Dr. Schunck on Colouring Matters. 217 



ing solution of perchloride or pernitrate of iron, and is precipitated 

 together with rubiacine and rubiacic acid when muriatic acid is 

 added to the solution. It is separated from the rubiacine and rubi- 

 acic acid by means of alcohol, in which it is easily soluble, while the 

 two former are but little soluble. It has a dark brown or reddish- 

 brown colour. When cold it is brittle, and may be easily pulverized. 

 It begins to become soft at 150° F., and melts to dark brown drops 

 between 200° and 212°. When heated on platinum-foil it melts, 

 swells up, and burns with flame, leaving much charcoal, which how- 

 ever burns away without leaving any residue. When heated in a glass 

 tube it swells up, gives an oily sublimate, and evolves a strong smell, 

 leaving at last a bv.lky carbonaceous residue. It is slightly soluble 

 in boiling water, to which it communicates a yellow tinge. On the 

 solution cooling yellow flocks are deposited, which are increased in 

 quantity by adding an acid. It dissolves in alcohol with an orange 

 colour ; water makes the solution milky, and on the addition of an 

 acid the resin is completely precipitated in orange-coloured flocks. 

 The alcoholic solution does not redden litmus paper. It dissolves 

 in concentrated sulphuric acid with a dark orange colour, and is 

 reprecipitated by water in yellow flocks. It is decomposed by boil- 

 ing concentrated nitric acid ; on evaporating the acid a resinous mass 

 is left. It dissolves in caustic and carbonated alkalies with a pur- 

 plish red colour. The solution in ammonia does not lose its am- 

 monia on boiling, but on evaporation the resin is left in combination 

 with a little ammonia. The ammoniacal solution gives purple pre- 

 cipitates with the chlorides of barium and calcium, arid a dirty red 

 precipitate with alum. It dissolves in perchloride and pernitrate of 

 iron with a dark reddish-brown colour, and is re-precipitated by acids 

 in flocks. The alcoholic solution gives red precipitates with alco- 

 holic solutions of sugar of lead and acetate of copper. If chlorine 

 be passed through a solution of the resin in caustic potash, it is 

 decolorized ; acids however now produce no precipitate, so that the 

 resin seems to have been entirely decomposed by the chlorine. 

 If mordanted cloth be introduced into boiling water, in which a 

 quantity of the resin is suspended, the alumina mordant acquires 

 an orange colour, and the iron mordant a brown colour. Never- 

 theless these colours are so slight, that it is not likely that this resin 

 contributes in any way to produce the desired effect in the process 

 of madder-dyeing. I shall presently show that, on the contrary, it is 

 rather injurious than otherwise in this process, since those parts of 

 the cloth which should remain white acquire from it a disagreeable 

 yellow tinge, which cannot afterwards be removed by merely wash- 

 ing with water, so that even if it did contribute to produce any 

 greater intensity of colour on the mordanted parts, the advantage 

 would be more than counterbalanced by the injurious effect on the 

 unmordanted parts. 



Beta-resin. — This resin also forms a constituent of the dark brown 

 precipitate produced by acids in a decoction of madder. If this 

 precipitate be treated with a boiling solution of perchloride or per- 



