ON COLOURING MATTERS. 59 
water for several hours. The liquor, after being reduced by boiling to a 
‘convenient compass, was mixed with some yeast, and allowed to ferment. 
By distillation an alcoholic liquid was obtained, which, after a second distil- 
lation, gave 214 ozs. of aleohol of sp. gr. 0°985, which is equivalent to 9 ozs. 
of absolute alcohol. It is therefore evident that madder contains sugar of 
some kind or other. 
_ The precipitate produced by basic acetate of lead in the solution of the 
brown syrup was decomposed with sulphuretted hydrogen. The filtered 
liquid was evaporated, and left after evaporation a dark brown syrup, having 
_ astrongly acid taste and reaction. ‘The brown colour was no doubt due to 
xanthin in its oxidized state. After being repeatedly dissolved, and the solu- 
_ tion being each time evaporated, a dark brown powder was deposited, 
just as in the case of the original solution: nevertheless the acid taste 
always remained. It might be supposed that this taste was due to some 
vegetable acid; and indeed if any such acid, or the compound of any one 
_ with the alkalies or earths, had been extracted irom the madder by boiling 
_ water, it would most probably have been precipitated by the basic acetate of 
lead, and it would be in the liquid obtained by the decomposition of the lead 
_ precipitate that we should have to look for any such acid. Now the syrup 
_ obtained after decomposing the lead precipitate and evaporating the liquid, 
though intensely acid, contained no oxalic, tartaric, malic or citric acid ; 
_heither did it show the least sign of crystallization ; but the watery solution 
_ gave a crystalline precipitate with ammonia and sulphate of magnesia; and 
' after destroying the brown organic matter contained in it by adding nitric. 
acid and boiling, and then evaporating to drive away the excess of nitric 
acid, it gave a yellow precipitate with nitrate of silver and ammonia. I 
therefore infer that the acid to which the sour taste of the brown syrup was 
‘owing, was phosphoric acid*. The sulphuret of lead, produced by the de- 
composition of the lead precipitate, was treated with boiling caustic potash. 
A dark brown solution resulted, which after filtration gave with muriatic 
id a dark brown precipitate. ‘This precipitate, after filtration, washing and 
ying, cohered into masses, which were brittle and black, but became brown 
nen powdered. It was totally insoluble in boiling water and alcohol. It 
s decomposed by dilute boiling nitric acid, and changed into a yellow floc- 
ulent substance. It was soluble in concentrated sulphuric acid, forming a 
wn liquid, and was re-precipitated by water. I consider this substance, 
at formed in a solution of xanthin during evaporation by heat, and the dark 
wn substance contained in the precipitate produced by acids in a decoc- 
ion of madder as the same, and that they are all produced from xanthin by 
action of the oxygen of the air. 
It still remains for me to say a few words on the substances left behind in 
he root, after madder has been exhausted with boiling water. It has for 
me time been well known that if madder, which has already been used for 
€ purpose of dyeing, be treated with a strong acid such as sulphuric or 
iriatic, and the acid be then carefully removed by washing with cold water, 
tis capable of being again used for dyeing in the same way as fresh madder. 
‘It is in this manner that the article known in commerce as garanceux is 
he On one occasion, after having added nitric acid to the acid syrup and boiled, I obtained 
on evaporation crystals of an organic acid, very similar to alizaric acid, but not identical 
} it. It was sparingly soluble in cold water, but very soluble in hot. It was volatile. 
The watery solution gave with acetate of lead a crystalline precipitate soluble in boiling 
water, with perchloride of iron a cream-coloured precipitate, with acetate of copper a green 
| crystalline precipitate, and with nitrate of silver and ammonia a white flocculent precipitate, 
__ Alizarate of lead is quite insoluble in boiling water, and not in the least crystalline. 
