John, thank you for the citations.
 
>   "I visited Treblinka to find out how they carried out exterminations. The  
>    camp commander at Treblinka told me he used [carbon] monoxide gas and I 
>    did not think his methods were very efficient. So when I set up the   
>    extermination building at Auschwitz I used Zyklon B which is crystallized  
>    prussic acid which we dropped into the death chamber from a small opening. 
I think it is HCN absorbate on silica. HCN itself would have been much 
too dangerous (18 deg C b.p.), its solution in water is instable.
I have seen these holes in the ceiling in Dachau btw., though they didn't 
gass people there -- the installation was too new. And the average 
village Kraut _really_ didn't knew -- the first time they saw 
concentration campers was towards the end of the war, where advanced 
Allies fronts caused them to hurry up with the coverups -- marching 
columns in full daylight, shooting sick/exhausted people in the field.
> [...]
> 
> The reason that cyanide, the gas given off by Zyklon B, is very popular in 
> the termite killing business and very unpopular in the chemical warfare  
> business is that it leaves no residue, it does not last and in fact is 
Right, but it is also the chiefest advantage of HCN: after a day treated 
terrain is passable. This doesn't happen with VX. Btw, anybody knows what 
this Russian VX successor is, the one one order of magnitude better than VX?
> lighter than air. Unless it's confined in a building it becomes harmless 
> almost immediately.
Apart from the other nasties, the effects of HCN are briefly treated in 
"A Higher Form of Killing" by Robert Harris and Jeremy Paxman, 1982.
 
[...]
ciao,
'gene