58 REPORT—1848. 
and I shall presently describe a substance of almost identical properties 
formed by the action of the air on xanthin, the extractive matter of madder. 
There can however be no doubt that the brown colour of the precipitate, 
which is produced by acids in a decoction of madder, is due to this substance, 
for the other bodies contained in it are not brown, but yellow or orange- 
coloured in a precipitate state. This dark brown precipitate therefore con- 
sists of the following substances :—alizarin, rubiacin, alpha-resin, beta- 
resin, rubian, pectic acid, and oxidized extractive matter. 
I have examined the liquid filtered from the dark brown precipitate pro- 
duced by acids more minutely since making my last report. If oxalic acid 
be used as the precipitant, the excess of acid may afterwards be removed by 
chalk, without leaving any lime-salt in solution. ‘The liquid, which had a 
light yellow colour, was evaporated on the sand-bath. During evaporation 
it gradually became brown, and left at last a thick dark brown syrup, which 
never became dry, however long it might be exposed to the heat of the sand- 
bath. On re-dissolving this syrup in water, a considerable quantity of a dark 
brown powder remained behind. On again evaporating the filtered solution 
on the sand-bath, an additional quantity of this powder was deposited, just as 
in the case of extractive matter. There can be no doubt that this powder is 
formed by the action of the air, assisted by heat, on some soluble substance con- 
tained in the liquid. On burning a small quantity of the brown syrup in a 
crucible it swelled up enormously, and gave off a quantity of empyreumatic 
products, which burned with a flame, leaving at last a considerable quantity of 
white ash ; this ash was partly soluble, partly insoluble in water. The soluble 
part had a strong alkaline reaction ; it consisted of a trace of lime and mag- 
nesia, and a great deal of potash, combined with carbonic, sulphuric and 
muriatic acids. ‘The insoluble part consisted of carbonate of lime, carbonate 
of magnesia, a trace of alumina, phosphate of lime and phosphate of mag- 
nesia. ‘The solution of the brown syrup in water had an acid reaction. It 
gave no precipitate or peculiar colour with a persalt of iron, and therefore 
contained no tannic acid. The addition of alcohol produced no precipitate 
or coagulate, and therefore there was no gum present. On adding muriatic 
or sulphuric acid to it, and then boiling, it became dark-coloured and de- 
posited a green powder. Sugar of lead produced in the solution a dirty 
brown flocculent precipitate, and basic acetate of lead a still more copious 
precipitate. A considerable quantity of the brown syrup was dissolved in 
water, and basic acetate of lead was added until no more precipitate was 
produced. The precipitate was separated by filtration, and washed with 
water. The percolating liquid had a yellow colour. The excess of lead was 
removed from it by sulphuretted hydrogen, and the filtered liquid was eva- 
porated over sulphuric acid, since, if evaporated by the assistance of heat, 
the substance contained in it was changed by the air, became brown, and 
deposited a brown powder. After remaining over sulphuric acid for several 
weeks, there was left a yellow or brownish-yellow syrup like honey, which 
did not become dry. This substance, though not pure (as it contained salts 
of lime, magnesia and potash), I conceive to be identical with Kuhlmann’s 
xanthin and Runge’s madder-yellow. 
If madder contains sugar, it is evident that, provided the method of ope- 
rating described above be followed, it must be contained in the same liquid 
as this xanthin. I have however not been able to prove its presence by 
direct experiment; but I have succeeded in ascertaining indirectly that 
madder does in reality contain sugar of some kind by means of the following 
experiment. Half a hundred-weight of madder was treated with boiling 
