CLEANSING OF GLASSWARE(Analytical assignment)

CLEANSING OF GLASSWARE(Analytical assignment)


Good laboratory practice requires clean glassware as the most carefully performed part of work may give an inaccurate result if unclean glassware is used. In all cases, glassware must be physically and chemically cleaned, and in many cases, it must be bacteriologically clean and sterile. All glassware must be totally Grease free. The safest criterion of cleanliness is constant wetting of the surface by distilled water. Grease and other contaminating materials will prevent the glass from becoming uniformly vetted. This in turn will change the volume of residue stick to the walls of the glass container and thus disturb the volume of liquid delivered.

Meniscus Reading:

Additionally, in burettes and pipettes, the meniscus will be misleading and correction cannot be made. If glassware cannot be cleaned immediately through a thorough cleaning then it should be soaked in water. All glassware needs to be cleaned immediately after use otherwise it may become impossible to remove the residue. As most new glassware is a little alkaline in reaction, it should be soaked several hours in one percent hydrochloric or nitric acid solution before washing.

Metal Brushes:

Brushes with metal handles will scratch or abrade glass surface hence it is recommended to use brushes with wooden or plastic handles.

CLEANSING OF GLASSWARE(Analytical assignment)

Use of Washing Powder:

Washing can be carried out using cleansing powder (with or without an abrasive) soap or detergent may be used with hot water. For exceptionally dirty glassware cleaning powder with a mild abrasive action that should not scratch the glass will give more satisfactory results.

During the washing, all portions of glassware should be carefully brushed. This means that a full set of brushes must be available to fit small and large test tubes, Funnel, burettes, graduate cylinders, and various sizes of bottles and flasks. If a large number of bottles or tube needs to process, motor driver revolving brushes are valuable.

Removal of Organic Matter:

If glassware becomes excessively dirty or clouded are contains coagulated organic matter, it must be cleaned with a chromic acid solution.

Chromic Acid:

Potassium or sodium dichromate is used to make a chromic acid solution which is a potent and carcinogen that needs to handle with extreme care. When the chromic acid solution is used the glassware may be rinsed with it or it may be filled and allowed to stand for a time period which purely depends on the amount of contamination on the glassware. Relatively clean glassware may require rinsing only for a few minutes however if the debris is present glassware may be dipped in chromic acid all night.

Removal of Precipitates:

Some types of precipitate may require removal with very corrosive substances like sulphuric acid, nitric acid, or aqua regia.

Removal of Grease:

Grease can be removed best by boiling in a weak solution of Na2CO3 also known as sodium carbonate. Acetone should be helpful in removing grease as any other fat solvent could also be fruitful. Strong alkalis are not recommended to be used. Silicone grease can be easily removed by soaking glassware for 2 hours in warm decahydro-naphthalene followed by rinsing web fuming sulfuric acid or acetone for 30 minutes. It is imperative to wash glassware with an excessive amount of tap water followed by 4-5 times rinsing with distilled water. An electrically heated chamber or specially design dryers are available for various types of glassware. Pipettes should be used for transferring infectious material, should have a cotton plug placed in the top and of the people before sterilizing. The plug will prevent the material which is measured from the reagent bottle and being drawn accidentally into the pipetting device.

CLEANSING OF GLASSWARE(Analytical assignment)

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