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Author: Subject: Diving Into the World of Fulminates
Rosco Bodine
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[*] posted on 23-4-2010 at 15:54
method for taming silver fulminate?


I have an idea for a possible way of making silver fulminate in a less sensitive form, and a proposed experiment.

A smaller particle size will generally result in less sensitivity, and greater safety in handling .....and it would seem likely that this generality would apply to silver fulminate. Also
it can accomplish a further desensitizing for particles to be coated with a less sensitive or inert material, and this may also be applicable to silver fulminate.

Recrystallization of mercury fulminate can be done from boiling water and this may also be possible for silver fulminate, either from boiling or near boiling hot water.
There is an enormous reduction in solubility with decreasing temperature, so it would seem likely that a very fine particle size of silver fulminate could be obtained by rapidly streaming
a very hot solution containing about two and one half grams per liter of silver fulminate into a rapidly stirred larger quantity of ice water, perhaps with crushed ice then added
to rapidly precipitate the silver fulminate as very small particles. Then a solution of sodium or ammonium dichromate
is added to the stirred suspension of microcrystalline silver fulminate, which should result in each silver fulminate particle
becoming coated, sealed and encased in a microscopically thin layer of adherent and low solubility, and relatively inert silver dichromate. The chromated silver fulminate anticipated to result should be a brilliant red colored material.

The supernatant solution could be decanted and the material rinsed with distilled water onto the filter.





[Edited on 23-4-2010 by Rosco Bodine]
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hissingnoise
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[*] posted on 24-4-2010 at 02:37


Silver fulminate is much less soluble than MF.
What's wrong with MF?



[Edited on 24-4-2010 by hissingnoise]
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Rosco Bodine
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[*] posted on 24-4-2010 at 04:38


I'll try to again find the reference, but I think a solubility of about 2.7% is what is found for silver fulminate in boiling water, decreasing to something like twenty milligrams per liter or similar tiny amount in the cold and for the chromate of silver even lower solubility still.

edit: I just checked one reference. Federoff is showing solubility 2.5 grams per liter H2O at 100C and .075 grams per liter at 13C.

There is a disadvantage about mercury fulminate because it requires a substantial amount of it on the order of a quarter gram, where is its critical mass to detonate high order, therefore it is not as useful as an accellerant in synergistic mixture with another material like lead styphnate in the same way
as would be for example lead azide. Silver fulminate is easily made and would have greater usefulness if not for its extreme senstivity. And that sensitivity
may not be an insurmountable problem, if it is indeed a problem of crystal size as has been the factor noted to be probable in the literature. A similar sensitivity
issue can arise for other primary explosives and process modifications can be made to produce a material having improved handling safety.

[Edited on 24-4-2010 by Rosco Bodine]
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[*] posted on 24-4-2010 at 06:42


Quote: Originally posted by Rosco Bodine  
I have an idea for a possible way of making silver fulminate in a less sensitive form, and a proposed experiment.
I can't say I'm very familiar with sol-gel reactions, but they seem to be the ordinary way that folks make micron-scale particles these days. I mention this because these techniques give rather good consistency in particle sizes. The problem I foresee with a mechanical precipitation is too much variation in particle size. In the case of silver fulminate, one large particle is enough to ruin your day.

Having said that, I'd suggest using a micro-orifice and a high enough output velocity to generate plenty of shear force in the liquid, but not enough to cause cavitation. Lots of shear force should drop your particle size down appreciably. Injecting into a stream of cooling water moving transverse to the direction of injection would further prevent fluid hot spots from forming.
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Rosco Bodine
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[*] posted on 24-4-2010 at 07:38


Actually this is not a colloid about which I am thinking, even though there are references to small particulate silver fulminate and lead azide and other materials as "colloidal" or amorphous in form ....in reality the particles are definitely microcrystalline and are grown crystals in a specifically small size range rather than being a dispersion from some sort of wet milling operation. The technique which I am contemplating is a crash precipitation / crystallization of a near saturated hot solution, by rapid cooling.......a sort of wet method for doing the same thing as a flash evaporation of a hot liquid being sprayed as an atomized mist into a vacuum.....which can produce even smaller crystals. Adding a soluble starch like dextrin can inhibit crystal growth and keep the crystals small. The chromating step which I was contemplating should stop the redissolving and crystal growth of the silver fulminate crystals and thereby stabilize the material.
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[*] posted on 24-4-2010 at 08:03


