FIELD AND LABORATORY EXERCISES 431 



water, and as the lime begins to heat, pour on a little more water to prevent 

 its burning. After the slaking is completed, increase the quantity of water 

 to make two gallons, which should be of a creamy consistency. Strain this 

 through cheesecloth. Keep this as a stock solution in a covered vessel to 

 prevent evaporation. 



4. Make Bordeaux mixture from a little of each of the two stock solutions 

 described above. Stir each one thoroughly and take an equal amount of each 

 in two cups or glasses. Dilute each with four times its volume. Then pour these 

 two solutions into a third vessel so that the streams mingle while pouring. 

 Note the change of color. Stir immediately. This is Bordeaux mixture and 

 is to be used as soon as possible after mixing. Put enough water with it to 

 make the same proportion as called for in the formula, which is one pound of 

 lime and one pound of copper sulfate in ten gallons of water. The equivalent 

 of this may be obtained by dividing each by sixteen which will equal one ounce 

 of lime, one ounce of copper sulfate in five pints of water. Keep the stock 

 solution for future use. 



5. Mix Paris green with some Bordeaux at the rate of one level teaspoon- 

 ful of powder with five quarts of the Bordeaux mixture. This makes a com- 

 bined spray material suitable for combating biting insects and plant diseases. 



6. Test Bordeaux mixture by putting a clean steel knife blade in the so- 

 lution for a moment when the mixture is first made and properly diluted. If 

 a deposit of copper forms on the blade, more lime is needed. A little more of 

 the lime water should then be added. 



7. Another test for Bordeaux mixture is to pour a little of the solution in a 

 shallow plate and allow it to stand for ten minutes or more, undisturbed. 

 If the Bordeaux has sufficient lime, a thin film will be formed over the top of 

 the mixture, which is detected by looking across the surface. Touch the sur- 

 face with the point of a tooth pick. If a good film is found, it will show plainly. 

 If the mixture does not stand this test, add more lime water, as there is more 

 danger of injuring the foliage if there is not enough lime present. 



8. Paris Green Spray. Make a mixture of one level teaspoonful of Paris 

 green in five quarts of water. Use this with a small blow spray for plants 

 attacked by biting insects, as Irish potatoes. Keep well shaken while using. 

 Note the results the following day. Do you find any dead potato beetles? 



9. Test for free arsenic in a mixture of Paris green and water by pouring 

 off some of the clear water after the Paris green has settled. Put a few drops 

 on a silver coin .or on a clean tin surface. If free arsenic is present, a deposit 

 of metallic arsenic will discolor the other metal. As free arsenic is usually 

 present in a mixture with Paris green, lime should always be added. Use one 

 or two pounds of lime to each fifty gallons of water. The free arsenic will thus 

 be taken up, and injury of the foliage is largely prevented. 



10. Make a solution of ar senate of lead in water, calculating the pro- 

 portions to agree with those given in this chapter. Test this solution for free 

 arsenic as in the above exercise. Can you give a good reason for using arsenate 

 of lead instead of Paris green on trees and other plants? 



11. Compare several of the poison mixtures with each other and see which 

 ones remain in suspension best. What danger is likely to occur with those 

 which settle quickly? 



12. Make a stock solution of kerosene emulsion, using the directions and 

 formulas given in this chapter. 



13. Killing Plant Lice. After properly diluting a part of the stock solu- 

 tion, use it as a spray on plant lice, or on soft-bodied insects, and note the 

 effects. 



14. Make a concentrated lime-sulfur solution, reducing the quantities 

 to suit the laboratory requirements. If possible, test this for specific gravity, 

 label it and save as a stock solution for future use. 



