8. Acids, Bases and Salts (41.1 MB)

Acids, Bases and Salts
The temperature is not allowed to rise beyond 100°C otherwise whole of water of
crystallization is lost and anhydrous calcium sulphate is produced which is called
‘dead burnt’ as it does not have the property to set after mixing with water.
(b) Uses
1. In making casts for manufacture of toys and statues.
2. In medicine for making plaster casts to hold fractured bones in place while they
set. It is also used for making casts in dentistry.
3. For making the surface of walls and ceiling smooth.
4. For making decorative designs on ceilings, walls and pillars.
5. For making‘ chalk’ for writing on blackboard.
6. For making fire proof materials.
MODULE - 2
Matter in our Surroundings
Notes
8.6.4 Bleaching Powder
Have you ever wondered at the whiteness of a new white cloth? How is it made
so white? It is done by bleaching of the cloth at the time of its manufacture. Bleaching
is a process of removing colour from a cloth to make it whiter. Bleaching powder
has been used for this purpose since long. Chemically, it is calcium oxychloride,
CaOCl 2 .
(a) Manufacture
1. Raw material required: The raw material required for the manufacture of
bleaching powder are:
Slaked lime, Ca(OH) 2
Chlorine gas, Cl 2
Waste gases
Slaked lime
Chlorine
Bleaching powder
Fig. 8.10 Hasen-Clever plant for manufacturing of bleaching powder
SCIENCE AND TECHNOLOGY
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