Flasks may be kept conveniently by inverting them over wooden
pegs driven in the edge of the shelf over the analyst's table. The
pegs should be about three inches high, about 5-16 inch in diameter,
and should incline at a slight angle toward the operator.
A quarter inch glass tube six inches long may be used as a
pipette for taking out the extra solution whenever, in analysis, a
flask is accidentally filled above the mark.
5. Funnels and Filter Paper. Funnels for sugar analy-
sis should be about 3 ^ inches in diameter and ot either
glass or hard rubber. The rubber funnel is much more
serviceable, but most chemists prefer the glass funnel, as
dirt or sugar can be detected on the latter more readily
than on the former. The stems on funnels should not be
more than half an inch long.
Filter paper should be in sheets 23 inches square.
When a sheet of this size is cut into nine equal square
parts, each part folded will be of the proper size for use in
analysis. After folding, cut each filter paper round and of
such size that the edges will not extend above the funnel.
Heavy white paper is the best for sugar analysis ; gray
paper is much cheaper but it filters too slowly.
In trimming filter papers save the scraps for cleaning polariza-
When a solution filters slowly, cover the funnel with a watch
glass to prevent evaporation.
Creasing a filter paper makes a solution filter faster.
28 INSTRUMENTS FOR ANALYSIS AND THEIR USK.
6. Beakers to receive the filtrates in analysis are
usually small common glass tumbers, which are lipped in
the laboratory where they are employed. Tumblers of the
following size will be found very convenient: Three
inches high, two inches inside bottom diameter, and two
and one-half inches inside top diameter. The writer has
used tumblers slightly smaller than this, each measure-
ment being an eighth of an inch less, and believes that
they cannot be excelled for practical work. They each
weigh about 92 gr . Lips are not at all necessary on beakers
of this size. (See F 34.) Another good form of beaker
is shown in F 31. It is 4 inches high, with a diameter
of \y( inches at the top and of 2^ inches at the bottom,
inside measurement. One American factory tried alumi-
num beakers, but found them unsatisfactory as they were
too hard to clean.
Discard the first few drops of a filtrate.
When the filtrate of syrups and juices is too dark to be read in
the polariscope, add about 1 gr. of finely powdered bone dust to the
filter paper and filter again. As the bone dust may absorb a small
amount of sugar, discard the first half of the second filtrate.
Beakers are more easily cleaned with cold water than with hot,
on account of the lead on them. (J. E. VARNER.) They must be
7. (a) Polariscopes.* When a ray of light passes
through a crystal of Iceland spar it is divided into two rays
of equal intensity, one of which is called the ordinary ray
and the other the extraordinary ray. The former is in
the principal plane and the latter is in a plane at right
angles to the principal plane. When the rays possess this
* The explanation of the polariscope here given is necessarily very brief.
The student is referred to Ganot's Physics or I^andolt's Handbook of the Polar-
iscope for a complete and clear description of the instrument.
INSTRUMENTS FOR ANALYSIS AND THEIR USE. 2Q
peculiarity they are said to be polarized. Polarization may
also be effected by reflection, as on water, mirrors, etc. In
most polariscopes the light is polarized by means of a
Nicol's prism which is so constructed that it transmits only
one ray, while the other is suppressed by reflection out of
the prism. The prism is placed in the polariscope so that
the transmitted ray goes straight through the instrument.
Two lenses are used to intensify the light from the lamp
before it meets the Nicol's prism. The use of the polar-
ized ray may be described as follows :
Polariscopes designed for sugar analysis (called saccha-
rimeters) are based on what is termed rotatory polarization.
This is the effect produced by certain substances (most
notably quartz) and solutions (e. g., sugar) which have the
power of rotating to a different degree the planes of polari-
zation of the various colored rays which compose white
light. To illustrate : If a thin section of a quartz crystal
cut at right angles to its axis is placed so that a ray of
polarized light passes through it and falls upon a mirror,
the image of the quartz will appear in color in the mirror.
If the mirror is on an angle and is slowly turned, the colors
of the image will change and appear in the same order as
is found in the solar spectrum red, yellow, green, blue
and violet. In some varieties of quartz these colors are
shown in the order named when the mirror is turned to the
right, and in others when it is turned to the left. Violet
rotates the plane of polarization to the greatest degree and
red to the least, and the extent of the rotation depends
upon the thickness of the quartz plate which is traversed.
