NaCl(aq), NaCl(aq), C C C C C C C was the equation that the chemist was thinking of when he knew he needed a vacation. What did it mean?

Saline, saline, over the seven Cs

It's raining raincoats

When it rains, it pours. The only way to stay dry when there are strong winds is a raincoat. You may use one when you go to school or you may have seen your dad wear one when he goes for work in the rainy season. Haven't you ever wondered how these raincoats are different from the normal clothes you wear?

The first raincoats

Charles Macintosh was the first person to invent the raincoat in 1823. Living in rainy Scotland, he needed a way to stay dry. In fact it is due to his invention that for long-time raincoats was known as Macintoshes. People have tried to make water-resistant fabrics since the 13th century when the people of South America coated fabrics with natural latex to make water-resistant footwear.

Waterproof mixtures

In 1748, French scientist Francois Fresneau invented a way to use turpentine as a rubber solvent. He used this to coat fabrics, making them waterproof. It was only after 70 years that James Syme discovered that coal tar naphtha (a hydrocarbon mix) could dissolve rubber and can be used for waterproofing. Coal tar was available as a by-product of the coal based gas street lamps.

The original Macintosh

Macintosh bought coal tar from the Glasgow Gas Light Company. He first tried to extract ammonia from this mixture to use in his father's dye company. He still had extra coal tar naphtha. Soon he discovered that rubber could dissolve in this. Fabric that was coated with this mixture became waterproof. The problem though was that this fabric remained sticky and had a bad smell. The sticky problem was resolved by sticking two sheets with the rubber between them. Early raincoats were also stiff to wear.

Turpentine and coal tar naphtha are used to dissolve rubber to coat fabrics.

Improvements in rainwear

Over the years others have improved on Macintosh's discovery. The discovery of cold cure vulcanization removed the stickiness of the coal tar and naphtha mixture. This meant that multiple layers were no longer necessary.

Making modern raincoats

Today's raincoats are made of synthetic polymers and come in various colours. A major difference between the raincoat you wear today and the first raincoats is that new raincoats allow your perspiration to escape. This is achieved by a polyurethane layer that absorbs water.

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