[ps2id id=’background’ target=”/]
BACKGROUND
Centrifugation is a unit operation employed for separating the constituent present in a dispersion with the aid of centrifugal force. Centrifugal force is used provided driving force for the separation.1,2 The equipment in which centrifugal force is implied on dispersion is called centrifuge. Separating power of a centrifuge is expressed as centrifugal effect. It is a ratio of centrifugal force to gravitational force. Centrifugal effect can be calculated by using the following equation.3,4
Centrifugal effect=2.013dn2
Centrifugal effect is directly proportional to diameter of rotation and is also directly proportional to square of the rpm. Inequation, n is expressed in s-1 and d in meters.
Aim: To study the influence of centrifugal effect in separating the solid from suspension.
[ps2id id=’requirements’ target=”/]
REQUIREMENTS
Apparatus: Centrifuge with graduated tubes
Stirrer
Weighing balance
Beakers
Measuring cylinder
Calcium carbonate powder
Water
[ps2id id=’procedure’ target=”/]
PROCEDURE
5gm of CaCO3 was weighed and transferred to a motor. 50 ml of water was added and triturated to get a smooth paste. The contents were transferred into a measuring cylinder under 100 ml. The mortar and pestle were washed with 10 ml of water. The washing was transferred into the measuring cylinder. The volume was made up to the mark 100 ml by adding water. The suspension was shaken thoroughly. The diameter was measured between the tip of the centrifuge tube to centre of the centrifuge and the value was noted. The calibrated centrifuge tubes were cleaned labelled and filled with CaCO3 suspension, up to 10ml mark. The tubes were placed in basket. The cover of the centrifuge was closed. The centrifuge was switched on. The speed control knob was turned clockwise from the ‘0’ position to ‘1’ position (1000 rpm). The centrifuge was allowed to exert centrifugal effect on the suspension for 5 min. After 5 min the centrifuge was switched off. The centrifuge lead was opened and the centrifuge tubes were taken out. The volumes of the solids separated which is present as a lower layer in the test tube was noted. The same experiment was repeated for 3000rpm and 5000 rpm by keeping the speed knob position 3&5 respectively. A graph was plotted by taking centrifugation time on X-axis and percent volume of CaCO3 separated on Y-axis. Centrifugal effect was calculated after 30 min of centrifugation in each cases. A graph was plotted by taking speed in rpm on x-axis and log centrifugal effect on Y- axis.
Observations and calculations
Table 1: (Separation of CaCO3 from suspension at 1000rpm)
| Time of Centrifugation |
Volume of solid separated |
Average volume |
% CaCO3 separated |
|
|
Test tube 1 |
Test tube 2 |
|||
| 5 | ||||
| 10 | ||||
| 15 | ||||
| 20 | ||||
| 25 | ||||
| 30 | ||||
Table 2:(Separation of CaCO3 from suspension at 3000 rpm)
| Time of Centrifugation |
Volume of solid separated |
Average volume |
% CaCO3 separated |
|
|
Test tube 1 |
Test tube 2 |
|||
| 5 | ||||
| 10 | ||||
| 15 | ||||
| 20 | ||||
| 25 | ||||
| 30 | ||||
Table 3:(Log centrifugal Effect for different rpm levels)
|
Sl.No. |
d, m |
rpm, n |
n2 |
Centrifugal effect =2.013 d n2 ,m/s2 |
Log centrifugal effect |
|
1 |
|||||
|
2 |
|||||
|
3 |
[ps2id id=’conclusion’ target=”/]
CONCLUSION
The influence of centrifugal force in the given sample is ___
[ps2id id=’references’ target=”/][ps2id id=’1′ target=”/]
REFERENCES
- Subrahmanyam CVS, Setty JT, Suresh S. Laboratory manual of pharmaceutical engineering ( Unit operations) Delhi Vallabh Publications.
- Pharmaceutical Engineering by K.Sanbamurty (New Age International, New Delhi).
- Cooper and Gunn’s Tutorial Pharmacy Edited by S.J.Carter (CBS Publishers, Delhi).
- Pharmaceutical Dosage forms by Aulton.(Churchill Livingstone, Edinburg).
