Title: Limit Test for Clarity of solution
- Objective: Using identical test tubes of colourless, transparent, neutral glass with a flat base and an internal diameter of 15-25 mm, compare the liquid to be examined with a reference suspension.
- Principle: A liquid is considered clear if its clarity is the same as that of water or of the solvent used when examined under the conditions described above, or if its opalescence is not more pronounced than that of reference suspension OS1.
3. Procedure:
- Preparation of Standard Solutions:
Note: All solutions should be prepared in Distilled/Purified Water.
- Hexamine solution (10% w/v): Dissolve 2.5 g of Hexamine in water and dilute to 25.0 ml with water.
- Suspension: Dissolve 1.0 g of Hydrazine sulphatein sufficient water to produce 100.0 ml and set aside for about 6 hours. To 25.0 ml of this solution add 25.0 ml of Hexamine solution (10 % w/v), mix well and allow to stand for 24 hours. Keep in a glass container with a smooth internal surface in which the suspension does not adhere to the glass. Store in this manner, the suspension is stable for about 2 months.
- Standard Suspension: Prepare the standard suspension by diluting 15 ml of the well-mixed suspension to 1000 ml with The standard suspension should be used within 24 hours of preparation.
- Opalescence Standards: Prepare the Opalescence Standards by mixing aliquots of the Standard Suspension with water as indicated in Table No.: 01. Each opalescence standard should be shaked well before use.
Table No.: 01
| Opalescence Standard | Standard Suspension (ml) | Water (ml) |
| OS1 | 5.0 | 95.0 |
| OS2 | 10.0 | 90.0 |
| OS3 | 30.0 | 70.0 |
| OS4 | 50.0 | 50.0 |
- Method:
Transfer to a flat-bottomed test-tube of neutral glass, 15 to 25 mm in diameter, a suitable volume of the solution under examination such that the test-tubes is filled to a depth of 40 mm. Into another matched test-tube add the same volume of the freshly prepared Opalescence Standard. After 5 minutes, compare the contents of the test-tubes against a black background by viewing under diffused light down the vertical axis of the tubes.
- Clarity or opalescence:
Express the degree of opalescence in terms of the opalescence standard. A liquid is considered clear if its clarity is the same as that of water or of the solvent used for preparing the solution under examination or if its opalescence is not more than that of opalescence standard OS1.