-
- The following book is provided in full, via OCR (text) with
scanned figures. Krayer is particularly valuable for the setup
and adjustment of an analytical balance. It was referenced in
William McNiven's The Analytical Balance: Its Care and Use.
(1951), which is still held by HSU's library (1997).
-
- Copyright © 1998 Richard A. Paselk
-
-
CONTENTS.
-
- A Method of Weighing · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · 5
- Setting Up a Balance · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
5
- Temperature · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · 7
- Testing a Balance for Zero Point · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
9
- Arm Length · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · 9
- Testing a Balance for Arm Length · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · 10
- Testing for Sensibility · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·11
- The Rider · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· I6
- Improperly Adjusted Balances-How to Adjust Them ·
· · · · · · ·
· · · · · · I8
- To Use a Balance when the Arm Length is Incorrect
· · · · · · ·
· · · · · · ·
· 26
- Rules to be Observed when Cleaning Balances ·
· · · · · · ·
· · · · · · ·
· · · · 27
- The Effect of an Electric Lamp · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· 28
- Vibration · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· 30
- The Staudinger Balance · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · 31
- Assay Balances · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · 34
- To Replace the Glass Base · ··
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · 35
-
- WEIGHTS
- Kinds of Weights . · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · 38
- Care of Weights · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · 39
- Standard for Calibrating Weights · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
39
- Calibrating Weights · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· · · · · · ·
· 40
- Recipe for Lacquer for Aluminum, German Silver and
Brass · · · · · · ·
· · 42
-
-
- 5
The Use and Care of a Balance.
- A METHOD OF WEIGHING.
- For accurate weighing it is customary to make a Balance oscillate
four or five divisions on each side of the zero point. To do
this the weigher is obliged to force an oscillation, by means
of pushing in the pan arrest two or three times, or as often
as necessary to create the necessary oscillation. As the rider
is usually in use on the beam it cannot be used for that purpose.
With a container, such as a crucible or bulb that is first weighed,
then charged and then weighed again, it is best on the first
weighing to add, say one milligram by moving the rider, or make
the balance swing out to the left five divisions and back to
the zero point. On the second weighing do the same thing making
it swing out to five divisions and back to the zero point. The
weighing will be correct as the extra weight will be added to
the crucible or bulb and not to the object weighed.
-
- SETTING UP A BALANCE.
- When a balance has been unpacked and is ready for setting
up, clean the balance case, pillar, beam and stirrups. Screw
the index tightly upon the beam. using a pin on indexes having
a hole drilled in the upper part for
-
- 6
- that purpose, until the screw on the little adjusting weight
upon the index is directly in front. Then place the beam into
its position by placing the socket on the beam onto the ball
on the beam support, at the same time lowering the beam supports
about half way. Then swing the beam oil the socket until the
bearing on the other side comes directly over the point. Raise
the beam support and bring the beam into its proper position.
-
- The stirrups are marked with one dot (') or two dots ("),
as are the beam supports. They should he placed upon their supports
according to these marks. Care should be taken that all marks
come to the front. The bow wires or pans are marked (') or ("),
or the pans are stamped "L" or "R" for left
and right respectively. In placing the pans upon the hooks of
the stirrups care should be taken at all times to have the marks
to the front, or the letters so that they call be read correctly
from the front.
-
- This point may seem insignificant, but as a matter of fact
it is very important. When bows are placed upon the balance with
the marks to tile rear or the letters in 3 position to he read
backwards they are not in the same position in which they were
M-hen the balance was finally · adjusted by the manufacturer.
This reversal of the bows from their correct positions. often
throws them out of
-
- 7
- adjustment with the pan arrests, causing the index to go
to one side of the zero point.
-
- It must be assumed that the balance has been perfectly adjusted
before leaving the factory and that every part has been placed
ill its proper position. The index should be firmly screwed upon
the beam, and the screw head of the sliding weight on the index
should be facing the front. If the balance has been correctly
adjusted by the manufacturer, the sliding weight will naturally
go into its proper position upon the index being screwed tightly
into the beam. If, however, when the index is screwed tightly
into the beam, the sliding weight does not face properly, the
weight should be turned so as to bring thee screw head to the
front. Be careful not to raise or lower the weight while doing
so.