Quote: Originally posted by Rosco Bodine  
in reality the particles are definitely microcrystalline and are grown crystals in a specifically small size range rather than being a dispersion from some sort of wet milling operation.
The end-product you're suggesting seems like quite a good idea. Your post on this had three interrelated items: 1) small crystal sizes, 2) chemically inert coating for them, and 3) a means of making them. I wasn't adequately clear, but I'm suggesting sol-gel as an alternate only for number 3. You'd use a hot sol, as before, and then some kind of flash gellation, not that I know how to do that, but there seem to be some awfully rapid phase transitions available. The key would seem to be to have the gellation not involve the fulminate directly, but rather to trap the fulminate in the gel matrix while it's still in solution. Then when the gel cools off, you get your fine particles. So there are three phase regimes (temperature-determined, presumably): a) sol with fulminate in solution, b) gel with fulminate in solution, c) gel with fulminate microcrystals. Since you've already suggested dextrin, it's certainly possible that there's some appropriate polysaccharide to use for the gel matrix; the food industry has certainly done a lot of engineering work on this class of chemicals.

The advantage, particularly for the amateur, if this can be made to work, is that there's no mechanical devices to get just right or that need tuning. It's just heating, mixing, and cooling.
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Rosco Bodine
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[*] posted on 24-4-2010 at 08:39


What may work is simply to pour the boiling near saturated solution of silver fulminate over crushed ice, in a quantity that all of the ice will be melted and the resulting mixture will be at perhaps 5 or 10C, and then the mixture is stirred up and an ice cold solution of a dichromate is added in a lump, with everything kept in suspension for a few minutes to complete the reaction.
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[*] posted on 24-4-2010 at 09:48


Quote: Originally posted by Rosco Bodine  
What may work is simply to pour the boiling near saturated solution of silver fulminate over crushed ice [...]
That sounds more reliable as far as mechanical means go, as 1) you've got the latent heat of melting ice providing a larger heat reservoir and 2) less concern about adequate liquid/liquid mixing. It seems that you could modify an ice cream churn with a dropping funnel for the process.
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Rosco Bodine
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[*] posted on 24-4-2010 at 10:09


Even if it worked it would still be something of an academic curiosity, or an
improvisational alternative. Still it is intriguing if there could be such a way of desensitizing silver fulminate, since it has been for so long a material known for sensitivity and unpredictability....it is something of an intellectual challenge to
formulate any solution for those issues.
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[*] posted on 24-4-2010 at 15:04


There was a patent mixing of Ag & Hg in a fulminate synthesis. If I remember correctly the purpose was to "concentrate" the weight of mercury fulminate needed for a given cap size. TTBoMK it was not used commercially.
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Rosco Bodine
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[*] posted on 24-4-2010 at 15:41


Yeah, earlier in the thread I speculated about the possible existence of a double fulminate of mercury and silver before finding references that it is indeed known.
And it would make sense that the silver fulminate content would act as an accellerator for the mercury fulminate. I am not inclined to favor a mercury containing compound where alternatives may serve as well or better. It is a matter of curiosity to me if organic fulminates may be possible or complexed metal fulminates, and what efforts may have been made to produce obscure fulminates
via the sodium nitromethane intermediate.
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[*] posted on 25-4-2010 at 02:50


Are you accually going to try this desensitizing method? Solving 'intellectual challenges' for the sake of 'academic curiosity' has little meaning without experimentation.
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Rosco Bodine
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[*] posted on 25-4-2010 at 06:18


Honestly I do not know for certain if I will ever actually perform this experiment or not. My attention and time seems to be constantly diverted and required by other matters than enjoying experimentation which I would like to be doing.

