The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1856-1888, 1875-10-16

copper solution are to be placed in a clean por-
celain dish, diluted with distilled water to con
yenience, the whole brought up to point of boil
ing, and the dilute sugar solution added from n
graduated burette until the precipItated oxide Of
copper has a vermilion color. The lamp or
burner is then removed and the precipitate al
lowed to settle. The dish must then be held IN
a good light, and gently tilted 10 one side so as
10 allow the clear liquid to flow over the porce-
lain not covered with the preeipitate. Ii any
blue color remains, more sugar solution must be
added, while boiling, and when the color is
wholly discharged the operation is ended. TIE
ascertain whether the whole Of the copper has
been precipilated, a drop of the liquid may be
tested from time to time with ferrocyanid of
potassium solution, ieebly acidifed. which pro
duees a reddish brown precipitate or coloration
80 long as a trace of copper remains in solution.
1t is then only necessary to note the quantity of
sugar solution used. as indicated by the gradua-
ton on the burette, and to make the calculation.
Suppose, for example, it requires 25 cubic
centimeters of sugar solution to discharge the
color from SO cubic c~entimeters OF the copper
solution. One hundred cubic centimeters of the
sugar solution, representing one gramme Of the
sugar under examination, would equal 200 cubic
c~entimeters Of the copper solution or one gramme
of grape sugar, and the ample would analyze 100
per cent. grape or % per cent. cane sugar.
Again, suppose it takes GO cubic centimeters of
the sugar solution to precipitate the copper in 50
cubic Of the standard solution; it
will require 240 to precipitate the whole of the
copper in 200 cubic centimeters, or to equal one
gramme grape sugar-and we have the equation
240 100: l ,4l6 or 4l.6 per cent. grape sugar
which is equal to 39.5 per cent, cane sugar.
As almost all RAG sugar contains more or less
grape sugar, it is necessary when Analysing raw
sugars to make two tests-one with the raw sugar
before inversion, and the other after inverting as
before described. The first test will show the
amount Of grape sugar contained in the sample,
which must be deducted from the amount of
grape sugar found to be contained in a ike
ample after Inversion, and the remainder will be
the amount of grape sugar which represents the
amount of cane sugar in the sample tested. For
instance, taking the same weights and measures
as before, We find it requires 200 cubic centime-
tors of the sugar solution that has not been
inverted to discharge the color from fifty cubic
centimeters of the copper solution then 800 will
equal one gramme, and we find our sample con-
bHtsfo A-O ~ 6"RN oN6"' nv
sample. being inverted, requires hut 35 cubic
centimeters to precipitate the copper in SO cubic
centimeters, and we find contains ia per cent.
grape sugar. Deducting the first amount We
have $50 per cent. of grape or 55.95 per cent.
cane Sugar as the strength Of the sample tested.
The analysis of sugar by polarization is based
upon the peculiar effects of cane and grape
sugars upon polarized light, and like the chemi-
ool m na lyaia "a "a co1ono4ot,,,a oaa-; a tho affaot
produced by the sugar in question is compared
with the known effect of pure sugar.
1t has been found that quartz cut across the
axis of a pure crystal will rotate or twist a ray
of polariaed light a considerable distance to the
right in some crystals, to the left in others, and
called therefore % right hand auartz'' or : left
hand quartz" as the case may be. Although
but few SOLID substances possess this property,
numerous liquid organic substances do. This is
remarkably the case with sugar. Cane sugar
rotates the ray to the right, while grape sugar
turns it TO the Lgi..
In the Polariscope the light is polarized by an
aehromatic Nieol prism, so named from its in
ventor, and which is made by joining together
the two halves of a prismatic crystal with Can
ada Balsam. JEA
As it is upon the action of light when SO po-
larized, and brought into contact with the sugar,
that our analysis depends, n few words upon
" polarized light" may not be amiss. Light
which has been relracted from certain surfaces,
or transmitted through certain substances, under
certain special conditions, assumes new proper
ties, and is no longer reflected, ~refracted, or trans
mitted as before. This change in the action Of light
is called polarization, and a ray thus modified is
said to be polarized. According to the undula-
tory theory, common light is assumed to be pro.
duced by vibrations of the ethereal particles in
two planes at right angles to the progress of the
wave there are perpendicular vibrations, and
there are horizontal vibrations. Polarized light,
on the contrary, is light occasioned by vibrations
taking place in only one plane-the effect of
whatever produces polarization being to suppress
all the vibrations which take place in one plane
at right angles to the other.
Light may be polarized in three different ways.
First-When it is reflected from glass at an angle
of incidence of ffty-six degrees. f~orty-fve minutes
from the perpendicular.
Secondly-By transmission through a bundle
consisting of from sixteen to eighteen plates OF
thin glass or mica.
Thirdly-By passing through certain transpar-
ent crystals, especially those which possess the
property oil double refraction.
One of the peculiarities of polarized light is
that it will not pass through certain substances
which are transparent to common light. and as
sugar in solution is one of these substances, we
are able to test the comparative strength OF
sugars by the difference in their action upon the
polarized light.
To return to our description Of the polariscope.
At the end Of the machine where the light is
received is placed a Nicol prism, and Mt the other
end are an eye-piece and an a~nalyzer. If this
was the whole of the instrument the light would
alternately appear and disappear, on rotating