106 Dr. Prout on the ultimate Composition 



long enough,) above which point they rapidly undergo decom- 

 position, &c. 



Lignin, or the Woody Fibre. 

 Messrs. Gay Lussac and Thenard first showed that the hy- 

 drogen and oxygen in this principle exist in it in the propor- 

 tions in which they form water, a result fully confirmed by 

 my experiments. The variety of forms in which lignin occurs 

 in different woods is so great, that an examination of them all 

 would be quite out of the question ; I therefore selected two, 

 viz. the woods of the Box and Willow, which appeared to pre- 

 sent the greatest contrast ; the one being among the densest, 

 the other the lightest of the woods. These were both treated 

 exactly in the same manner ; that is to say, they were first re- 

 duced to the form of a coarse powder by rasping, then well 

 pulverized in a Wedgwood mortar, and afterwards sifted. 

 Being by these means reduced to the form of impalpable pow- 

 ders, they were boiled in repeated portions of distilled water 

 till that fluid came off unchanged : a tedious process, requir- 

 ing several days to accomplish perfectly. After this they were 

 similarly treated with alcohol, and finally again with distilled 

 water. They were now exposed to the atmosphere, when in 

 a dry and favourable state; and when they ceased to lose 

 weight were submitted to analysis, and found to consist of 

 (abstracting foreign matters) 



Box. Willow. 



Carbon 42*7 42-6 



Water 57*3 57-4- 



A known weight of each was then exposed for twenty- four 

 hours to a temperature of 212°, and afterwards for six hours 

 longer (by means of an oil bath) to a temperature between 

 300° and 350° ; and at the end of this time they were found 

 to have lost, per cent. 



Box. Willow. 

 14-6 14*4 

 Analysed in this state of desiccation, they were found to con- 

 sist of Carbon 50*0 49*8 



Water 50'0 50*2 



showing that the loss of weight arose from the escape of water. 

 These latter results nearly agree with those of MM. Gay 

 Lussac and Thenard, as obtained from the analyses of the 

 woods of the Oak and Beech, and seem to show beyond a doubt, 

 that the composition of all of them is similar, or that they con- 

 sist of equal weights of carbon and water ; to which simple 

 analogy this important principle probably owes its stability. 

 Lignin undoubtedly exists in many other forms besides the 



woody 