-
- TEMPERATURE
- The place for setting up a balance must be carefully selected
and pains must be taken to insure uniform temperature throughout.
Do not allow the heat from a radiator to strike the beam from
one side. The heat from any artificial heater, or even the sun,
when reflected more upon one end of the beam than on the other
will cause a greater expansion of the nearer end of the beam,
thus throwing the balance out of equilibrium. by changing the
arm length.
-
- 8
- The importance of temperature may be illustrated by the following
experiment:
-
- Take two brass weights of about 10 grams each. Place the
weights in the balance, allowing them to remain there for about
one half hour, in order that they may acquire throughout the
same temperature as that of the interior of the balance. Place
one on each scale pan and balance them with the rider. Then with
a pair of forceps take one weight out of the balance, placing
it in the palm of the hand and closing the fingers over it. Hold
it in this manner for about a minute. Then replace it upon the
scale pan. Note that they do not now balance. To complete the
experiment and to fully appreciate the absolute necessity for
uniform temperature for exact weighing, leave the rider in its
position on the beam. Allow the weight thrown off by the change
in temperature to remain on the balance pan, and from time to
time test it, and note the length of time required for it to
again regain thee temperature, as nearly as possible, of the
original weighing. When the weights balance, or almost balance,
it shows that the weight experimented with has almost regained
the temperature of the first weighing.
-
- There are very few balances that will not change arm length
with a change in temperature. The arm length of a balance can
often be regulated with the temperature
-
- 9
- in the room; that is, the arm length of a balance adjusted
to a temperature of 85 degrees may not be equal in a temperature
of 75 degrees, but by raising the temperature to 85 degrees it
will be found to be correct.
-
- TESTING A BALANCE FOR ZERO POINT.
- After a balance has been set up according to directions,
and time has been allowed for temperature, the balance should
be carefully released. A perfectly adjusted balance will not
oscillate; but. all conditions being perfect, the index will
remain stationary at the zero point.
-
- To obtain an oscillation of the index, place the rider upon
the beam at the two milligram division, picking up the rider
as soon as the beam is brought into motion. This will create
the desired swing or oscillation. Five divisions on the index
plate are generally obtained. Take five oscillations in the usual
way to obtain the equilibrium, or zero point.
-
- ARM LENGTH.
- The distance on the beam, between the bearing point of the
center knife-edge and the bearing point of the right end knife-edge
is the right arm length. The distance between the bearing point
of the center knife-edge and the bearing point of the left end
knife-edge is the left arm length.
-
- 10
- TESTING A BALANCE FOR ARM LENGTH.
- First: Place the rider upon the one milligram division, and
see how many divisions it will indicate on the index plate. It
should swing to five and back again to zero.
-
- Then place fifty grms. upon each pan. If the weights are
of equal value, the zero point will be retained as at first,
provided, however, that the arm length of the beam and the line
of the knife edges are perfect. Then again place the rider upon
the one milligram division, with the 50 grams still upon the
pan. The index should show five divisions on the index plate
to be perfect.
-
- When a balance, upon testing with fifty grms. in each pan,
swings for instance, five divisions to the right, and by changing
the weights (that is, the weight from the right hand pan to the
left hand pan, and that from the left hand pan to the right,)
the balance still shows five divisions to the right, the weights
are of equal value, but the arm length of the balance is out
five divisions, the left arm being longer than the right, so
that if the sensibility of the balance was found to be five divisions
to one milligram, the balance is out one milligram on each weighing.
-
- When a balance, upon testing with 50 grams in each pan, swings,
say five divisions to the right and hack to the zero point, and
by changing the weights from left to
-
- 11
- right and from right to left, it swings five divisions to
the left, the weights are out and the arm lengths of the balance
are equal.
-
- But if it swings five divisions to the right and three divisions
to the left, both balance and weights weights are inaccurate
That is, the weights are off three divisions plus one-half the
difference between five divisions and three divisions, or two
divisions, which is one division. Three plus one equals (3 +
I = 4) four divisions for the weight, and one division for the
arm length of the beam.
-
- TESTING FOR SENSIBILITY.
- When a balance, on testing for sensibility, shows five divisions
for one milligram without weight, and reduces in sensibility
with 50 grams in each pan it is due to either of two causes.
