Bordeaux Mixture 71 



compounds or mixtures of them. With a 

 large excess of the base the compound 

 (IV) is produced having the formula 

 CuS04-9CuO.CaS04-3CaO. This is stiU 

 more basic in that it contains some of the 

 basic calcium sulfate in addition to the basic 

 copper suKate. Such a compound the ordi- 

 nary Bordeaux mixture is said to be. 



From the symbol of the copper compound 

 in ordinary Bordeaux, CuS04-9CuO-CaS04' 

 3CaO, an equation may be written to account 

 for the formation of such a substance, 



IOCUSO4 + 12Ca02H2 = CuS04-9CuO. 

 CaS04-3CaO + 8CaS04 + I2H2O. 



From this it is seen that considerable cal- 

 cium sulfate is formd at the time the Bor- 

 deaux is made. Calcium sulfate is soluble 

 in water at 25°, to the amount of 0.21 gram 

 per Uter. If any free lime is left over, which 

 is always the case, the solubihty is lessend, 

 as both compounds contain a coromon cal- 

 cium ion. 



A rough calculation on the part of the 

 student will show that 8 grams of copper 

 sulfate require about 2 grams of lime to 

 react with it. For example, the formula for 

 the precipitate in ordinary Bordeaux is 

 given as CuS04-9CuO.CaS04-3CaO. Lime is 

 used to produce the 9CuO and the 3CaO 



