Analytical Chemistry

Qualitative Analysis
General Laboratory Directions:
• Scale of the operations:
semi micro (1 drop(0.05mL) - 1mL)
• Apparatus:
>10mL test tubes
>long droppers(12cm)with the tip of
1.5mm
>stirring rods(small 125x3mm)
 Precipitation
• Is done in 10 mL test tubes
• Precipitating reagent is added to
the sample solution dropwise with
constant stirring until no more
precipitate is formed.
 Heating of Solutions

• Must be done in water bath

 Evaporation
•Solution is transferred to a porcelain
casserole and heated over an open flame.
•When a small amount of solution is left,
the flame is removed and the heat of
the casserole is allowed to finish the
evaporation process.
 Centrifuge
• In a semi micro analysis the process of filtration is
replaced by centrifugation
• Centrifugation is the process with which precipitate
is settled in the bottom of a small test tube by
centrifugal force and the centrifugate is then remove
by a dropper without disturbing the precipitate.
• When centrifuging, solutions should be balanced by
placing another test tube containing water of the
same quantity on the opposite hole.
 Washing of the Precipitate
• After separating the solid from the supernatant
liquid, the solid may still be contaminated with
ions from the centrifugate.
• Wash the precipitate with distilled
water(5drops) and mixed thoroughly by
stirring.
• The washing is then removed by the dropper
and discarded. This is done once or twice.
 How to do flame test
• Make a loop on one end of the nichrome wire.
• To clean the wire, dip the loop in conc. HCl
and heat in flame until red hot.
• Dip the wire into the solution to be tested.
Make sure a thin film of the solution is in the
loop of the wire. Insert the wire into the blue
cone of the burner flame. Repeat the operation
several times to confirm the color of the flame
 Groupings of the Ions
• Groupings was established by the use of group
reagents which precipitates related ions:

1.) Group I Cations is composed of ions whose

chlorides are insoluble in acid.
2.) Group IV Cations are cations of alkaline
earth metals and Magnesium and its
phosphate salts are insoluble in water
 Groupings of the Ions
3.) Group V cations are not precipitated by chlorides, sulfide and
phosphate. Sometimes called as the soluble group. There is no
precipitating agent for the group

4.) Group II anions are the chromate and sulfate anions which are
precipitated by Barium acetate as barium chromate and barium
sulfate

5) Group III anions are anions whose cadmium salts are insoluble
in slightly basic and neutral solutions. These includes sulfide,
ferrocyanide and ferriccyanide.
 Expt. 1 Qualitative Analysis of
Gp I Cations
• Procedure:
Addition of HCl to precipitate Ag+, Hg+2, Pb+2

Ag+ + Cl- AgCl

Hg2+2 + 2 Cl- Hg2Cl2
Pb+2 + 2 Cl- PbCl2
 Analysis
Separation and test for the presence of Pb+2
• Add 6-7drops of water and heat.
• PbCl2-soluble in hot water
• Add K2CrO4

Pb+2 + CrO4-2 PbCrO4

yellow ppt.
 Group 1 Cations
Chloride Form Ksp
PbCl2 1 X 10 -4

Hg2Cl2 2 x 10 -18

AgCl 1.56 x 10-10

*Note:
• Lead chloride solubility in water at varying
temperatures:
0.673g/100mL at 00C to 3.34g/100mL at 1000C
• Lead is seldom separated completely
 Analysis
Separation and test for the presence of Ag+ and Hg+2
• Add 10 drops 3F ammonia
*Ag+ is removed from the ppt by conversion to:

Ag+ + NH3 Ag(NH3)2+

Make acidic with HNO3.

*Solution must be acidic to convert Ag(NH3)2+ to AgCl

Ag(NH3) + + Cl- + H3O+

2 AgCl + 2NH4+ + 2H20
white ppt.
 Analysis
Separation and test for the presence of Hg+2
Procedure:
Wash with 10 drops of water. Dissolve ppt in 2
drops conc. HNO3 . Dilute with 5 drops water.
Add 1 to 2 drops SnCl2.
*Black residue after the removal of Ag+ maybe
Hg and HgNH2Cl:
Ammonia water does not only react with AgCl but also
auto redox reaction with Hg2Cl2 to form black ppt
Hg2Cl2 + 2NH3 Hg NH2Cl + Hg + NH4+ + Cl-
 Analysis
Final reaction:

