156 FORMATION OF SUGAR. 



we may convert flax, hemp, or woody fibre of any 

 kind, even old rags, for they consist chiefly of lignin, 

 into sugar. When the change is complete, the sul- 

 phuric acid may be neutralized by the addition of a 

 quantity of chalk ; sugar, and a little sulphate of lime, 

 will then be left in solution. By continuing to boil 

 starch with dilute sulphuric acid, in the manner just 

 described, after it has all been converted into gum, 

 sugar is also obtained. 



362. In these very curious transformations, the 

 sulphuric acid employed does not undergo any altera- 

 tion whatever: none of it is decomposed, it retains all 

 its powers unimpaired, and it is easy to recover, at 

 the end of the operation, the whole of the acid origin- 

 ally employed. It does not abstract anything from 

 the substances with which it is boiled, nor does any 

 part of the acid unite or combine with them. 



363. All the eff'ect which the acid produces is, that 

 its presence under these circumstances causes a change 

 in the chemical nature of the substances with which 

 it is boiled. In the case of starch, it is thus enabled' 

 to take up and combine with about one-sixth of its 

 weight of water, or rather of oxygen and hydrogen, 

 in those proportions which would form water, and in 

 so doing the starch is converted into sugar. The 

 same eff'ects may be produced with many other acids 

 besides the sulphuric (373). 



364. Sugar, spirit of wine, and vinegar consist of 

 the same elements : they contain oxygen, carbon, and 

 hydrogen ; but the elements are united in different 



