(a) The adding of 200 cc. of copper sulphate solution is equivalent to adding how many 

 grams of copper sulphate crystals? 



(b) What volume of liquid does each 500 cc. beaker contain? 



(c) If you were to make up SO gallons of each of these five strengths of Bordeaux mix- 

 ture how might you state their formulas, using pounds and gallons as units of measure? 



(d) *To determine which of these various strengths of Bordeaux mixture are safe to use 

 on tender foliage, immerse a wire nail or tip of a knife blade in the solution for at least one min- 

 ute. If metallic copper is deposited on the iron or steel, i. e., the iron or steel becomes the color 

 of copper, it is not safe to apply the mixture to tender foliage. On the other hand, if the iron 

 or steel remains unchanged, it is safe to conclude that the mixture is all right. By this test, 

 which of the five mixtures are safe to apply to tender foliage? 



(e) Which are not? 



(f) Another test for the proper strength of Bordeaux mixture may be made by blow- 

 ing over the surface of the mixture for at least one-half minute. If properly made, a thin 

 oil-like scum will form on the surface. Do the results of this test agree with those of the 

 former? 



(g) A third test may be made by dipping a strip of paper into a weak solution of 

 ferrocyanide of potassium and then into the Bordeaux mixture. If there is not enough lime 

 present, a dark reddish-brown substance will form. If enough lime is present, it will remain 

 unchanged. In which mixtures does this test show a lack of lime? 



(h) Does this agree with the former tests? 



Part B. Kerosene Emulsion — A Contact Insecticide. 



3. The formula for kerosene emulsion is usually given as follows: 



Kerosene (coal oil), 2 gallons. 



Water, 1 gallon. 



Soap, one-half pound. 

 To kill plant lice, dilute with 40-60 gallons of water. 



To illustrate the preparation of this insecticide in the laboratory, dissolve one-half gram 

 of soap in 8 cc. of water by boiling it in a test tube. After the soap is dissolved, remove 

 the test tube from the flame and add 16 cc. of kerosene. Shake the contents of the tube 

 until a creamy emulsion is formed. After you have obtained a creamy emulsion, dilute it 

 with about 350 cc. of water. When diluted to this extent it will kill plant lice and at the 

 same time do very little harm to the plant foliage. 



(a) Why not apply Paris green to plant lice instead of kerosene emulsion? 

 Reference. "Elements of Agriculture," Warren, Article 235. 



(b) How would you prepare Paris green as a poison for insects? 

 Reference. "Elements of Agriculture," Warren, Article 239. 



Part C. Wax — A Protective Covering for Plant Wounds. 



4. To make a small sample of a very reliable wax, melt together in an evaporating 

 dish 8 grams of resin, 4 grams of beeswax and 2 grams of tallow. After melting the material, 

 put it into a vessel of cold water. Then grease the fingers a little and pull the wax until 

 it is almost white. State two reasons why it is necessary to protect fresh grafts with such 

 material. 



5. Remelt the wax which you have just prepared. Into the melted wax dip a piece of 

 knitting cotton or a short strip of calico. When saturated allow it to cool. When this 

 material is used for wrapping plant wounds it should be warm enough to stick without tying. 

 What advantage is there in the use of waxed cloth or string over wax alone? 



♦ Note. Bordeaux mixture should always be well stirred before testing. 



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