Hg2Cl2 + SnCl4= Hg + SnCl6=

Gray residue is the combination of

Hg, Hg2Cl2, Hg NH2Cl

White or gray precipitate confirms the presence

of Hg+2
 Expt. 2 Qualitative Analysis of Group IV
Cations
• Ca+2, Ba+2, Sr+2 and Mg+2 ions of alkaline earth
metals.
• Forms insoluble phosphate salts with
(NH4)2HPO4
• Separation of individual cations is difficult due
to a very small difference of Ksp values.
 Analysis
Procedure:
To the clear sample, add 10 drops 0.5 F (NH4)2HPO4 conc.
Ammonia until strongly ammoniacal. Centrifuge, and test for
complete precipitation by adding a few more drops of 0.5 F
(NH4)2HPO4
• Precipitate:
Ca3(PO4)2
Ba3(PO4)2
Sr3(PO4)2
Mg3(PO4)2
• Discard Centrifugate
 Analysis
• Separation of Ba+2
Procedure:
• To the precipitate, wash once with 5 drops of water.
• Discard washings .
• Treat precipitate with 5 drops of concentrated HC2H3O2, stir
thoroughly.
• Dilute the solution to 2mL, and add 5 drops of 1F K2CrO4 and
stir for 1min.
• Centrifuge and test for complete precipitation.
BaCrO4 formed was volatilized by addition of conc. HCl and
subsequent evaporation. Ba++ ions emit yellow green flame on
flame test.
 Analysis
Centrifugate :
• Ca+2, Sr+2 and Mg+2 and excess chromate ions. Make
solution strongly ammoniacal with ammonia, centrifuge.
Discard centrifugate
Precipitate:
• Phosphates of Ca+2, Sr+2 and Mg+2 dissolve in 5 drops
conc. HC2H3O2; dilute with 5 drops of water. Add 5
drops 1 F (NH4)2SO4 heat to boiling in water bath, cool
and centrifuge. Test for complete precipitation by adding
1 drop of (NH4)2SO4 to the clear centrifugate.
 From previous slide

Precipitate:
Maybe SrSO4. wash 3 x with hot
water and discard washings. Add 3
drops of conc. HCl. Confirm the Centrifugate :
presence of Sr+2 may contain Ca+2 and Mg+2 Add 5 drops
by flame test (crimson red flame) 0.25F ( NH4)2C2O4 and heat to boiling in
water bath. White ppt confirms the
presence of Ca+2. centrifuge

Precipitate: Centrifugate:
Maybe CaC2O4. Add 2 drops of conc. May contain Mg+2. add 1 to 2 drops of p-
nitrobenzeneazoresorcinol and 3FKOH. Heat
HCl and confirm the presence of Ca 2+
in water bath for 5 min then centrifuge.
by flame test (brick red flame)
Formation of blue ppt confirms thye presence
of Mg2+
Expt. 3 Qualitative Analysis of Group V Cations
Objectives: To analyze the soluble cations which were not
precipitated by the chloride, sulfide and phosphate
Identification of sodium and potassium ions
• to 2mL of unknown solution add 1 drop of conc. HCl and make
a flame test for sodium and potassium ions
• clean a nichrome wire until it gives no color to a non-luminous
flame.
• Test for the presence of Na+ by flame test and is confirmed by
intense yellow flame persisting for 5 sec.
• In the absence of Na+, K+ flame test will give pale violet color.
• Test for the presence of K+ by flame test is confirmed by reddish
violet flame persisting for 2 sec. viewed with cobalt glass.
Identification of NH4+:
• Place 5 drops of the original solution in small
beaker and 5 drops of water.
• Make the solution alkaline with 3F KOH.
• Immediately cover the beaker with a watch glass
to which adheres a moistened red litmus paper in
the inner side in contact with the fumes coming
from inside the beaker.
• Warm solution gently for 1min.
• Even shading of litmus paper from red to blue
confirms the presence of ammonium ions
Expt no. 4 Qualitative Analysis of
Group II Anions
Objectives:
To separate and detect the presence of
group II anions in a sample solution

Procedure:
To the given sample solution add 1M
Ba(C2H3O2)2 dropwise until precipitate is
complete. Centrifuge, discard the
centrifugate.
 Analysis
Procedure:
Precipitate
Wash precipitate with 10 drops of water. Discard
washings . Add 5 drops of 3M HCl stir and centrifuge.
Precipitate:
White residue indicates the presence of sulfate. Wash
precipitate with 10 drops 3M HCl. If white residue
remains, presence of sulfate is confirmed
* BaSO4 is insoluble from 3M HCl.
 Precipitation of Group II Anions

Centrifugate:
Add 10 drops of 2.5 M NaC2H3O2. The presence
of a yellow precipitate confirms presence of
chromate.