Certainly it was not my intention to cause annoyance by sharing thoughts on this or any other proposed experiment. I read about and post concerning many more experiments than I actually have the time to do or may not even be inclined to do. I often share my thoughts with others who may have a particular interest and who are actively or periodically experimenting with a particular type of compound. An untested idea may have no substance in the present sense but may have value as a kind of proposal for where things may logically be going next in further experiments which may be worthwhile doing later.

I have a huge backlog of experiments to do, but that should not be a reason to keep secret or keep silent about something like this which may be pertinent to a particular line of research where others are already looking.

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[*] posted on 25-4-2010 at 11:59


Quote:
My attention and time seems to be constantly diverted and required by other matters than enjoying experimentation which I would like to be doing.

What we have here is a clear case of Da Vinci Syndrome. . .



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[*] posted on 25-4-2010 at 12:16


Quote: Originally posted by hissingnoise  
Quote:
My attention and time seems to be constantly diverted and required by other matters than enjoying experimentation which I would like to be doing.

What we have here is a clear case of Da Vinci Syndrome. . .




So it has a name? :-) I thought I was the only one.

Work, the curse of the leisure class.
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Rosco Bodine
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[*] posted on 25-4-2010 at 17:23


I believed it better that rather than to keep silent,
that I should share whatever I can while I still can,
but if you wish it to be otherwise......
then I apologize for the imposition

http://www.youtube.com/watch?v=k0J7Zx-F1uA&fmt=18 Deep Peace
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[*] posted on 26-4-2010 at 05:29


For the man who shared clathrates with the majority of energetic materials hobbyists and related issues, silence would be a terrible waste of a vast pool of knowledge.
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hissingnoise
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[*] posted on 26-4-2010 at 05:40


Seconded. . .
We're all ears - I mean eyes!




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[*] posted on 29-4-2010 at 12:41


I've always heard that the less common fulminates were prepared via metathesis with the mercury salt, but I just stumbled across this http://books.google.com/books?id=J55D3HcgPuoC&pg=PA119&a...

Doesn't sound like something I'd want to try though.
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[*] posted on 29-4-2010 at 15:19
copper fulminates


Be wary of anything written in that book, it also claims NH4ClO3 is stable.

Early chemists have tried to make copper fulminate from the same way as with Hg, Ag, and failed. I had, but lost a reference where this was mentioned and other metals were tried as well but also didn't work.

Note how there are zero references above. Note also how there are no descriptive details at all about the compound.

Cupric fulminate doesn't even exist as far as the literature is concerned. It's not listed in Federoff, Gmelin, etc. Cuprous fulminate is known but it is easily oxidized, and has to be made e.g. from Hg(II) fulminate and copper. Then there are also complexes of copper fulminate.

That procedure is a phony.
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[*] posted on 25-5-2010 at 13:38


