16 BULLETIN 355, U. S. DEPARTMENT OF AGRICULTURE. 
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 teaspoon ful 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. What effect does it have upon 
limewater? Put a small piece of blue litmus paper into the water through 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 limewater into a clean glass and let it set 
for some hours, or even days, in a place not dusty. What 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 under- 
stand how plants get dissolved mineral foods from the soil? 
