Chemistry. xv 
IX. VEGETABLE BODIES. 
This department of chemistry is still in a very imperfect state, 
though it is obviously advancing with considerable rapidity. 
The first part of its progress will undoubtedly greatly increase 
the number of vegetable bodies. Though it is likely that when 
accurate formulas are fixed for procuring each of these bodies in 
a state of purity, so as to enable us to compare the various 
vegetable principles with each other, their number will be con- 
siderably diminished, or at least they will come to be arranged 
under a small number of genera. I shall proceed to state the 
most important facts in the chemistry of vegetables which have 
been ascertained during the last year. 
1, Sugar.—Mr. Daniell has published some valuable experi- 
ments and observations on sugar. (See Institution Journal, 
vi. 32.) He found that if Kirchhoff’s process for converting 
starch into sugar was stopped betore the saccharine change was 
completed, that the starch acquired the properties of gum. This 
was observed long ago by Kirchhoff himself, and was, indeed, 
the circumstance that led that chemist to the discovery of starch 
sugar. The object which he had in view was to convert starch 
into gum. On trying the action of sulphuric acid he succeeded 
in part ; but the gum formed did not possess all the requisite 
qualities. Hopes were entertained that by prolonging the boil- 
ing, these qualities would be developed. ‘the experiment was 
tried, but the starch was found to be converted into sugar in-, 
stead of gum. 
Mr. Daniell has found that the supposed gum into which 
sugar was converted by Mr. Cruikshanks, by treating it with 
phosphuret of lime, is nothing else than a compound of hme 
and sugar. Sugar and lime may be easily united by boiling 
them.together in a sufficient quantity of water, It would ap- 
pear from the experiments of Mr. Daniell, that when this com- 
pound is kept for a considerable time, the sugar is altered in its 
nature, and converted into gum. Lime is employed in the 
West Indies by the sugar boilers, and there is reason to believe 
that it is often employed in excess. Hence raw sugar always 
contains a portion of it. Now it has the property of converting 
strong sugar into weak sugar: that is to say, of changing sugar 
from a crystallized compound, consisting of grains easily sepa- 
rating from each other like sand, of a grey colour and trans- 
el into a clammy yellow sugar having the feel of flour. 
e use of lime in sugar refining, Mr. Daniell thinks, is to ren- 
der the colouring matter more soluble, and of course more easily 
removed by water. 
2. Manna.—Bouillon Lagrange informs us that manna con- 
sists of two distinct substances, one soluble in cold alcohol, 
another insoluble in cold, but soluble in hot alcohol. The first 
Vou, XI. e 