I have been playing with Silver Fulminate a bit lately and thought I'd post my process and results.
-1.1g silver
-9mL 85% HNO3
-9mL H2O
Unless I messed up somewhere this should give me nitric acid of a little over 50% concentration (wt%).
In place of pure ethanol I used 9mL of my 90% pure homemade ethanol, and 3mL of hardware acetone.
Process:
I first dissolved the silver in the HNO3 using a hot water bath to help. I used a 600mL beaker and a small pot that the beaker sat in sidways with the top sticking out/laying against the top of the pot. I filled the pot with boiling water from a kettle. After silver was dissolved I let it cool to room temperature. Some silver nitrate precipitated so I added water dropwise with swirling till all was dissolved. I prepared a cold water bath right beside my hot water bath. I next heated the silver nitrate-nitric acid solution back up to around 50C, then added the ethanol-acetone (12mL). The reaction didn' t start, so after adding fresh boiling water to my hot water bath, heated the reaction beaker up to 60C or so and kept it there until after a few minutes the reaction started. This is where it gets tricky, once the reaction starts the temperature can jump very quickly, and there is not far to go before the reaction is ruined. I have found that much over 80C and the product is seriuosly degraded, and up to 90C or more it is ruined. If you keep a close eye on the thermometer and when the temperature starts to rise on its own get ready with the cold water bath and swirling to prevent hot spots, overheating, and over 80C decomp. Through the course of the first few minutes the water bath will be needed less and less till the temperature starts to drop slowly on its own as the reaction slows. It took about 15 minutes for the reaction to come to completion, just letting it cool naturally on its own to room temperature. Rinse with water the same as with mercury fulminate to get ride of acid and contaminants. I did four or five small rinses, but some books say to do 10-12. It is very insoluble in cold water, so it wouldn't hurt to do more probably. The first few if done properly, are the most important obviously.
I blotted out most of the moisture with paper towel, then put the filter paper and SF on a small plate, and put the plate over a bowl filled with hot water from the tap(72C). I had 0.53g of dry SF in 30min. I felt perfectly safe doing this as it was a very gentle heat, and much below the lowest explosion temp I have seen(in book) of 130C for dry SF.
I keep getting about 0.5g from a gram of silver, which seems to be about half what I should be getting from what I can read. It is nice stuff though:).
I find the stuff to be powerful and sensitive, but I feel much of its bad reputation comes from people confusing fulminating silver for fulminate of silver(Silver fulminate).

[Edited on 25-5-2010 by Hennig Brand]
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[*] posted on 25-5-2010 at 14:04


Oh, I woudn't feel too safe with 5 grams of SF around, which is plenty enough to vaporize some fingers. More crystals=more friction=more chances for an accident to take place.
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[*] posted on 25-5-2010 at 14:58


Oh shit I meant 0.53 grams, sorry about that. Yes the half gram kind of makes me pay attention actually:)
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[*] posted on 25-5-2010 at 15:48
beware of fulminate itch


Contact dermatitis from silver fulminate - fulminate itch
IAN R. WHITE AND R. J. G. RYCROFT
Department of Occupational Dermatology, St. John's Hospital for Diseases of the Skin.
Contact Dermatitis 1982; 8: 159-163

Although fulminates were widely used in the past as explosives, they are now little
encountered. Fulminate itch is of historical interest. We have investigated a factory
utilizing silver fulminate in the manufacture of explosive snaps. Workers in this factory
still experience the 'itch', which we consider to have both an irritant and an allergic
basis.

Few industries have a unique location, but we have investigated a skin problem in a
factory manufacturing silver fulminate and there is no similar installation in the Western
World. The related compound mercury fulminate has, however, been manufactured in
many places and in large quantities at various times because of its use as a detonator
in percussion caps. The only commercial use of silver fulminate is producing the
explosive 'snaps', to be found, for example, in Christmas crackers.

Mercury fulminate is well known to cause a dermatitis which has been termed 'fulminate
itch'. Little investigation has been made concerning the mechanism of this problem. A
similar itch has been found to occur amongst workers engaged in producing 'snaps'
from silver fulminate.

The Factory

Silver fulminate is produced by the reaction of ethanol with silver nitrate in the presence
of nitric acid. comes down as a flocculent precipitate which is filtered off and washed to
remove the excess acid.

The fulminate is mixed with a water soluble adhesive to form a creamy paste which is
then hand painted onto one end of strips of manilla cardboard, (Fig. la). This process is
called 'lining'. The painted strips are air dried in trays and then taken into a room where
they are individually fed by hand into machines which semi automatically tape them to
similar strips which have one end coated with sand (Fig. I b). This procedure is termed
'bonding' and it produces the final snap. Pulling the two ends of the snap causes friction
between the fulminate and sand with a consequent explosion (Fig. I c).

The Problem

The majority of employees in the factory Silver fulminate is produced by the reaction are
female and most (about 50) work at the 'bonding' process which takes place in a well
ventilated room, but as some five million snaps are produced each week, one would
expect that some fulminate dust would be found on machinery and in the air. Over many
years the factory management have noticed that most of the employees who have been
troubled by skin irritation have worked in the bonding room. New employees are warned
that they may develop a dermatitis; a proportion do and a number of them subsequently
leave. A core of relatively 'resistant' workers remains. The only two males employed in
the manufacturing process actually make the silver fulminate, and in the past one of
these had had a number of small painful ulcers on his hands which had been difficult to
heal, but since has had no eruption of any kind.

