Detergents were developed due to the problems that occurred when organic soap was used in areas
of hard water. Hard water contains the ions of Calcium and Magnesium in high amounts and these
are substituted onto the soap molecule in place of sodium. The salts of Calcium and Magnesium are insoluble and
form a precipitate, this is what leaves a 'ring' around the bath.
Other problems were encoutered in the textile industry where acid solutions are used in the dying process. The free
H+ ions replace the sodium ion reforming the fatty acid which affects
the application of dyes and leaves spots on fabrics.
The first synthetic detergents were developed following the first world war by the Germans so that fat could be used
for other purposes. The first synthetic detergents were Short-chain Alkyl Napthalene Sulphonates which were
later discovered to be only moderately good detergents and so were improved, but are still used today as wetting agents.
In the 1920's and 30's Straight chain alcohols were sulphonated to give straight chain detergents. In the 30's
long chain alkyl and aryl sulphonates with benzene as the aromatic nucleus were developed. (the alkyl
portion was derived from kerosene) By the end of World War 2 alkyl aryl sulphonates swamped the detergent market over alcohol
sulphates which later became useful in the shampoo industry.
It was a popular complaint at this time that whites dulled after washing, they weren't as white as white should be and this was linked to
the use of synthetic detergents. Even though they were just as good as soaps at removing dirt, they were poor at holding it in
suspension and the particles redeposited onto the clothing. The problem was overcome by the addition of CMC (carboxy methyl cellulose).
More recently the limiting factor that affected the production of specific detergents was availability of raw materials. This lead to the development of Igepon compounds in Germany and the USA (for example Igepon-T, the sodium salt of oleyl tauride), Mersolates in Germany (alkane sulphates), and Teepol in England (a secondary Olefine Sulphate from petrochemical sources). Alkyl Benzene Sulphonate was top of the market due to its ease of manufacture and versitility.
Between 1950 and 1965 more than half of the detergents were based on a propylene tetramer coupled to benzene (PT benzene), but they were later blamed for a rise in eutrophication in lakes and streams because they contained phosphates (from Sodium triphosphate). This problem has not been fully resolved in some cases, in some countries there has been a 'gentlemans agreement' to reduce the use of phosphates but in countries where it is not a major problem no such action has been taken. The problem was set down to the branched chain formation of PT benzene which resulted in the inability of bacteria to degrade them. Straight-chain alcohols are degradable, so steps were taken to produce a linear alkyl benzene molecule. To replace the phosphate based portions, in Scandinavian countries they now use NTA (Nitrilo triacetic acid).