22 GENERAL SCIENCE 



3. Make some soap by boiling a mixture of lard and some strong 

 base, as potash. (To see if the soap is done, mix a little of it with 

 soft water. If no fat globules appear on the surface of the water 

 the soap is ready for use.) 



4. Make an emulsion by thoroughly mixing a fat or oil with some 

 base and water. Let it stand a few hours to see if the fat will come 

 to the surface. 



5. If you have no hard water, make some by adding a few drops 

 of some acid or calcium sulphate solution, and divide the water into 

 two parts. Try some soap in one part and observe the result. Place 

 some washing soda in the other part and then try soap in it. Now 

 compare the result with that of the first trial. 



6. Examine the inside of your teakettle to see if any hard sub- 

 stance has collected on the bottom and sides. If so, what is it? 



