How melting point apparatus is calibrated?

PROCEDURE

Operate the instrument as per the SOP for operation of melting range/point apparatus. Perform the temperature check for calibration of the instrument. Dry the reference/standard material as per their specified condition. Perform the test with each selected reference/standard material. 

Pack dry powder of Vanillin, Sulfanilamide and Caffeine reference materials in the capillary tubes such that a 3 mm packed columns are made.

Start the apparatus, put ‘on’ the heater and stirrer (as applicable).
Heat the sample plate / silicon oil by setting the control parameter/knob.

A- Vanillin
Insert the three capillary tube filled with sample.
Set the temperature program as below.
Initial temperature     70°C
Rate --- 1°C/min
Final temperature    87°C
Note down the temperature at which the first and last particle Of Vanillin melts.    
Acceptance criteria: Vanillin : between 81°C to 83°C.

B -- Sulfanilamide
Insert the three capillary tube filled with sample.
Set the temperature program as below.
Initial temperature     155°C
Rate --  1°C/min
Final temperature    170°C
Note down the temperature at which the first and last particle of Sulfanilamide melts.    
Acceptance criteria:    Sulfanilamide : between 164.5°C to 166.5°C.

C-- Caffeine 
Insert the three capillary tube filled with sample.
Set the temperature program as below.
Initial temperature -- 225°C
Rate    -- 1°C/min
Final temperature    245°C
Note down the temperature at which the first and last particle of Caffeine melts.    
Acceptance criteria:    Caffeine: between 234°C to 237°C.