*NaC2H3O2 buffers the hydronium ions of the

solution sufficiently to precipitate chromate ions
Expt. 5
Qualitative Analysis of Group III Anions
Objectives:
To separate and detect the presence of group
II anions in a sample solution
Procedure:
From the sample solution, transfer 10 drops to
a test tube.add 1M Cd(C2H3O2)2 dropwise until
precipitation is complete. Centrifuge. Wash
precipitate twice with hot water, discarding
Washing. Divide precipitate into three portions.
Add 3 drops of 3M HCl. Cover with strip of filter paper
moistened with 0.5 M Pb(C2H3O2)2 brown or black
coloration in the paper caused by PbS formation confirms
the presence of Sulfide

Second portion:

Transfer in a spot plate. Add 1 drop of 3M HCl. Add 1 drop

of 1 M FeCl3. Appearance of dark blue precipitate
(Fe4[Fe(CN)6]3) confirms the presence of ferrocyanide
Third portion:
Dissolve with 1drop of 3M HCl. Add 3 drops of
water and small crystals of ferrous sulphate to
the solution dark blue precipitate (Fe 3[Fe(CN)6]2)
confirms the presence of Ferricyanide
Notes:
• Ferricyanide, ferrocyanide, sulfide, anions of
gp. III is precipitated fairly completely with
cadmium.
• Ferricyanide and sulfide cannot exist together
in solution. Ferricyanide will oxidize the
sulfide ion to free sulfur. The ferricyanide is
then reduced to ferrocyanide.
• Sulfide is converted to H2S which is detected
on lead acetate paper to produce a black lead
sulfide.
The End
Unit 2
CHEMICALS AND APPARATUS
Chapter 2 : CHEMICALS and
CHEMICALS AND APPARATUS
APPARATUS
Putting Tools to Work:
• The tools of analytical chemistry has
been developed since 2 centuries ago,
timeless and has been tried to be true.
• The technology of analytical chemistry
has improved with the advent of
electronic, automated, fast , convenient
and accurate instruments.
 .
1. Selecting, Handling Reagents and other Chemicals:

Classifying Chemicals
• Technical grade
• Reagent grade(minimum standard)
• USP grade (United States pharmacopeia)
• Primary- standard grade(extraordinary purity)
• Special-purpose reagent Chemicals (used for
analysis using instruments)
2. Rules for handling Reagents and
Solutions

1. Select the best grade of chemical available for

analytical work.
2. Whenever possible, pick the smallest bottle that
will supply the desired quantity.
3. Replace the cap of every container immediately
after removal of the reagent; do not rely on
someone else to do this.
4. Hold the stoppers of reagent bottles between
your fingers; never set a stopper on a desk top.
Different Kinds of Reagent
bottles
 CLEANING AND MARKING OF
LABORATORY WARE
• Each vessel holding a sample must
be labelled.
• Used glasswares should be cleaned
with hot detergent and rinsed with
water repeatedly. Finally it is rinsed
with deionized/distilled water.
• Properly cleaned glassware will be coated
with a uniform and unbroken film of
water.
• It unnecessary to dry the interior surface
of glassware before use: drying is
ordinarily a waste of time and a potential
source of contamination at worst.
• An organic solvent, such as benzene or
acetone, may be effective in removing
grease films.
 EVAPORATING LIQUIDS
Evaporation is frequently difficult to
control because of the tendency of
some solutions to overheat locally.
-Careful and gentle heating
-glass beads will also minimize
bumping.
Evaporating liquids
EVAPORATING LlQUIDS
to decrease the volume of a
solution that contains a non-
volatile solute ribbed covered
glass permits vapours to escape
and protects the remaining
solution from accidental
contamination.
 EVAPORATING LlQUIDS
Some unwanted species can be eliminated
during evaporation like:
chloride and nitrate-add a solution of sulfuric
acid and evaporating until copious white
fumes of sulfur trioxide are observed (this
operation must be performed in a hood).
Urea is effective in removing nitrate ion and
nitrogen oxides from acidic solutions.
Ammonium chloride -by adding concentrated
nitric acid and evaporating the solution to a small
volume.
Ammonium ion is rapidly oxidized when it is
heated; the solution is then evaporated to
dryness.
Organic constituents-by adding sulfuric acid and
heating to the appearance of sulfur trioxide
fumes (in a hood); this process is known as wet
ashing. Nitric acid can be added toward the end
of heating to hasten oxidation of the last traces of
organic matter.
Terms:
• Wet ashing is the oxidation of the
organic constituents of a sample
with oxidizing reagents such as
nitric acid, sulfuric acid, hydrogen
peroxide, aqueous bromine, or a
combination of these reagents.
 Measuring Mass
 The Analytical Balance is an
instrument for determining mass with
a maximum capacity that ranges from I
g to a few kilograms with a precision of
at least I part in 105 at maximum
capacity.
 The precision and accuracy of many
modern analytical balances exceed I
part in 106 at full capacity.
Types of Weighing apparatus

