Editing Nitroglycerin (section)

== Instability and desensitization ==
In its undiluted form, nitroglycerin is a [[contact explosive]], meaning physical shock causes it to explode. If it has not been adequately purified during manufacture it can degrade over time to even more unstable forms. This makes nitroglycerin highly dangerous to transport or use. In its undiluted form, it is one of the world's most powerful explosives, comparable to the more recently developed [[RDX]] and [[PETN]].

Early in its history,  liquid nitroglycerin was found to be  "[[Phlegmatized|desensitized]]" by freezing it at a temperature below {{Convert|45|to|55|F|C}} depending on its purity.<ref name="Tallini5">{{Cite web |title=Is Nitroglycerine In This? Page 5 |url=https://www.logwell.com/tales/frozen_nitroglycerin.html |access-date=2024-02-20 |website=www.logwell.com}}</ref> Its sensitivity to shock while frozen is somewhat unpredictable: "It is more insensitive to the shock from a [[Detonator|fulminate cap]] or a rifle ball when in that condition but on the other hand it appears to be more liable to explode on breaking, crushing, tamping, etc."<ref name="LSMI1">{{cite journal |url=https://www.michigan.gov/documents/deq/GIMDL-LSMI1911B_301826_7.pdf |title=Accidents in the Transportation, Storage, and Use of Explosives |first=Charles S. |last=Hurter |date=August 22, 1911 |volume=16 |journal=Proceedings of the Lake Superior Mining Institute |page=70}}</ref> Frozen nitroglycerin is much less energetic than liquid, and so must be thawed before use.<ref name="LSMI2">{{cite journal |url=https://www.michigan.gov/documents/deq/GIMDL-LSMI1911C_301829_7.pdf |title=Accidents in the Transportation, Storage, and Use of Explosives |first=Charles S. |last=Hurter |date=August 22, 1911 |volume=16 |journal=Proceedings of the Lake Superior Mining Institute |page=71}}</ref> Thawing it out can be extremely sensitizing, especially if impurities are present or the warming is too rapid.<ref name="Tallini4">{{cite web |last=Tallini |first=Rick F. |title=Tales of Destruction...Thawing Can Be Hell |url=http://www.logwell.com/tales/second_nitro_death.html |website=Analog |series= |publisher=Analog Services, Inc.}}</ref> [[Ethylene glycol dinitrate]] or another polynitrate may be added to lower the melting point and thereby avoid the necessity of thawing frozen explosive.<ref name="fn_1">{{cite encyclopedia|url=https://www.britannica.com/nobel/micro/426_77.html | encyclopedia=Encyclopaedia Britannica | title=Nitroglycerin | access-date=2005-03-23 |archive-url=https://web.archive.org/web/20020912025024/https://www.britannica.com/nobel/micro/426_77.html |archive-date=2002-09-12 }}</ref>

Chemically "desensitizing" nitroglycerin is possible to a point where it can be considered about as "safe" as modern [[high explosive]]s, such as by the addition of [[ethanol]], [[acetone]], or [[dinitrotoluene]].<ref name="Tallini12">{{cite web |last=Tallini |first=Rick F. |title=Tales of Destruction...Is Nitroglycerin In This? |url=http://www.logwell.com/tales/red_glycerin.html |series= |publisher=Analog Services, Inc.}}</ref> The nitroglycerin may have to be extracted from the desensitizer chemical to restore its effectiveness before use, for example by adding water to draw off ethanol used as a desensitizer.<ref name="Tallini12"/>