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XXVIII. On Ruhian and its Products of Decomposition*, 

 By Edwaed Schunck, FM.S. 



Part III. 

 Combined Action of Alkalies and Oxygen on Ruhian. 



IN the preceding part of this paper t I have given an account 

 of the action of alkalies on rubian and of the products of 

 decomposition thereby formed. I have shown that these pro- 

 ducts are, with one exception^ identical with those which the 

 action of strong acids gives rise to, the rubianine produced by 

 acids being merely replaced by rubiadine when alkalies are em- 

 ployed. Now though I found this to be in all cases the final 

 result of the action of alkalies, there still remained a possibility 

 of the existence of bodies intermediate between rubian and the 

 final products of decomposition. Such bodies do in reality exist, 

 but their formation is dependent, at least in part, on the simul- 

 taneous action of oxygen. 



If to a solution of pure rubian baryta water be added in excess, 

 if a current of carbonic acid gas be passed through the solution, 

 until the whole or a great part of the baryta has been converted 

 into bicarbonate of baryta, and the filtered solution be left ex- 

 posed in a shallow vessel to the atmosphere, its surface becomes 

 covered in a short time with a thin film of a beautiful scarlet 

 colour, which, when viewed under a lens, is seen to consist of 

 small interlaced crystals. If this film be broken so as to cause 

 it to sink to the bottom, a new one is formed on the surface of 

 the liquid. This process continues for some time, but at last 

 ceases. On gently evaporating the solution, an additional quan- 

 tity of this red substance separates in thick flocks. After being 

 collected on a filter and washed with cold water, it appears of a 

 fine scarlet colour. On drying it becomes brown, but if then 

 reduced to powder the colour changes to a cinnabar-red. If it 

 be suspended while still moist in water, and a current of car- 

 bonic acid gas be passed through the liquid, it dissolves again 

 entirely, forming a yellow solution ; but if this solution be eva- 

 porated, its colour changes to red, and it again deposits red 

 flocks, after which it becomes almost colourless. The red flocks 

 contain two organic substances in combination with baryta. On 

 adding to them dilute sulphuric acid the former dissolve, giving 

 a yellow solution. The excess of sulphuric acid having been 

 removed by means of carbonate of lead, the solution is filtered, 

 and the insoluble matter left on the filter is treated several times 



* From the Philosophical Transactions, Part II. for 1855, having been 

 received by the Royal Society June 13, 1855, and read June 21, 1855. 

 t See Phil. Mag. vol. v. pp. 410, 495. 



