EXPERIMENT 62. TO MAKE SOAP 



(a) Put a pinch of caustic soda in a small beaker of 

 water and add about a teaspoonful of lard or olive oil. 

 Allow this to boil for almost half an hour and then set 

 aside to cool. When cool, mix a little of the solution with 

 hot water and see whether it forms a lather. 



(b) Put soda and lard in a beaker as in (a), and let it 

 boil for half an hour as before. Then add slowly four tea- 

 spoonfuls of common salt, stirring constantly until the salt 

 is dissolved. Set the vessel aside to cool, and when con- 

 venient, remove the solid cake which floats on top. Mix some 

 of the solid with water and see whether it forms a lather. 



(c) Make a lather of the soap with distilled water, and 

 test with litmus paper to see whether it is neutral or 

 whether it contains an excess of acid or base. 



(a) In similar manner test the specimen of school soap 

 furnished by your teacher. Bring from home a few shav- 

 ings of the laundry soap used by your mother. Is it pure 

 and fit for fine work ? 



EXPERIMENT 63. HARD WATER SOAP 



In order to obtain a specimen of genuine hard water, put 

 a pinch of plaster of Paris, calcium sulphate, into a test tube 

 of clear cold water. Shake the test tube thoroughly, then 

 filter the contents. The filtrate will be hard water. 



(a) To hard water in a test tube add a drop or two of liquid 

 soap, and shake the mixture. Do suds form ? Does a 

 precipitate form ; if so, what is the cause of the precipitate ? 

 Why is hard water not suitable for laundry and bath? 



(b) To another specimen of hard water add a small 



