THE CHEMICAL LABORATORY
A laboratory is a building or a room used for scientific experiments, research, testing
and the preparation, on a small scale, of drugs, chemicals or other products or
substances. The chemical laboratory may be used for teaching purposes, for routine
analysis, testing and control, for fundamental (pure) research or applied research, or as
an adjunct to development or production for industry. There are also specialist types
of laboratories, for example those for nuclear research.
The typical chemical laboratory usually consists of a large room with a weighing
(balance) room, a reagent room and sometimes a darkroom.
The balance room is specially constructed to be free from external disturbances. The
balances stand on firm stone shelves. The analytical balance is kept in a glass case. It
is the basic tool in all quantitative analysis and is used for the accurate weighing of
samples and precipitates. The material to be weighed is transported to and from the
balance room in a filled dissicator.
The reagent room is used for storing chemicals and apparatus. Chemicals are stored
on shelves in labelled bottles and other containers.
The laboratory itself is fitted with benches, sinks, fume cupboards or hoods, electric
drying chambers and steam ovens. Distilled water is usually stored in glass tanks or
containers.
The laboratory usually has facilities for glass blowing. Heating is generally done
directly by the Bunsen burner. Test-tubes are held above the flame in wooden holders
or tongs. Solutions are heated in beakers and flasks on wire gauzes or asbestos boards,
supported by tripods. Solids are heated in crucibles supported by triangles. Crucibles
have lids.
Vessels and tubes are generally closed by means of glass stoppers, rubber bungs or
corks.
Materials are pulverised by a mechanical grinder or by a pestle and mortar. Liquids
are stirred with a glass rod.
Filtration is carried out by allowing the liquid to percolate (strain) through a filter,
such as a filter paper folded to fit a filter funnel. The filter paper is a circular sheet of
paper, which has very fine pores through which liquids can pass but not solids. When
a mixture is filtered, the clear liquid which comes through the filter paper is called the
filtrate and what is left on the filter paper is known as the residue.
Samples of gases may be collected for experimental purposes in air-tight gas
containers over water or mercury by displacing air with the gas. The method of
collection varies according to the solubility and density of the gas. A gas-jar is made
of thick glass and has a ground glass top, which can be made "gas-tight" by placing on
it a ground glass cover smeared with a thin film of petrolatum.
More complex pieces of apparatus all have glass connections, although rubber tubing
may also be used.
GLASSWARE
A. CONTAINERS
a) open containers:
1) test-tubes
2) beakers
3) flasks
a) conical flasks
b) round-bottomed flasks
c) flat-bottomed flasks
b) closed containers -bottles:
1) reagent bottles (with glass stoppers)
2) screw-capped bottles
3) wash-bottles
B. tubing:
a) hollow:
1) tubes
b) solid:
rods
a) straight tubes
b) U-shaped tubes
c) bent tubes
C. special apparatus:
a) measuring
1) graduated cylinders
2) burettes
3) pipettes
b) pouring
1) funnels
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EXERCISES
A. The instructions below are in the wrong order. Reorder them in the
right way and suggest a suitable heading:
HEADING: ____________________________________
Tear off the corner of the first fold.
Fit the paper into the funnel.
Fold a piece of paper along its diameter.
Pour out any excess water from the filter before using it.
Press the paper down until it fits tightly and leaves no air spaces.
Wet the paper with a few millilitres of distilled water to ensure that it
stays in place.
Fold it again at slightly less than a right angle to the first fold.
Open the paper to form a cone.
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B. Complete the following passage using imperative verbs from the list.
Some verbs may be used more than once.
try
bathe
keep wipe up
dip
take
wash
burn
wash up
drink
ACCIDENTS WITH LIQUIDS
Sometimes specimens are spilled in the laboratory. If this happens,
quickly ________
a piece of
cotton-wool, ___________ it in an antiseptic and
__________ every drop carefully. ____________ the cotton-wool
afterwards and ___________ your hands.
If an acid splashes into the eye, ___________ calm. ___________ it with
water from a wash-bottle and ___________ it using an eyebath with a
5% solution of sodium carbonate. Then ___________ any other drops of
acid from the bench.
If a strong acid or alkali is swallowed by mistake, there is a danger of
poisoning. First ___________ the mouth immediately and then
__________ several glasses of water. If an acid has been swallowed, also
__________ some milk of Magnesia. If an alkali has been swallowed,
____________ some very weak acetic acid. In either case, do not
____________ to vomit.
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EXERCISE C.
Read the following passage and then do the tasks below.
USE OF THE BUNSEN BURNER
Turn on the gas and, after a few seconds, light the burner by bringing a
lighted match from the side to the top of the burner. Do not hold a lighted
match over the burner when turning on the gas. Adjust the gas valve and
rotate the collar over the air vents until the flame has an inner blue cone
and is about 10 cm high.
To heat a liquid in a flat-bottomed flask or a beaker, place the container
on a wire gauze placed on a tripod stand. Do not fill the container more
than two-thirds full. Adjust the apparatus so that the tip of the inner blue
cone – the hottest part of the flame – touches the wire gauze.
To heat a liquid in a test-tube, adjust the burner to give a softer flame.
Fill the test-tube no more than two-thirds full and hold it in a test-tube no
more than two-thirds full and hold it in a test-tube holder. Heat the liquid
at a short distance from the flame and agitate the tube continuously. Also
move the test-tube in and out of the flame.
Task 1 Translate the text into Croatian
Task 2 Change the instructions given in the passage into a description of
how to use the Bunsen burner. Some changes will have to be made.
Begin like this:
The gas is turned on and….
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THE CHEMICAL LABORATORY
GLOSSARY
on a small scale
- u malom omjeru
proportion,n.
- omjer
precipitate,n.
- talog, ostatak
residue, n.
- ostatak, talog
weigh, v.
- vagati
balance, n.
- vaga
disicator,n.
- eksikator
tongs,n.
- kliješta
beaker,n.
- laboratorijska čaša
flask,n.
- tikvica
crucible, n.
- talionik
lid,n.
- poklopac
vessels,n.
- lab. posuđe
tube,n.
- cijev
glass stopper
- stakleni zatvarač
rubber bung
- gumeni čep
cork,n.
- pluto
pulverize,v.
- usitniti pretvoriti u prah
grind,ground, ground, v.irr. - zdrobiti, samljeti
electrical/mechanical grinder - el. drobilica
pestle,n.
- batić
mortar,n.
-tarionik
stir,vt.
- miješati
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rod,n.
- štapić
percolate,v.
-cijediti (se), kapati
strain,v.
- cijediti, kapati
fold,v.
- svinuti, presaviti
funnel,n.
- lijevak
fine,adj.
- sitan
clear,adj.
- bistar
air-tight,adj.
- nepropusan za zrak
solubility,n.
- topljivost
density,n.
- gustoća
ground glass top
- vrh napravljen od
brušenog
stakla
smear,n.
- razmaz, premaz
smear,v.
- premazati
a thin film
- tanki sloj
petrolatum,n.
- lab. mast
glassware,n.
- stakleno lab. posuđe
screw-capped bottles - boce s navojem
U-shaped tubes
bent tubes
burettes
pipettes
- kapaljke, pipete
measuring
- mjerenje
pouring
- lijevanje
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