VIII 
HYDROCYANIC-ACID GAS FUMIGATION IN" CALIFORNIA. 
Fumigation of citrus trees — Continued. Page. 
Time of the year for fumigation . 61 
Fumigation for the mealy-bug 63 
Fumigation during the blossoming period 64 
Fumigation while the fruit is of small size 65 
Fumigating lemons 65 
Effects of fumigation on unhealthy trees 66 
Greater susceptibility to injury of some varieties than others 67 
The distribution of gas within a tent 67 
Fumigation for physiological effects 67 
Effects of meteorological elements on fumigation 68 
Injury to sprayed trees 72 
The appearance of fumigated trees 73 
The presence of old scales on fumigated trees 74 
A device for covering fumigation generators 74 
The effect of climatic conditions on scale insects 76 
The effect of fumigation on ladybirds (Coccinellidae) and Scutellista cyanea 
Motsch 77 
The cost of fumigation 78 
General cautions 80 
List of the writer's published articles and addresses on the fumigation 
investigation in California 81 
The value of sodium cyanid for fumigation purposes R. S. Woglum. . 83 
Introduction 83 
Strength of sodium cyanid expressed in terms of potassium cyanid 85 
Proportion of chemicals 85 
Field tests 86 
Action of sodium chlorid 87 
The kind of cyanid to purchase . 88 
Dosages with sodium cyanid 88 
Dosages recommended for scale pests 89 
Comparison of sodium cyanid and potassium cyanid for general fumigation. 90 
Chemistry of fumigation with hydrocyanic-acid gas C. C. McDonnell. . 91 
Introduction 91 
I. Analyses of chemicals used for the production of hydrocyanic-acid gas. 91 
Sulphuric acid 91 
Cyanid samples 92 
II. Proportion of cyanid, sulphuric acid, and water for best yield of gas. . 93 
Potassium cyanid 93 
Sodium cyanid 93 
III. Action of mineral acids on cyanids and hydrocyanic acid 96 
Action of sulphuric acid on hydrocyanic acid 97 
Action of hydrochloric acid on hydrocyanic acid 98 
Effect of the presence of sodium chlorid in cyanids on the yield of hydro- 
cyanic-acid gas in fumigations 99 
Description of apparatus - 100 
Details of manipulation 100 
Results of experiments 101 
Ammonia formed from the decomposition of the cyanid 102 
Effect of the presence of sodium nitrate in cyanids on the yield of hydro- 
cyanic-acid gas 103 
Summary 104 
Index 107 
