Realgar & Orpiment

My old pal Bob Winokur has been doing some pyro-sleuthing and came up with a small stash of two pyro chemicals which are largely unobtanium now: Realgar and Orpiment, both arsenic compounds.

He was able to supply us with a little of each. You can order it below.

This has been an interesting process. Both of these chemicals are naturally occurring minerals. They are often found together, as you can see in the photo below:

Orpiment and Realgar (from Peru)

The reddish crystals are realgar, and the yellow stuff is orpiment. They occur together and are very close to the same chemistry.

The powder we have was produced by first harvesting crystals of both chemicals and then grinding them into very fine powder. Suffice it to say, the whole process is mostly manual, expensive, and time consuming, and not much of it is available. To my knowledge, neither of these chemicals is produced synthetically in the US, if anywhere.

Realgar was most commonly used to produce white flames in fireworks before powdered metals such as aluminum, magnesium, and titanium became widely available. It was also used with potassium chlorate to make impact explosives. I have heard of crackling stars being made with it as well.

I do not suggest that you come to rely on either realgar or orpiment for any formulas that you want to make on a regular basis. They are both poisonous, of course, and I don’t know if we can or will continue to stock either chemical. Best to consider both of these as exotic pyro antiques, more a curiosity than a practical ingredient.

CAUTION: Both realgar and orpiment are sulfur compounds and will explode when mixed with chlorates. They are both arsenic compounds and highly poisonous. The resulting ash from burned pyro compositions is likely to contain water soluble arsenic oxide, which is considerably more toxic than either of the sulfides.

In addition to the information listed with each chemical on, here is some historical info Dr. Winokur worked up on these two very old pyro chemicals.

You should treat the units of measure given in the tables below as parts by weight, unless otherwise noted. They do not necessarily add up to 100 in each column.

Some formulations found in the pyrotechnic literature of interest both pyrotechnically and historically that utilize orpiment (arsenic trisulfide (As2S3) - (May 2010)

By R. M. Winokur

Note that in some formulations realgar and orpiment are listed as equivalent alternatives. The number of formulations using realgar well out number those stipulating orpiment, however it sees likely that with a little adjusting, orpiment can be made to substitute for realgar in many instances. Only those formulations specifically mentioning orpiment have been listed below, although in many instances the historical authors note that realgar may be substituted for orpiment.

"Flower pot" (fountains and gerbs exhibiting spur-fire)

Lancaster (2006) ----------Kentish (1905)---------
Component 1 2 3 4 5 6 7
Potassium nitrate 54 32 16 10 32 11 20 15
Sulfur 24 14 5 16 6 9 7
Red orpiment 8 Realgar or
sulphuret of
2 1 1 2 1 1 1
Meal powder 8 3 17 4 5 4
Gas black (lampblack) 4 Vegetable black 7 2 3 4 2 4 3
Charcoal (150 mesh) 2 Charcoal 4 1 1 1

Bengal Lights

Kentish Bloxam(1913)*
Potassium nitrate 54 14
Sulfur 6 3-5
Antimony sulfide 20
Arsenic sulfide (either
realgar or orpiment)
2 1 (orpiment)
Red lead 1


Kentish (1905)
Potassium nitrate 2 3
Sulfur 2 3
Meal powder 26 35
Vegetable black
1 2
Orpiment (or realgar) 2 3

Chemistry Inorganic and Organic, 10th edition, rewritten and revised by authors G. Bloxan and S. Judd Lewis, P. Blakiston’s Son and Co., Publishers, Philadelphia

Lance and stars

Kentish (1905) lists realgar or "sulphuret of arsenic" in yellow, green and crimson stars and lances with potassium chlorate. Because of the associated hazards of mixing arsenic sulfides and potassium chlorate, these formulations cannot be recommended. Kentish also lists four white or bright stars containing arsenic sulfide as follows:

White or bright stars and lances (Kentish)

Meal powder 1 1
Potassium nitrate 5 6 24 34
Sulfur 2 2 5 7
Sulphuret of arsenic,
1 1 3 5
Antimony trisulfide 5 6
Red lead (Pb3O4) 2

"Fire white that one can scarcely look at them without being dazzled" *

Potassium nitrate 3 lbs.
Sulfur 1 lb.
Orpiment 1/4 lb. (4 oz.)
Gum Arabic 1/2 lb. (8 oz.)
Coarsely ground glass (crystals, not powder) 1/2 lb. (8 oz.)
Moisten with brandy

*Hanzlet Lorrain (Jean Appier) 1630 "La Pyrotechnie" See page 55 in Davis (1943).

