86 HYDROCYANIC-ACID GAS FUMIGATION IX CALIFORNIA. 
FIELD TESTS. 
In August, 1909, H acres of orange trees at Whittier, Cal., severely 
infested with the purple scale (LepidosapJies heclcii Newm.), winch 
was largely in the egg stage — the most difficult one in which to 
destroy it — were fumigated with a 124 per cent sodium cyanid, using 
the 1—1 J— 2 formula. The length of exposure was one hour. Three 
strengths of gas were used, calculated from the cyanogen present in 
the cyanid as equivalent to 1, 1J, and H, of the strength of regular 
schedule No. 1 of potassium cyanid, as given in this Bulletin. The 
writer says strengths equivalent to these different schedules of potas- 
sium, because it is known from previous discussion that an ounce of 
high-grade sodium cyanid will produce considerably more gas than an 
ounce of high-grade potassium cyanid owing to its higher cyanogen 
content. In the 124 per cent sodium cyanid the advantage in favor 
of that product is practically one-fourth. It foUows that if a high- 
grade sodium cyanid is used with dosages of the same size as three- 
fourths of schedule No. 1 of potassium cyanid practically the same 
strength of gas will be given off as with potassium cyanid at the 
dosages of full schedule No. 1 of potassium cyanid. 
In examining the results where the equivalent of schedule No. 1 of 
potassium cyanid was used, only 4 live insects, 2 with healthy eggs, 
were found, these being distributed between 3 different trees. Xo 
live insects or eggs were found on the trees treated with dosages 
equivalent to 1J and H of schedule No. 1 of potassium cyanid. 
Experiments against the purple scale where potassium cyanid was 
used have shown that it required a 1| schedule of that chemical to 
produce practically the same results as have been secured in this 
experiment with sodium cyanid at a strength equivalent to No. 1 
schedule of the potassium cyanid. With this high-grade sodium com- 
pound the equivalent of a 1J schedule of potassium cyanid eradicates 
the purple scale, whereas with potassium a 1J schedule has been 
required to accomplish this result. Hence this field experiment 
would indicate that under the crude conditions of orchard work 
sodium cyanid produces not only as good a generation as the potas- 
sium but a decidedly superior one. 
In a second experiment an acre of orange trees very severely 
infested with purple scale was fumigated, partly with a high-grade 
sodium cyanid and partly with the regular potassium cyanid. The 
tents used were of a new character of material of very tight texture. 
The sodium cyanid produced exactly as satisfactory results in this 
experiment as the potassium cyanid. 
During November, 1909, a 4-acre block of orange and lemon trees 
severely infested with the purple scale was fumigated with sodium 
cyanid by an outfit of the Whittier Citrus Association, using the 
