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Melting Point/Refractif
indexs/DSC
By : TEAM
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Melting Point & RefractiveIndex
Elements of the Experiment
Melting Point
Theory and Background
Uses
Measurement Techniques & Equipment
Melting Point Range
Refractive Index
Theory and Background
Temperature Correction
Measurement Techniques & Equipment
Refractive Index, with temperature correction for a known
and unknown compounds
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Melting Point Theory & Background
Melting Point
Temperature pada kondisi transisi yang terjadi antara fase
solid dan liquid
Temperature pada saat kesrtimabangan exists antara kondisi
kristal (teratur) dan keadaan liquid (random)
Melting Point Range Onset point (temperatur rendah) ketika temperature pada
fase liquid pertama terlihat
Meniscus point ketika solid phase di dasar dan fase liquid
diatas dengan miniscus yang terlihat disebutPelting Point
The Clear point ketika semua substance menjadi liquid semua
Used as Melting Point in USA
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Melting Point Uses
Identifikasi senyawa
Mencari kemurnian dari senyawa
Melting Point Depression
Pure compounds display little, if any, melting point range,
i.e., they have sharp melting points
Mixtures of substances, i.e., the contamination of one
compound by another, whose components are insoluble in
each other in the liquid phase, display both a melting point
depression and, instead of a sharp melting point, a melting
point range The size of the melting point depression depends on the
composition of the mixture
Secara umum, 1% pengotor manghasilkan 0.5oC perberdaan
dengan yang murni.
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Melting Point
Melting Point Indicates Purity in Two Ways
The Purer the Compound, the Higher the Melting Point
The Purer the Compound, the Narrower the Melting Point Range
Melting point of A decreases as impurity B is added
Eutectic Point is the Solubility Limit of B in A; Thus, it isthe Lowest Melting Point of an A/B mixture
(Note: Sharp melting point, i.e., no range, at eutecticoint3/15/2013 5
Liquid A + B
Solid A + B
RangeClear Point
Onset Point
mp A
mp B
0% B 0% A
Temperature
Eutectic Point
mpB > mpA
MP Range
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Melting Point
The Experiment
Determine the melting point range of:
Two Known Compounds
A Mixture of the Two Known Compounds
An Unknown Compound
Mixture of Unknown Compound and a Known compound.
Note: The Unknown might have to be mixed with additional
known compounds until the melting point of the known and
the known/unknown mixture match.
Identify the unknown compound.
Equipment Capillary Tubes
Mel-Temp Melting Point Apparatus (Obtain from PrepRoom)
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f i d
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Refractive Index kegunaan Identifikasi senyawa
Mengukur kemurnian Latar Belakang Refractive Index is a physical property of liquids &
solids
Light travels at different velocities in condensedphases (liquids or solids) than in air.
Light travels more slowly through a denser substance.
The Wavelength of light is also different in condensedphases.
As the velocity decreases, the wavelength decreases.
The Frequency of light in condensed phases does notchange.
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Refractive Index The Refractive Index for a given medium
depends on two (2) variables:
Refractive Index (n) is wavelength () dependent.
Sumber sinar dengan perbedaan panjang gelombang di refrasikan
manjadi different extents in the same medium, sehaingga,
menghasilkan refractive indek yang berbeda.
Refractive Index (n) is temperature dependent.
sebagai perubahan temperature, density berubah; sehinga
kecepatan nya juga () changes.
Density dari medium menurun sebagai akibat kenaikan temperatur
Kecepatan cahaya dalam medium meningkat akibat temperatur naik
dan density menurun.
Ratio dari kecepatan cahaya dalam vacuum vs. speed cahaya dalam
medium menurun, sehingga, Refractive Index menurun akibat
temperatur naik.3/15/2013 8
f i d
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Refractive Index For a given liquid and temperature, the ratio dari
kecepatan sinar dlm vacum (c) and kecepatan
cahaya dalam medium () adalah constant (n).
ratio kecepatan cahaya juga proporsional dengan rasiodari sinus sudut udara dan sinus sudut refraksi.
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nv
c
nV
Vliquid
air Constant
sin
sin
2
1
1 - Angle of Incidence (air)
2 - Angle of Refraction (sample)
(Index of Refraction)
(Refractive index)
R f i I d
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Refractive IndexConsider two (2) media: air (or vacuum) & organic
liquid
Frequency of light in both media remains constant
Divide 1 by 2
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1 1v f
2 2=v f
v f
v f
2 2
= =f f f
(velocity) (Frequency * Wavelength)v f
R f ti I d
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Refractive Index Since:
Then:
Substitute in original refractive index equation
Note: n1 for air (or vacuum) = 1.03/15/2013 11
1 1 1
2 2 2
sin v Refractive Index
sin v
2
1
nn
n
1 2
1 2
&c c
= =n n
v v
c
v ncv
nn n
2
1
n
n
1
2
R f ti I d
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Refractive Index The Instrument Abbe Refractometer (Bausch
& Lomb)
Clean prisms with tissues & Methyl Alcohol BEGENTLE!!
Do not touch prism with fingers or other hard objects,use tissues
Use 3 4 drops of sample
Close hinged prisms together - Gently
Turn on the light - Preferred light source is a sodiumdischarge lamp producing yellow light at 589 nmalso called Sodium D light.
Move hinged lamp up into position
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R f ti I d
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Refractive IndexAbbe Refractometer (Cont)
Rotate coarse and fine adjustment knobs on the rightside of instrument until the horizontal dividing line(may not be sharp at first) between the light upperhalf and dark lower halve of the visual field coincidewith the center of the cross-hairs.
Use eyepiece to focus cross-hairs
If horizontal line dividing light & dark areas appears asa colored band (chromatic aberration), adjust with theknurled drum knob on the front of the instrument
Press small button on left side of instrument to makethe scale visible.
Read refractive index value to 4 decimal places
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Differential Scanning
Calorimetry
Stephen Collins
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Technical Group Talk
Definitions
Acalorimetermeasures the heat into or out of asample.
Adifferential calorimeter measures the heat of a
sample relative to a reference.Adifferential scanning calorimeterdoes all of the
above and heats the sample with a linear temperature
jalur.
Endothermicheat flows into the sample.Exothermicheat flows out of the sample.
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Technical Group Talk
Differential Scanning Calorimetry(DSC) measuresthe
temperatures and heat flowsassociated with transitions in
materials as a function of time and temperature in a
controlled atmosphere.
These measurements provide quantitative and qualitative
information about physical and chemical changes that
involve endothermicor exothermicprocesses, orchanges
in heat capacity.
DSC: The Technique
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Technical Group Talk
Conventional DSC
Metal
1
Metal
2
Metal
1
Metal
2
Sample Empty
Sample
TemperatureReference
Temperature
Temperature
Difference =
Heat Flow
A linear heating profile even for isothermal methods
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Technical Group Talk
What can DSC measure?
Glass transitions
Melting and boiling points
Crystallisation time and temperature
Percent crystallinityHeats of fusion and reactions
Specific heat capacity
Oxidative/thermal stability
Rate and degree of cureReaction kinetics
Purity
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Technical Group Talk
6
DSC Thermogram
Temperature
H
eatFlow
->exothermic
GlassTransition
Crystallisation
Melting
Cross-Linking(Cure)
Oxidation
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