Calibration of Digital Analytical Balance and Melting Point Apparatus

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Hello my dear Pharmainfo friends, let us start our first basic step from calibration of basic lab requirements to sophisticated instruments.

Digital Analytical Balance:
It will not be shocking to say that digital balance is the first and foremost lab requirement. Accurate weighing results in desired finished product. It plays an important role at each and every stage. Therefore this blog emphasized on calibration of digital analytical balance.
The calibration is done using different standard weights. Example, the calibration of a digital analytical balance whose maximum capacity is 220 grams and minimum capacity is 10 mg includes the use of following standard weights and tolerance limits as per I.P.
20 mg:19.98 mg-20.02 mg (+-0.1)
50 mg: 49.95-50.05 (+-0.1)
2.00 gms: 1.9980-2.0020 (+-0.1)
10.00 gms: 9.99-10.01 (+-0.1)
Calibration should be done daily to avoid errors.
Operation of analytical balance should be done by choosing an optimum location with firm base, vibration free position with no extreme temperature fluctuation and excessive drafts (powerful air currents of fume hoods) for obtaining high accuracy.

Melting Point Apparatus:

It is used to identify a given sample or purity of a sample. It is the point at which a compound changes from solid to liquid. The point at which a compound starts melting and completes melting is called melting range.
No two solids or liquids have same melting or boiling point. We can determine melting point using capillary tube method.
Calibration of melting point is done using standard materials as listed

Table 1. Calibration of Melting Point Apparatus as per W.H.O.

Trouble shooting:
First each and every parameter like media, thermometer, capillary tube and heater are checked. If the problem is not solved then it is sent for service engineering. Generally the problem may be chucked at the initial stages of calibration and verification of all parameters.

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Teena Bio labs Pvt. Ltd. (An ISO: 9001:2000 certified company), Bachupally is highly acknowledged for supporting this blog.


W.H.O. - World Health Organization


About the Author

TK Indira's picture
Author: TK Indira

Indu Roy is post graduate in pharmacy and working as Research Officer, Formulation-IPR Department at Mylan Laboratories Limited (A subsidiary of Mylan Inc) .
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P.V.ABHIGNA's picture

Dear Indira, Thats a nice piece of work......Can u elaborate the melting point apparatus a bit like its arrangement and all.. Regards,


TK Indira's picture

Thank you for your comment.

Well coming to the query,
Let me explain the different parts of melting point apparatus

- Beaker with a length of 1.4cms and capacity 250 ml.

- Thermometer to detect the temperature
- Capillary tube (a thin layer)with thickness of 0.2-0.3 mm, length of 10-12 cms, internal diameter of 0.8-1.2 mm. It may be made up of borosilicate glass that can resist high temperature. Sample may be filled upto 1/4th of capillary tube.

- Different medias may be used like water/silicon, glycerine, liquid paraffin to maintain uniformity of temperature or equilibrium state.

Water may be used up to temperature of 600C

Glycerin may be used up to temperature of 1500C

Liquid paraffin may be used up to temperature of 2500C

Silicon oil may be used up to temperature of 3500C

Still more queries???feel free to interact.

T.K. Indira.

-- "Our greatest glory is not in never falling, but in rising every time we fall..." Team 'Char'minar.

S.M. Habibur rahman's picture

Its really an useful information.
TK Indira's picture

Thank you for your comment.

T.K. Indira.

-- "Our greatest glory is not in never falling, but in rising every time we fall..." Team 'Char'minar.

Niklesh Rao V's picture

Very good information ma'am. We hardly used to calibrate our equipment during my B. Pharmacy. It changed in my final year of study though. By that time we had prepared proper SOP's for each and every equipment and followed them every time we used the equipment.

Regards, Niklesh Rao V

TK Indira's picture

Thanks for your comment. Generally we do skip to perform calibration which is the first and foremost prerequisite. Periodic calibration of equipments and following SOP's right from lab would really help us to end with promising results as research starts at our lab scale.

T.K. Indira.

-- "Our greatest glory is not in never falling, but in rising every time we fall..." Team 'Char'minar.

Amol Malpani's picture

Dear Indira, Whatever standard materials you mentioned for calibration of m.p. apparatus. How much pure these materials should be what is the minimum level of their purity so that they give specified values if apparatus is working fine? Regards,
Uma Pratyusha's picture

Dear Indira, Very well explained in a precise way. Can you tell me how much variation there would be if we don't follow the standardization and SOP'S for a period of time?


Uma Prathyusha

Venkata Ram Sudhir Kakarlapudi's picture



if drug contain more impurity what is effect on melting point ?


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