ON COLOURING MATTERS. 67 
__ I. 0°3785 grm. rubiacic acid, dried at 212° and burnt with oxide of copper, 
gave 0°7940 carbonic acid and 0:0845 water. 
__ If. 0°3605 grm. of another preparation gave 0°7610 carbonic acid and 
0°0795 water. 
III. 0°4670 grm. of the same preparation as the preceding gave 0°9775 
carbonic acid and 0°1050 water. 
_ Hence was deduced the following composition :-— 
Bho t Calculated Found. 
my: anche I Il. Ill. 
_ 8l eqs. Carbon .. 186 57°76 57°21 57°57 57°08 
5 8 ,, Hydrogen 8 2°48 2°48 2°45 2°49 
mi6;; Oxygen... 128 39°76 = 40°31. 89°98 = 40°43 
322 10000 100°00 100°00 100-00 
_ 0°3150 grm. rubiacin, dried at 212° and burnt with oxide of copper, gave 
0°7740 carbonic acid and 0°0935 water. 
_ This gives the following composition :-— 
Ne 
Calculated. Found. 
31 eqs. Carbon........ 186 67°63 67°01 
9) 4y, Elydrogen: iwi. 9 3°27 3°28 
10 ,; Oxygen ....-», 80 29°10 29°71 
a 275 100-00 100-00 
_ The formula of rubiacin being C3, Hy Oj, and that ofrubiacic acid Cs, H; Org 
it follows that when rubiacin is converted into rubiacic acid, it loses one 
equivalent of hydrogen and takes up six equivalents of oxygen, and that 
when rubiacic acid is reconverted into rubiacin, it loses six equivalents of 
ygen and takes up again one of hydrogen. This oxidation and reduction 
$ accomplished with the same certainty and precision as any similar process 
with inorganic bodies. 
_ Alpha-resin.—This resin is a constituent of the dark brown precipitate 
roduced by acids in a decoction of madder. It dissolves together with 
jiacin, when this precipitate is treated with a boiling solution of perchlo- 
or pernitrate of iron, and is precipitated together with rubiacin and 
acic acid when muriatie acid is added to the solution. It is separated 
a the rubiacin and rubiacic acid by means of alcohol, in which it is easily 
jluble, while the two former are but little soluble. It has a dark brown or 
eddish-brown colour. When cold it is brittle, and may be easily pulverized. 
_ begins to become soft at 150° F., and melts to dark brown drops between 
and 212°. When heated on platinum-foil it melts, swells up, and burns 
flame, leaving much charcoal, which however burns away without leaving 
sidue. When heated ina glass tube it swells up, gives an oily sublimate, 
volves a strong smell, leaving at last a bulky carbonaceous residue. It 
‘slightly soluble in boiling water, to which it communicates a yellow tinge. 
ie solution cooling yellow flocks are deposited, which are increased in 
ty by adding an acid. It dissolves in alcohol with an orange colour ; 
ater inakes the solution milky, and on the addition of an acid the resin is 
mpletely precipitated in orange-coloured flocks. The alcoholic solution 
Des not redden litmus paper. It dissolves in concentrated sulphuric acid 
dark orange colour, and is re-precipitated by water in yellow flocks. 
decomposed by boiling concentrated nitric acid ; on evaporating the acid 
nous mass is left. It dissolves in caustic and carbonated alkalies with 
irplish red colour. The solution in ammonia does not lose its ammonia 
oiling, but on evaporation the resin is left in combination with a little 
F2 
