Black Powder - VI: Serpentine Powder

In our last few posts, we looked at how grain sizes of black powder are/were classified in the US and in 19th century England. In today's post, we will look at an early form of black powder, that was called "serpentine powder".

In the earliest days of firearms, the three ingredients of gunpowder, namely saltpeter, charcoal and sulfur were combined together in a dry state. This powder was often referred to as "serpentine" powder. Why the name "serpentine"? Well, there were some early forms of cannon called the "Cannon serpentine" and "Serpentine". The table below shows some details:

Types of Cannon in England during the 16th-17th century. Public domain image. 

Note that serpentine cannon date back to a few hundred years before this list was made.

Some authorities say that "serpentine" artillery tended to be long and thin, resembling a snake, which is why they were named that way. Other authorities claim that "serpentine" is an allusion to the serpent in the Garden of Eden, who was Satan in disguise, and cannon were considered to be the work of the devil in the middle ages.

Also, in early matchlock weapons, the serpentine was an S-shaped lever that held the burning match. When the user pulled on one end of the serpentine lever, it would apply the other end with the burning match to the pan, thereby igniting the black powder. Perhaps the S shape resembled a serpent, thereby giving the name "serpentin" or "serpentine"

Early gun with serpentin trigger. Public domain image.

Whatever the origin of the name, the powder made for such weapons was called "serpentine powder".

To prepare serpentine powder, the saltpeter, charcoal and sulfur were first ground up separately using a mortar and pestle, then the three ingredients were mixed together in the desired ratio to form the serpentine powder.

Since the three ingredients were mixed together in a dry state, there was the potential of explosive dust floating around and many powder makers met with accidents during work. Even after it was mixed together, serpentine powder was somewhat unstable and had the tendency to absorb moisture from the air (due to impurities in the saltpeter), which could cause it to spoil. The reliability of serpentine powder was also not very good and its explosive force was hard to predict. If it is packed too tightly into a gun, the charge may fizzle out or it may develop cracks and detonate, destroying the gun.

One more problem with serpentine powder is since the ingredients are ground up separately and then combined, the ingredient particles would often be of different sizes. What this meant was when transporting a barrel of gunpowder in a cart across bumpy and muddy roads, the vibrations would cause the ingredient with the smallest particles to settle at the bottom of the barrel and the ingredient with the larger particles to move to the top. We discussed why this happens a few posts earlier. Since the three ingredients are particles of three different sizes, this would cause the ingredients to separate themselves, so pulling a sample of powder from the top of this barrel would consist of largely charcoal, but very little saltpeter or sulfur, which would not ignite very well. This meant that they would have to remix the ingredients again at their destination, to ensure the proper proportions of the gunpowder mixture. This was a hazardous procedure that produced clouds of explosive dust and wasn't convenient to do in the middle of a battle.

Due to the variable size of ingredients, serpentine powder has a variable burn rate as well and has about 50-60% the energy of modern black powder. The following video shows the burning rates of equal quantities of serpentine powder and modern black powder.

Video courtesy of fido969 at youtube.

As you can see from the video, there is a pretty big difference in the combustion rates of the two powders and serpentine powder produces less power.

In our next article, we will look into the corning process, which solves many of the problems of serpentine powders.

Black Powder - III

In our last post, we studied some of the physical and mechanical properties of gunpowder, information which will come in handy when we study manufacturing methods in some detail. In today's post, we will look at factors that influence the rate of combustion of black powder.

As we saw in the first post of our black powder series, the ratio of saltpeter, sulfur and charcoal in gunpowders varied at different times and in different countries, but by the 19th century, many people had generally settled to using the ratio of 75% saltpeter, 10% sulfur and 15% charcoal. However, powders made by different manufacturers had different pressures and combustion properties even when they were using the same ratio of the ingredients. We aren't even talking about manufacturers from different countries, they could be manufacturers in the same country or even different powders from a single manufacturer. Clearly there must be some other factors that explain why this happens. That is what we will study about in today's post.

The action of black powder depends not only on the composition of its ingredients, but also the size of the grains, shape of the grains and the density of the grains among other things.There are other factors that influence the rate of burning, but these three are the most important. The reason is because black powder is surface-burning. Smaller grains of gunpowder will have more surface area exposed to ignition than a larger grain of the same weight, therefore smaller grain powder will burn faster than the larger grained type. However, if the powder is packed too densely, the flame cannot easily spread from grain to grain, than the same weight of powder packed in a less compact manner. Therefore, very small grain mealed powder and very large grain powder are both slower burning. The shape of the grain also will affect the burn rate, because of the surface area exposed to ignition. Shapes like cubes or spheres offer less surface area than irregular shaped grains of the same mass, therefore they burn slower. This is why laminated or flaky powders burn much faster than normal and diamond shaped grains burn more rapidly than rounded grains.

