184 SCIENCE AND FRUIT GROWING 



fact that an investigation of the subject carried out at the 

 Woburn Farm showed that the carbonate formed consisted of 

 5CuO,2CO 2 , the proportions in which the hydrated reagents 

 react being I of copper sulphate to 1-84 of sodium carbonate, 

 according to the following equation 



5CuSO 4 -f 8Na 2 CO 3 + 3H 2 O == 5CuO,2CO 2 + 6NaHCO 3 

 + 5Na 2 S0 4 . 



Hence, the proportions of i : 1-15 give a deficit of soda, leaving 

 some of the copper unprecipitated ; but not so much as might be 

 expected, for the bicarbonate of soda (NaHCO 3 ) formed, is itself 

 capable of precipitating most of the copper left in solution, with 

 the production of another basic carbonate of copper. The 

 percentage of copper left in solution when the proportion of the 

 reagents are varied are as follows, the values applying to a case 

 where the copper sulphate taken amounted to 20 Ibs. in 100 

 gallons 



Carbonate to Copper left ri 



i of Sulphate. dissolved. Changes in 



1. i-oo -034 per cent. 13 days 



2. I-I5 -021 3 



3. 1-84 -003 10 

 4- 2-30 -008 33 

 5. 2-80 -008 ,, 39 ,, 



Thus the copper left in solution when such wrong proportions, 

 as in No. 2, are taken, is seven times greater than when the correct 

 proportions are used (No. 3), and amounts to 4 per cent, of the 

 total copper present. The damage to the plant, when such is 

 caused by Burgundy mixture, 1 appears, however, to be due, not 

 to this comparatively large amount of dissolved copper, but to 

 the by-products present sodium bicarbonate and sodium sul- 

 phate these two together amounting to 2 per cent, of the 

 liquid. Experiments were made by immersing leaves for 24 

 hours in Burgundy mixture on the one hand, and, on the other, 

 in solutions containing such by-products as would be present 

 in this mixture ; and, as will be seen, the scorching produced by 

 both by-products together, measured by the percentage of the 



1 This damage appears to have been very considerable in many cases 

 in 1917, and is attributed in the leaflet referred to above to various " con- 

 comitant " circumstances. Concomitant circumstances, however, are 

 always present, yet they do not appear to result in damage by spraying 

 when it is Bordeaux mixture or paste which is used. 



