Soaps, detergents and agrochemicals: Key terms, quiz and sources

Understanding Chemicals / Module 9: Soaps, detergents and agrochemicals Wrap-up

Soaps, detergents and agrochemicals: review

Key terms

Triglyceride: An ester of glycerine with three fatty acids; more than 95% of most fats and oils.
Iodine value: A measure of a fat's unsaturation; the higher it is, the more double bonds and the lower the melting point.
Saponification value: Milligrams of potassium hydroxide needed to saponify one gram of fat; used to calculate the caustic dose.
Saponification: Reaction of a fat with alkali to give soap and glycerine.
Fat splitting: Hydrolysis of a fat with water at high temperature and pressure to give fatty acids and glycerine.
Sweet water: The dilute glycerine solution, typically 10-25%, that leaves a fat splitter.
Neat soap: The hot, fluid soap phase of about 30% water that leaves a soap plant before drying.
Spent lye: The salt and glycerine solution separated from soap after saponification, sent to glycerine recovery.
Surfactant: A molecule with a water-loving head and a water-hating tail that lowers surface tension and lifts oily soil.
Micelle: A cluster of surfactant molecules in water with tails inward, which holds oily soil in its core.
Builder: A detergent ingredient, such as STPP, zeolite or soda ash, that removes water hardness and boosts cleaning.
Zeolite A: A crystalline sodium aluminosilicate that softens wash water by exchanging sodium for calcium.
Optical brightener: A fluorescent dye that converts ultraviolet light into blue-white light to make fabric look whiter.
Spray drying: Atomising a detergent slurry into hot gas in a tower to form hollow, free-flowing granules.
Agglomeration: Building detergent granules by spraying liquids onto dry powders in a mixer; lower capital and energy than spray drying.
Mode of action: The biochemical target a pesticide acts on, such as an enzyme or nerve receptor; the basis of resistance management.
Systemic pesticide: A pesticide absorbed by the plant and carried in its sap to parts remote from where it was applied.
Emulsifiable concentrate (EC): A formulation of active ingredient in solvent with emulsifiers that forms a milky emulsion in the spray tank.
Suspension concentrate (SC): A formulation of finely milled solid active suspended in water with thickeners and dispersants.
Generic pesticide: An off-patent active sold under the generic maker's own registration after showing equivalence to the original.

Try it in the table

Open the Fatty acids and Fatty alcohols tiles. Check which feedstocks they name (palm kernel, coconut, tallow or petrochemical routes) and compare with the lauric versus C16-C18 split in this module's fatty acid table.
Open the Glycerine tile and see how much supply it attributes to biodiesel rather than soap and fatty acids. Relate this to Wittcoff's warning that a large new methyl ester outlet could flood the glycerine market.
Open Linear alkylbenzene and Surfactants side by side. Find what share of LAB goes into LAS, and whether the surfactant market is described as led by consumer brands or by chemical producers.
Open the Herbicides tile and look for glyphosate and 2,4-D. Note whether they are described as off patent and who the main producers are, and compare with Kent's 30/40/30 split between patented, off-patent proprietary and generic sales.
Open Insecticides and Fungicides and compare their market sizes and leading chemical classes with the IRAC and FRAC groups in this module. Check whether India appears as a major generic producer.
Open the Chlorine and Caustic soda tiles and find how much of each goes to soaps, detergents and pesticides. Compare with Dryden's figure of 38,000 tonnes of chlorine for Indian pesticides in 1990.

Final quiz

Kent gives 14.09 g of NaOH per 100 g of beef tallow. About how much 50% caustic soda solution saponifies one tonne of tallow?

1,000 kg x 0.1409 = 141 kg of NaOH, which is 282 kg of 50% solution, matching Kent's 28.2 g per 100 g.

Which method separates stearic acid from oleic acid in tallow fatty acids?

Kent explains that C16-C18 saturated and unsaturated acids boil too close to separate by distillation, so their very different melting points are used instead.

Why must fats for continuous saponification be of better colour and odour than fats for the kettle?

Kent: in continuous saponification most oil- and alkali-soluble colour bodies stay in the product, so the starting fat must be cleaner.

In Shreve's heavy-duty granule, which input is largest by weight apart from water?

500 kg of STPP per tonne of product, against 150 kg of oleum, 125 kg of silicate and 75 kg each of alkylbenzene and fatty alcohol.

How does an optical brightener make white fabric look whiter?

Kent: brighteners are fluorescent; they absorb UV and emit blue-white light that masks yellowing or greying, at only 0.05-0.2% of the formula.

Which insecticide class shares its mode of action with the organophosphates?

Both are IRAC group 1 acetylcholinesterase inhibitors (carbamates 1A, organophosphates 1B).

Kent quotes 80% deposition, 50% retention, 50% uptake and 10% translocation for a systemic spray. What share reaches the target site?

0.8 x 0.5 x 0.5 x 0.1 = 0.02. This is why formulation, adjuvants and seed treatment have so much value.

Roughly what share of the 2009 global pesticide market did Kent attribute to generics?

Generics were about 30%, roughly $13 billion; patented and off-patent proprietary products together were about 70%. The 86% figure is crop protection's share of the total.

Next module: Pharmaceuticals and fermentation: from molecule to medicine →

Sources for this module

Kent, J.A. (ed.), Handbook of Industrial Chemistry and Biotechnology, 12th ed., Springer, 2012. Ch 36 Soap, Fatty Acids, and Synthetic Detergents (Chupa, Misner, Sachdev, Wisniewski, Smith) · pdf pp. 1431-1470
Kent (2012), Ch 34 Animal and Vegetable Fats, Oils, and Waxes (Lusas et al.) · pdf pp. 1332-1337, 1347, 1363-1377
Kent (2012), Ch 17 The Agrochemical Industry (Singh and Merchant) · pdf pp. 652-706
Austin, G.T., Shreve's Chemical Process Industries, 5th ed., McGraw-Hill, 1984. Ch 29 Soap and Detergents · pdf pp. 547-570
Shreve (1984), Ch 26 Agrichemical Industries · pdf pp. 480-493
Gopala Rao, M. and Sittig, M., Dryden's Outlines of Chemical Technology for the 21st Century, 3rd ed., East-West Press, 1997. IIIA Edible and Essential Oils; IIIB Soaps and Detergents, Glycerin · pdf pp. 294-319
Dryden (1997), IVG Pesticides; chlorine use pattern; Table IB-1 · pdf pp. 15, 207, 553-563
Wittcoff, H.A., Reuben, B.G. and Plotkin, J.S., Industrial Organic Chemicals, 2nd ed., Wiley, 2004. Ch 13 Fats and Oils · pdf pp. 438-457