As a general rule, the larger the grain, the less violent will be the action of gunpowder (i.e.) its combustion will be more gradual. On the other hand, smaller grain powders also cause pellets to scatter much more rapidly than larger grain powders because a smaller grain powder expends all its force before the shot pellets reach the muzzle, whereas a larger grain powder causes the shot pellets to increase their velocity right up to the muzzle of the gun. Therefore, powder designed for weapons with shorter barrels, such as revolvers and pistols, must be of smaller grain, so that they can finish burning before the powder leaves the barrel. Similarly, powders meant for rifled guns are generally a larger grain than those intended for smooth bores, as a more gradual action is required to avoid putting too much strain on the gun barrel.

Since the same manufacturer often makes black powder of different grain shapes, densities and sizes for different types of guns, therefore the shooting qualities of black powder will vary accordingly. We will look at some powders from the 19th century:

Samples of different powders made by Britsh manufacturers.

Click on the image to enlarge. Public domain image.

The above image shows various black powders made in the 19th century by two large British manufacturers Curtis & Harvey and Pigou, Wilks & Laurence. As you can see, the "Revolver" powder is made of very small grains and designed to be fast burning, while Curtis & Harvey's "Col. Hawker's Duck Powder" and Pigou's "Special Punt Powder" are larger grained and designed to be used by very large bore punt guns. Similarly, Diamond #4 and Alliance #4 were generally used for hunting with shotguns, while #6, Rifle, and Martini-Henry powders were designed for rifles. Other large powder manufacturers in England included the E.C. Powder Company, Schultze Gunpowder Company, Kynoch Ltd., Hall, Coopal, Dittmar etc.

Powders made in other countries also varied in grain size, shape and density:

Black powders from different countries.

Click on the image to enlarge. Public domain image.

The above image shows some sample powders made in different countries. Of course, this is only a very small sample. For instance, in the United States in the late 19th century, there were various powder manufacturers, each making multiple types of powder for different applications: DuPont, Hazard Powder Company, Laflin & Rand, Hercules etc.

Various types of black powder made by DuPont

Various types of black powder made by Laflin & Rand.

Images courtesy of the Haglin Museum and Library

Incidentally, the reason why many of Laflin & Rand's black powder offerings were sold under the "Orange" brand name (e.g. Orange Ducking Powder, Orange Rifle Powder, Orange Lightning, Orange Extra Sporting etc.) is because their original production plant was named "Orange Mills" and happened to be located in Orange County, New York.

The quality of charcoal is also a significant factor in the burning rate of the black powder. If the charcoal is improperly charred, then the oxygen and hydrogen retained in it cause it to burn more rapidly than if it is reduced to a pure carbon. The source of wood for the charcoal is also a factor. Experiments conducted in the 19th century showed that there were significant differences in the amount of gas produced by charcoal made from different types of wood. For instance, dogwood charcoal was found to yield about 25% more gas than the same weight of charcoal made from fir, chestnut or hazel trees and 17% more gas than charcoal made from willow. This is why dogwood was preferred for black powder intended for pistols and rifles, while willow charcoal was preferred for making powder for cannons.

In our next post, we will study more into the classification of grain sizes and shapes.

Black Powder - II

In our last post, we studied the composition of different kinds of black powder as manufactured in various countries. In today's post, we will study some of the physical and mechanical properties of black powder. Gaining some knowledge of this will help understand the reasoning behind the processes of manufacturing the powder when we study that later on.

The first thing we should note about black powder is that it is a mixture and not a compound. Your humble editor will explain what that means:

A compound is formed when different substances combine with each other at a molecular level. The compound will often have properties different from its component substances. For instance, hydrogen and oxygen atoms can combine together to form water (a compound substance), which is a liquid at room temperature, whereas hydrogen and oxygen are gases at the same temperature. Oxygen can help substances burn rapidly, whereas water can be used to stop fires. So you can see that a compound (in this case, water) has quite different properties than its original ingredients (in this case, hydrogen and oxygen).

On the other hand, a mixture is when multiple substances are physically mixed with each other, but do not react at a molecular level. This means that they may be separated from each other by some physical means and mixtures often retain the physical properties of their separate ingredients. For example, you can make a mixture of iron filings, sand and sugar crystals. However, the iron filings can easily be removed from the mixture by passing a magnet over it, while the sugar can be separated out by dumping the mixture in water and letting the sand settle at the bottom while the sugar dissolves in water. Another example could be sand and glass marbles, which can be mixed together easily, but trivially separated by passing the mixture through a sieve, which will allow the sand to pass through, but retain the glass marbles. Black powder is a mixture of potassium nitrate (saltpeter), sulfur and carbon (charcoal). The three substances do not chemically react with each other at room temperature and therefore it is a mixture. Only when the powder starts to burn do the three substances react with each other and form multiple compounds.

