viscometer

04/07/2023 VISCOMETER 1

VISCOMETERInstrument

seminar

ByDr. Basavaraj N


Contents• Introduction• Objective• History• Types• Description• Technique• Method Of Use• Unit• Applied Aspect• Limitations• Precautions• Discussion• Conclusion


Introduction

• A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid. For liquids with viscosities which vary with flow conditions, an instrument called a rheometer is used. Viscometers only measure under one flow condition.

• In general, either the fluid remains stationary and an object moves through it, or the object is stationary and the fluid moves past it. The drag caused by relative motion of the fluid and a surface is a measure of the viscosity. The flow conditions must have a sufficiently small value of Reynolds number for there to be laminar flow.

http://en.wikipedia.org/wiki/Viscosity

http://en.wikipedia.org/wiki/Fluid

http://en.wikipedia.org/wiki/Flow_conditioning

http://en.wikipedia.org/wiki/Rheometer

http://en.wikipedia.org/wiki/Reynolds_number

http://en.wikipedia.org/wiki/Laminar_flow


Objective

• To know the Instrumentation of VISCOMETER Apparatus


History

• In 1938, Izmailov and Shraiber described the basic principles underlying the process and used it for separation of plant extracts.

• In 1958, Stahl who is mainly credited with bringing out the work on preparing plates and separation of wide variety of compounds.


Types

• 1 Standard laboratory viscometers for liquids– 1.1 U-tube viscometers– 1.2 Falling sphere viscometers

• 2 Falling Piston Viscometer• 3 Oscillating Piston Viscometer• 4 Vibrational viscometers• 5 Rotational viscometers– 5.1 Stabinger viscometer

• 6 Bubble viscometer• 7 Micro-Slit Viscometers

http://en.wikipedia.org/wiki/Viscometer















Description

• Brackets and stands• Brackets made of stainless steel• suitable for use with all Ubbelohde viscometers• Stands made of PTFE• LabPump• Temperature stabilization jackets• AVS measuring stands• Silicone rings


http://en.wikipedia.org/wiki/File:Ubbelohde.jpg


Contd….

• The component with more affinity towards the stationary phase travels slower.

• The component with lesser affinity towards the stationary phase travels faster.

• AdsorbentThe adsorbent is a relative thin uniform layer or

a dry finely powdered material applied to a glass/ plastic/ metal sheet



• glass plates are most commonly used in laboratory. • Identification can be effected by observation of spots of identical

RF values

• Apparatus:1. flat glass plates.2. Hot surface (tray)3. Adsorbent/ coating substances4. Storage rack5. Developing chamber6. Graduated micro pipettes7. Reagent spray8. UV light

Contd………..



Flat Glass Plates.

• Types of plates

Three types : they are ,

1) Full plate : 20cm × 20 cm.

2) Half plate : 20cm × 10 cm.

3) Quarter plate : 20cm × 5 cm.

Microscopic slides can also be

used for Monitoring the progress of a chemical reaction.



Contd…….

• Types of preparation of chromatoplates• Pouring• Dipping• Spraying• Spreading – 2 types Moving spreader Moving plates.



Technique• Operating Instructions Ostwald Micro Viscometer • 1 Preparation of sample • Low-viscosity samples must be filtered through a SCHOTT glass filter

porosity 2 to 4 (10 ... 100 lm) before the measurement; high-viscosity samples, through a sieve with 0.3 mm mesh width (test sieve cloth 0.2, DIN 4188). Samples, whose stock value in accordance with DIN 51 583 or pour point in accordance with DIN 51 597 is not at least 30 °C lower than the test temperature, must be heated up to 50 °C before the measurement.

• 2 Selection of capillary • The size of the capillary is to be selected in such a way that the uncertainty

inherent in the Hagenbach Correction does not exceed the allowable error for the time measurement (see table). For precision measurements should, therefore, be chosen no flow times below 30 seconds. If necessary, a viscometer with a smaller capillary is to be used.



• 3 Cleaning of viscometer • Before the first use, a cleaning with 15 % H2O2 and 15 %

HCl is recommended. The viscometer should then be rinsed with a suitable solvent. It must be completely dry and dust-free.

• 4 Measuring operation • Exactly 2 ml of the sample liquid are filled with a pipette

into the wider one of the viscometer tubes. • Hang viscometer with its stand Type No. 053 97 into a

Glass-Panelled Thermostatic Bath from SCHOTT-GERÄTE GmbH.



• To obtain the measuring accuracy of the viscometer, the constant temperature bath should maintain the set temperature at a constant ± 0.01 °C (Glass-Panelled Thermostatic Baths from SCHOTT-GERÄTE GmbH). Differences in temperature of only 0.1 °C may cause an error of as much as 0.6 % in mineral oils. Measuring should take place only after an equilibration time of approx. 5 minutes.