Sugar solutions have the power of rotating planes of
polarization,, and, as in the case of quartz crystals, some
solutions rotate the plane to the right and others to the
left. The former are said to be dextrogyrate, as sucrose
30 INSTRUMENTS FOR ANALYSIS AND THEIR USE.
and raffinose, and the latter laevogyrate, as laevulose and
sorbinose. The rotatory power of a concentrated sugar
solution is only about 1-36 of that of quartz, hence the
column of solution to be traversed by the polarized light
must be of considerable length. The plane of the polar-
ized light is rotated to a greater or less extent, according to
the concentration or dilution of the solution. Sacchari-
meters are constructed so that this angle of rotation may
be determined. After the polarized light passes through
the column of sugar of known length it is met by a layer
of quartz which has a variable thickness and can be moved
either to the right or to the left, to compensate for the
rotation produced by the sugar solution. This movement
is effected by means of a rackwork and pinion turned by a
milled head, and as the plate is moved its thickness at the
point where the light passes through is measured by a
scale. The thickness of a plate necessary to compensate
the rotation of a definite amount of pure sugar made up in
a certain way is marked as 100 on the scale, and the thick-
ness of the plate which gives a clear view when no active
substance is in the polariscope, is marked as zero.- The
scale is then sub-divided into 100 parts, and when a solu-
tion of sugar prepared in the necessary way, is read in the
instrument, the scale not only measures the thickness of the
plate which compensates for the rotation of the solution,
but in doing so shows the percentage of sugar the solution
contains. The reading of this scale will be described
later. After passing through the movable plate the light
meets a double refracting prism (usually a Nicol's prism)
which is called the analyzer. This prism gives a field of
vision by which the polar iscopist, in reading the instru-
ment, can tell when the movable quartz plate is in proper
position. This field is circular and is divided in half by a
INSTRUMENTS FOR ANALYSIS AND THEIR USE. 31
perpendicular line. The observation of it is described in
the next paragraph.
The optical arrangement of a single compensation
Schmidt and Haensch polariscope,* is shown in the follow-
ing figure :
1. 2. 3. 4. 5. 6. 7. 8. 9.
3. Nicol prism, analyzer.
4. Quartz wedge, fixed, bearing vernier.
5. Quartz wedge, moveable, bearing scale.
6. Quartz wedge, having rotatory power opposite to 4 and 5.
7. Nicol prism, polarizer.
9. Lens. *
In Fig. 12, the arrangement of the double compensa-
tion polariscope is shown. The two prisms /N1 and /\2
are of opposite rotatory power, one being dextro- and the
other laevo-rotary. At H is the screw for adjusting the
analyzer. The screw for setting the scale (see next para-
graph,) is on the left side of the instrument, between the
two moveable wedges. The inclined mirror above K is one
of the latest Schmidt and Haensch improvements, and is
for the purpose of doing away with a second lamp for read-
ing the scale.
* The Schmidt and Haensch polariscope is the only instrument described
here, as it has been adopted by the U. S. Government, and most of the sugar
factories in operation in this country.
32 INSTRUMENTS FOR ANALYSIS AND THEIR USE.
INSTRUMENTS FOR ANALYSIS AND THEIR USE. 33
(.b) Operation. Adjust the lamp so that it gives a
bright steady light. Turn the polariscope towards the
lamp and look through the telescope J. (See Fig. 12.) A
round luminous field will be seen, and the telescope should
be focused by moving it in or out until the field is clear,
and has a well defined line passing through the center.
One side of the line may be darker than the other, but by
turning the milled head which operates the moveable
quartz plate the two halves of the field may be made to
have an equal intensity of light.
In Fig. 13 R shows a picture of the field when the
milled head must be turned to the right (the thumb of the
hand moving toward the lamp) to effect neutrality, L a
picture when it must be turned in the opposite direction
and E shows the field when neutral.
When the vision is that illustrated in E, look through
the reading glass K (see Fig. 12,) and read the scale. The
small scale appearing above is called the "vernier," and
its zero should exactly correspond to the zero of the larger
scale below. If they are not in line, they should be made
to coincide by turning the nipple, provided for the pur-
pose. This should be done only by some one acquainted
with the polariscope, as in single compensation instru-
ments this screw is easily mistaken for the screw in con-
nection with the analyzer.
