THE LEAD ARSENATES. 



13 



With commercial acid lead arsenate paste (Fig. 9) the safety lines are 

 very similar to those given in Fig. 8, though a little lower. The difference 

 is insignificant, however. With the commercial acid lead arsenate powder 

 (Fig. 10) the results are also similar, but there seems to be less difference 

 between clear and cloudy weather in producing injury. 



The tests with the neutral lead arsenate paste support those on the 

 apple in indicating higher T and H as necessary to cause burning. In 

 Fig. 11a few of the actual tests are recorded, those marked by circles being 

 clear weather tests and those by crosses, cloudy weather ones. The two 

 interrogation mark tests were clear weather tests, and whether they were 

 really spray injuries is at least doubtful. The two marked "t" and the 

 "s" were cloudy weather tests. 



Humidity. 

 70 / 



Fig. 12. — Cherrt — Safety Lines for All Lead Arsenates. 

 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, same, cloudy weather; 7, pure 

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

 weather. 



A combination of all the safety lines is given in Fig. 12. The conver- 

 gence of the lines, in many cases almost to a common point, produces a 

 rather confusing diagram, the significant features being the detached 

 position of the neutral arsenate (1 and 2), the practical parallelism of the 

 other materials in clear weather, and the fact that these are all located 

 at higher H than the same materials in cloudy weather. The arbitrarily 

 placed line AB may be regarded as the safety line for the cherry ^\'ith any 

 rehable lead arsenate, either in clear or cloudy weather. 



