142 The Spraying of Plants. 



soda in cold water; add the two together; dilute in 25 gallons." 

 The preparation possesses no special fungicidal value. 



COPPER SULPHATE; SULPHATE OF COPPER; BLUE VITRIOL; 

 BLUE STONE; CuSO 4 ; CuSO 4 -{-5H 2 O. This chemical is formed 

 by uniting metallic copper and sulphuric acid, the product being- 

 formed in several different ways. The substance is deposited 

 from solutions in the form of large, blue, transparent crystals 

 containing 25.46 per cent of actual copper, and it is in this 

 form that the salt is commonly sold. Granulated copper sul- 

 phate is formed by breaking up the larger crystals ; otherwise, 

 it is identical with the other form. On account of the fine- 

 ness of the particles, the mass loses its deep blue color, and for 

 this reason the granulated form offers greater temptations for 

 adulteration. A pure solution of copper sulphate forms a red- 

 dish-brown discoloration with a solution of the ferrocyanide of 

 potassium, and this may be used as a test for the purity of the 

 copper compound. 



Copper sulphate is readily soluble in cold water, and still 

 more so in hot water. A solution may be quickly made by 

 hanging the material in a coarse sack near the surface of the 

 water. This is done so that the dissolved portion may settle to 

 the bottom as fast as it enters into solution, for in this manner 

 the crystals are continually surrounded by clear liquid. If the 

 crystals are placed in the bottom of the vessel, they are soon 

 surrounded by a saturated solution which prevents them from 

 being dissolved until the contents of the vessel are stirred so 

 that the more clear liquid may come in contact with the crystals. 



Copper sulphate should always be dissolved in wooden or 

 earthen vessels. If an iron vessel is used, the copper will be 

 deposited upon the iron, forming a copper-plated portion 

 wherever the two come in contact. 



A simple solution of copper sulphate should be sparingly 

 applied to foliage, for when the liquid is sufficiently concen- 

 trated to have a decided fungicidal action it causes so much 

 injury to most foliage that its use cannot be considered safe. 

 This compound is more caustic than some other forms of 

 copper, but Professor Taft recommends the use of a simple 

 solution of copper sulphate instead of ammonia solution of 

 copper compounds. lie has sucessfully applied solutions con- 

 taining 1 part of blue vitriol in 1000 parts of water to plants 