The Patients

10 females who had been working with silver fulminate for varying periods of time were
examined, and of these 7 said that they had had rashes whilst employed. The 10
subjects were patch tested with 1% silver fulminate in pet. and also with 1% aqueous
silver nitrate and 1% ammoniated mercury in pet. In addition control patients in our clinic
were tested with the same preparation of fulminate. The histories of the 7 people who
had problems are as follows. No patient gave a history of atopy or previous allergy
except where indicated.

Patient no.1 had been in the bonding room for two weeks when she developed a rash
in the nasolabial folds, an itchy nose, running eyes and a burning sensation of the
eyelids. Her hands and wrists were also affected and she had blisters in the mouth.

The eruption settled whilst away from work but within two days of return she had
developed erythema and esiculation around the mouth, under the chin, on the back of
the neck and on the hands. She also had a nose bleed.

Patient no. 2. had worked in the factory for 40 years and on examination was foundto
have the greyish pigmentation of argyria in the conjunctivae, pertoral area and on her
fingers. She remembered developing an itchy red rash on her face shortly after
starting employment but she continued at her work and the rash settled. She had had
flexural eczema as a child.

Patient no. 3 developed a papulovesicular eruption on her face and arms three
weeks after working in the bonding room. The rash settled after three weeks away from
work, but despite returning to the same job she has had no further problems in the last
two years.

Patient no. 4 noticed red, itchy spots on her forearms six months after starting work as
a bonder, they cleared several weeks later despite continuation of her work. She has
had no problems during the subsequent two years.

Patient no. 5 had a transient rash on her face when she first started lining and
frequently had an itchy red rash on her forearms in the ensuing three years. She did not
develop any problem whilst in the bonding room for six months.

Patient no. 6; during nine months employment as a bonder, she had frequently
experienced irritation and redness on her face, neck, arms and hands. At no time had
there been any vesiculation and examination showed only lichenification in the dorsum
of her hands. She suffers from hay fever.

Patient no. 7, who had been employed for nine months developed pert
orbital oedema after three weeks of bonding but no rash elsewhere. A similar but more
severe episode occurred six months later. She noted that her eyes were frequently red
and itchy, with the problem starting early during the working week and settling over the
weekend.

Results

The results of patch testing at 2 days with 1% silver fulminate in pet. are shown in Table
1. No reactions were seen to silver nitrate or ammoniated mercury. 'Altest' strips (Imeco,
Sweden) were used on the factory patients and 'Finn chambers' (Epitest, Finland) on
the controls. The results show that patient no. 1 had a marked reaction to silver
fulminate which was of a quite different order to the irritant reactions produced in her
colleagues who had had a history of a rash and another colleague who did not have this
history.

At 2 days an irritant response of varying degrees was found in 12 of the 34 control
patients; this had completely faded in all but 5 patients after 4 days.

Discussion

Mercury fulminate was discovered by Ed ward Howard (1774 1816) and since 1814 has
been used by the military as a detonator in percussion caps. In 1842 Henry Hennell
destroyed both himself and part of the Apothecary's Hall in London whilst working with 6
lb of mercury fulminate intended for use in the 1st Afghan war.

Leibig analysed the elemental composition of silver cyanate and silver fulminate in
1823. He found that although the two compounds had the identical formula AgCNO they
had quite different chemical and physical properties. Three isomers with the general
formula HCNO are known.

isocyanic acid HN = C = 0
cyanic acid HO—C = N
fulminic acid HO—N = C

Of these cyanic acid and isocyanic acid are tautomers but fulminic acid is a simple
isomer with no tendency to equilibrate with the other two substances.

