Sodium

• Symbol : Na
• Atomic number :11
• Electronic configuration : [Ne]3s¹
• Nature of sodium : Bright silvery metal.
• Properties : Soft & highly reactive

The important point about sodium is that it is an alkali metal. Their compounds are widely used in the manufacture of soap, paper, textiles, chemicals etc.

Lithium

Most chemistry students know the importance of Lithium.Actually this is an alkali metal.

• Symbol : Li
• Atomic number : 3
• Electronic configuration : [He]2s¹
• Flame color : Crimson color
• Metallic lithium has a silver like appearance.

Uses of lithium

• Heat transfer applications
• As an alloying agent
• For battery anodes
• Drying agents.

Scandium

Scandium is a silvery white metal which when exposed to air turns yellow or pink. Actually this is a very light soft metal.

• Symbol : Sc
• Atomic number : 21
• Electronic configuration : [Ar]4s² 3d¹
• Radioactive isotope : Sc-46

Uses of scandium

For crude oil Sc-46 is used as a tracer in refinery crackers.The important use of scandium is that it is used to make high intensity lamps.

What is the function of polymerised 1,2-dihydro-2,2,4-tri-methyl quinoline in typical passenger tire treads?

• Antioxidant

What is the role of stearic acid & ZnO in typical passenger-tire treads?

• Accelerator activator

Composition of skim latex

• The average size of rubber particles present in skim latex is smaller than that of field latex.This is because the larger particles separate more readily into the concentrate fraction.
• Some factors renders coagulation more difficult in skim latex. Do you know which are they? Here the rubber particles are small. Skim latex contains water soluble substances in serum. Also the proteins present are distributed as adsorbed film on the surface of rubber particles. Due to the small size of rubber particles, the protein content per unit weight of rubber is more. This renders coagulation more difficult.
• Skim contains ammonia which adds to the cost & difficulty of acid coagulation.
• With the increasing efficiency in concentration the dry rubber content of the skim fraction decreases & the difficulty & the cost of any recovery process increases.

Skim latex

When the field latex is centrifuged,in addition to the concentrate containing most of the rubber, an equal fraction in volume containing very small proportion of rubber is obtained. This is known as skim latex.
But the centrifuging process has a normal efficiency of 75-90%. The 10-5% of the incoming rubber goes to the skim. As rubber is having some importance, it is necessary to recover the rubber in the skim latex.