Equipment for weighing in laboratory
Chaus
5.0.10 mechanical balance1.
Specification
of the cahus5.0.5.10 balance-
1.
Mechanical single beam
scale no separate weight are required.
2.
Readability of 0.0Ig
3.
Capacity of 50.5g
using a two pose system.
4.
Easy to use with
mechanical damping
5.
Zero balance
adjustment using the foot screw
6.
Easily maintained by
the user.
Use and careful handling of a balance:
A
balance is a delicate instrument that requires practical instruction in its
correct use.
1.
Read carefully the
manufactures instruction ; prepare a stock record card and written sop, covers
the use clearing and care of the balance.
2.
Always the balance
with care.
3. Position the balance
on a firm bench away from vibration draughts and direct sunlight and make sure
the balance is level. If necessary the screw should be adjusted .
4.
Before starting to
weight zero the balance has instructed .if using a beam balance check the
position of the beam.
5.
Weight chemicals at
room temperature in a we scoop or small beaker. Never directly on a balance par
place the weight vessel in the centre.
6.
When adding or
removing a chemical, remove the container to avoid spilling any chemical on the
balance pan.
7.
If using a box of
weights always use the forceps provided to add weight protect the weights from dust moisture and
fungal growth.
8.
After completing the
weighing return the balance to zero weight and use a small brush to wipe away
any chemical which may have been spilt.
9.
In humid climates use
self-indicating silica gel indeed the case of analytical balance,
10.
Keep a small
notebook by the balance in which to make
the necessary weighing calculations and to record the data of preparation of
reagent.
11.
Keep the balance clean
being particularly careful not to dirt accumulate near the pivots and bearing.
Types of Equipments for weighing:
Types :
2 types-
1.
Mechanical balance
2.
Electronic balance
Characteristics of mechanical balance:
A.
Mechanical balance
includes:
1.
Single pan
2.
Trip
3.
Torsion.
B.
They do not require
electricity or batteries.
C.
Less expensive.
Characteristics of Electronic balance:
1.
Electronic balances
are single pan balances
2.
Use electromagnetic
force instead weighs
3.
Operated by
electricity or battery power
4.
They weigh rapidly and
usually have built in tae which allows the weight of the weighing vessel to be
zeroed.
5.
Humidity reduced
working life electro storms also interfere its performance.
6.
Very expensive.
Balance used in district laboratory:
Mechanical balance with read ability of 0.10. g are best
suited for the district laboratory work. The chaus model 311 is recommended for
district laboratory and the simple low capacity chaus scale 5 .0.5 is suitable
for health center.
Specifications of the chaus 311 balance:
It has a-
1.
No separate weights
are required
2.
Readability of 0.01 g
3.
Capacity of 311 gm
4.
Easy to use with magnetic
dumping.
5.
Zero adjustment.
6.
Stainless steel
removable pan
7.
Easily maintained by
the user
8.
The methods are
divided between four beams
a.
1 st beam 0 to 1 gm
with 0.01 gm divisions
b.
2 nd beam 0 to 10 gm
with 1 gm divisions.
c.
3 rd beam
0to 100 gm with 10 gm divisions .
d.
4 th beam 0 to 200 gm
with 100 gm divisions.
Method of purification:
1. Distillation usin a
still.
2. Filtrations using a gravity filter and reusable care
filter.
3. Deionization using
mixed bed colour change deionization resins.
Distillation:
It is the
process by which water is boild as steam
is produced and condensed on a cold surl (condenser) to from chemically pure
distilled water.
Criteria of distilled water:
i.This water is free
from volatile organic and inorganic materials.
ii.Distillation does not
remove dissolved ionized gases such as ammonia.carbandixide, chlorine.
iii.Distilled water is
clear, colorless and odorless,
iv.This water should be pyrogen
free.
v. A considerable volume
of running water is required to operate a still(Usually not less than 60 liters)
vi.To condense the steam.
Use and care of a still:
i. Read
carefully the manfourers instruction prepare a stock record card and written
sops covering the use cleaning a care of the still.
ii. Ensure there is a sufficient supply of cool
running water to feed the condenser.
iii. Do
not allow the boiler to run dry .
iv.
Collect the distilled water in a clear glass or plastic container previously
rinsed with fresh distilled water. Do not waste waste the water by allowing the
container to overfill .
v . Avoid storing the distilled water for more
than a few days. Keep the container capped.
vi.Regularly
clean the still.
vii.Do
not use a still if any of the glass components appear cracked.