29 



that required to combine with all the copper will destroy foliage. There- 

 fore, in making- Soda Bordeaux, it is important to add just the exact 

 quantity of the soda required to change all the bluestone to copper hyd- 

 rate. This is done by adding- the soda solution slowly to the copper solu- 

 tion, mixing thoroughly after each addition, and testing for the neutral 

 point with litmus paper. The moment the litmus paper takes on a faintly 

 blue tinge is the time to stop adding. The copper is then all in the form 

 of a sediment and any more alkali added will be left in the free state. 

 The following tentative formula can be given : 



Soda 2 pounds. 



Copper sulphate 6 " 



Lime 5 ounces. 



Water 40 gallons. 



In making, add three-quarters of the soda solution at once, mix 

 thoroughly and then add the rest gradually, mixing and testing until the 

 proper quantity is present. It may not require the whole amount recom- 

 mended, and it may require more, depending- upon the quality of the 

 soda. When the alkaline value of a sample of soda is once ascertained, 

 then one can proceed with much more rapidity. The small amount of 

 lime is added to make the mixture decidedly alkaline, and, therefore, safe, 

 and to cause the precipitate to remain blue instead of changing to dark 

 brown or black, which it does after standing some time where an excess 

 of soda is used. 



Caustic soda can be bought retail or in drums of one hundred pounds, 

 from or through any chemist, while Gillett's lye, which is familiar to 

 everyone, is a convenient form of soda for use in making Soda Bordeaux. 



Soda Bordeaux has an advantage over the ordinary Bordeaux in 

 that it is just as good a fungicide, and, at the same time is made without 

 the labor of slaking and preparing- of lime. There are disadvantages, 

 however : 



1. Great care is necessary in the addition of the caustic soda. Any 

 added in excess is dangerous to foliage ; an excess of lime is not harm- 

 ful, although not advisable. 



2. Unless exactly neutral, the addition of an arsenical to Soda Bor- 

 deaux to impart to it an insecticidal power, is dangerous. Any free 

 alkali will act upon the arsenic compound and form sodium arsenite, 

 which, being soluble, will scorch foliage. 



This last difficulty has already been experienced by orchardists in 

 the Niagara fruit district, and for this reason they may be prone to con- 

 demn Soda Bordeaux. However, if care enough be exercised, no harm 

 *5an result from this source. 



Copper Carbonate. 



This valuable fungicide can be readily and easily made at home at 

 much less cost than for what it can be bought on the market. The fol- 



