16 BULLETIN 355, U. S. DEPAETMENT OF AGEICULTURE. 



noting taste, put a small piece of blue litmus paper into the solution. What happens? 

 After noting properties of the acid, discard this solution. 



(b) Now take the original strong solution of the sodium hydroxid and very slowly 

 add muriatic acid, drop by drop. Place piece of blue litmus paper in the solution, keep 

 stirring while slowly dropping in the acid, and stop adding acid the instant that the 

 blue litmus paper turns red. Now pour the solution into a porcelain dish and boil 

 until all the liquid has evaporated and the remaining substance is completely dry. 

 Taste the residue. What is it? It was formed from a chemical reaction between an 

 acid and a base. 



Carbon dioxid of carbonic-acid gas. — Put a piece of burnt lime one-half the size of 

 your fist into a pint fruit jar. Add water to slake the lime. Now add more water 

 until can is nearly full, put on cover, shake thoroughly, then set away to settle. (One 

 can of the liquid will probably suffice for the use of the class.) Put a glass tube 

 through a one-holed stopper. {Be careful not to break the tube and cut the hands.) 

 Fit a piece of rubber tubing over the end of the glass tube. Put a small piece of 

 Limestone into a bottle in which the stopper containing the glass tubing fits. Pour a 

 little of the prepared limewater into one glass dish, or bottle, and a little water into 

 another. Dilute not over one-half teaspoonful of muriatic acid by adding about 4 or 

 5 teaspoonfuls of water. Have the bottle containing limestone, the bottle contain- 

 ing limewater, and the bottle containing water all in readiness, then pour the dilute 

 acid upon the limestone and quickly insert stopper containing glass tube. Put end of 

 rubber tube into bottle containing limewater so that end of tube is below the surface. 

 After the gas has passed into the limewater for a little time, remove the rubber tube 

 and place it under the water in the' other glass dish or bottle. The gas escaping from 

 the bottle containing limestone is carbon dioxid. "^^Tiat effect does it have upon 

 limewater? Put a small piece of blue litmus paper into the water thi'ough which 

 the carbon dioxid has been passing for some time. What happens? Do you see 

 why the gas is sometimes called carbonic-acid gas? Wash one of your glass dishes or 

 test tubes thoroughly, then add another small quantity of limewater. Use a glass or 

 rubber tubing and blow your breath through the limewater. What does your breath 

 contain? Pour another small portion of limeAvater into a clean glass and let it set 

 for some hours, or even days, in a place not dusty. WTiat gas is shown by this experi- 

 ment to be present in the air? The result can be shown much more quickly by 

 using a bicycle pump and forcing air through the limewater. 



Root hairs and the action of roots. — Place a square piece of polished marble slab at 

 the bottom of a box about 4 or 5 inches deep, with the other dimensions equal to that 

 of the slab. Place the polished surface up and fill the box with moist soil of a sandy 

 nature. Plant a few kernels of corn in this soil. Put in a warm place and keep the 

 soil moist. When the plants have grown at least 6 inches high, remove them very 

 carefully. Note how the rootlets cling to the soil grains. Now clean the rootlets 

 carefully with water and examine near the ends with the magnifying glass for root 

 hairs. Remove the soil from the box and note the effect of the roots on the polished 

 marble. 



Osmosis. — Using sealing wax and a piece of glass tubing about 4 or 5 inches long; 

 seal the tubing on the small end of an egg. Very carefully break and remove the 

 shell, or outer covering, from a small portion of the other end of the egg. Fill a wide- 

 mouthed pickle bottle with a strong solution of common salt and set the egg, tube 

 upward, in the opening of the bottle. Now run a hatpin down the glass tubing and 

 carefully break through both coverings of the end of the egg. Keep the bottle full of 

 water and leave the egg set up in this way for several hours. What results? Stick 

 the hatpin into the solution within the egg and taste. Do you now begin to vmder- 

 stand how plants get dissolved mineral foods from the soil? 