First, the beam is not constructed strongly enough to bear the
weight; or, second, the center knife-edge is above the end ones,
thus, as in Fig. I, caused by the knife-edges being worn, or
improperly adjusted. If the sensibility should increase, then
the knife-edges are as in Fig. 2, that is, the center knife-edge
is lower than the end ones. In either case the sensibility cannot
be made uniform by the adjusting weight upon the index.
-
- If the sensibility, with and without weights, remains
-
- 12
- the same, then the knife-edges are as in Fig. 3, that is,
they are in a perfect line.
- If the knife-edges are found to be as in Figs. I and 2, the
sensibility cannot be regulated by the weight for that purpose
on the index. In Fig. I, the more weight placed upon the pans,
the less sensitive it becomes; in Fig. 2, with each addition
of weight in the pans, the sensibility increases up to the point
where the beam begins to bend; it will then gradually decrease,
and continue to decrease as weight is added.
-
- In Fig. 3, however, the sensitiveness can be regulated at
-
- 13
- any desired sensitiveness, five or ten divisions upon the
index plate for one milligram, and will remain so up to the point
where the beam begins to bend. When this point is reached care
should be taken not to exceed this weight, for it will injure
the balance if too frequently done.
-
- If a balance, when tested, is found as in Fig. 3, the latter,
after being in use for some time, it is found as in Fig. I, the
knife-edges have become worn, and must be sharpened and brought
back to their former position.
- Figs. 4, 5 and 6 show three views of the Sartorius beam.
Fig. 4, shows the front view of the end of the beam, without
the knife-edge. Fig. 5 shows end view of beam with knife-edge
upon it. Fig. 6, shows front view of end of beam with knife-edge
upon it.
-
- By viewing Fig. 4, it will be seen that the ends thereof
are slit, thus having two parts. It will be seen further
-
- 14
- that a hole is drilled through the lower part. This hole
is partly threaded and a steel pin is inserted into it; a screw
is then screwed in forcing the pin up against the
- under side of the top of the beam. Often when removing this
screw, the pin drops out and is lost, causing much annoyance.
-
- In Fig. 6, two screws will be observed, marked "A";
- three screws marked "D"; one screw marked "C"
and one marked "E."
-
- 15
- If, when testing a balance, the knife-edges are found as
in Fig. I loosen two screws (Fig. 6) marked "A." and
three screws "D" and fasten screw "C" so
as to force the steel pin up against the under side of the top
of the beam, thus forcing the latter up in turn. Then fasten
two screws "A" until the knife-edges are found as in
Fig. 3.
-
- The arm length is adjusted by the screw "E" upon
the side found to be the shortest, by unscrewing the screw "E"
until the arm length is found to be equal.
-
- Some Sartorius balances have a sliding weight upon the index,
others have a sliding weight upon the beam and still another
kind has a screw extending up and down between two upright parts
of the beam in the center, for the purpose of adjusting the sensibilities.
-
- The following rules for adjusting for sensibility in these
balance are applicable only in the last two cases: To raise the
sensibility, raise the sliding weight or screw (in the last mentioned
case, screw) on the beam for that purpose, upward. To lower the
sensibility, lower the sliding weight, or screw downward the
screw on the beam for that purpose.
-
- On balances having the sliding weight on the index the adjustment
for sensibility is made in the same manner as on other balances;
that is, to raise the sensibility, raise the weight and to lower
it, lower the weight.
-
- 16
- THE RIDER.
- The graduation on the beam has for its object the doing away
with small weights below five or ten milligrams. Therefore, to
determine the weight of the rider required on the balance it
is well to know that the distance between the center knife-edge
and the end knife-
- edge is divided into a given number of parts, usually five
or six, and ten or twelve; each of these subdivided into five
or ten parts.
-
- Some beams have an extension over the end knife-edge, as
in Fig. 7, while others have not, as in Fig. 8. In the
- case of Fig. 7, the rider may be placed directly over the
knife-edge and the beam may be divided into five or ten parts,
the rider weighing five or ten milligram, corresponding with
a five or ten milligram weight in the opposite pan. Thus each
part corresponds to one milligram.
