[Alt-photo] Antwort: Re: DAS

udo.schnitzbauer at access.uzh.ch udo.schnitzbauer at access.uzh.ch
Mon Apr 11 10:50:23 UTC 2016


DAS is a organic azide. 
Please look at "Safety and Regulations" at
http://www.tcichemicals.com/eshop/en/us/commodity/D1606/#tabPanel02
plus this MSDS: https://www.spectrumchemical.com/MSDS/TCI-D1606.pdf

Additional reading: http://www.ehs.ucsb.edu/files/docs/ls/factsheets/Azides_FS26.pdf
and important from the article 
http://onlinelibrary.wiley.com/doi/10.1002/1521-3773(20010601)40:11%3C2004::AID-ANIE2004%3E3.0.CO;2-5/abstract
which is mentioned in above PDF:
[...][77] ªAzidophobiaº seems to be largely based on the fact that a number of
metallic azides are shock sensitive. However, certain organic azides,
especially small ones, are also explosive. The following points are
noteworthy. Sodium azide is relatively safe, especially in aqueous
solution, unless acidified to form HN3 , which is volatile and highly
toxic. For organic azides, the ªrule of sixº is very useful: six carbons (or
other atoms of about the same size) per energetic functional group
(azide, diazo, nitro, etc.) provides sufficient dilution to render the
compound relatively safe. Note that the presence of acetylenic groups
or other energy producers with an azide makes for increased hazard.
Decomposition of organic azides can be catalyzed by certain transition
metal species (especially those from the Fe and Co triads) and by
strong acids (that is, the same catalysts that are most effective for
decomposition of organic peroxides). Azide groups attached directly
to olefinic, aromatic, or carbonyl moieties are much less stable and,
other things being equal, more dangerous than aliphatic azides (the
approximate activation energies for unimolecular loss of N2 being 29
and 49 kcalmolÿ1, respectively). For these reasons, azides should not
be distilled or treated in a careless fashion. However, when common
sense is employed, they can be prepared, stored, and used without risk
in the standard organic chemistry laboratory: We have never
experienced a safety problem with these materials. See: M. Peer,
Spec. Chem. 1998, 18, 256 ± 263.
[...]

In case of DAS you have two Azide-Groups attached directly to a aromatic Moiety and 
between that two, there is a double bond which is not so stable like a single bond, but more stable as a triple bond.

The equation which is mentioned means "(Number of Carbons + Number of Oxygens) / N of Nitrogens"
Source: https://web.stanford.edu/dept/EHS/prod/researchlab/lab/safety_sheets/08-203.pdf

If you are allowed to include all Oxygen-Atoms (even the water, because it´s a hydrate) then you get a ratio of 4
If you only count the oxygen atoms of the two sulfo-groups then the ratio will be 3.333 and if you a not allowed to count the oxygen, then the ratio will be 2.333.
I do not know if you can count the oxygen atoms...but I think if there is the possibility that the compound get dry, than you should be really careful. 

If somebody wants make a test: Put a FEW grains at a aluminum foil. Remove your supply container and then with a lighter heat slowly the foil and look what the compound will do. If you get a popping sound or a flash than you know that this substance should stay moist....

Greetings

Bj68






-----"Alt-photo-process-list" <alt-photo-process-list-bounces at lists.altphotolist.org> schrieb: -----
An: alt-photo-process-list at lists.altphotolist.org
Von: rowan Bloemhof via Alt-photo-process-list	
Gesendet von: "Alt-photo-process-list" 
Datum: 11.04.2016 11:57
Kopie: rowan Bloemhof <bloemhofster at gmail.com>
Betreff: Re: [Alt-photo] DAS

Kees, Perhaps a tad offtopic. But I've been looking into acquiring DAS for
some time now, even more so with the news of a ban on dichromates. Do you
by chance know of any sources that deliver in the Netherlands? I've read
about the group purchase thing on APUG I believe, but that seemed to have
been a one time thing.

Rowan

2016-04-10 22:10 GMT+02:00 Kees Brandenburg via Alt-photo-process-list <
alt-photo-process-list at lists.altphotolist.org>:

> DAS is Disodium 4,4'-Diazidostilbene-2,2'-disulfonate Tetrahydrate, CAS
> Number:2718-90-3. It was the light sensitive component in the Ultrastable
> carbon tissues. It is non toxic or at least toxicity has never been
> perceived (or researched). It has no dark effect which makes it possible to
> presenstitize!
>
> I have bought my first bacht here in the Netherlands in 2010, purchased
> also some with the group batch and imported a kilo from China. I keep my
> stock in the freezer, some in the fridge and keep a lighttight container
> with ~100gr powder at hand at room temperature. I also keep a 500ml brown
> glass bottle with a 3% slotion at room temperature for immediate use. I
> never had anything going bad or changing color or showing strange behaviour
> etc.
> From Charles Bergger and other sources I know that when kept cool DAS will
> last for years.
>
> I am mainly using it for carbon and casein. It does not work with gum.
>
> Kees
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