1854.] OF THE ROYAL INSTITUTION, 383 
II. On the Sweetness of different liquids. 
That sugars are of different kinds is easily seen by the different 
effects of the same test; but the most delicate test of all is polarised 
light. There are three different kinds of sugar, which when present 
in different solutions in equal quantities rotate the polarised ray in 
different degrees and directions, Cane sugar rotates the light to the 
right ——>, and if treated with acid for a few minutes it is entirely 
changed into sugar which rotates to the left<——. This is called 
uncrystallisable sugar; for if the solution be even evaporated to 
dryness, it is changed into sugar which again rotates to the 
right——>. This sugar is called grape sugar or glucose, and this 
undergoes no change when again treated with acid. 
By means of the saccharometer of Soleil the degree of rotation 
to the left or right can be measured, and thus the quantity of sugar 
in a solution can be determined; with cane sugar alone the results 
are probably perfectly accurate. With the other sugars the results 
are not yet so fully established: still at least the minimum amount 
will be obtained. It is essential that the fluids to be examined 
should be decolorised first with one tenth of a solution of subacetate 
of lead, and afterwards if requisite with animal charcoal. 
Previous to the determination of the quantity of sugar present 
in these liquids, when decolorised they were examined by other 
tests for sugar, by the sulphate of copper test, by the liquor 
potasse test, and with the polariscope. I found no Sherry, Port, 
Madeira, or Champagne that did not contain more or less uncrys- 
tallisable sugar; two samples of sherry excepted which were free 
from any sugar. I met with no Claret, Burgundy, Rhine, or 
Moselle wine, excepting only one sample of Sauterne, which was 
not free from every kind of sugar. Usually spirits contain no 
sugar; but one specimen of genuine French brandy had some cane 
sugar added toit. All kinds of Ale, Porter, and Stout contain much 
glucose. Hard cider I found also to be perfectly free from sugar. 
Sweet cider contained uncrystallisable sugar. 
The particular results will be given in the Tables; the general 
results may be here stated. 
Amount of Sugar in an 
ounce of fluid. 
In Sherry the sugar varied from 2. a 9 <— 4 grs. to 18 grs. 
Port 
; ; . 8tol7 = 16 to 34 
Madeira A - 3 to 10 ree to 20 
Malmsey Madeira . 28 to 33 = 56 to 66 
Tokay . : ae = 74 
Samos . ‘ 44 oe 
Paxarete y ; 47 = 94 
Cyprus. ; 51 = 102 
Champagne . : 3 to 14 ks 
Sweet Cider ; . 9 to 22 = 18 to 44 
Bitter Ale 7 y 12 to 130—»= 12 to 130 
Porter y 23 to 40 = 23 to 40 
Stout . : } 45 to 64 = 45 to 64 
