Determination Of Physical Characters Of Materials

Determination of the appearance of the substance:
- Take about 1 g of the substance to be examined on a glass watch.
- Examine under white illumination.
- Determine the color and appearance of the substance.

Determination of hygroscopicity:
- This method is to be carried out on a substance that complies with the test for loss on drying or water content of the monograph
- The method gives an indication of the degree of hygroscopicity rather than a true determination.
- Use a glass weighing vessel 50 mm in external diameter and 15 mm high.
- Weigh the vessel and stopper (m₁).
- Place the amount of substance prescribed for the test for loss on drying or water in the vessel and weigh (m₂).
- Place the un-stoppered vessel in a desiccator at 25 ^ºC containing saturated solution of ammonium chloride or ammonium Sulphate or place it in a climatic cabinet set at 25 ± 1⁰C and 80 ± 2 percent relative humidity.
- Allow to stand for 24 h.
- Stopper the weighing vessel and weigh (m3).
- Calculate the percentage increase in mass using the expression:

Deliquescent: sufficient water is absorbed to form a liquid.
Very hygroscopic: increase in mass is equal to or greater than 15 percent (≥ 15%).
Hygroscopic: increase in mass is less than 15 percent and equal to or greater than 2 percent (≥ 2% and < 15%).
Slightly hygroscopic: increase in mass is less than 2 percent and equal to or greater than 0.2 percent < 2% and ≥ 0.2%).

Determination of Solubility procedures

- - Very soluble substance:
    - Weigh accurately 1.0 g of finely powdered substance, in a stoppered tube (16 mm in internal diameter and 160 mm long), or volumetric flask 10 ml add 1.0 ml of the solvent.
    - Shake vigorously for 1 min and place in a constant temperature device (Incubator), maintained at a temperature of 25.0 ± 0.5 °C for 15 min.
    - If the substance is not completely dissolved, repeat the shaking for 1 min and place the tube in the constant temperature device for 15 min.
    - If the substance is completely dissolved, it is very soluble

- - Freely soluble substance:
    - Weigh accurately 1.0 g of finely powdered substance, in a stoppered tube, or volumetric flask 25 ml, add 1.1 ml of the solvent.
    - Shake vigorously for 1 min and place in a constant temperature device (Incubator), maintained at a temperature of 25.0 ± 0.5 °C for 15 min.
    - If the substance is not completely dissolved, add gradually another 8.9 ml of the solvent (0.5 ml in each addition) and after each addition, repeat the shaking for 1 min and place the tube in the constant temperature device for 15 min.
    - If the substance is completely dissolved, it is freely soluble in that specified volume of solvent

- - Soluble substance:
    - Weigh accurately 1.0 g of finely powdered substance, in a stoppered tube, or volumetric flask 50 ml, add 10 ml of the solvent.
    - Shake vigorously for 1 min and place in a constant temperature device (Incubator), maintained at a temperature of 25.0 ± 0.5 °C for 15 min.
    - If the substance is not completely dissolved, add gradually another 20 ml of the solvent (1 ml in each addition) and after each addition, repeat the shaking for 1 min and place the tube in the constant temperature device for 15 min.
    - If the substance is completely dissolved, it is soluble in that specified volume of solvent.

- - Sparingly soluble substance:
    - Weigh accurately 1.0 g of finely powdered substance, in a stoppered tube, or volumetric flask 100 ml, add 30 ml of the solvent.
    - Shake vigorously for 1 min and place in a constant temperature device (Incubator), maintained at a temperature of 25.0 ± 0.5 °C for 15 min.
    - If the substance is not completely dissolved, add gradually another 70 ml of the solvent (5 ml in each addition) and after each addition, repeat the shaking for 1 min and place the tube in the constant temperature device for 15 min.
    - If the substance is completely dissolved, it is sparingly soluble in that specified volume of solvent.

- - Slightly soluble substance:
    - Weigh accurately 0.250 g of finely powdered substance, in a stoppered tube, or volumetric flask 250 ml, add 25 ml of the solvent.
    - Shake vigorously for 1 min and place in a constant temperature device (Incubator), maintained at a temperature of 25.0 ± 0.5 °C for 15 min.
    - If the substance is not completely dissolved, add gradually another 225 ml of the solvent (5 ml in each addition) and after each addition, repeat the shaking for 1 min and place the tube in the constant temperature device for 15 min.
    - If the substance is completely dissolved, it is slightly soluble in that specified volume of solvent.

- - Very slightly soluble substance:
    - Weigh accurately 0.100 g of finely powdered substance, in a stoppered tube, or volumetric flask 1000 ml, add 100 ml of the solvent.
    - Shake vigorously for 1 min and place in a constant temperature device (Incubator), maintained at a temperature of 25.0 ± 0.5 °C for 15 min.
    - If the substance is not completely dissolved, add gradually another 900 ml of the solvent (50 ml in each addition) and after each addition, repeat the shaking for 1 min and place the tube in the constant temperature device for 15 min.
    - If the substance is completely dissolved, it is very slightly soluble in that specified volume of solvent.

- - Practically insoluble or insoluble substance:
    - Weigh accurately 0.100 g of finely powdered substance, in a stoppered tube, or volumetric flask 2000 ml, add 1100 ml of the solvent.
    - Shake vigorously for 1 min and place in a constant temperature device (Incubator), maintained at a temperature of 25.0 ± 0.5 °C for 15 min.
    - If the substance is completely dissolved, it is practically insoluble or insoluble substance.

Descriptive	Parts of solvent required for 1 part of solute
Very soluble	Less than 1
Freely soluble	From 1 to 10
Soluble	From 10 to 30
Sparingly soluble	From 30 to 100
Slightly soluble	From 100 to 1000
Very slightly soluble	From 1000 to 10000
Practically insoluble or insoluble	More than 10000