100 CHEMICAL COMPOSITION OF SUGAR. 



and by models of its crystalline forms. It was stated that the 

 taste of sugar was nearly peculiar to it, among vegetable sub- 

 stances, but that the metallic salts called acetate of lead 

 (sugar of lead) and nitrate of silver also possessed it, especially 

 the latter. " But in these salts," it was remarked, " the sweet 

 taste is succeeded by a very nauseous one, while in sugar it is 

 permanent and pure ; remaining as long as there is any sugar 

 acting upon the organs of taste, and remaining the same to the 

 last." The pupils were cautioned, by reference to these facts, 

 never to regard any particular taste or smell, or any other 

 merely sensible property, as certain evidence of the presence 

 of any particular substance, whilst that evidence should be 

 unconfirmed by other tests. 



Some preparative illustrations of the difference between a 

 mere mixture and a chemical combination having been given, 

 the chemical composition of sugar was now explained. It was 

 stated to consist of Carbon (or Charcoal] and Water, as the 

 most familiar mode of representing the subject ; but in order 

 that the pupils might not in any degree be misled by this state- 

 ment, the constitution of the water entering into the compo- 

 sition of sugar, as being itself a compound of oxygen and hy- 

 drogen, was also stated, in the diagram exhibiting the relative 

 proportions, in which the elements of sugar are combined. 

 Dr. Prout's views on the nature of sugars being partially 

 adopted, pure Cane-Sugar and Honey-Sugar were selected 

 for description upon this occasion, as being the extreme terms 

 of the series which is formed by the different varieties of this 

 substance. An experimental proof, well known to chemists, 

 of the existence of carbon in sugar, and of the sensible identity 

 of that carbon with charcoal, was here introduced, by immer- 

 sing a quantity of finely-pulverized loaf-sugar in concentrated 

 sulphuric acid, when the carbon, being extricated in great 

 volume by the action of the acid, rises up from the glass in 

 which the experiment is made, in the form of an apparently 



organized substances here alluded-to, may be connected with what Dr. 

 Prout has termed Mer organization ; and thus the fixed fat, sugar of milk, 

 Cholesterine, and Urea, of animals, may be, in the crystalline state, the ori- 

 ginal definite principles, which, when merorganized, constitute, respectively, 

 those elements of living animals to which we apply the same appellations; 

 while lignin may, in like manner, be the definite basis (merorganized by 

 water?) of wood, as Dr. Prout has stated sugar to be of starch. I am not 

 aware of any saline compound which can be pointed out in a merorganized 

 form, (unless the carbonate of lime which occurs in certain Cryptogamous 

 plants be an example,) but it seems probable, I think, that the siliceous 

 concretion of the Bambu, called Tabasheer, may be merorganized silica, 

 and in that case it will probably be found that the epidermis of the Gramme*, 

 &c. consists rather of that substance, than of silica in an absolutely pure and 

 mineral state. 



