66 SOME RECENT OBSERVATIONS. 



graph, in which we place 5 lbs. of commercial sulphuric acid 

 with a specific gravity of 1.83 or over, and 7^ lbs. of water. 

 When everything is ready, provision made for outside ventila- 

 tion, etc., the package of cyanide is dropped into the jar, and 

 the operator leaves the room. As the gas formed is lighter 

 than air, and ascends, the one dropping the charge must go 

 down to the story below, not to the one above. 



The question, as to how much time elapses between the 

 dropping of the charge and the first giving off of the fatal 

 gas is a vital one, in view of the deadly nature of the gas 

 and one we have endeavored to settle by various experiments. 

 In doing the work personally, I have allowed fifteen seconds 

 as a conservative estimate in this direction, and acted accord- 

 ingly. To place this matter beyond any doubt, however, we 

 have, this fall, made several trials, timing the interval between 

 the dropping of the double bag of cyanide into the jar, and 

 the first appearance of the fumes (see figure), with surprising 

 results. A double manila sack was used in each case, that is, 

 one sack inside another, and various makes of sacks. One 

 yellow, marked "Pacific;" another, H. P. B. sugar sack; 

 another, "Mayflower" No. 17, etc. In each case the liquid 

 was quite warm (the heat being caused by adding water to 

 the acid), but no observation was made on its exact tempera- 

 ture. We found in a series of trials that this interval varies 

 from 29 seconds, the lowest, to four minutes, the latter being 

 the highest, the variation, evidently, being largely due to vari- 

 ations in the thickness and character of the paper of which 

 the sacks are made. Of course, a variation in the warmth 

 of the liquid would cause a difference. 



In connection with these experiments, the question arose, 

 "Is it not possible that fumes which would be fatal if breathed, 

 rise from the jar before they are visible ?" This was answered 

 in the negative, by placing a live guinea pig in a wire cage 

 about six inches above the top of the jar, immediately after 

 the charge of cyanide had been lowered into the acid. Visible 

 fumes began to rise two minutes after placing the charge, and 

 a few seconds later the guinea pig succumbed, showing that 

 the dangerous gas was not given off in a fatal amount until 

 fumes were observed. It would seem, then, from these results, 

 that on a very conservative estimate one can depend upon, at 



