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XII. Account of a Violet Dye produced from the Leaves of ' Succo* 

 trine Aloes, which rejijls the Ablion of Oxygen, Acids and Al- 

 kalis. By Mr. FABBRONI. From the Annales de Chimie, 

 Vol. XXV. 



JL O increafe the number of dyeing fubflances, and to be 

 able to vary the tone and fhades of the different known 

 colours, is an object of no fmail utility. Several manufac- 

 tures, as is well known, have been indebted for their reputa- 

 tion and credit to the pofleffion of.a particular dye. 



Without fpeaking of the Tyrian purple, who is ignorant 

 how much value the modern fcarlet has given to the Dutch 

 cloths and to thofe of the Gobelins ? Who does not know 

 that the beautiful black of Florence, which has never yet 

 been imitated, has railed the Florentine fluffs all over Europe 

 to a price to which that of no other country ever attained ? 



Scarlet and black belong to that clafs of colours called 

 •noble or fixed, becaufe they are not fufceptible of being ftained, 

 and becaufe they experience no alteration either from the air 

 or from light. The beautiful red colour alfo given to filk by 

 fafflower is recko ted among the noble colours, though it 

 does not withfland the influence of tlicfe two agents, which 

 foon deftroy it or render it pale. 



All other red dyes for filk, in order to be durable, muft be 

 compofed, in part, of cochineal, which is a colouring fub- 

 ftance exceedingly conftant. 



Argol and all the other lichens produce a very beautiful 

 violet •, but the fun alters, this, colour and makes it turn 

 blue. 



I am of opinion, therefore, that if means could be dif- 

 covered to compofe, without cochineal, colours graduated 

 from the mod delicate to the darkeft violet; purple, which 

 might be proof againft the action of acids and of the air, in- 

 finite advantages would thence refult to the manufacturers of 

 cloth and to the public. 



