In his recent analysis, Dan Kaszeta provides some interesting chemical analysis of the recent UN report, and also suggests Hexamine could be the smoking gun of the Ghouta attack, going so far as describing it as "very damning evidence of government culpability".
The reasoning could be summarized as follows:
- Hexamine was reported by the OPCW as part of the Syrian chemical program. This implies it had a purpose in the program, rather than being used for explosives manufacturing etc.
- Hexamine can be used to bind the HF generated during the sarin binary process.
- No one else is known to use Hexamine for this purpose.
- Hexamine was found in multiple samples taken by the UN in Ghouta (both Zamalka and Moadamiyah).
- It is unlikely the opposition will choose the same HF binding chemical as the government, implying government culpability.
I believe there is a much more plausible explanation for these findings:
- As Dan notes, the standard chemical for binding HF in the sarin binary process is isopropylamine. It was used by the US for this purpose, it was declared by the OPCW (in the same report), and it was ordered by Al-Nusra in Turkey. There is no reason to believe Syria decided to replace it with Hexamine.
- So why was it part of Syria's chemical program? This is easily explained when remembering Syria produced not only sarin, but also mustard gas. Hexamine is a well-known stabilizer for mustard gas, discovered in 1945 and adopted by the US Army's Chemical Warfare Service.
- Which now requires us to explain the Hexamine findings in the field. These are not surprising given the many uses and high accessibility of Hexamine. Specifically of interest are its uses in explosives (which were used to disperse the sarin) and as heating tablets for camping stoves, which are probably widely used in these neighborhoods under siege.
This conclusion is further strengthened when considering that (a) Hexamine was reported in several samples that did not contain any indications of sarin, and (b) some samples contained other explosive-related chemicals such as TNT and trinitro triazine.
Dan Kaszeta has referred me to this US Army publication, which states on page II-38 that "a small amount of degradation occurs when stored in steel ton containers for over 50 years". It should be noted this refers to the pure form of mustard gas (HD), which is different than the Levinstein Mustard (H) mentioned in the patent above (70% purity). Dan claims H is an obsolete agent, and since "pure HD is quite stable on its own", Hexamine could not be a mustard gas stabilizer, as previously claimed.
This is an important correction which requires revisiting the analysis.
First, we should confirm that Syria indeed stores HD and not H. There is no direct evidence that this is the case, but given that Iraq's inferior program reached purity levels of 90-95%, it is fair to assume Syria does have HD.
Second, we need to confirm that HD does not require stabilizers. The above US Army publication seems to imply it doesn't, but this one states "The stability of Levinstein mustard which has been purified by various methods is also improved by the addition of 1 per cent hexamine" (p. 42), and this patent discusses methods of stabilizing HD, stating "mustard gas thus purified still corrodes steel containers and the corrosion rate is fairly rapid at temperatures in the range of 110F. to 150F". Additionally, when considering that "pure" HD is actually only 96% pure, it makes sense that while it should degrade slower it might still need some stabilization.
Trying to settle this discrepancy I looked into the sources of the first publication and found the most significant one to be this research, which I could not find in full. However, according to its summary it is based on samples taken from US stockpiles held for 50 years. Obviously, these stocks were intended for long-term storage, which according to the other sources contain stabilizers.
So apparently, the low degradation findings refer to the actual final product (containing Hexamine), and not the hypothetical chemical.
While investigating this issue, I also found this interesting quote (here):
"Regardless of the exact reasons for the instability of Levinstein mustard, the problem is fully recognized and is extremely serious during time of war and national emergency when it becomes necessary to build up a very great strategic reserve of this chemical warfare agent in contemplation of the fact that chemical warfare may, at any time, be resorted to."
This brings up another option: That the Hexamine in Syria's stockpile was intended for emergency production of large amounts of H. Since HD's advantage over H is in storage and not in battlefield use, this is a very plausible scenario.
Finally, Dan's response still fails to explain why Hexamine was found in the sarin-negative samples.
As a more general claim: Hexamine seems to have multiple uses in chemical warfare and multiple reasons to be found in the field samples (see many more here). Correlating the two is impossible before meticulously striking off all the alternative causes.
Conclusion: The Hexamine findings in the impact sites are not indicative of Syrian government culpability as they are not reliably linked to the Hexamine from Syria's chemical stockpiles.
Did I miss anything? Please share your evidence and analysis and help improve the conclusions.