Analytical Balance

Top loading balance

Commonly encountered analytical
balances
 macrobalances- have a maximum capacity
ranging between 160 and 200 g. with these
balances, measurements can be made with
a standard deviation of ±O.l mg.
 semimicroanalytical- balances have a
maximum loading of 10 to 30 g with a
precision of ± 0.01 mg.
 microanalytical balance -has a capacity of I
to 3 g and a precision of ± 0.001 mg.
Evolution of the Analytical Balance
• The traditional equal-arm balance.
• The first single-pan analytical balance
appeared on the market in 1946.
• Presently- electronic analytical
balance, with the speed, ruggedness,
convenience, accuracy, and capability
for computer control and data logging.
Evolution of the analytical
balance

Equal arm balance Single pan balance

 Precautions in Using an Analytical Balance

Observe the following general rules for

working with an analytical balance
regardless of make or model:
1. Center the load on the pan.
2. Protect the balance from corrosion.
Objects to be placed on the pan should be
limited to nonreactive metals, nonreactive
plastics, and vitreous materials.
3. Observe special precautions for the
weighing of liquids.
4. Consult the instructor if the
balance appears to need adjustment
(adjustment of the analytical balance
will be discussed in the laboratory).
5. Keep the balance and its case
scrupulously clean. A camel's hair brush
is useful for removing spilled material or
dust.
6. Always allow an object that has been
heated to return to room temperature
before weighing it.
7. Use tongs or finger pads to prevent
the uptake of moisture by dried objects.
 Sources of Error in Weighing
• Buoyancy
This will affect data if the density of the object being
weighed differs significantly from that of the standard
masses. This error has its origin in the Temperature
Effects
• Temperature
When different from that of its surroundings will
result in a significant error. Failure to allow sufficient
time for a heated object to return to room
temperature is the most common source of this
problem.
Errors due to a difference in temperature
have two sources.
1. convection currents within the balance case
exert a buoyant effect on the pan and object.
2. warm air trapped in a closed container weighs
less than the same volume at a lower
temperature.
Both effects cause the apparent mass of the object to be
low.
• This error can amount to as much as 10 or 15 mg for a
typical porcelain filtering crucible or a weighing bottle
heated objects must always be cooled to room
temperature before being weighed.
 • Other Sources of Error:
1. A porcelain or glass object will
occasionally acquire a static charge
sufficient to cause a balance to
perform erratically; this problem is
particularly serious when the
relative humidity is low.
2. A low-level source of radioactivity
(such as a photographer's brush) in
the balance case will provide sufficient
ions to relieve the charge.
Alternatively, the object Can be wiped
with a faintly damp chamois.
 Auxiliary Balances
Balances that are less precise than analytical balances.
These offer the advantages of speed, ruggedness, large
capacity, and convenience; they should be used whenever
high sensitivity is not required.
Top-loading auxiliary balances.
• A sensitive toploading balance will accommodate 150 to 200g
with a precision of about I mg an order of magnitude less than a
macroanalytical balance.
• Some balances of this type tolerate loads as great as 25.000 g
with a precision of ±0.05 g.
• Most are equipped with a taring device that brings the balance
reading to zero with an empty container on the pan.
• Some are fully automatic. Require no manual dialing or mass
handling, and provide a digital readout of the mass.
• triple-beam balance
• with a sensitivity less than that of a typical top-
loading.
• This is a single-pan balance with three decades of
masses that slide along individual calibrated scales.
• The precision of a triple-beam balance may be one
or two orders of magnitude less that of a top-
loading instrument but is adequate for many
weighing operations.
• This type of balance offers the advantages of
simplicity, durability. and low cost.
Weighing Bottles

