Processes far preparing Lake from Madder. 121 



•Kcellent for many purposes, yet I consider the colour pro- 

 duced by the union of the two colouring matters, as aiven 

 in the first process, as ftir preferable for general use, beintr 

 of a very beautiful hue when used thin, and po^sessino- un- 

 rivalled depth and richness either in oil or water, when laid 

 on in greater body. 



If but half an ounce of alum be added to the two ounces 

 of the root, the first precipitate v.iil be nearly similar to 

 that when an ounce is employed ; but the second, or lake 

 precipitate, will be less in quantity, and of a deeper 

 and richer tint. In this case the v.hole of the colourino- 

 matter, as before observed, is certainly not combined with 

 the alumlne; for, on addmg m.ore alum to the remainimr 

 liquor, a precipitate is obtained of a light purplish red. la 

 this process, -when two ounces of madder and an ounce of 

 alum are used, the first precipitate has about 20 per cent, 

 ofahuiiine, and the second, or lake precipitate, about 53 

 per cent. ; but these proportions will vary a little in repetl-. 

 tions of the process. 



Process 3. 



If the madder, instead of being washed and triturated 

 with cold water, as directed in the foregoing process, be 

 treated in exactly the same manner with bollini>- water, the 

 colour obtained will be rather darker, but scarcely of so 

 good a tint ; and th" residuum of the root, however care- 

 fully pressed and washed, will retain a strong purplish hue ; 

 a fidl proof that some valuable colour is retained in it, pro- 

 bably fixed in the woody fibre by the action of heat. Mr, 

 Watt, in his ex-cellcnt Treatise on Madder above mentioned, 

 observes, that cold water extracts the colour bctler than hot 

 water ; and I have reason to suspect that a portion of that 

 colouring n)atter, which produces the bright red piijment, 

 distinguished before by the name of madder lake, remains 

 attached to the root when acted on by boilintr water. 



Process 'I. 

 If to two ounces of madder a pint of cold wafer be 

 added, and the whole be suthjrcd to stand for a few days 

 (three or four days) in a wide-moulhed bottle, lifrhtly 

 corked, in a femperuture of between 50" and Co", and ofteii 

 shaken; a slight fermentation will take place, the infusion 

 will acquire i vinous smell, and the nuicilaginous part of 

 the root will be in a great degree destroyed, and its vcllow 

 colour mucli lessened. If the whole be tlien poured into a 

 calico bag, ami the liquor be suffered to drain away witlumt 

 pressure, and then the root remaining in the ba*^ be heated 



with 



