The Laundry 1115 



sodium lye, for it can be produced at a smaller cost. It is safe to say 

 that much of the soap on the market is made from sodium lye. 



Fats. — Fats are compounds formed by the union of a class of sub- 

 stances known as fatty acids, with glycerin. The natiire of a fat depends 

 on the fatty acids that enter into its compo^tion. For example, in tallow 

 the chief fatty acid is stearic acid. Tallow, in common with other fats 

 containing relatively large proportions of stearic acid, has the property 

 of " hardness " and a high melting point. The chief fatty acid in olive 

 oil is oleic acid, which gives to the oil the characteristic softness and low 

 melting point of fats rich in oleic acid. 



When lye is mixed with a fat it breaks the fat up into the fatty acids 

 and glycerin, of which it is composed. The lye unites with the fatty acids 

 to form a new compound, called soap, and glycerin remains. This is the 

 process of soap-making called saponification. As may readily be seen, the 

 nature of the soap formed will depend, first, on the nature of the fats 

 used, whether they are hard or soft, clean or rancid; second, on the kind 

 of alkali used, whether potash lye or soda lye; third, on the nature and 

 amount of impurities contained in both fat and alkali ; fourth, on the com- 

 pleteness of the process of soap-making (saponification). If the operation 

 of soap-making is not properly conducted, the reaction between the fat 

 and the lye is incomplete and a soap is produced that contains free fat 

 and an undue amount of free alkali. Such soap is greasy, undtdy active, 

 and a poor cleansing agent. 



The adulteration of soap. — It is not uncommon to find some foreign, 

 insoluble substances in soap, which have been added merely to increase 

 its weight and bulk. In cheap soaps resin is often added as an adulterant. 

 It is rather difficult to say when resin may be considered an adulterant, 

 for in small quantities it is of value in laundry soaps because it whitens 

 the clothing. Resin gives a brown color to soap, therefore a dark brown 

 soap may safely be rejected as containing an excess of resin. 



The best advice to give the housekeeper is: Select soap manufac- 

 tirred by a reliable firm and give it a trial. It is not economy to use cheap, 

 poorly-made soaps in the laundry. A common mistake is to think that 

 the use of one kind of soap will prove satisfactory for all purposes; this 

 common belief possibly accounts for much of the dissatisfaction that exists 

 regarding the various soaps on the market. In the manufacture of soap, 

 when just stifficient alkali is used to change completely all the fat present 

 into soap, the soap is known as a mild soap. If an excess of alkali is used, 

 either a medium or a strong soap is produced, the degree of strength 

 depending on the amount of free alkali left in the soap. Every laundry 

 should contain all three grades of soap, mild, medium, strong. A mild 

 soap should always be used when the presence of even a small amount of 



