New York Agricultural Experiment Station. 369 



for cucumbers^ put it into a loose bag (a fertilizer bag is good) 

 and suspend it in the barrel in such a manner that the copper 

 sulphate will be near the top of the water. If allowed to rest on 

 the bottom of the barrel it will require longer to dissolve. 



Preparing the Limb. 



Take four pounds or more of the best unslaked lime obtain- 

 able (air-slaked lime should not be used), put li into a separate 

 vessel and slake it as for white^Nash. It is well to have this 

 vessel of -good size so that after the lime is slaked considerable 

 water may be added to dilute and cool it. Formerly, the amount 

 of lime required was determined by weighing, but we now have 

 a chemical test called the potassium ferrocyauide test (to be 

 described presently) which does away with the necessity of 

 weighing the lime. 



Mixing the Copper Sulphate and Lime Water. 



When the copper sulphate is dissplved and the lime slaked, 

 fasten a fertilizer bag or other coarse cloth over the top of the 

 barrel for a strainer. Have at hand a small bottle containing a 

 little potassium ferrocyanide (yellow prussiate of jjotash) dis- 

 solved in water. Now, strain the lime water into the copper 

 sulphate solution until a considerable quantity has been added. 

 Next, remove the strainer and give the mixture in the barrel a 

 thorough stirring; then add a drop of the potassium ferrocyanide 

 solution. If enough lime has been added no change of color will 

 take place when the drop of potassium ferrocyanide strikes the 

 mixture, but if more lime is needed the drop will change to a 

 reddish brown color. Continue to add lime until the mixture 

 does not change color when tested, being careful to stir thor- 

 oughly each time before testing; and after the test shows that 

 there is enough lime add yet a little more lime in order to be sure 

 that there is enough. If too little lime is used the plants will be 

 injured in the manner described on page 359, but an excess of 

 lime will do no harm. 



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