Cooperative Spraying Experiments. 



175 



are Bordeaux mixtures properly made with dilute mixtures of lime and 

 sulfate of copper, the former having been made with a prepared lime and 

 C with a good stone lime. Note the striking difference in the fiocculency 

 of the mixtures B and C as compared with the poorly made mixture at 

 A. Mixtures B and C could be kept in suspension in the spray tank with 

 less stirring and would not be so apt to clog the nozzles as the coarser 

 and heavier mixture at A. 



I was also interested to know whether it would take more " new- 

 process " lime than stone lime to make a good Bordeaux mixture. I found 

 that about one-half the quantity of stone lime, or about 2^ pounds, was 

 sufficient to thoroughly neutralize the five pounds of copper sulfate, but 

 that an equal quantity of " new-process " lime was not quite enough to 

 overcome the acidity of the copper sulfate. This result was rather sur- 

 prising, because I had thought that the formula did not call for such an 

 excess of lime over enough to neutralize the copper sulfate. This result 

 shows that by the use of the ferro-cyanide test, by which one can readily 

 determine when enough lime has been added, that much lime can be saved 

 and thus the mixture cheapened. It is ^«=,=^ 



always advisable, however, to add about 

 as much more lime, especially during 

 rainy seasons, when weather conditions 

 act upon the spray after it is on the 

 foliage, and unless there is plenty of lime 

 considerable injury to the foliage may re- 

 sult. Doubtless the reason why it takes 

 more " new-process " lime than stone 

 lime to make a good Bordeaux mixture 

 is because the former limes are about 

 one-third magnesia, which does not enter 

 chemically into the Bordeaux mixture. 

 Fresh, " new -process " limes, except the 

 one mentioned above, which was de- 

 scribed as " freshly burned and finely 

 ground," are limes which are water- 

 slaked dry. The lime just mentioned is 

 not slaked, however, and when put into 

 water will finally slake, like stone lime. 

 It is cheaper than the other " new- 

 process " limes, but it will not keep so 

 long in good condition, hence there would be a little more risk in getting it. 



Some other results of the tests are that one should never attempt to 

 make Bordeaux mixture with air-slaked lime. I am informed that sorne 



Fig. 48. — Bordeaux mixtures which 

 have stood six and one-half 

 hours. See page i j4for detailed 

 description. 