Solids are
conveniently dried
and stored in
weighing bottles
 Desiccators and Desiccants
:
To minimize the uptake of moisture, dried
materials are stored in desiccators while
they cool.
The base section contains a chemical drying
agent, such as anhydrous calcium chloride,
calcium sulfate (Drierite), anhydrous
magnesium perchlorate (Anhydrone or
Dehydrite), or phosphorus pentoxide. The
ground-glass surfaces are lightly coated with
grease.
Components of a typical desiccator
Desiccators and Desiccants

• Oven drying is the most common way of removing

moisture from solids.
• This approach is not appropriate for substances
that decompose or for those from which water is
not removed at the temperature of the oven.
• When removing or replacing the lid of a desiccator,
use a sliding motion to minimize the likelihood of
disturbing the sample.
• An air-tight seal is achieved by slight rotation and
downward pressure on the positioned lid.
Heating apparatus
 increase in pressure as the enclosed air is warm

may be sufficient to break the seal between lid

and base.
 seal is not broken, the cooling of heated
objects can cause a partial vacuum to
develop.
although it defeats the purpose of the
desiccator allow some cooling to occur before
the lid is seated. It is also helpful to break the
seal once or twice during cooling to relieve
excessive vacuum.
Arrangement for drying of sample

Results of an analysis maybe affected by

moisture content of the sample. Sample is
heated inside the oven for 105 to 1100C for 1
to 2 hours. This is done repeatedly several
times as in a cycle of heating-cooling and
weighing until a constant weight is achieved.
Manipulations Associated with weighing
Weighing by Difference
1. The bottle and its contents are weighed.
2. One sample is then transferred from the
bottle to a container; gentle tapping of the
bottle with its top and slight rotation of the
bottle provide control over the amount of
sample removed.
3. Following transfer, the bottle and its residual
contents are weighed. The mass of the sample
is the difference between the two weighings.
Weighing Hygroscopic Solids
1. Place the approximate amount of
sample needed in the individual
bottles and heat for an appropriate
time.
2. When heating is complete, quickly
cap the bottles and cool in a
desiccator.
3. Weigh one of the bottles after opening it
momentarily to relieve any vacuum.
4. Quickly empty the contents of the bottle
into its receiving vessel, cap immediately,
and weigh the bottle again along with any
solid that did not get transferred.
5. Repeat for each sample and determine the
sample masses by difference.
Weighing Liquids
 The mass of a liquid is always obtained by
difference.
 Liquids that are noncorrosive and relatively non-
volatile can be transferred to previously weighed
containers with snugly fitting covers (such as
weighing bottles); the mass of the container is
subtracted from the total mass.
 A volatile or corrosive liquid should be sealed in a
weighed glass ampoule.
The ampoule is heated. and the neck is then immersed
in the sample; as cooling occurs, the sample is drawn
into the ampoule which is then inverted and sealed.
FILTRATION AND IGNITION OF
SOLIDS
• Simple crucibles serve only as containers.
• Porcelain, aluminum oxide, silica, and
platinum crucibles maintain constant mass-
within the limits of experimental error- principally
to convert a precipitate into a suitable weighing
form.
>The solid is first collected on a filter paper. The
filter paper and contents are then transferred to a
weighed crucible, and the paper is ignited.
Crucibles of nickel, iron, silver,
and gold
 for the high-temperature fusion of
samples that are not soluble in
aqueous reagents.
 attack by both the atmosphere and the
contents may cause these crucibles to
suffer many changes. Moreover, such