INSTRUMENTS FOR ANALYSIS AND THEIR USE.
Now fill a polarization tube with a properly prepared
solution (see next paragraph,) and place it in the polar-
iscope. Make the observation as above, bringing the two
halves of the field of vision to an equal shade. Then make
the reading. Find the number of whole degrees the zero
of the scale has moved from the zero of the vernier. In
Fig. 14 it is 29. To determine the tenths, note the point
1 1 1 1
1 1 1 1
1 1 1
1 1 1 1
1 1 1 1
1 1 1 1
1 ! 1
at which a line on the vernier coincides with a line on the
scale. In this illustration it is at 4. Therefore, the read-
ing is 29.4, and the solution read contains 29.4 per cent,
A polariscope fitted with the double compensators and
two scales, gives four checks on the correctness of the
reading. The upper scale and the milled head which
moves it are black. The lower scale is red, and its milled
head brass. In making a test, set the red scale at zero and
use the black scale. Then remove the polarization tube
from the instrument and make the field neutral by using
the brass screw. The readings of the two scales should
correspond. For an invert reading, set the black scale at
zero and use the red scale.
(c) Testing a Polariscope. No instrument should be
used unless it has been found to be accurate. The exami-
nation is most easily made by means of the control-tube or
quartz plates. The control-tube can be lengthened or
INSTRUMENTS FOR ANALYSIS AND THEIR USE. 35
shortened and, as a scale is attached which shows the length
of the tube in millimeters, the reading which the instrument
ought to give may be easily calculated. If quartz testing
plates are used, their value should be determined by check
analyses, e.g-., with cc "known sugar" solutions. Table III
gives the number of gr. of chemically pure sugar which
must be made up to 100 CC to give any desired polariscope
reading. By the use of the control-tube, quartz testing
plates, and <c known sugar" solutions, it may easily be de-
termined whether the instrument, is correct for readings on
all points of the scale. Uneven quartz wedges will make
a polariscope accurate for some readings and inaccurate for
The accuracy of the zero point may be found by read-
ing the instrument itself, and a solution of chemically pure
sugar may be used for the 100 mark. Chemically pure
sugar is prepared as follows :
Wash a quantity of the best granulated sugar repeatedly with
an 85 per cent, alcohol. Three to five times the volume of sugar is
sufficient alcohol to use. After washing, dry the sugar thoroughly
at 100 degrees Centigrade and keep in an air-tight jar. 26.048
grammes of this sugar dissolved in 100 CC of water at 17^ C should
have a specific gravity of I.IIII.
In the laboratory, a polariscope that is accurate under
normal conditions may become incorrect through the
influence of heat or some other cause. The instrument
should be thoroughly examined at least once a week, and
each chemist should read for the zero point at least twice a
day, say at the beginning of each half-day. These exami-
nations ought to be sufficient to insure its accuracy.
(d) Tubes and Weights. The Schmidt and Haensch
polariscopes are so constructed that 26.048 gr of chemi-
36 INSTRUMENTS FOR ANALYSIS AND THEIR USE.
cally pure sugar dissolved in 100 CC of water will read 100
in the polariscope, when a polarization tube 200 mm long is
used, in sugar analysis, when these instruments are used,
26.048 r is called "normal weight," 13.024* r "half nor-
mal weight," and 52.096* r "double normal weight." A
polarization tube 100 mm long is called a "half tube," and
one 400 mm long a " double tube," the "normal" tube being
200 mm . Any one of these weights and tubes may be used
in analysis, but it is always best to use the largest weight and
longest tube practicable. All readings must be figured on
a basis of normal weight and normal tube, hence if a
shorter tube or a lower weight is used, the reading must be
multiplied, and if a larger weight or a longer tube is used
the reading must be divided. In case of an error, if the
reading is multiplied the error is multiplied, and if the
reading is divided the error is divided. In very dark solu-
tions the half tube must sometimes be used, and when there
is only a small amount obtainable of the solution to be
analyzed, half normal weight must be used. In general
the most practical combination is double normal weight and
normal tube. The double tube cannot be used accurately
except with very light solutions. All readings may be
figured to normal by the following table :
length of Tube
To Make Normal.
Multiply by 4.
Multiply by 2.
