Velp Scientifica
– UDK139 Operating Manual
10004762/B5
10
2.
Chemicals
2.1.
Products used
The chemicals used for distillation and titration are potentially dangerous and must
be handled with care and with personal protective equipment: gloves, goggles and
pincer removal of the reaction hot test-tubes.
1) Boric acid (H
3
BO
3
):
4% solution. The low concentration is due to the fact that
boric acid crystallizes at low temperatures and this can cause problems in the
hydraulic circuits of the instrument. Ingestion or absorption may cause nausea,
vomiting and diarrhea. Diluted solutions are used as an antisceptic.
2) Sodium hydroxide (NaOH):
Velp recommends a 30-35% w/v solution of sodium
hydroxide in order to avoid violent reactions in the test-tube. Corrosive to all body
tissues. Can cause severe burns. Protect the skin and the eyes. If the solution is
prepared using flakes or pellets, add these to water and not vice versa. Ingestion can
cause vomiting, prostration, collapse. Constrictive scarring can occur.
Caution:
in case of ingestion DO NOT attempt to evacuate the stomach.
Chemicals used during the digestion phase:
3) Sulphuric Acid (H
2
SO
4
):
concentrated (96-98%). Corrosive to all body tissues.
Skin contact can produce necrosis. Protect the skin and the eyes. When diluting, the
acid must be added to the diluent to prevent the generation of excessive heat and
the danger of splashes. Neutralize spills with dry sodium bicarbonate or calcium
carbonate powder.
4) Hydrogen peroxide (H
2
O
2
)
: 30% w/w. Can cause severe burns. Wear goggles
and rubber gloves. Avoid contact with combustible materials: drying of concentrated
solutions on paper, clothing and so on, can cause combustion. Heavy metals and
their salts, dust, irregular surfaces, can cause rapid decomposition resulting in the
production of oxygen and increased pressure. Stored hydrogen peroxide solutions
decompose slowly but nevertheless bottles must be fitted with vent caps. Empty
bottles must be rinsed with clean water. In case of contact, rinse immediately with
plenty of water.
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