Although mercury fulminate explodes violently on percussion, silver fulminate is more
inert to such treatment but it is very sensitive to friction, when it will explode with greater
force than its mercury counterpart. Both compounds can be handled safely when they
are damp. It is be cause of the characteristics of silver fulminate that the only
commercial application of the compound is in the manufacture of 'snaps'. Most of the
dermatological literature concerning fulminate relates to the cutaneous reactions
amongst those handling mercury fulminate in munitions factories during the two World
Wars when 'fulminate itch' was a well recognised problem. It is considered that the two
fulminates induce similar skin eruptions.

Although the 'itch' was frequently encountered in the munitions factories, there was
great individual susceptibility to the problem such that the majority of individuals were
slightly affected and only a few badly so (1). The condition tended to be worse in warm
weather and the exposed parts of the body were the areas normally involved. The
published accounts all describe similar clinical appearances of the 'itch' (2
4). In the mildest cases there might be erythema on the anterior surface of the forearms
and dorsa of the hands. More severely affected individuals might have facial erythema
especially around the nose, mouth and chin but also on the neck and behind the ears,
and pert orbital oedema was frequent amongst these individuals. In extreme cases,
vesicles, bullae and pustules could be found at all the above sites. The dermatitis was
considered to be particularly bad after 5 to 6 days of continuous exposure to fulminate.
Dermatitis could be produced on covered areas of the body as dry fulminate permeated
workers clothing. Folliculitis was occasionally reported as occurring on hairy limbs.

A conjunctivitis was often found to be an early complaint amongst susceptible individ
uals and nasal irritation was also common (5). Perforation of the nasal septum similar to
that caused by chrome has also been described.

Great care was needed when fulminate was being used by individuals who already had
a cut or abrasion on their hands as small necrotic ulcers were prone to develop (6).
These 'powder holes' could take several weeks to heal and might even progress to
penetrate joints and bone.

Silver fulminate was known in the trade as “white salt.” It was reported to induce a
stomatitis easily in females soon after they started work using the compound (2). Al
though relapses were said to be rare, a few individuals showed great sensitivity to this
salt.

In none of the quoted accounts was patch testing performed, although the words 'ir
ritant' and 'sensitization' can frequently be found. Although we were able to examine
only one patient with an active dermatitis, it can be seen from the characteristics of this
eruption and from the accounts of her colleagues who had been affected in the past,
that the present problem is similar to the historical descriptions. In view of this and the
results of our patch tests, we consider that it is the fulminate moiety of the compounds
which is responsible for the cutaneous complaints.

Our prime patient under investigation developed an exudative dermatitis of her arms
and face two weeks after starting her job, and on recovery developed a vesicular
eczema in the same area after only two days of re-exposure. The story suggests that
she became rapidly sensitised to fulminate which was confirmed by the positive patch
test reaction to silver fulminate.

We believe that fulminate is able to induce both an irritant and an allergic contact
dermatitis. That some workers develop a rash which becomes less of a problem as they
continue to work, suggests a process of 'hardening' against allergic or irritant factors.

References

1. Hunter D. The Diseases of Occupations, 5th Ed. London: English University Press,
1975:312 315.
2. Prosser White R. The Dermatergoses or Occupational Affections of the Skin, 3rd Ed.
London: H. K. Lewis, 1928: 125:186-190.
3. Schwartz L. Dermatitis from explosives. Journal of the American Medical Association
1944: 125:186 190.
4. Schwartz L, Tulipan L, Birmingham D J.Occupational Diseases of the Skin, 5th Ed.
London: Henrv Kimpton, 1957: 446.
5. Swanson C. Effects on the skin of irritant explosives. Proceedings of the Royal
Society of Medicine 1943: 36: 633 638.
MacLeod J M H. Necrosis of the skin from handling 'composition' (an explosive). British
Journal of Dermatology 1916: 28: 135.

Fig. 1. A manila strip with one end coated with fulminate: (a) is taped to a similar strip
tipped with sand (b). Pulling the two ends apart causes friction on the fulminate and an
explosion ensues (c).
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[*] posted on 25-5-2010 at 16:05


Interesting, I particulary like the description of how the Christmas crackers are made.
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