-
- 17
- In the case of Fig. 8, however, the beam must be divided
into six or twelve parts, so that the rider weighing six or twelve
milligrams when placed upon the five or
- ten division will correspond with a five or ten milligram
weight in the opposite pan; so that, while the number five or
ten may be the largest stamped on the beam, that does not signify
the weight of the rider required.
-
- The rider is carried along on the beam by a hook upon
-
- 18
- a rod called the rider-rod. This rider-rod should run parallel
with the beam.
-
- Very often the thumb screws that fasten the stand or pillar
to the case become loosened and allow the pillar to turn, so
that the beam is no longer parallel with the rider-rod. This
may occur in shipment or later, the shrinking of the wood in
the case; or the washers (some having washers between the metal
nuts and the glass plates), causing the riders to be thrown from
the beam. To correct this error turn the pillar so that the beam
is again brought parallel with the rider-rod and fasten the pillar
to the case by the two thumb screws marked "A" in Fig.
9.
-
- IMPROPERLY ADJUSTED BALANCES,
- HOW TO ADJUST THEM.
- Note I.--When a beam is supported the center knife-edge
should be free, so that day light can be seen between the knife-edge
and the plane. The same should be observed in the end knife-edges,
between the knife-edges and the stirrup planes. When the center
knife-edge rests upon the center plane, that is, the beam supports,
Fig. 10, do not raise the beam sufficiently to see daylight between
the center knife-edge and the plane, while daylight can be seen
between the end knife-edges and the stirrup planes, (the thumb
screws "A," Fig. g, being firmly fastened;) then the
beam must be raised by means of
-
- 19
- the screws "A," "A" in the Beam Support,
Fig. 10, until
- daylight can be seen between the center knife-edge and the
plane.
-
- 20
- In so doing always observe the index, keeping the point at
the zero point on the index plate. Sometimes the screws "A,"
Fig. 10 become loosened and by so doing lower the beam supports,
and the beam can be raised to its proper position by fastening
them.
-
- Note 2.--When, on releasing the beam the index deviates
to the right or left, and back to the zero point, before releasing
the pan rests, it is an indication that one stirrup is raised
more from the knife-edge than the other. If the index deviates
to the left, then the left hand stirrup is raised more from the
knife-edge than the right. If the stirrup support is raised from
Fig. 10, the left hand stirrup should be lowered by means of
the screws "E," "E" (Fig. 10) until the index
does not deviate but remains perfectly stationary at the zero
point. If it is found that the stirrup support rests firmly upon
Fig. 10 on the left hand side, then the right hand stirrup must
be raised by means of the screws "E," "E"
on the right hand side, until the index does not deviate, but
remains perfectly stationary at the zero point.
-
- Note 3.--When the index deviates to the right and
back again to the zero point, then the right hand stirrup is
raised more from the knife-edge than the left. If the stirrup
support is raised from Fig. 10 on the right hand side, the right
stirrup should be lowered by means
-
- 21
- Of the screws "E," "E" (Fig. 10) on the
right hand side, until the index does not deviate from the zero
point (or the stirrup support rests upon Fig. 7). If, when the
stirrup support rests upon Fig. 10, the index still deviates
to the right, it is adjusted by raising the stirrup support by
means of the screws "E," "E" Fig. 10, on
the left hand side, until the index does not deviate but remains
perfectly stationary at the zero point.
-
- Note 4.--When the beam is arrested and the index does
not point to the zero point on the index plate, the index, not
having been bent by accident, it is caused by the loosening of
screw "D," Fig. 10. In this case, if the index points
to the left it will be found that the right hand stirrup is raised
more from the knife-edge than the left, and the center knife-edge
rests upon the plane, screw "D" on the right hand side
of Fig. 10 should be raised until daylight can be seen between
the knife-edge and the plane, when the index points to the zero
point. If, when the index is brought to the zero point, and the
stirrups are in proper position, and the center is still not.
brought into its proper position, further adjustment must be
made by the screws "A," "A," Fig. 10, until
daylight can be seen between the center knife-edge and the plane.
-
- Note 5.--When the index, upon arresting the beam,
deviates back towards the index plate, it will be found
-
- 22
- that the end knife-edges and the stirrup planes are not parallel.
On balances not having adjustment upon the beams, as in Fig.
