of NORTHAMPTON, President, in the Chair.
Justus Liebig, Johannes Midler, and Jacques Charles Francois Sturm, were severally elected Foreign Members of the Society.
The Right Rev. the Lord Bishop of Norwich, Lieut. Thomas Cook, R.N., and WilHam Hutton, Esq., were balloted for, and duly elected into the Society.
A paper was read, entitled, " Contributions to the Chemical Hi- story of Archil and of Litmus." By Robert Kane, M.D., M.R.I.A. Communicated by Francis Baily, Esq., V.P.R.S.
After a preliminary sketch of the labours of Heeren and of Robi- quet in investigating the origin of the beautiful colouring materials termed Archil and Litmus, obtained from different kinds of colourless lichens, and their detection of the two proximate principles termed erythrine and orceine, the author states the object of the inquiries de- tailed in the present paper to be threefold ; viz. first, to ascertain the primitive form of the colour-making substance in a given species of lichen, and trace the stages through which it passes before the co- loured substance is developed ; secondly, to determine the nature of the various colouring substances which exist in the archil of com- merce ; and thirdly, to examine the colouring materials of ordinary litmus. He finds in the lichen Roccella tinctoria the following bodies, either pre-existing in the plant, or formed during the pro- cesses employed for its analysis : 1. Erythryline ; 2. Erythrine (the Pseudo-erythrine of Heeren) ; 3. Erythrine bitter ; 4. Telerythrine ; and 5. Roccelline (the Roccellic acid of Heeren). The properties and constitution of these substances are then described, and the che- mical formulae given, which are deducible from their respective ana- lyses. The author finds the archil of commerce to consist essen- tially of three ingredients, namely, orceine, erythroleic acid, and azoery thrine ; of each of the two former there exist two modifications.