attack will contaminate the sample
with species derived from the crucible.
The crucible whose products will offer
the least interference in subsequent
steps of the analysis should be used.
 Filtering Crucibles
 Filtering crucibles serve not only as
containers but also as filters.
 A vacuum is used to hasten the
filtration: a tight seal between
crucible and filtering flask is
accomplished with any of several
types of rubber adaptors
 Collection of a precipitate with a
filtering crucible is frequently less
time consuming than with paper.
•Sintered-glass (also called fritted-glass)
crucibles
• are manufactured in fine(f), medium(m), and coarse(c)
porosities .
• The upper temperature limit for a sintered-glass
crucible is ordinarily about 200°C.
Filtering crucibles made of quartz can tolerate
substantially higher temperatures without damage.
The same is true for crucibles with unglazed porcelain
or aluminum oxide frits. The latter are not as costly as
quartz.
Gooch crucible
>has a perforated bottom that supports a fibrous mat.
Asbestos was at one time the filtering medium of choice
for a Gooch crucible; current regulations concerning this
material have virtually eliminated its use.
>Small circles of glass matting have now replaced
asbestos; they are used in pairs to protect against
disintegration during the filtration.
>Glass mats can
tolerate temperatures in excess of 500°C and are
substantially less hygroscopic than asbestos.
• Filter paper
>is an important filtering medium.
All filter papers tend to pick up moisture from the
atmosphere, and ashless paper is no exception so
that it is necessary to destroy the paper by ignition
if the precipitate collected on it is to be weighed.
Ashless paper is manufactured from cellulose
fibers that have been treated with hydrochloric
and hydrofluoric acids to remove metallic
impurities and silica; ammonia is then used to
neutralize the acids.
• The residual ammonium salts in many filter
papers may be sufficient to affect the
analysis for nitrogen by the Kjeldahl
method
• Typically, 9- or II-cm circles of ashless paper
leave a residue that weighs less than 0.1
mg, an amount that is ordinarily negligible.
Ashless paper can be obtained in several
porosities.
• Gelatinous precipitates, such as
hydrous iron(III) oxide, clog the pores
of any filtering medium.
-A coarse-porosity ashless paper is most
effective for filtering such solids, but even
here clogging occurs.
-This problem can be minimized by mixing a
dispersion of ashless filter paper with the
precipitate prior to filtration. Filter paper
pulp is available in tablet form
 Heating Equipment
• Drying oven-electrically heated , capable of maintaining a
constant temperature to within 10C . The maximum attainable
temperature ranges of 140 to 2600C
• Microwave laboratory ovens –greatly quickens drying
time.
E.g. slurry samples which dries in 12-16 hours,
dries in 5-6 min
• Ordinary heat lamp-
• Burners –Meker provides the highest temperature
followed by Tirril and Bunsen.
• Muffle furnace-heavy- duty electric furnace, capable of
maintaining a temperature of 11000C
Filtering and Igniting
Precipitates
• Preparation of Crucibles
• A crucible used to convert a
precipitate to a form suitable for
weighing must maintain-within the
limits of experimental error-a
constant mass throughout drying or
ignition.
• The crucible is first cleaned thoroughly
(filtering crucibles are conveniently cleaned
by backwashing –turning the crucible upside
down in the adapter and sucking water
through the inverted crucible) and then
subjected to the same regimen of heating
and cooling as that required for the
precipitate.
• This process is repeated until constant mass
has been achieved, that is, until consecutive
weightings differ by 0.3 mg or less.
 Filtering and Washing Precipitates

