STARCH, ITS VARIETIES AND CHANGES. 
249 
If starch be boiled for some time in very dilute acids, the 
like change will be effected ; but if the quantity of acid be 
increased, the dextrine becomes transformed into grape sugar . 
“A mixture of 15 parts of potato-starch, 60 parts of water, 
and 6 parts of sulphuric acid, may be kept boiling for about 
four hours; the liquid neutralized with chalk, filtered, and 
rapidly evaporated to a small bulk. By digestion with 
animal charcoal and a second filtration, much of the colour 
will be removed, after which the solution may be boiled 
down to a thin syrup, and left to crystallize : in the course 
of a few days, it solidifies to a mass of grape sugar/ 5 
During the germination of seeds or the malting of barley, 
the like metamorphosis obtains. This is brought about by a 
nitrogenized principle contained in them, probably the gluten 
which, undergoing transformation, gives rise to diastase , the 
ultimate composition of which is not known, it never having 
been separated in a state of absolute purity. It is stated by 
Brande to be white, soluble in water and dilute alcohol, but 
insoluble in strong alcohol; its aqueous solution is tasteless, 
and soon decomposes. By it the farina is first converted 
into dextrine, and then into grape sugar or glucose. 
The relationship that exists between these substances will 
be seen by the following analysis: 
Starch 
Amidiue 
Dextrine . 
Grape Sugar 
„ „ Crystal 
C 94 B20 ^20* 
C24 H20 C^o* 
C 24 If 20 ^20* 
C 24 11 21 0 2 \. 
C 24 H 21 0 21 +3II0. 
The first three being identical in composition, their altered 
properties can only result from a new arrangement of their 
particles; their conversion into the last two, it is equally as 
clear, depends upon the fixation of the elements of water. 
The following are his comparative analyses of unmalted 
and malted barley, showing 
the changes 
that have taken 
place in the quantities of the proximate 
principles by the 
operation : 
Barley. 
Malt. 
Gum .... 
5 
14 
Sugar .... 
4 
16 
Gluten .... 
3 
1 
Starch 
88 
69 
100 
. 100 