100 :nm .
per cent, sugar.
Multiply by 2.
per cent, sugar.
Divide by 2.
per cent, sugar.
Divide by 2.
52. OH 6
Divide bv 4.
INSTRUMENTS FOR ANALYSIS AND THEIR USE. 37
The continuous polarization tube (Fig. 15) may be used
when a large number of solutions of comparatively the same
sugar content are to be tested, as in beet analysis. A
funnel is fitted to one end and a rubber tube is attached to
the other, the opposite end of the tube being in a bucket on
the table when the tube is in the instrument. The solu-
tion to be read is poured in the funnel, the surplus fluid
going out of the tube. After reading, the next solution is
poured in the funnel, and so on. The use of this tube
saves a great deal of time in beet tests and the results are
The preparation and polarization of a solution should be made
at the same temperature.
Readings are made more quickly when the polariscope is cov-
ered with a box, or is in a place darkened by curtains.
The lamp should be about 200 mm from the end of the polari-
38 INSTRUMENTS FOR ANALYSIS AND THEIR USE.
scope and the instrument should be protected
from the heat by a wooden partition or screen ,
with an opening about ^ of an inch in diam-
eter for the light to pass through. (See F 44.)
When gas is obtainable, the lamp shown
in Fig. 16 is a good form to use. It may be
raised or lowered on the stand A. The
shade B gives a concentrated light. The
Students' is a good oil lamp. (See F. 38.)
Always turn the polariscope away from the
light when you have finished reading. Heat
affects the cement holding the prisms.
Polarization tube discs (glasses) sometimes cause
inaccurate readings. They may be tested by putting
them in polarization tubes and reading for the zero
Do not screw on the ends of the polarization tube
too tight. The compression of the discs may make
them double refracting, and the reading will be wrong- Fig. 16.
Discs may be wiped off with the pocket handkerchief. It is
the quickest way to clean them. A scrap of filter paper is also
Rinsing the tube three times is nearly always sufficient to
insure its cleanliness. This, of course, means to rinse it with the
solution to be read.
In every test with a single compensation polariscope, make
three readings and take the average. Rest the eye for 15 or 20 sec-
onds after each reading.
When the zero point in an instrument is .1 or .2 wrong it is
unnecessary to adjust it, but a correction must be made for read-
ings. If, instead of the polariscope showing zero, it shows .2 then
.2 should be subtracted from every reading of solutions, and vice
versa. Thus, if the reading is 18.6, the correct reading would be
18.4, because the polariscope shows .2 more sugar than is really
contained, and if the zero point is .2 to the left then 18.6 would be
18.8, for the polariscope shows .2 less than is really contained.
Bach analysist doing general work should have two or three
polarization tubes, to be used for special tests. For example, a tube
for only pulp and waste waters, one for cosettes, syrups, etc., and
one for high tests, such as sugars and massecuites.
INSTRUMENTS FOR ANALYSIS AND THEIR USE. 39
8. Scales. Four different kinds of scales are neces-
sary in beet sugar analysis. The common scale with plat-
form and scoop is used for weighing beet samples, a
druggists' balance is most convenient for weighing lime
cakes, a balance having a carrying capacity of 300 gr and
sensible to l mg is necessary for sugar analysis and spe-
cific gravity determinations, and a delicate balance with
agate bearings made for a charge of 100 gr and sensible to
l-20 mg is used for finer analytical work. These scales
are shown respectively in Figs. 26, 30, 24 and 41.
To test the sensibility and accuracy of a balance, first
adjust it properly by its regulating screws. The smallest
weight the balance is sensible to is placed on one scale pan
and the balance must turn very distinctly. Each pan is
then charged to its full carrying capacity and the small
weight added again. The balance will oscillate more
slowly than before, but should turn to the same extent.
Place the same weight, say 50 gr , on each scale pan,
and if necessary adjust the scale so that the index for mark-
ing oscillations will be exactly in the middle. Interchange
the weights and the balance should remain in equilibrium.
Remove the weights and set the balance in slight motion.
It must resume its original equilibrium. Load one scale
pan and repeated weighings of it should give same result.
