On the BffeSi cf AJlrlngeni Vegetables in Dying. 13.I 



from light grey to deep black ; iimply by pafEng the cottons, impregnated with the aflringent 

 principle, into a foliuibn of iron. The oxydc is then precipitated by the principle which is 

 fixjd in the ftuft". 



It is an obfervation which may become of high value in the art of dying, that the aftiingent 

 vegetables moft ■ commonly ufed afford a colour which is not very bright, but of high value for 

 its durability. This yellow colour is brightened in the feries of vegetables, in proportion as 

 the aihing! nt principle is left in quantity, and the livelinefs of the colour is alfo increafed in 

 the (dma proportion. It is, therefore, difficult to obtain yellow colours which (hall be at the 

 fame time folid and bright. Thefe two valuable qualities are inverfely proportioned to each 

 other. But it is poffible to join thefe colouring principles in fuch a manner as to add brightnefs 

 to folidity. Green oak-bark joins perfe6lly with woad, and fumach with quercitron. By 

 this mixture, we may fucceed in combining with the oxyde of iron fuch vegetable colours as 

 unite durability with brightnefs. 



I fhall conclude thefe obfervations with a remark concerning the ufe of aftringents in the 

 dying of cotton. 



It has been pretended, that by increafing the proportions of fumach, or the bark of alder, 

 or oak, it may be prafticable to fupply the place of galls in the red dye for cotton. I fhould 

 be fo much the more gratified if this were true, as the galls confiderably add to the expence of 

 our colours, and fumach may be had at a low price, becaufe it grows almoft every where in 

 the dry fituations of our fouthern climates ; but I can affirm that the fubftitution is impoffible, 

 however large the dofe of this aftringent may be ; for the colour is much paler, with lefs body 

 and durability. I know that this is not the cafe with regard to wool and filk, in which this 

 article is ufed with fuccefs ; and in giving an account of this difference, I think it may be af- 

 cribed to the nature of the nut-gall itfelf i. The acid, which it contains exclufively of the 

 other aftringents, as Berthollet has proved, facilitates the decompofition of the foap, with 

 which the colours have been impregnated ; and then the oil remains fixed in their texture in 

 a much larger quantity, and more intimately combined. 2. The nut-gall, which owes its 

 developement to animal bodies, retains a character of animalization, which it tranfmits to the 

 vegetable piece ; and by that means, increafes its affinities with the colouring principle of the 

 madder ; for it is known how ufeful animal fubftances are to facilitate this combination. This 

 animalization becomes ufelefs in operations upon wool or filk. 



VIII. 



AtnUfti of the Expirimenfs «f Citizen Clouet, on the different States' tf lro% and its Con- 



•Oerfion into Gajl-fieel*. 



H E learned reporter begins his account, by giving an hiftoric^ fketcK of the fcientific 

 and correft information we pofTefs, refpefting the art of fleel-making. He flates, that from 



♦ From the report of Citizen Guyton, made to the National Inftitute of France, on i6th Meflidor in the 

 year VI. (July 4, i7981> inferred- in the Aiinales de CHimie, XXVIII. 19. 



S 2 the 



