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 