The regular weights used for analytical purposes and
sugar weights (normal, half normal and double normal)
should be verified" when purchased, but if taken care of
properly they are not liable to either lose or gain in weight,
and need not be tested unless there is special reason to be-
lieve they have been affected. Scoops constantly lose in
weight by daily use, and the counterpoise weights must be
INSTRUMENTS FOR ANALYSIS AND THEIR USE.
repeatedly filed down. If any weight is too light, un-
screw the plug on top and insert tinfoil. If it is too
heavy, file off the surplus weight.
Do not touch weights with the fingers.
FRESBNIUS says : "The balance ought to be arrested every time
any change is contemplated, such as removing weights, substituting
one weight for another, etc., or it will soon get spoiled."
A substance when hot creates a draught upward and, if weighed,
its weight is less than it would be at normal temperature.
Weights should be kept in a box away from the fumes of acid,
but the tarnishing coat which forms on brass weights is so extrerm ly
thin that it is of no consequence.
There is a circular spirit level on every good
balance. If the bubble is not in the center, ad-
just the scale by the screws underneath.
Have a camel's hair brush two inches wide
for dusting the wood-work around a balance.
9. Other Apparatus. Water and
Lead Bottles. The siphon bottle shown W
in Fig. 17, is used for water and lead.
The following points should be observed
in making one of these bottles : Use a
gallon bottle, ^ inch glass tubing, and
rubber tubing to match ; have the rubber
tube long enough so that when the bottle
is on the shelf the lower end of the tube
will be on a level with the eye ; have the
air-tube bent down so as to exclude dust,
make the nozzle about two inches long,
and for rapid work the point should not
be drawn too small ; and have a Mohr's
pinch-cock immediately above the nozzle. Fig. 17.
INSTRUMENTS FOR ANALYSIS AND THEIR USE.
() Acetic Acid Bottles for lime cake analysis are made
as above described but smaller. (See F. 13.)
(c) Washing Bottle. This is shown in Fig. 18. It
is a bottle of about 750 CC to
800 CC capacity, and the neck
is wrapped with twine to pro-
tect the hand when hot water is
used. Heavy glass tubing of 3-16
iiich inside diameter may be used.
The nozzle is drawn to a fine point,
and a rubber tube is used to con-
nect the siphon tube with the noz-
zle so that it may be turned in any
direction. The air-tube should be
on a plane with the nozzle as the
operator can better direct the
(aO Burettes for Fehling's Solution, normal acids, etc.,
may be placed in a burette stand like that shown in F. 20.
The cheapest and very satisfactory
burettes are Mohr's, for use with
pinch-cocks shown in the illustration.
A T-tube connection for filling
burettes is shown in Fig. 19. The
use of red lead or chalk, as described
in 3 makes the graduations clearer.
If Erdmann's floats are used with
burettes, the graduation on the
burette corresponding to the line on
the float is the correct reading. If
floats are not used, the reading is at
the bottom of the meniscus (4).
42 INSTRUMENTS FOR ANALYSIS AND THEIR USE.
(X) Thermometers for sugar analysis are
preferably those with large enough bulbs so that
they will only be about half immersed when
placed in a fluid. (See Fig. 20.) They may
be graduated from to 130 F., or 20 to about
130, and should be of the common
kind, that do not register too
quickly, as the reading might
change during the time the instru-
ment is taken from the fluid to be
(/; Mohr's Pinchcocks (fig.
21) are the most handy clamps for
Fig. 21. water-bottles, burettes, etc. They
are made in three sizes, the middle
size being the one most often used in sugar
(g) Kipp's Apparatus shown in Fig. 22 may
be used for the generation of carbonic
acid i n experimenting with lime and
to neutralize alkaline solutions. Lime-
stone is placed in the middle bulb
and crude muriatic acid is poured in the
safety tube at the top. The apparatus may
also be used for the generation of hydrogen
sulphide and other gases in chemical
(/O Indicator Bottles may be either a
dropping ftask or an ether bottle, both of
which are described in 4. The former is
preferable. Phenol is considered the most
Fig. 22. suitable indicator for sugar work.
GENERAL METHODS OF ANAU.
10. Introductory. Nearly all sugar analyses are
figured for "purity." (See 19.) In exact analysis
the "real purity " is obtained by weight, but in analysis
where only approximate exactness is required, the "appar-
ent purity " is determined by some method which combines
the greatest accuracy with the quickest operation. Three
of these methods are given in the following paragraphs.
All are theoretically correct and it is a matter of opinion