A UNIT IN AGRICULTURE 47 



it desirable to leave canned fruit open a few minutes before covering 

 after cooking? Why? 



Prick one of the sound apples in several places with a pin. Put 

 the pin into the rotten apple and then into the other sound apple. 

 Repeat this in several places. Set the two sound apples aside for 

 about a week. Note what happens and account for the different 

 results. 



What is pasteurization, and how may it be performed at home? 

 Why discard the first few streams of "foremilk ?" Why not feed just 

 before milking? Explain sour bread and formation of vinegar from 

 cider. What principle is employed in preserving silage? 



Ex. 48. Preparation of Bordeaux Mixture. 



Material : copper sulphate, lime, potassium ferrocyanid, balances, 

 two Mason fruit jars (quart size). 



Bordeaux mixture is prepared by using 2 to 6 pounds of copper 

 sulphate to 50 gallons of water and adding enough lime to neutralize 

 it. Four pounds to 50 gallons of water is a good formula for use on 

 many plants. 



(a) Put five cents' worth of potassium ferrocyanid into a 4-ounce 

 bottle of water and label it "poison." (b) Dissolve 2 ounces of cop- 

 per sulphate in a pint of water, (c) Slake about 4 ounces of lime. 

 Put 3 fluid ounces of (b) into each of the two jars. Fill the second 

 jar nearly full of water. Add some of (c) to each jar and test with 

 (a). If there is enough lime to neutralize the copper sulphate, (a) 

 will retain its yellow color when a drop of it is added. If there is 

 not enough lime, it will assume a decided brown red color. Add (c) 

 until the test is satisfied. Then add as much more. Now fill each 

 jar with water. In which case does the mixture settle more quickly 

 and what is its color? These proportions give a mixture at the rate 

 of 4 pounds of copper sulphate to 50 gallons of water. It is usually 

 best to use double the lime called for by the test, because there is then 

 less danger of injuring the plants sprayed. Note that the mixture 

 containing the copper sulphate solution diluted before adding lime 



