Making soap as an experiment [local] has the advantage of students being able to relate to the topic. Once fat is broken down into glycerine and fatty acids the next step is an acid (fatty acid) + base (NaOH) reaction that makes a salt of a fatty acid (soap) and water. The entire process is called saponification. Making soap is dangerous. Working with 6 N NaOH requires goggles, rubber apron and gloves and careful attention. The NaOH must not be added too quickly. The recipe needs to be carefully followed or the resultant soap will contain excess lye. This particular lab has clear admonitions posted in the write-up. It does not prescribe the type of fat which would make a difference in the amount of lye required. See the soap section.