Since it is a mixture, the various ingredients of black powder must be ground into particles of roughly the same size as each other to stay mixed together (especially before corning of black powder was invented). Otherwise, the mixture could separate out where the ingredient with the smallest size particles ends up at the bottom of the box, given enough vibration to the box. This is because the smaller particles fit in easily between the gaps of the other particles and fall to the bottom, thereby pushing the bigger particles up. The same phenomenon can be observed with a bag of potato chips (it doesn't matter what flavor of chips!). Notice that when you buy a bag of potato chips, the smallest broken chips are always at the bottom of the bag, whereas the larger pieces end up on top. This is because the bag is shaken during transport from the factory to the grocery store and from the grocery store to your home and the smaller chips end up fitting into the gaps between the larger chips, making their way to the bottom of the bag eventually and thereby pushing the larger pieces upwards. The same principle used to apply to gunpowder before they learned to cake the grains and manufacture them to the same uniform particle sizes. In fact, one of the problems of early black powders (also called serpentine powders) was that when they transported the powder to the battlefield via carts drawn by horses or oxen, the bad roads would cause the barrels of gunpowder to shake heavily, thereby moving the smaller particles to the bottom of the barrel. Therefore, if the ingredients were ground up into particles of different sizes, the ingredients would separate out into three separate layers by the time the barrel got to the battlefield, with the sulfur ending up at the bottom of the barrel and charcoal rising to the top. This is why they would remix the ingredients right there in the field before the battle commenced, which was a somewhat hazardous procedure that produced clouds of potentially explosive dust.

Black powder can be ignited in three different ways: the first method is by contacting it with sparks or open flame, the second method is by a sharp blow and the third method is by increasing its temperature rapidly beyond a certain point.

The first method (exposing it to open flame or sparks) is the principle that different ignitions systems such as matchlocks, wheel locks, flintlocks, percussion locks etc. use. However, the source of the flame or sparks must be hot for the powder to ignite. It is possible for a shower of lower temperature sparks to fall upon black powder without igniting it, whereas a single spark of great intensity can start combustion.

The second method (striking it between two objects) is because black powder is somewhat impact sensitive. Experiments by Aubert, Lingke and Lampadius verified that black powder can be ignited by striking iron on iron, iron on brass, brass on brass, and less easily by a blow of iron on copper, or copper on copper. Of course, some of this might be explained away by the impact causing sparks which ignite the powder. Experiments in 19th century England showed that black powder is also ignited by striking brass on copper, iron on marble, quartz on quartz, lead on lead and lead on wood (a lead bullet was shot against a wooden pendulum covered with powder). Mining accidents over the years showed that striking copper on stone or even wood on stone could occasionally cause ignitions of black powder. One Dr. Dupre even showed that there is hardly any explosive, which, when laid in a thin layer on a wooden floor, will not explode, when it receives a glancing blow with a wooden broom-stick.

The third method (heating it beyond a certain temperature) has some interesting effects. Black powder may be ignited when heated rapidly above a certain temperature, even without the presence of an open flame. The temperature at which this happens depends on the nature of the powder and the proportions of its ingredients and grain size. An experiment by Horsley in the 1800s showed that black powder could be ignited by heating it to around 600 °F (about 315 °C) by heating a saucer in an oil-bath, with the temperature of the oil being taken by a thermometer dipped into it. Experiments by Leygue and Champion in 1871 used a more precise method to determine ignition temperatures and the found that a common sporting powder ignited around 550 °F (about 288 °C), while cannon powder ignited around 563 °F (about 295 °C). However, note that we said that the powder should be heated rapidly for it to ignite. What if it is heated slowly?? Leygue and Champion detail some interesting issues here: They discovered that the grains of corned black powder cake together on account of the sulfur they contain. However, note that black powder before ignition is a mixture, which means it retains many of the physical properties of its separate ingredients. When the temperature of black powder is slowly increased beyond 212 °F (about 100 °C, the temperature of boiling water), the sulfur begins to volatilize and turn into vapor. The volatilization of sulfur rapidly increases with temperature and if the temperature is slowly increased upwards, but kept below the boiling point of sulfur, then the sulfur can be completely driven out of the powder without any ignition taking place. When the sulfur is completely eliminated from the mixture, the temperature can be further increased, so that even the saltpeter melts, and the charcoal ends up floating on top of it, thereby separating out the two ingredients from each other. If, on the other hand, the temperature is rapidly increased before the sulfur is completely volatilized, then the sulfur vapor is ignited and causes the powder to explode. The shape and size of the grains of black powder have considerable influence on the temperature of ignition as well.

