1^4 Ohfervations on MaJderlng^ 



their origin to the tanning principle ? This remains to be 

 examined. 



The quantity of madcliT to be employed in dyeing ought 

 not only to be proportioned to the extent of the furfaces to be 

 niadclered, but alio to the concentration of the liquors of the 

 acelite of alum'ine and iron, improperly called mordants ; that 

 is to fay, to the greater or lefs quantity of alumine and oxide 

 of iron which thcfe (aline liquors, either iufulaied or mixed 

 together, when thev dry on the articles to be (.\\i:i\, may have 

 left or depofiled there by the evaporation of the acetic acid. 

 It the objects to be dyed arc not numerous, and, in parti- 

 cular, when bright iliadcs only are to be produced, they may 

 be maddered only (mce ; but when they are numerous, and 

 intended to have dark thades, the maddering mult be repeated 

 twice, and even thrice. Three quarters of a pound of madder 

 of a good quality are lufiicicnt for dycino; a piece of white In- 

 dian cloth often ells in length and three quarters broad, in- 

 tended to exhibit only a few coloured objects: the quantity 

 of the Colouring fubUauce muil be increafed in the ratio of 

 the mafs of aluminc and oxide of iron, fixed on a piece of 

 ^ufF of the above dimenlions. It may be extended to 6, 8, 

 ■JO, and even 12 pounds, for a ground well covered with a 

 lively and very intenfe colour. Intelligence and practice in 

 the management of a dye-houfe will not fail to indicate 

 nearly the proper proportions. 



Whatever care may be employed in maddcrina to avoid 

 the adhefion of the yellow parts, the colours obtained will 

 be far from having all the beauty and fixity which they 

 might acquire by clearing, preceded by very long ebullition 

 in exceedingly pure water. This ebullition alone, by the 

 addition of bran, will ferve to brighten the colour: more 

 roly red.s will be obtained by employing foap with or without 

 the addition of bran ; carbonate of potalh or of foda, fubfti- 

 luted for bran, will make the reds incline to crimfon; but 

 I muft obierve, that unlefs the workman choofes to run the 

 rifk of making the reds entirely brown, and in fuch a man- 

 ner that it will not be poffible to rellore them, it will be 

 neceflary, before fuap and alkalies are applied to the (lufis, 

 to expofe them to the uAion of the ftrongeit heat that can 

 be communicated to water. This operation will be attended 

 with fuccefs, if as little pafTage as polfible be afforded to the 

 fleam, and if the boilers employed be converted into a fort 

 of digeliers. The fixity of the colours will be proportioned 

 to the time employed in expofing them to the action of the 

 boilinF water. It is needlefs to obfervCj that there is no 



danger 



