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


The analyzation of Sugar having become a sub
Jet of more than ordinary importance and inter-
est to our community, through the fact of our
planters selling 50 largely of their crops to go to
the San Francisco Refineries at a price based upon
the analysis Of the sugar, we give space to a de-
scription OF the different methods of Analysing
as p~raetised by Mr.. Kinney, when our sugars
were sold to the refners some years since, and by
Colonel Spalding in the present instance. The
latter method is that known az Polarization,
while formerly the Copper test was employed.
This is the most commonly used of the chemical
methods for analysing, or estimating the strength
of sugar, and is based on the action of grape
sugar upon OIide Of copper. Grape sugar at
14O0 Fahr. precipitates red sub oxide of copper
from alkaline solutions containing the oxide of
copper, while cane sugar does not exercise the
same action under the same circumstances but
cane sugar may easily be converted into grape
sugar by means of heat and acid.
The reaction that takes place between grape
sugar and the oxide Of copper under these Cir
cumstances is of such a nature that one equiVa-
lent Of grape sugar will effect the reduction Of
ten equivalents of oxide of copper, and knowing
this it is easy to see that a comparison may be
made between the action of pure cane sugar,
changed or inverted into grape sugar, and that of
the sugar, also SO inverted, we may wish to ana
lyze. This determination, however, is attended
with difficulties which render the result more or
less Inaccurate, according to the skill of the
chemist in the practical manipulation of the test
and it is the work of hours to determine the
strength Of a single sample. I'm the first place,
a solution Of copper must be made in which the
oxide of copper shall bear a definite proportion
to the volume of the solution, and it is therefore
called a Standard Copper Solution" This
may of course be made of any strength, but for
convenience we say it is required that the oxide
of copper in a Hire Of the solution shall equal 5
grammes of grape sugar or in other words that
5 grammes of grape sugar will precipitate the
whole of the oxide Of copper contained / in a litre
of the standard solution. The Oxide required is
found as follows
One equivalent of grape sugar. at 2l2o Fahr.
has the following composition.
IL parts Carbon, atomic weight.
- " Oxygen, " .......-...s6
Atomic weight grape $50
Ten equivalents of oxide of copper have the
following composition.
10 parts Copper atomic wsaigh'-.~-.~,"".--;sio
Atomic weight of 10 parts oxide Copper .39I
Therefore as one part Cor l gramme) of grape
sugar will precipitate 10 parts (or 10 grammes)
of oxide of copper, We have the equation 1870:
397 5 II .03 the oxide required to precipitate
5 grammes grape sugar.
Now one equivalent of ~sulphate of copper con-
sists Of
l part Oxide Copper. atomic
8 " Wafer, " " :"":.""""":.46
Atomic weight i part sulphaie l24.7
And we have the further equation of 1917
1884, :: IL .O3 "a 6 the amount of sulphate of
copper which contains the requisite quantity of
oxide of copper to neutralize the 5 grammes Tor
parts) of grape sugar. Therefore 34.64 grammes
of pure and dry crystallized sulphate of copper
(blue vitriol) are to be dissolved in 200 cubic
centimeters of distilled water, and in another
vessel l73 grammes of double tartrate of soda and
potash (Rochelle salty is dissolved in 4s0 cubic
centimeters of a solution of pure caustic soda of
specific gravity LA. The two are then mixed
and the deep blue solution diluted to the volume
of one litre Zone thousand cubic eentimeters) and
filtered. This solution will keep for some time,
in full bottles and in a dark place, and when in
proper condition can be boiled without decompo-
sition. Its strength and purity must be proved
by direct experiment. We have seen that the
atomic weight of grape sugar is $50; now one
equivalent of pure cane sugar consists Of
IL parts
IL /"
IL "
Atomic weight cane sugar III
And the equation $50 III 100 :95 shows that
100 parts of grape sugar equal 95 parts of cane
sugar, and that as it is intended 5 grammes of
grape sugar shall precipitate the oxide of copper
in a litre Of the solution, SO should AIS grammes
cane sugar effect the same result when inverted
or changed into grape sugar.
In making an analysis of cane sugar, the
strength of which is unknown, it is necessary to
carefully weigh a definite quantity - say 10
] grammes-which is to be dissolved in about 300
cubic ~centimeters of distilled water and boiled
for half an hour with 10 cubic centimeters of
dilute s~ulphuric acid. Care must be taken to
keep the volume about the same, by replacing
the evaporated water from time to time, in order
to prevent burning or carbonizing the sugar on
the sides of the dish, and, after boiling, the acid
is to be neutralized with carbonate of soda.
Where it is necessary, on account of the iInpuri-
ties contained in the sugar, milk of lime is to be
| added and the whole thrown on u filter in which
some animal charcoal has been placed, and when
the solution has nearly all run through the filter
it is to be washed with distilled water until every
diluted { ,the volume of one iitre, when of course,
every lou cubic c~entimeters viii contain 1 gramme
of The cane sugar SO inverted. .Asr es,
Then so cubic centimeters of the standard