22 MANUAL OF GENERAL AGRICULTURE. 



(c) Illustration and test for a salt. Pour out 10 cc. 

 of hydrochloric acid into an evaporating dish and add an 

 equal volume (10 cc.) of water. Add sodium hydroxid 

 made in (b) until the solution is neutralized; i. e., until 

 neither shade of litmus is changed in the solution. Evap- 

 orate to dryness by heating. Watch the evaporating 

 toward the end and if spattering is too vigorous remove 

 the flame a moment. When evaporation is complete re- 

 move the salt and add a little water. 



Note the taste and action on litmus. This is a com- 

 mon table salt (sodium chlorid). 



Questions: 1. Name three classes of chemical sub- 

 stances and in tabular form give their characteristic prop- 

 erties as indicated in this experiment. 2. What is meant 

 by a neutral substance? 



21. PREPARATION OF POTASH. 



Materials: Wood ashes, pan, evaporating dish. 



Potash is easily prepared from wood ashes. Place 

 wood ashes into a pan, filling it about one-third full. Pour 

 in water until the pan is about two-thirds full and stir 

 vigorously for about two minutes, in order to dissolve the 

 potash in the ashes. When the ashes have settled pour 

 off the clear liquid and test with litmus paper. Result? 

 Potash is one of the alkalis, which always have this effect 

 upon litmus. Notice the soapy feel and the bitter taste. 



22. PREPARATION OF CRUDE PHOSPHORIC ACID. 



Materials: Bones, mortar and pestle, red and blue 

 litmus paper, sulphuric acid, stirring rod, beaker, filter 

 and filter paper, nitric acid, test tube, ammonium molyb- 

 date.* 



Obtain some bones of any kind and burn them until 

 white. This white substance is for the most part a com- 

 bination of phosphoric acid and lime. To remove the 

 lime, take about 10 gr. of burned bone and pulverize in a 

 mortar, transfer to a beaker, add 50 cc. of water and 5 cc. 

 of sulphuric acid and stir with a stirring rod a few min- 



*For the preparation of ammonium molybdate see page 28. 



