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58 NITRO-GLYCERINE. 



platinum wire heated by electricity was substituted for tbe spark 

 discharge, the same results were observed. From tbese experi- 

 ments he concluded that it is impossible to explode nitro-glycerine 

 by contact with a source of heat until the intensity or duration of 

 the heat brings about decomposition of some portion of the nitro- 

 glycerine, which in its turn, determines the explosion of the rest. For ' 

 this effect, it is necessary that the heat should not only be intense, 

 but also long continued. I have never succeeded in exploding nitro- 

 glycerine by contact with a red hot wire— under these circumstances, 

 indeed, it usually refuses even to take fire, and the wire cools before 

 the nitro-glycerine has attained the temperature required for ignition. 

 "When the temperature of the wire is maintained at a high point by 

 electricity, as in Abel's experiments, time is allowed for the nitro- 

 glycerine to reach its point of ignition, and hence the result which 

 he observed. When heated to 100° 0, or a little less, it slowly 

 evaporates. Abel kept it for four days at this temperature, confined 

 in a sealed glass tube, without its exploding. 



Leygue and Champion have shewn that nitro-glycerme is ignited 

 when its temperature is raised to 257° C. They conducted their 

 investigation by means of a bar of copper, to one end of which heat 

 was applied, and upon the other end of which the nitro-glycerine was 

 placed. The bar was grooved, and in the groove fusible metallic 

 alloys were placed, by means of which the exact temperature of the 

 bar, at any particular point, could be ascertained. 



When nitro-glycerine is heated in a dish of copper or platinum 

 over a lamp, it gives off dense white fumes, and is soon completely 

 dissipated, but gradually, and without noise or -violence. Under 

 certain circumstances, however, it may, when treated in this way, 

 explode with great violence. A student in the laboratory of M. ' 

 Gorup Besanez * was heating ten drops of nitro-glycerine in an iron 

 saucepan, over a Bunsen burner, when it exploded. Every pane of 

 glass in the laboratory (46) was smashed ; the saucepan was hurled 

 through a brick wall ; the iron retort stand that supported the Sauce-. 

 pan was split and twisted, and the Bunsen burner was split and 

 flattened in a remarkable manner. Most fortunately there was no- 

 body hurt. 



Nitro-glycerine is, as we have seen, easily exploded if laid on an 

 iron anvil and struck with a hammer. If a drop be placed on a 



* Am. des Claem. & Pharm., March, 1871. 