• The liquid is siphoned above the upper measuring mark M1. Then the flow time between the two timing marks M1 and M2 is measured. The measuring operation can be repeated as often as necessary.

• When using the viscometers in automated viscosity-measuring units (AVS) by SCHOTT-GERÄTE, the vis-cosity is measured automatically.



• Subjective measuring errors are eliminated, and the efflux times measured are available as a printed-out document. According to the type and number of samples to be measured, an optimum measuring device may be assembled which can be expanded to an automatic sampler. Rinsing and filling of viscometers and measuring of sample with subsequent changing of sample is performed automatically. The timing marks required for manual measuring are replaced by light barriers.

• The accuracy obtained with the AVS automated measuring system is greater since certain parameters such as errors in reading, clock errors, etc. are eliminated. 6



• 5 Calculation of viscosity • The seconds contribution given in the table for the Hagenbach Corrections is to be

subtracted from the measured flow time for the various capillaries. Intermediate values can be interpolated.

• With absolute measurements, the corrected flow time multiplied by the viscometer constant K, produces the kinematic viscosity [mm2/s]* directly.

• ν = K (t - ϑ) • The viscometer constant K is mentioned in the enclosed production certificate. • 6 Example of calculation • Ostwald Micro Viscometer • Type No. 516 10 • Capillary I • Constant =0.0100 Flow time (averaged) =40.00 s Hagenbach Correction for 40,00 s ϑ

=0.18 s Kinematic viscosity ν = K (t - ϑ) =0.0100 (40,00 – 0,18) =0.3982 [mm2/s]* * previously centistokes [cSt]; 1 cSt = 1 mm2/s



Contd……

• The position of sample spot is marked by lead pencil.

• When the spot is dried, then the plate is placed vertically in suitable tank with its lower edge immersed in selected mobile phase.



Hot Surface (Tray)

• Hot surface tray are used for drying of plates.



Adsorbent/ Coating Substances

• Organic:1. Cellulose and its Acetylates for amino acids &

sugars2. Charcoal and activated carbon for aromatic

substances• In-organic:1. Silica gel for amino acid,alkeloids etc2. Alumina for steroids, aromatic substances3. magnesia



Solvents

• The different types of solvents are :• Petroleum ether,• Benzenes• Pyridine• Acetone• Methanol• Glycol• Glycerol etc….



Developing Chamber


• The types and size of chamber also decides the success of Rf value. They are classified acc. To separation technique as follows

• Tanks for ascending development• Tanks for descending development • Tanks for horizontal development

Contd…..


Ascending Development Descending Development

Horizontal Development


Graduated Micro Pipettes• Normal pipettes(Capillary).

• Graduated Micro Pipettes.


Reagent spray

• Different types of sprays are used• Ex. Dragendroff’s reagent spray for alkeloids• Ferric chloride solution spray for phenolic

compounds• Ninhydrin spray for amines

Spraying bottle for spraying reagents on the developed TLC plate spot.


Contd……….

• Ammonia vapor reagent is used for flavonoids.• Blue tetrazolium is used for cortico steroids.


UV light

• Used to detect spots not visible in normal light.

UV Cabinet Visualization of spot under UV light


Method Of Use

Preparation of plates:1. Preparation of a suspension of the coating

substance2. Spread a uniform layer 3. Heat up to 100- 105 at least 1hr4. Store5. At the time of use dry the plates


Unit

TLC is measured by RF value

RF= Distance travelled by sample distance travelled by solvent


Applied aspect

1) Separation of mixture of drug of chemical, biological, plant origin.

2) Separation of Carbohydrates, vitamin, antibiotics, proteins, etc.

3) Identification of drug. Ex :Amoxicillin, Levodopa

4) Detection of foreign substances.

5) To detect the decomposition products of drug.


Limitation

• Quantitative analysis is very difficult by this method


Precautions

• One should not touch the plate• Thickness of adsorbent should not be more• Low polar solvent must be chosen.


Conclusion

• Easy to perform• Different types of adsorbent are available silica gel is

commonest one.• Good for qualitative analysis• economical • In conclusion, today, when the world demand for herbal

medicine is on the rise, these herbals, the use of traditional medicine with integration of modern evaluation techniques to support the claim is the need of the hour, so that such medicine can be used for a better healthcare for humanity....


Discussion

• Usefulness to ayurvedic research.


Thank U


LINOMAT 5

(Camag)TLC SCANNER 3

(Camag)

INSTRUMENTATION OF HPTLC

viscometer

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