A Dye from the Leaves of the Aloe. ty 



It was in hopes of discovering fuch a colour that I dire&ed 

 my refearches towards a fubftance which hitherto has not 

 been ranked among thofe called colouring fubftances. 



I was perfuaded that the matter of the brilliant colours 

 prefented to us in thofe fruits, flowers, and plants, which 

 have undergone a fpontaneous alteration, pre-exifts in the 

 mafs of the fluids that circulate in thofe organs, where it is 

 diiperfed or concealed ; and that to be able to turn it to ad- 

 vantage, nothing would be wanting but a method to feparatc 

 it, and to modify it in a proper manner. 



The cochineal infect, which lives on the nopal [caBm coc- 

 cem/ifer), can extract with itsprobofcis the red juice, or juice 

 fufceptible of becoming red, of that plant ; which afterwards 

 communicates its colour to the infect, and which, in my 

 opinion, is the fame as that exhibited to us naked in the ripe 

 fruit of the fame plant. 



The beautiful fcarlet colour aflumed by the dead leaves of 

 fome fpecies of ftrawberry blite {blitum) is not perhaps 

 brought forwards but in confequencc of the decompofition 

 of the dead leaf. Would it be impoflible then for art to 

 feparate this colour, and to modify it in the like manner ? 



Having obferved that the fucculent leaves of the aloe fuc- 

 cotrina angujlifolia^ as they dried on the plants, aflumed an 

 agreeable violet colour, I tried to feparate the colouring mat- 

 ter, or principles of that fine colour, from the living leaves. 



I found by experiments, that acids as well as alkalis 

 ffpeedily gave to this almoft colourlefs juice a red colour, and 

 formed a fucceflive precipitation of colouring molecuk* 

 which had the fame colour. 



Oxygen gas produced the like effe£r, j and it is highly 

 pleafing to fee how the juice of aloes, merely by being ex- 

 pofed to the air, with or without the contact of the light, 

 fucceflively reddens, beginning at the parts more immediately 

 in contact, and is gradually converted into a very dark and 

 lively violet purple. 



This 



