104 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 



SUMMARY. 



In order that the results may be more readily compared they are all 

 presented in one table, as follows: 



Comparison of results obtained on evolution of hydrocyanic-acid gas under different 



conditions. 



Ex- 

 peri- 

 ment 

 No. 



10 



11 

 12 

 13 

 14 

 15 

 16 

 17 



Material. 



Sodi- 

 um 

 chlorid 

 in sam- 

 ple. 



Sodium cyanid 



....do...: 



do 



do 



do 



do 



Potassium cyanid. . . 



Sodium cyanid 



do 



do. 2 



Potassium cyanid . . . 



do 



Sodium cyanid (?) 2 . 



Sodium cyanid . 



do 



do 



do 



Per ct. 



0.00 



9.00 



16.66 



33. 33 



50.00 



66.66 



.40 



14.20 



.57 



5.82 



.60 



.77 



6.15 



Sodi- 

 um 

 nitrate. 



9.00 



16.66 

 50.00 

 66.66 



Equiv- 

 alent of 

 HCNin 

 sample. 



Per ct. 

 51.82 

 47.16 

 43.18 

 34.55 

 25.91 

 17.27 

 40.42 

 41.78 

 51.22 

 41.45 

 39.96 

 39.28 

 41.02 



47.16 

 43.18 

 25.91 

 17.27 



HCN 



evolved. 



Per cent. 

 49.35 

 41.96 

 27.42 

 10.57 

 5.85 

 1.27 

 37.95 

 26.22 

 48.31 

 36.93 

 37.51 

 36.71 

 35.17 



39.92 

 37.73 

 21.22 

 13.12 



HCN 



remain- 

 ing in 

 residue . 



Per ct. 



1.48 



.66 



1.71 



.37 



.05 



.10 



1.22 



1.32 



2.31 



2.04 



1.71 



1.40 



1.84 



1.26 

 1.32 

 1.14 



.79 



HCN 

 decom- 

 posed 

 (by dif- 

 fer- 

 ence). 



Per ct. 



0.99 



4.54 



14. 05 



23.61 



25.91 



15.90 



1.25 



14.24 



.30 



2.48 



.74 



1.17 



4.01 



5.98 

 4.13 

 3. 65 

 3.36 



Per cent of total HCN- 



Evolved. 



95.23 

 88.98 

 63.49 

 30.61 

 22.58 

 7.35 

 93.88 

 62.76 

 94.32 

 89.10 

 93.87 

 93.46 

 85.75 



84.66 

 87.39 

 81.51 

 75.95 



In resi- 

 due. 



2.86 

 1.40 

 3.97 

 1.06 

 .21 

 .63 

 3.03 

 3.17 

 5.09 

 4.92 

 4.27 

 3.57 

 4.49 



2.67 

 3.05 

 4.40 

 4.56 



Decom- 

 posed. 



1.91 



9.62 



32.54 



68.33 



7 7.21 



92.09 



3.09 



34.07 



.59 



5.98 



1.86 



2.97 



9.76 



12.67 



9.56 



14.09 



19.49 



1 Average of five determinations. 



2 A mixture of potassium and sodium cyanid and sodium chlorid. 



These experiments show conclusively that the presence of chlorids 

 and nitrates in cyanids which liberate hydrochloric and nitric acid 

 respectively, together with hydrocyanic acid, on treatment with 

 sulphuric acid cause very marked decomposition of the hydrocyanic 

 acid. The effect produced by hydrochloric acid is much more marked 

 than that produced by nitric acid. In one case (experiment 10) 

 over 92 per cent of the hydrocyanic acid was decomposed and only 

 a little over 7 per cent evolved. This is a larger amount of sodium 

 chlorid than would ever be found in a commercial sample, but it shows 

 the important bearing this impurity has upon the results. Practi- 

 cally all commercial potassium and sodium cyanids contain sodium 

 chlorid in greater or less amount. Potassium cyanid is frequently 

 sold as " 98-99 per cent pure," which in reality is a mixture of 

 potassium cyanid, sodium cyanid, and sodium chlorid and on 

 analysis may show even 100 per cent expressed as potassium cyanid 

 yet there may be several per cent of sodium chlorid present. For 

 fumigation w x ork an analysis of a cyanid is of little value unless the 

 chlorin content is also determined. In order that satisfactory results 

 may be obtained in the fumigation of trees for the control of insects 



