(Source: http://www.nizkor.org/ftp.cgi/camps/aus ... yanide.002 )Relating this to the gas chambers at Auschwitz, the small
amounts of prussian blue in extermination facilities can be easily
explained. According to the testimonies of Hans Stark {14},
Auschwitz Commandant Rudolph Ho"ss {15}, and former inmate
Marie-Claude Vaillant-Couturier {16}, it would take around one
half hour to complete the gassing process and begin ventilation of
the chamber.
Based on this testimony, it would seem reasonable that very
little prussian blue would accrete on the walls of homicidal gas
chambers, given the very slow rate of formation and the very short
gassing times at Auschwitz. Thirty minutes is not enough to time
to produce much [Fe(CN)6]-4, as this reaction takes many hours.
Pressac, cited in the above URL, has this to write:
(same source as above)The contact time for the hydrocyanic acid with
the walls of the homicidal gas chambers never exceeded about
ten minutes per day at a temperature below 30 degrees Celsius.
However, the co-authors (Harmon and Stein) do not seem entirely sure (hence my bold emphasis). It would seem that on its own, due to the time periods allocated the Prussian Blue effect would ebb; hosing down probably contributed greatly.
Indeed, with the destruction of all the Kremas, save one, it is posited that rain has in all probability eroded the physical blue evidence even further. A bit too technical for me, but this is what is written (same source):
It is unfortunate that the two co-authors chose only to analyse the lack of Prussian Blue in the homicidal gas chambers from the perspective of time (ie. the 20 mins) only and not on any other factors such as the hosing down of the corpses as Mr Thompson pointed. The only reference to such matters apears in the conclusion wherein it is stated:Would rain be of the correct pH to dissolve prussian blue? Based
upon a study of acid rain {22} in Northern Europe, the pH of
rainfall steadily drops from about 5.8 to 5.0 over a twenty year
period (1955 - 1975). An average pH level for the past fifty years
could then be very roughly estimated at 5.4 units. Given that
prussian blue begins to dissolve at a pH of 4.0, and that any
prussian blue on Krema II, III, IV, V has been exposed to this rain
for almost fifty years, it is surprising that any such traces remain
at all.
A more wholistic round-up of this theme would have been very much appreciated since the writing style in this particular document is easier to understand than Pressac's.Prussian blue is a sparingly soluble salt with the chemical
formula Fe4[Fe(CN6)]3. It forms rather slowly, and is quite
insoluble at acidic pH. It will dissolve readily at pH of 6.0 or
above. Other components formed during prussian blue formation
would be soluble and be washed away almost if not completely in a
short time.