Soap and Detergent Manufacture NZIC（肥皂和洗涤剂制造NZIC）.pdfVIP

SOAP AND DETERGENT MANUFACTURE Soaps and detergents are widely used in our society. Soaps are the product of the reaction between a fat and sodium hydroxide: fat + 3NaOH → glycerine + 3 soap Soap is produced industrially in four basic steps. This article lists different steps because in the industrial processes described each of these is done over several process steps, but in principle it could be done in the three steps outlined here. Step 1 - Saponification A mixture of tallow (animal fat) and coconut oil is mixed with sodium hydroxide and heated. The soap produced is the salt of a long chain carboxylic acid. Step 2 - Glycerine removal Glycerine is more valuable than soap, so most of it is removed. Some is left in the soap to help make it soft and smooth. Soap is not very soluble in salt water, whereas glycerine is, so salt is added to the wet soap causing it to separate out into soap and glycerine in salt water. Step 3 - Soap purification Any remaining sodium hydroxide is neutralised with a weak acid such as citric acid and two thirds of the remaining water removed. Step 4 - Finishing Additives such as preservatives, colour and perfume are added and mixed in with the soap and it is shaped into bars for sale. Detergents are similar in structure and function to soap, and for most uses they are more efficient than soap and so are more commonly used. In addition to the actual detergent molecule, detergents usually incorporate a variety of other ingredients that act as water softeners, free-flowing agents etc. INTRODUCTION Soap is integral to our society today, and we find it hard to imagine a time when people were kept sweet-smelling by the action of perfume rather than soap. However, the current widespread use of soap is only a very recent occurrence, despite the fact that it