474 Royal Society. 



rubiacine, before being converted into rubiacic acid ; while by the 

 action of reducing agents rubiacic acid is reconverted, first into rubi- 

 acine, and then into rubiafine. 



Rubiagine is never obtained in well-defined crystals. When its 

 alcoholic solution is evaporated spontaneously, it is left behind in the 

 shape of small lemon-yellow spherical grains, which M'hen crushed 

 and examined under a lens, are found to consist of small crystalline 

 needles grouped round a centre. When heated it melts, and is de- 

 composed without being volatilized. It is quite insoluble in boiling 

 water. It is soluble in boiling nitric acid, with a yellow colour, and 

 crystallizes out again on the solution cooling in shining needles. Its 

 alkaline solutions are blood-red. The alcoholic solution gives on 

 the addition of acetate of lead at first no precipitate, but the colour 

 of the solution becomes dark yellow, and after some time, provided 

 the solution be not too dilute, an orange-coloured granular precipi- 

 tate subsides, which is the lead compound of rubiagine. If no de- 

 posit is formed, then the addition of water causes an orange-coloured 

 flocculent precipitate, which after being washed with water, in order 

 to remove the excess of acetate of lead, is found to be very little 

 soluble in boiling alcoliol, but is easily soluble in a boiling alcoholic 

 solution of acetate of lead with a dark yellow or orange-colour. 

 When rubiagine is treated with a boiling solution of perchloride of 

 iron, it dissolves slightly, but is not converted into rubiacic acid. 

 Rubiagine is distinguished from rubianine by its insolubility in 

 water ; from rubiadine, for which it might most easily be mistaken, 

 by its being incapable of sublimation ; and from rubiafine by its not 

 being convertible into rubiacic acid. Its behaviour towards acetate 

 of lead, which is different from that of all the other three substances, 

 also serves to characterize it. The most probable formula for ru- 

 biafine is C,., H,4 Oio> from which it appears that it differs from the 

 substances just named merely by the elements of water. Its forma- 

 tion from rubian, like that of the substances allied to it, indicates 

 the simultaneous formation of sugar. 



Rubiadipine is a body of a fatty nature, as its name indicates. In 

 its appearance and general properties it resembles rubiretiue. It 

 differs from the latter in always remaining soft and viscid, and never 

 becoming hard and brittle, however long it may be heated. Its colour 

 is yellowish-brown. When heated in a tube it emits acrid fumes, 

 similar to those produced by fat when exposed to destructive distil- 

 lation. When thrown into boiling water it melts and forms oily 

 drops, which rise to the surface. Its alcoholic solution gives with 

 acetate of lead a pale reddish-brown precipitate, soluble in an excess 

 of the precipitant. An analysis of the lead compound conducted to 

 the formula C30H04 Or,-|-PbO. If this formula be accepted as the 

 true one, the author confesses his inabiUty to explain the formation 

 of rubiadipine from rubian. The great excess of hydrogen contained 

 in it shows that some substance must be formed simultaneously con- 

 taining a large proportion of oxygen, which has hitherto escaped 

 detection. 



Having examined generally the action of erythrozym on rubian, 