Bright incendiary powder*

Cannon powder*

Gingko biloba 1 lb.
Bamboo charcoal 3 oz.
Rosin 1 lb.
Sulfur 2 lbs. 6 oz.
Orpiment 3 oz. 1 oz.
Male arsenic (realgar) 3 oz. 0.5 oz.
Saltpeter (potassium nitrate) 7 lbs. 10 oz.

*From an early Chinese document called the "Wu Pei Chih" by Mao Yuan-I, written about 1621. As cited by T. L. Davis and J.R. Ware 1947: Early Chinese military pyrotechnics American Journal of Chemical education Vol. XXIV p. 522

Orpiment has been used in smoke compositions with potassium nitrate, sulfur and sometimes a little meal powder or charcoal. Both white and yellow smoke can be produced with realgar and probably also orpiment.

Yellow smoke
Attilio Izzo "Pirotecnia E Fouchi Artificiciali" 1950

Component A B C D
Potassium nitrate 27 56 33.3 20
Sulfur 27 27 33.3 20
Orpiment 27 7 33.3 20
Antimony sulfide 19 19 20
Meal powder 20

Explosive powder? (Dangerously sensitive)

Apparently utilized by pyrotechnists in India with frequent disastrous results. No specific formulations found but brief mentions of mixtures with potassium chlorate are mentioned in several sources.

Ellern (1968) stated:

"White stars are usually made with potassium nitrate, sulfur, gunpowder and antimony, but red orpiment can also be used and has the advantage of good ignition under the most difficult circumstances."

An interesting reference although it has only a little on pyrotechny

Orpiment and realgar in Chinese technology and tradition, E.H. Schafer - Journal of the American Oriental Society, 1955 -

From Faber (1919)

"At the present time, arsenic disulphide is only used in smoke-tracer composition for rockets, in which it is combined with potassium nitrate and sulphur. We find that certain manufacturers use a composition containing saltpeter 18 parts, sulphur 15 parts, disulphide of arsenic 12 parts, while others use a mixture of 32 parts of saltpeter, 22 parts of sulphur and 32 parts of disulphide of arsenic. In these compositions, it may be assumed that the saltpeter and sulphur react liberating sufficient heat to volatilize the disulphide of arsenic, which passes out from the openings in the containers in a gaseous form, condensing immediately upon contact with the cold air, to a cloud of dense yellow smoke. It owes its efficacy to the fact that it is sufficiently stable to withstand the temperature without decomposition, until volatilized."

Presumably similar and roughly equivalent phenomena would occur if one were to substitute orpiment for realgar. In many instances formulations listing realgar provide that orpiment may be substituted.

It is clear however that potassium chlorate with either realgar or orpiment is a dangerous combination and should be avoided. Formulations dating from the 1800’s for white fire in stars and in lances sometimes included potassium chlorate and orpiment (although either the realgar or the orpiment was usually only a small percent). Nevertheless such mixtures are liable to ignite in ordinary handling, and the pyrotechnic literature mentions that orpiment and potassium chlorate have been used in India where it resulted in many uncounted disasters in rural fireworks factories.

If one substitutes orpiment for realgar in Black Powder type mixtures, one should carefully note the production of ash and burning rate and it might be desirable to add or subtract meal powder or oxidizers. It is generally believed that the addition of orpiment to a star or lance increases its ignitability and probably also increases its burn rate. Orpiment can be seen as a sulfur substitute, but it is more reactive than sulfur.

Also keep in mind that the combustion products of any mixture containing either realgar or orpiment will contain the water soluble arsenic oxide which is considerably more toxic than either of the sulfides.

It found use in early signal fires used at sea where it was sometimes labeled as "Bengal Fire" or Bengal Lights." Classical Bengal fire features antimony sulfide instead of arsenic sulfides. The term "Bengal fire" however have also been more recently used for any flare used for signaling or illumination, and many modern "Bengal Light" formulations contain color flame mixtures containing strontium or barium salts and potassium chlorate or perchlorate, but not orpiment or realgar.

Orpiment has been used in smoke compositions with potassium nitrate, sulfur and sometimes a little meal powder or charcoal. Both white and yellow smoke can be produced with realgar and probably also orpiment.
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