11, it will be seen that the planes, upon either the right or
left hand stirrup or both strike the knife-edge upon one point
and slide into position. They should be adjusted by the screws
"E" Fig. 10. When the index goes back to the index
plate, the stirrup support
- should be raised by the front screw "E," Fig. 10,
until the knife-edge and plane are parallel. When the index deviates
towards the front, away from the index plate, then the stirrups
are in opposite positions and adjustment is made by the back
screw "E," Fig. 10 until knife-edges and plane are
parallel. In balances having upon the beam for a support an adjustment
such as Fig. 11, the index deviating back towards the index plate,
it is ad-
-
- 23
- justed by screwing down screw I, Fig. 11, and if the index
deviated out from the index plate it is adjusted by screwing
down screw 2 Fig. 11, until index does not deviate. (This adjustment
is not favored by the writer
- for the reason that it conceals an error that may exist as
in Note 5). The distance between the center knife edge and the
plane where the beam is supported and the distance between the
end knife edges should be equal.
-
- 24
- Note 6.--The stirrups, Fig. 12, should balance per-
- fectly upon the knife-edges; that is, first remove the bow
from the right hand side, then gently release the beam; if
-
- 25
- the lower part of the stirrup or hook swings in towards the
pillow, and by tapping the base gently with the hand, the stirrup
falls off the knife-edge, the stirrup support, which supports
the stirrup, extends out too far. By loosening screw "B,"
Fig. 10, one screw "C" in front the stirrup support,
Fig. 10 can, by a gentle pressure in towards the pillar, be brought
to its proper position so that it will balance the stirrup upon
the knife edge. If the stirrup swings out from the pillar, then
the stirrup sup-
- port must be brought out until the stirrup balances on the
knife-edge, then fasten screws "B" and "C."
Upon the Sartorius Balance the pillar "C" must be shifted
in the place of stirrup support on the Becker and Troemner Balances.
Upon releasing a balance, the pan should lightly touch the pan-arrest.
If, upon releasing the beam, the index does not remain at the
zero point, it is adjusted by the milled head screw upon the
right hand side of the pan arrest, or scale-stop. The Becker
has only one of these screws. while the Troemner has one on each
side.
-
- 26
- TO USE A BALANCE WHEN THE ARM LENGTH
- IS INCORRECT.
- A balance of unequal arm length may be used by adding or
subtracting the amount of the error, or by changing the theoretical
zero point on the index plate. For
- instance: If the arm length is five divisions out either
way to the left or right with fifty grms., the index swings out
five divisions and back again to the zero point, the
-
- 27
- zero point would be two and one-half divisions in the direction
in which it swings, and in weighing, that would constitute the
theoretical zero point.
-
- RULES TO BE OBSERVED WHEN CLEANING BALANCES.
-
- First.--Remove the bows and stirrups.
-
- Second.--Take hold of the index, or pointer, with
the
- right hand, with a gentle pressure to the right, and turning
the key with the left hand, bring the right end of the beam forward
and the beam will follow it. Take a clean
-
- 28
- cloth and wipe the knife-edges and center and end bearings.
Then with a camels hair brush carefully remove all dust from
the beam stirrups and other parts, particularly from the planes,
as they should always be as free as possible from dust. To replace
the beam, lower the beam supports by using the key, and place
the socket on the ball; then bring the other end of the beam
around until the center knife-edge is over the center bearing.
At the same time raise the beam supports. Replace the stirrups
and hangers after cleaning and dusting.
-
- Third.--Let the balance stand for about one-half hour,
in order to allow the temperature to become uniform.
-
- Fourth.--The friction caused while wiping glass apparatus,
such as glass pans, watch glasses, etc., with a cloth for cleaning
purposes electrifies the glass. The charge may be quickly dissipated
by gently breathing upon the glass. As a matter of fact this
acts instantaneously. The glass should then be placed in the
balance and a little time should be allowed for temperature.
-
-
- 29
- THE EFFECT OF AN ELECTRIC LAMP.
-
- Fifth.--Do not place electric lights too close to
the top of the balance case, in order to maintain the uniformity
of temperature.
-
- When an electric lamp is placed over the top of a balance
so that the heat from the lamp affects the balance--the more
powerful rays of heat strike the center of the beam, and naturally
the temperature of that part of the beam is higher than the ends,
and causes the beam to expand from that point, with the result
that, although it may not affect the arm length, it will lower
the end knife- edges and reduce the sensibility of the balance.
