on the colouring Matter of Vegetables: 129 
tolleagues, being.informed of the objeét of my refearches, 
cailéd my attention to the aloe. C. Desfontaines was fo 
kind as to procure me feveral fpecies, but I fhall {peak only 
of that known under the name of the fuccotrine aloe. -I 
accordingly tried experiments on this plant, one of the 
richeft in colour, though it has not the flighteft appearance 
of it while the equilibrium of its principles is maintained by. 
vegetable life. The woody fibre which is on the outfide 
ferves as a covering to a very vifcous matter of a whitith, 
green colour, weakly acid; but fcarcely has this matter ~ 
been expofed to the air when it affumes a very lively purple 
red colour, which becomes extremely abundant by the progrefs 
of fermentation. Of this matter [ have formed lakes with 
alumine, the oxyd of tin, and the white oxyd of zinc: but 
none could bear a comparifon with that prepared by means 
of tungften. I have no doubt that the oxyd of this new metal 
thay be employed in the compofition of colours for dyeing, 
at leaft for the dyeing of filks which are not intended to be 
fubjeéted to boiled leys. The oxyd of tin may be employed. 
for that purpofe with advantage, as it is not eafily injured by 
acids: but our oxyd is abfolutely infoluble. 
I fhall conclude with a reficétion which may add Fp 
intereft to thefe refearches :— Wolfram, from which this oxyd, 
is obiained, is found in the territories of France *, feveral 
mines of it are already known, and the French chemifts 
haye been employed for fome years in endeavouring to 
fimplify the procefies for freeing it from foreign fubftances : 
we hope then, that the properties I have explained, will 
fupply artifis with new means to enfure duration to the pro- 
duétions of their genius, and open a new branch of national 
indufiry. 
* It is found in abumdance in the tin mines in Cornwall. Epit, 
t 
Vou. Ul, K IV. Ev 
