CHEMISTRY OF FUMIGATION. 

 Experiments on commercial cyanids. 



103 



Ex- 





peri- 



Serial 



ment 



No. 



Xo. 





11 



6523 



12 



6524 



13 



6525 



14 



6526 



15 



6527 



16 



6528 



17 



6529 



Material. 



Equiv- Sodium 

 alent of chlorid HCN 

 HCNininsam- evolved, 

 sample, i pie. 



Potassium cyanid . . . 



Sodium cj ariid 



do 



do. 1 



Potassium evanid 



do 



•• Sodium eyanid " 1 . . 



Per ct. 



Per ct. 



40.42 



0.40 



41.78 



14.20 



51.22 



.57 



41.45 



5.82 



39.96 



.60 



39.28 



.77 



41.02 



6.15 



Per ct. 

 37.95 

 26.22 

 48.31 

 36.93 

 37.51 

 36.71 

 35.17 



HCN 

 remain- 

 ing in 

 residue. 



Per ct. 

 1.22 

 1.32 

 2.31 

 2.04 

 1.71 

 1.40 

 1.84 



HCN 

 decom- 

 posed 

 (by dif- 

 fer- 

 ence). 



Per ct. 



1.25 



14.24 



.30 



2.48 



.74 



1.17 



4.01 



Per cent of total HCN- 



Evolved. 



93.88 

 62.76 

 94.32 

 89.10 

 93.87 

 93.46 

 85.75 



In resi- Decom- 

 due. posed. 



3.03 

 3.17 

 5.09 

 4.92 

 4.27 

 3.57 

 4.49 



3.09 

 34.07 

 .59 

 5.98 

 1.86 

 2.97 

 9.76 



i A mixture of potassium and sodium cyanids and sodium chlorid. 



This work shows the great variation in the yield of hydrocyanic 

 acid obtained when using samples as they appear upon the market, 

 nearly twice as much being obtained from sample No. 6525 as from 

 Xo. 6524. In view of such varying results as these it is not surprising 

 that fumigation has so often proved a failure. 



EFFECT OF THE PRESENCE OF SODIUM NITRATE IN CYANIDS ON 

 THE YIELD OF HYDROCYANIC-ACID GAS. 



Experiments carried out in the same way, using the same pure 

 sodium cyanid, to which vandng proportions of sodium nitrate had 

 been added, gave results similar to those in which sodium chlorid was 

 present. This fact is of no practical utility in so far as fumigation 

 work is concerned, as cyanids do not contain nitrates as an impurity. 

 Commercial sulphuric acid may contain traces of nitric acid, but 

 the amount is so minute that it would have no appreciable effect on 

 the results. Aside from this, the action of such an energetic oxidizing 

 agent as nitric acid, in the presence of strong sulphuric acid, upon 

 cyanids would be attended with some danger. The results of these 

 experiments are given in the following table: 



Effect of nitrates on the yield of hydrocyanic-acid gas. 





Equiva- 

 lent of 

 HCN in 

 sample. 



Sodium 

 nitrate 

 in sam- 

 ple. 



HCN 

 evolved. 



HCN re- 

 maining 

 in resi- 

 due. 



HCN de- 

 com- 

 posed (by 

 differ- 

 ence). 



Per cent of total HCN— 



Experiment No. 



Evolved. 



In resi- 

 due. 



Decom- 

 posed. 



18 



Per cent. 

 47.16 

 43.18 

 25.91 

 17.27 



Per cent. 

 9 



16f 

 50 

 663 



Per cent. 

 39.92 

 37.73 

 21.22 

 13.12 



Per cent. 



1.26 



1.32 



1.14 



.79 



Per cent. 

 5.98 

 4.13 

 3.65 

 3.36 



84.66 

 87.39 

 81.51 

 75.95 



2.67 

 3.05 

 4.40 

 4.56 



12 67 



19 



9 56 



20 



14 09 



21 



19 49 







The presence of nitrates exerts a very decided decomposing action 

 on the hydrocyanic acid, but this action is much less than that pro- 

 duced by chlorid s. The nitrogen in the decomposed cyanid is in 

 this case also converted into ammonia. 

 67330°— Bull. 90—12 8 



