Successful experimental results can only be achieved by
using a clean apparatus. In all instances laboratory glassware
must be physically clean, in nearly all cases it must be
chemically clean and in specific cases it must be
bacteriologically clean or sterile. There must be no trace of
grease and the safest criteria of cleanliness is the uniform
wetting of the glass surface by distilled water - this being of
the utmost importance for glassware used for volumetric
methods. Any prevention of uniform wetting of the surface
will introduce errors such as distortion of the meniscus and
accuracy of volume
GENERAL CLEANING
- Cleaning of glassware which has contained hazardous
material must be solely undertaken by experienced
personnel
- Most new glassware is slightly alkaline in reaction. For
precision chemical tests, new glassware should be soaked
several hours in acid water (1% solution hydrochloric
acid or nitric acid) before washing
- Glassware which is contaminated with blood clots, culture
media, etc., must be sterilized before cleaning If glassware becomes unduly clouded or dirty or contains
coagulated organic matter, it must be cleaned with
chromic acid cleaning solution. The dichromates should
be handled with extreme care because it is a powerful
corrosive
- Wash glassware as quickly as possible after use but if
delays are unavoidable, the articles should be allowed to
soak in water
- Grease is removed by weak sodium carbonate solution
or acetone or fat solvents. Never use strong alkalis
-
Hot water with recommended detergents should be used
and if glass is exceptionally dirty a cleaning powder with
a mild abrasive action can be applied provided the surface
is not scratched
-
During the washing all parts of the article should be
thoroughly scrubbed with a brush selected for the shape
and size of the glassware. Brushes should always be in
good condition to avoid any abrasion of the glassware
-
When chromic acid solution is used, the item may be
rinsed with the cleaning solution or it may be filled and
allowed to stand - the amount of time depending on
amount of contamination of the glassware
-
Special types of precipitate material may require removal
with nitric acid, aqua regia or fuming sulphuric acid. These
are very corrosive substances and should be used only
when required
-
It is imperative that all soap detergents and other cleaning
fluids be removed from glassware before use. This is
especially important with the detergents, slight traces of
which will interfere with serologic and culture reactions.
After cleaning, thoroughly rinse with tap water ensuring
that containers are partly filled with water, shaken and
emptied several times. Finally rinse with deionised or
distilled water
- Drying can be undertaken either in baskets or on pegs in air or at a temperature not exceeding 120º C.
- Always protects clean glassware from dust by use of temporary closures or by placing in a dustfree cabinet.
|