APPARATUS REQUIRED:
Stand, Funnel, Pencil, Graph paper, Scale
CHEMICAL REQUIRED:
Sucrose
THEORY:
Angle of repose is the maximum possible angle between the surface of pile of powder /granules and the horizontal plane.
Angle of repose(θ) = tan-1 (h/r)
where,
h = height of the pile
r = radius of the base of the pile
When a powder material passes through an orifice, they are called free flowing; while those which do not pass even though the particles are very much smaller than orifice, are called cohesive, Angle of repose is one of the simplest techniques used to determine the flowability of powder materials.
| Angle of repose (θ) | Type of flow |
| <20 | Excellent |
| 20-30 | Good |
| 30-34 | Passable |
| >35 | very poor |
PROCEDURE:
A funnel was set up in the burette stand placing a graph paper below maintaining a height of 2.4cm. The sample whose angle of repose was to be determined was placed in the funnel allowing it to pass through the tip of the funnel. The sample was passed until the height of the pile reached to the tip of the funnel. After that, a circle was drawn outside the base of the sample in the graph assuming most of the sample lay inside the circle. Then, the sampler was removed, diameter from various angles were measured and 4 different radii were obtained whose average value was determined. The height of the pile was also measured. That process was repeated 2 times more to get the exact result.
CALCULATION:
| S.N. | Height of the pile (cm) | Diameter of the base of the pile (cm) | Radius of the base of the pile (cm) | Average radius of the base of the pile (cm) | tan(θ)= h/r | θ= tan-1(h/r) |
| 1. | 2.4cm | d1=9.6cm d2=9.3cm d3=10.2cm d4= 9.7cm | r1= 4.8cm r2=4.65cm r r4= 4.85cm | rav= 4.85cm | tanθ= 2.4/4.85 | θ=tan-1(2.4/4.85) =26.32° |
| 2. | 2.4cm | d1=9.2cm d2=9.1cm d3=9.5cm d4= 9.6cm | r1=4.6cm r2=4.55cm r3=4.75cm r4= 4.8cm | rav= 4.675cm | tanθ =2.4/4.675 | θ=tan-1(2.4/4.675) θ= 27.17° |
| 3. | 2.4cm | d1=9.1cm d2=8.5cm d3=9.2cm d4= 9.2cm | r1=4.55cm r2=4.25cm r3=4.6cm r4= 4.6cm | rav= 4.5cm | tanθ =2.4/4.5 | θ= tan-1(2.4/4.5) = 28.07° |
Also,
Average angle of repose (θav) = 26.32 + 27.17 +28.07 / 3
= 81.56/3
= 27.18°
RESULT:
The angle of repose of the given sample is found to be 27.18°. Hence, the given sample has good flow property.