Aim is To
determine the quantity of Casein present in different samples of milk.
Natural milk is an opaque white fluid Secreted by the mammary glands of Female
mammal . The main constituents of natural milk are Protein, Carbohydrate,
Mineral Vitamins, Fats and Water and is a complete balanced diet. Fresh milk is
sweetish in taste. However , when it is kept for long time at a temperature of
5 degree it become sour because of bacteria present in air. These bacteria
convert lactose of milk into lactic acid which is sour in taste. In acidic
condition casein of milk starts separating out as a precipitate. When the
acidity in milk is sufficient and temperature is around 36 degree, it forms
semi-solid mass, called curd. Casein is present in milk as calcium caseinate in
the form of micelles. These micelles have negative charge and on adding acid to
milk, the negative charges are neutralized.
Milk is a complete diet
as it contains in its proteins, carbohydrates, fats, minerals, vitamins and
water. • Average composition of milk from different sources is given below.
• Casein is the major
protein constituent presents in the milk and is a mixed phosphor-protein.
• Casein has isoelectric
pH of about 4.7 and can be easily separated around this pH.
• It readily dissolves in
dilute acids and alkalies.
Materials
Required:
Beakers (250 ml),
filter-paper, glass-rod, weigh-box, filtration-flask, Buchner-funnel, water
pump, test-tubes porcelain dish, burner, different samples of Milk, 1% acetic
acid solution, saturated ammonium sulphate solution.
Procedure
• Take a clean dry beaker,
put into it 20cc of goat’s milk and add 20 ml of saturated ammonium sulphate
solution slowly and with stirring. Fat along with casein will precipitate out.
• Filter the solution and
transfer the precipitates in another beaker.
• Add about 30 ml of
water to the precipitate.
• Only casein dissolves
in water forming milky solution leaving fat undissolved.
• Heat the milky solution
to about 40°C and add 1% acetic acid solution drop wise, when casein gets
precipitated.
• Filter the ppt., wash
with water, and let the ppt. dry.
• Weigh the dry solid
mass in a previously weighed watch glass.
• Repeat the experiment
with other samples of milk.
Observation Table
If an acid is added to
milk, the negative charge are neutralized and the neutral protein precipitated
out.
Ca+2 (Casemated) + 2CH3
COOH(aq) Casein(s)+(CH3COO)2 Ca (aq)
Volume of milk taken in
each case = 20 ml.
Conclusion
Different samples of milk
contain different percentage of Casein..
“Acid &
Bases on Tensile Strength of Strength of Fibres”
Declaration
I,
____________ student of ___________________ is doing project report entitled “Acid
& Bases on Tensile Strength of Strength of Fibres” being submitted
to ___________________is an original piece of work done by me and has not been
published or submitted elsewhere for any other degree in full or in part.
(Signature)
Study of Effects of Acids & Bases on the Tensile Strength of Fibres
Objective
"Study of Effects of Acids
& Bases on the Tensile Strength of Fibres"
The
aim and objective of this project is to
(i)
Compare the tensile strength of given samples of nylon and cotton fibres.
(ii)
To investigate the Effect of Acids and Alkalies on the tensile strength
of these fibres.
Introduction
Depending upon the
sources, the various types of fibres can be classified into the following three
main categories :
(i) Animal fibres
e.g. Wool & Silk.
(ii) Vegetable
Fibres e.g. Cotton & Linen.
(iii) Synthetic
Fibres e.g. Nylon & Polyester.
Besides their
chemical composition and properties, most important property of these fibres is
their tensile strength. Tensile strength mean the extent to which a fibre
can be stretched without breaking and it is measured in terms of minimum weight
required to break the fibre. To determine the tensile strength of any
fibre, it is tied to a hook at one end and weighted are slowly added to the
other end until the fibre break.
Since peptide bonds
are more easily hydrolyzed by bases than acids therefore wool and silk are affected by basis not by acids.
It is because of this reason that wool and silk threads breakup into fragments and ultimately dissolve in alkalines.
In other words
alkalines decreases the tensile strength of animal fibres (wool & silk).
Vegetable fibres (cotton & linen), on the other hand, consist of long
polysaccharide chains in which the various glucose units are joined by ethers
linkage. Since ethers are hydrolised by acids and not by bases therefore,
vegetable fibres are affected by acids but not by bases. In other words
acids decreases the tensile strength of vegetable fibres. In contrast, synthetics
fibres such as nylon & polyester practically remains unaffected by both
acids and bases.
Experiment-1 [Acid
and Bases]
Requirements :
(a) Apparatus :
Hook, Weight hanger and weights.
(b) Materials :
Cotton, Silk and Nylon fibres.
Chemistry Experiment
Acid and Bases Procedure
(i) Cut out equal lengths of a cotton fibre, nylon fibre and
silk fibre from the given sample of nearly same dia.
(ii) Tie one end of cotton fibre to a hook which has been
fixed in a vertical plane. Tie a weight hanger to the other end. The thread get
straight.
(iii) Put a weight to the hanger and observe the thread
stretch. Then, increase the weights gradually on the hanger until the breaking
point reaches and note the minimum weight needed for breaking the cotton fibre.
(iv) Repeat the above experiment by tying nylon and silk
fibres to the hook separately.
Sr.No.
Type of Fibre Minimum Weight
1.
Cotton
75 g.
2.
Nylon
375 g.
3.
Silk
150 g.
Precautions
(i) Thread must be of identical diameters.
(ii) Always take the same length of the threads.
(iii) Add the weights in small amounts very slowly.
Experiment - 2
Requirements :
(a) Apparatus : Hook, Weight Hanger and Weights.
(b) Materials and Chemicals : Wool, Cotton and Nylon Fibres,
dilute solution of hydrochloric acid and sodium hydroxide.
Procedure
(i) Cut out equal
lengths of wool, cotton and nylon threads from given sample of nearly same diameter.
(ii) Determine the
tensile strength of each fibre as explained in experiment-1.
(iii) Soak the
woolen thread in a dilute solution of sodium hydroxide for five
minutes. Take it out from hydroxide solution and wash it thoroughly with water
and then dry either by keeping it in the sun or in an over maintained at a
temperature of about 400C. Determine its tensile strength again as explained in
Experiment-1.
(iv) Now take
another piece of woolen thread of the same size and diameter and soak it in a
dilute solution of hydrochloric acid for five minutes. Take it out, wash
thoroughly with water, dry and determine the tensile strength again.
(v) Repeat the above
procedure for the samples of cotton and nylon fibre.
S.No.
Type of Wt.
Required Wt.
Required Wt.Required
Fibre
to break the to break
the to break
the
untreated fibre fibre
after
fibre after
soaking
in
soaking in
dilute
alkali
dilute acid
1.
Wool
750 g.
700
g.
750 g.
2.
Cotton
75 g.
75
g.
50 g.
3.
Nylon
375
g.
375
g.
375 g.
Result
(i) The tensile
strength of woolen fibre decreases on soaking in alkalies but practically
remains unaffected on soaking in acids.
(ii) The tensile
strength of cotton fibre decreases on soaking in acids but remains practically
unaffected on soaking in alkalies.
(iii) The tensile
strength of nylon fibres remain practically unaffected on soaking either in
acids or in alkalies.
Precautions
(i) Thread must be
of identical diameters.
(ii) Always take the
same length of the threads.
(iii) Add the
weights in small amounts very slowly.
Thank you it was helpful but you should have written the observation as well
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