• The steps involved in filtering an analytical

precipitate are decantation, washing, and
transfer.
In decantation, as much supernatant
liquid as possible is passed through the
filter while the precipitated solid is kept
essentially undisturbed in the beaker
where it was formed.
This procedure speeds the overall filtration
rate by delaying the time at which the pores of
the filtering medium become clogged with
precipitate. A stirring rod is used to direct the
flow of decantate .
When flow ceases, the drop of liquid at the
end of the pouring spout is collected with the
stirring rod and returned to the beaker.
Wash liquid is next added to the beaker and
thoroughly mixed with the precipitate again
decanted into the filter. This is done several
times.
The filtration Process
Directions for Filtering and
Igniting Precipitates
• Preparing the filter paper
• Transferring paper and Precipitate
to a crucible
• Ashing the filter paper
MEASURING VOLUME
• The precise measurement of volume is a
important to many analytical methods as the
precise measurement of mass.
Units of Volume
 liter (L), defined as one cubic decimeter.

milliliter (mL) is one one-thousandth of a liter

(0.00 I L) and is used when the liter represents
an inconveniently large volume unit.
microliter (I-LL) is 10- 6 L or 10 - 3 mL
The Effect of Temperature on
Volume Measurements
• volume occupied by a given mass of liquid varies with
temperature, as does the device that holds the liquid during
measurement. Most volumetric measuring devices are made
of glass, which fortunately has a small coefficient of
expansion.
• Consequently, variations in the volume of a glass container
with temperature need not be considered in ordinary
analytical work.
• The coefficient of expansion for dilute aqueous solutions
(approximately 0.0259CfDC) is uch that a 5°C change has a
measurable effect on the reliability of ordinary volumetric
measurements.
Eppendorf
Burettes
Volumetric Flask
Maintaining a Laboratory Notebook
• 1. Recordall data and observations directly
into the notebook in ink. Neatness is
desirable, but you should not achieve
neatness by transcribing data from a
sheet of paper to the notebook or from
one notebook to another. The risk of
misplacing-or incorrectly transcribing-
crucial data and thereby ruining an
experiment is unacceptable.
• 2. Supply each entry or series of entries
with a heading or label. A series of
weighing data for a set of empty crucibles
should carry the heading "empty crucible
mass" (or something similar), for example,
and the mass of each crucible should be
identified by the same number or letter
used to label the crucible.
• 3. Date each page of the notebook as it is
used.
• 4. Never attempt to erase or obliterate an
incorrect entry. Instead. cross it out with a
single horizontal line and locate the correct
entity as nearby as possible. Do not write over
incorrect numbers: with time, it may become
impossible to distinguish the correct entry
from the incorrect one.
• 5. Never remove a page from the notebook.
Draw diagonal lines across any page that is to
be disregarded. Provide a brief rationale for
disregarding the page.
 SAFETY IN THE LABORATORY

Work in a chemical laboratory necessarily involves a

degree of risk; accidents can and do happen. Strict
adherence to the following rules will go far toward
preventing (or minimizing the effect of) accidents.
• 1. At the outset, learn the location of the
nearest eye fountain, tire blanket, shower,
and fire extinguisher. Learn the proper use of
each, and do not hesitate to use this
equipment should the need arise.
•2. Wear eye protection at all times. The
potential for serious and perhaps
permanent eye injury makes it
mandatory that adequate eye protection
be worn at all times by students,
instructors. and visitors. Eye protection
should be donned before entering the
laboratory and should be used
continuously until it is time to leave.
• Regular prescription glasses are not adequate
substitutes for eye protection approved by the
Office of Safety and Health Administration
(OSHA).
• Contact lenses should never be used in the
laboratory because laboratory fumes may
react with them and have a harmful effect on
the eyes.
• 3. Most of the chemicals in a laboratory are
toxic; some are very toxic, and some-such as
concentrated solutions of acids and bases-are
highly corrosive. Avoid contact between these
liquids and the skin. In the event of such
contact. immediately flood the affected area
with copious quantities of water. If a corrosive
solution is spilled on clothing, remove the
garment immediately. Time is of the essence;
do not be concerned about modesty.
• 4. NEVER perform an unauthorized experiment. Unauthorized
experiments are grounds for disqualification at many
institutions.
• 5. Never work alone in the laboratory; be certain that
someone is always within earshot.
• 6. Never bring food or beverages into the laboratory.
-Do not drink from laboratory glassware.
-Do not smoke in the laboratory.
• 7. Always use a bulb or other device to draw liquids into a
pipet:
-NEVER use your mouth to provide suction.
• 8. Wear adequate foot covering (no sandals). Confine long hair
with A laboratory coat or apron will provide some protection
and may be required.
• 9. Be extremely tentative in touching objects that have
been heated; hot glass looks just like cold glass.
• 10. Always fire-polish the ends of freshly cut glass
tubing. NEVER attempt to force glass tubing through the
hole of a stopper. Instead, make sure that both tubing
and hole are wet with soapy water. Protect your hands
with several layers of towel while inserting glass into a
stopper.
11. Use fume hoods whenever toxic or noxious gases
are likely to be evolved. Be cautious in testing for
odors: use your hand to waft vapors above
containers toward your nose.
• 12. Notify your instructor immediately in the
event of an injury.
• 13. Dispose of solutions and chemicals as
instructed. It is illegal to flush solutions
containing heavy metal ions or organic liquids
down the drain in many localities; alternative
arrangements are required for the disposal of
such liquids.
• Tolerances, Class A Burets
• Volume, mL Tolerances, mL

•5 ±0.01
• 10 ±0.02
• 25 ±0.03
• 50 ±0.05
• 100 ±0.20
• Tolerances, Class A Burets
• Volume, mL Tolerances, mL
•5 ±0.02
• 10 ±0.02
• 25 ±0.03
• 50 ±0.05
• 100 ±0.08
• 250 ±0.12
• 500 ±0.20
• 1000 ±0.30
• 2000 ±0.50