218 Dr. Schunck on Colouring Matters. 



nitrate of iron, the beta-resin forms a compound with peroxide of 

 iron, which remains undissolved. By decomposing this compound 

 with muriatic acid, and dissolving the resin in boiling alcohol, it is 

 deposited on the alcohol cooling as a light brown powder. It 

 hardly melts at the temperature of boiling water, but merely becomes 

 soft and coheres into lumps. When heated on platinum foil, it melts 

 and burns, leaving a slight red ash. When heated in a glass tube, 

 it gives yellow fumes and evolves a disagreeable smell, leaving a car- 

 bonaceous residue. It is slightly soluble in boiling water, to which 

 it communicates a yellow tinge ; on the solution cooling nothing 

 separates, but on adding acid some yellow flocks are deposited, while 

 the liquid becomes colourless. Tlie alcoholic solution is dark yel- 

 low ; it reddens litmus -paper. Water renders it milky, and acids 

 precipitate the resin completely in yellow flocks. The resin dissolves 

 in concentrated sulphuric acid with a dark brown colour, and is re- 

 precipitated by water in light brown flocks. Concentrated nitric acid 

 dissolves it on boiling and decomposes it; on evaporation there is 

 left a yellow, bitter astringent substance. It dissolves in caustic and 

 carbonated alkalies with a dirty red colour, inclining to purple in the 

 case of caustic alkali. It is re-precipitated by acids in brown flocks. 

 If chlorine be passed through a solution of the resin in caustic pot- 

 ash, it is decolorized ; but the substance itself seems to be thereby 

 decomposed, as acids afterwards produce only a slight precipitate. 

 The ammoniacal solution gives with the chlorides of barium and 

 calcium dirty yellow precipitates. The alcoholic solution gives with 

 an alcoholic solution of sugar of lead a red precipitate, and with 

 an alcoholic solution of acetate of copper a brown precipitate. The 

 ammoniacal solution loses its ammonia on evaporation, and the resin 

 is left as a transparent brown skin. This resin has the same effect 

 on mordanted cloth as the preceding ; the alumina mordant acquires 

 an orange, and the iron mordant a brown colour, while the un- 

 mordanted parts become yellow and unsightly. These effects are 

 not however so decided as in the case of the alpha-resin, which is 

 probably owing to its being less soluble in water than the latter. 



Rubian. — I have given this name to the substance to which the 

 bitter taste of madder seems to be due. I have described its method 

 of preparation and properties in my last report. I may state, in 

 addition to what I there said, that rubian seems to be a nitrogenous 

 body, since, on treating it with boiling caustic alkali, ammonia is 

 evolved. This fact and the bitter taste seem to indicate that the 

 medical properties of madder, if indeed it possesses any, reside in 

 this substance. 



If a solution of rubian in water be evaporated in contact with the 

 air and with the assistance of heat, it deposits a dark brown sub- 

 stance, which sinks to the bottom in resinous drops, so that on treat- 

 ing the residue after evaporation with water, it is not completely re- 

 dissolved ; and if the filtered liquid be again evaporated as before, 

 a fresh quantity of the dark brown substance is formed, just as in 

 the case of extractive matter. This dark brown substance melts 



