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VI. A few facts relative to the colouring matters of some vege- 
tables. By James Smithson, Esq. F. R. 8 . 
Read December 18, 1817. 
J began, a great many years ago, some researches on the 
colouring matters of vegetables. From the enquiry being to 
be prosecuted only at a particular season of the year, the 
great delicacy of the experiments, and the great care required 
in them, and consequently the trouble with which they were 
attended, very little was done. I have now no idea of pur- 
suing the subject. 
In destroying lately the memorandums of the experiments 
which had been made, a few scattered facts were met with 
which seemed deserving of being preserved. They are here 
offered, in hopes that they will induce some other person to 
give extension to an investigation interesting to chemistry 
and to the art of dying. 
Turnsol. 
M. Fourcroy has advanced, somewhere, that turnsol is 
essentially of a red colour ; and that it is made blue by an 
addition of carbonate of soda to it ; and he says that he has 
extracted this salt from the turnsol of the shops. 
If turnsol contained carbonate of soda, its infusions should 
precipitate earths and metals from acids. 
I did not find an infusion of turnsol in water to have the 
least effect on solutions of muriate of lime, nitrate of lead, 
muriate of platina, or oxalate of potash. 
