Monthly Archives: September 2013

Hearing Protection

Exposure to noise at work causing hearing loss is still a significant occupational illness.

Employers have a duty of care to protect their employees while at work and this may mean providing personal protective equipment.  In the case of loud environments this may be ear plugs or ear muffs.

It can be tempting to pick the hearing protection with the highest level of protection (or attenuation), however ‘over attenuation’ can bring it’s own problems.  If the sound level at the ear is reduced too far, the wearer can become isolated, unable to hear people’s voices, moving vehicles or warning sounds/alarms.

In a workplace where noise may be an issue the noise level needs to be measured.  This is covered by the Control of Noise at Work Regulations 2005.  Between 80 and 85db(A) hearing protection is not compulsory but is made available to workers for their comfort and protection.  Above this hearing protection is compulsory.  These regulations give a new limit of 87db at the ear (under hearing protective equipment) which must not be exceeded.

Ear plugs can be used against various sound levels which are normally disposable.  Alternatively ear muffs similar to those shown above can be used.

Please check out the link below for more information.

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The Microscope

The optical microscope, often referred to as the “light microscope”, is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly designed in their present compound form in the 17th century. Basic optical microscopes can be very simple, although there are many complex designs which aim to improve resolution and sample contrast. Historically optical microscopes were easy to develop and are popular because they use visible light so that samples may be directly observed by eye.
Binocular Microscope

There are two basic configurations of the conventional optical microscope: the simple (single lens) and the compound (many lenses). The vast majority of modern research microscopes are compound microscopes while some cheaper commercial digital microscopes are simple single lens microscopes. A magnifying glass is, in essence, a basic single lens microscope. In general, microscope optics are static; to focus at different focal depths the lens to sample distance is adjusted, and to get a wider or narrower field of view a different magnification objective lens must be used. Most modern research microscopes also have a separate set of optics for illuminating the sample

It is difficult to say who invented the compound microscope. Dutch spectacle-makers Hans Janssen and his son Zacharias Janssen are often said to have invented the first compound microscope in 1590.
Christiaan Huygens, another Dutchman, developed a simple 2-lens ocular system in the late 17th century that was achromatically corrected, and therefore a huge step forward in microscope development. The Huygens ocular is still being produced to this day, but suffers from a small field size, and other minor problems.
In August 1893 August Köhler developed Köhler illumination. This method of sample illumination gives rise to extremely even lighting and overcomes many limitations of older techniques of sample illumination. Before development of Köhler illumination the image of the light source, for example a lightbulb filament, was always visible in the image of the sample.
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Radium is a chemical element with symbol Ra and atomic number 88. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in colour. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1601 years and decays into radon gas. Because of such instability, radium is luminescent, glowing a faint blue

Radium, in the form of radium chloride, was discovered by Marie Curie and Pierre Curie in 1898. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1910. Since its discovery, it has given names like radium A and radium C2 to several isotopes of other elements that are decay products of radium-226.

Radium is not very interesting to biologists because it is not necessary for life. It is, in fact, quite harmful to life due to its radioactivity and chemical reactivity. However, this did not stop a 30-year radium craze in the United States, where some people and manufacturers claimed radium to be a “wonder drug” and added it to all sorts of items, from toothpastes and suppositories to foods and even to drinking water, claiming it prevented or cured all sorts of ailments, ranging from arthritis and cancer to mental illness.  Yet at the same time that radium’s health effects were being touted, it was also being added to pesticides and insecticides.

Radium is luminescent, glowing a lovely pale blue colour. This quality led to it being incorporated into a paint for watch and clock hands and dials in the United States, causing the deaths of many dial painters (all young women) who used their lips to give their paint brushes a fine point. These women, dubbed “Radium Girls”, ended up suffering from a number of health problems such as anemia and cancer. Some Radium Girls ingested so much radium that their hair, hands, faces and arms glowed a luminous pale blue in the dark.

Radium covered watch hands under UV light

It wasn’t as though there wasn’t adequate warning of radium’s dangers; its discoverer, Nobel-laureate Marie Curie, noted that a vial containing radium that she carried in her pocket caused an ulcer to appear on her skin. She later died of aplastic anaemia, most likely due to her years of exposure to radiation.

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Desiccators are sealable enclosures containing desiccants used for preserving moisture-sensitive items such as cobalt chloride paper for another use. A common use for desiccators is to protect chemicals which are hygroscopic or which react with water from humidity.


The contents of desiccators are exposed to atmospheric moisture whenever the desiccators are opened. It also requires some time to achieve a low humidity. Hence they are not appropriate for storing chemicals which react quickly or violently with atmospheric moisture such as the alkali metals.

The lower compartment of the desiccator contains lumps of freshly calcined quicklime or (not as effective) calcined calcium chloride to absorb water vapours. The substance is put in the upper compartment (on the porcelain plate). The ground-glass rim of the desiccator lid must be thoroughly greased with a thin layer of petroleum jelly melted together with beeswax or paraffin wax.

In order to open the desiccator without damage, remove the lid sideways horizontally not to upwards. Cover the desiccator in the same way.

In laboratory use, the most common desiccators are circular and made of heavy glass. There is usually a removable platform on which the items to be stored are placed. The desiccant, usually an otherwise-inert solid such as silica gel, fills the space under the platform.

A stopcock may be included to permit the desiccator to be evacuated. Such models are usually known as vacuum desiccators. When a vacuum is to be applied, it is a common practice to criss-cross the vacuum desiccator with tape, or to place it behind a screen to minimize damage or injury caused by an implosion. To maintain a good seal, vacuum grease is usually applied to the flanges.
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