Page 43 - Curriculum Visions Dynamic Book

Bromide in photography
Film for black-and-white photography consists of a transparent plastic sheet on which is spread a thin layer of an emulsion consisting of a suspension of minute mixed crystals of silver bromide and silver iodide in gelatin. The gelatin not only holds the grains but also greatly increases their sensitivity to light. When light shines on this material, the silver aggregates into visible particles. These will form the image. Black and white processing paper also contains silver bromide.
EQUATION: Silver bromide and photographers’ hypo
emulsion: tiny droplets of one substance dispersed in another.
A common oil in water emulsion
is milk. The tiny droplets in an emulsion tend to come together, so another stabilising substance is often needed to wrap the particles of grease and oil in a stable coat. Soaps and detergents are such agents. Photographic film is an example of a solid emulsion.
Sodium thiosulphate (photographers’ hypo) + silver bromide ➪ silver complex + sodium bromide
2Na2S2O3(aq) + AgBr(s)
➪ Na3Ag(S2O3)2(aq) + NaBr(aq)  A black and white
Sulphur Sodium
Oxygen
+ Silver
Bromine
transparency.
➡
Bromine is part of a new disinfectant for swimming pools that has been designed to
get rid of several problems caused by the use
of chlorine alone. Chlorine is only effective for about a day, and it is irritating to the eyes because it has to be used in quite large concentrations.
The new disinfectant (1-bromo-3-chloro-4,4,5,5,- tetramethyl-2-imidazolidinine, or BCI for short) is colourless, has no taste or smell and lasts for about a month between treatments. The reason that chlorine has side effects is that it readily ionises
in water and reacts with organic impurities. The methyl groups in the new disinfectant stop the compound from breaking down as quickly.
When bromine does break free, it acts as a rapid disinfectant, while the rest of the molecule, containing the chlorine, acts as a longer-acting disinfectant.
Also...
All of the halogens can be made into useful solvents. Organic bromine complexes are used as paint strippers. Bromine is also used in compounds designed as flame retardants.
Also... A new disinfectant
Bromine
Oxygen
Hydrogen
Carbon
Nitrogen
Chlorine
43
43