THE LEAD ARSENATES. 



11 



In the case of commercial lead arsenate powder (Fig. 5), the results dif- 

 fer somewhat, the clear weather safety line beginning at a higher H than 

 in the other cases, but crossing these and running out on H90 at a lower 

 temperature. The total difference, however, is only 4°, so that, after all, 

 there is no great significance in this. The cloudy weather line nearly 

 parallels the clear weather one, and runs about 1° above the commercial 

 paste cloudy weather fine. 



Results from the use of neutral lead arsenate were rather different from 

 those following the other lead arsenates, this material being apparently the 

 safest of those used. No injury except one doubtful case was found, either 



Fig. 7. — Apple — Safety Lines for All Lead Arsexates. AB, 

 safety line for spraying with any reliable lead arsenate under all 

 weather conditions; 1, neutral lead arsenate, clear weather; 

 2, same, cloudy weather; 3, pure acid paste, clear weather; 

 4, commercial acid paste, clear weather; 5, (commercial acid 

 powder, clear weather; 6, pure acid paste, cloudy weather; 

 7, commercial acid (paste, cloudy weather; 8, commercial acid 

 jKJwder, cloudy weather. 



in clear or cloudy weather, at the combinations of T and H obtained, and 

 the safety lines were finally placed near the highest records taken. Fig. 6 

 shows these records and the placing of the safety line with reference to 

 them. So far as can be judged, then, this material is safe to apply under 

 any ordinary combinations of T and H up to the line AB of Fig. 6. 



A general conclusion on the apple is that apple foliage is quite resistant 

 to lead arsenate at high temperatures if the humidity is low, and at high 

 humidities if the temperature is low. Thus, sprajing appears to be safe 

 at T90 or higher if the H is below 66. With intermediate T and H, how- 

 ever, the two appear to combine, so that at T82, for example, H should not 

 be above 76. 