It will be readily seen that repeated changing, in turning on
and off the light will in time have its ill effect on the balance,
by permanently reducing the sensibility and also effecting the
arm length. It is best to have artificial light come from in
front of the balance.
- Sixth.--Use a little kerosene oil on a cloth with
which to clean the case, for it brightens the polish without
injuring it.
-
- Seventh.--Do not use sulphuric acid for a drier in
a balance having steel knife-edges. If a drier is used, calcium
chloride placed in a glass funnel over a beaker, should be used.
The moisture passing through the calcium chloride into the beaker.
Caustic soda should be used in another beaker in the balance
with the chloride.
-
- 30
- Fresh calcium chloride should be added from time to time.
- Eighth.--When a balance, after having been thoroughly
cleaned, is found to have lost in sensibility, the knife-edges
are worn and dull and must he sharpened. They should be attended
to at once by a manufacturer or a balance expert.
-
- VIBRATION.
- The best results are not obtained from a balance that is
subject to vibration. Nearly every laboratory is subject to more
or less vibration, but in the laboratories of large concerns
this is a particularly trying problem, as they are often improvised
in a portion of, or near, a building or buildings containing
heavy machinery, or near railroad tracks, etc., which, when operating
causes a constant vibration, impairing accurate weighing. This
has been made a subject of experiment, and a number of fairly
satisfactory methods have been devised for over- coming vibration.
- At the United States Metal Company, Grasselli, Ind., holes
are drilled in a table top about one-third the depth of a No.
5 rubber stopper. Number five stoppers are inserted into the
holes and a piece of lead weighing about 150 pounds measuring
a little longer and wider than a balance case is placed upon
the stopper. A heavy stone slab or a cast iron block would answer
just as well. The
-
- 31
- idea, however, is to get as much weight as possible. The
balance is placed upon this slab.
- At the laboratory of the Bethlehem Steel plant, pillars of
iron are embedded in a bed of sand in the basement of the building,
the pillars coming up through the floor. A slab is placed upon
these pillars, the top of which is about the height of an ordinary
balance table from the floor. This has been found very satisfactory
where heavy trains are constantly passing the laboratory.
- Where the installation of the above mentioned methods are
not practical for various reasons, I would advise the following
for ordinary purposes. Cut down two No. 5 stoppers about one-third
from the top. They must have one hole through the center. Place
these under the front set screws of the balance, with the plug
of the set screw resting in the hole of the stopper. For the
rear post of the balance use a whole stopper. This method proves
very satisfactory for ordinary purposes.
-
- THE STAUDINGER BALANCE.
- The Staudinger balance, sold by Arthur H.Thomas Co., is so
different in construction from the other standard balances in
general use, that it requires special adjusting instructions.
- The bearings for stirrups and beams are of agate. The front
pillars. a, a, a have a groove for the screw point to
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- rest into; while the rear pillars have a cone shaped socket
for the screw point to rest into. The pillar, a, a, a, must be
set so that the grove is in a direct line with the knife-edges;
thus, looking from the top, o -- - and not, thus, o --.
-
- The beam should be supported by the two screws in the center
knife-edge and the two screws f, f Fig. 17 and 18.
- When upon releasing the beam on these balances, the index
deviates towards or from the index plate, it is adjusted by the
screws in the center knife-edges. That is, if the index deviates
towards the index plate, the
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- screw in the front of the center knife-edge must be screwed
downward, until the index remains stationary upon releasing the
beam; if it deviates from the index plate, the screw in the back
of the center knife-edge must be screwed downward. Judgment must
he used in either case. If the center knife-edge raises sufficiently
from the plane, to allow the opposite screw to be raised, this
should be done. That is. if, as in the first case, the
- index goes towards the index plate, and the knife-edge is
sufficiently raised from the plane, to allow the rear screw to
be raised, it should be done instead of screwing the front one
downward. Also, in the other case, when the index moves from
the plate, raise the front screw instead of screwing down the
rear one.
-
- When, upon releasing the beam on these balances the index
goes to the right or left and back again to the zero point, the
trouble is with the stirrups. One of them is