If a small quantity of black powder is ignited in open air, it merely burns, but if larger quantities are ignited, or if the powder is ignited under higher pressure or in a closed space, then it explodes. The larger the grain size, the slower the combustion rate. We will study more about this in the next post when we study more about grain sizes.

If good quality black powder is ignited over a sheet of white paper, it will burn rapidly and leave no residue on the paper. If black spots are found, then this indicates that either the mixture contains too much charcoal or the powder is badly mixed. The same can be said for sulfur if yellow spots are left behind. If unburned grains are found, this indicates that the saltpeter is impure. The powder should not burn holes into the paper, as only moist or otherwise bad black powder does so.

As early as 1765, Papacino d'Antoni found that lower air pressures make it more difficult for black powder to ignite. Later experiments by Munke, Hearder, Bianchi, Heeren and Sir Frederick Abel showed that gunpowder didn't explode in a vacuum tube, even in the presence of a platinum wire glowing white hot. Heeren tried to explain this phenomenon by suggesting that at normal pressures, the hot gas escaping from an exploding body would communicate the flame to neighboring particles, but under low pressure, the gas expands so rapidly on account of the lack of resistance of the surrounding air, that it cools down below the ignition temperature of neighboring particles.

On burning gunpowder under normal or high pressures, the various ingredients of the mixture combine with each other chemically and produce gases and solid residue. While this was known from the day that gunpowder was invented, the nature of the gases and solid residue was not. In fact, given the primitive state of chemistry for centuries, it was not known if the products of combustion was just one or several gases. For instance, in 1705, the great Issac Newton thought that sulfuric acid formed by the combustion of sulfur drove out the spirit of niter from the saltpeter and burned it. The same view with slight modifications, was held in 1771 by Majow, who thought a mysterious substance called "phlogiston" (thought to exist in all flammable substances) combined with the nitric acid. It was left to the famous French chemists, Joseph Louis Gay-Lussac and Michel Chevreul, to determine exactly what gases and solid residues were produced. Their experiments showed that among the gases produced were carbonic acid, nitrogen and carbonic oxide, while the solid residues were potassium sulfate, potassium carbonate, potassium sulfide, potassium thio-sulfate etc. Incidentally, Gay-Lussac was the first to prove that water is made of hydrogen and oxygen and also worked on alcohol-water mixtures, the results of which are still used to today to measure alcoholic beverages in many countries around the world (a fact that drinkers will surely appreciate!)

In our next post, we will look into the effects of grain sizes of black powder and how/why different grain sizes were used for different applications.

Black Powder - I

A while ago, we studied about black powder in two separate posts. Since we've studied the processes of obtaining the basic ingredients of black powder (saltpeter, charcoal and sulfur) in great detail in some of our previous posts in the last few months, we will study the processes of combining them into black powder in some detail in the next series of posts.

Before we start our study of black powder manufacture, let us discuss the proportions of the ingredients of black powder. While it is true that many countries had settled with the proportions of 75% saltpeter, 10% sulfur and 15% charcoal by the 18th and 19th centuries, this wasn't always true in all countries. Moreover, the proportions also varied a bit, depending on the use for the black powder. For instance, powder intended for military rifles differed in composition than powders intended for sporting applications, which differed from powders used for blasting purposes, powder used for fireworks etc. We have some information about the composition of powders made in various countries, courtesy of Oscar Guttman's book "Manufacture of Explosives" from 1895 (note that some of the countries have different names now)

	Saltpeter	Sulfur	Charcoal
(a) Rifle Powders:
Austria-Hungary	75	10	15
Belgium	75.5	12	12.5
China	75	10	15
France	75	10	15
Germany	74	10	16
Great Britain	75	10	15
Holland	70	14	16
Italy	75	10	15
Persia	75	12.5	12.5
Portugal	75.7	10.7	13.6
Russia	75	10	15
Spain	75	12.5	12.5
Sweden	75	10	15
Switzerland	75	11	14
Turkey	75	10	15
USA	75	10	15
(b) Cannon Powders:
Austria-Hungary	74	10	16
France	75	10	15
Germany	74	10	16
Great Britain	75	10	15
Switzerland	75	10	15
(c) Sporting Powders:
Austria-Hungary	76	9.4	14.6
France	78	10	12
Germany	74	10	16
Great Britain	75	10	15
Switzerland	78	9	13
(d) Blasting Powders:
Austria-Hungary	60.2	18.4	21.4
France	72	13	15
Germany	70	14	16
Great Britain	75	10	15
Italy	78	18	12
Russia	66.6	16.7	16.7

As can be seen above, many countries varied the proportions of the ingredients based on the intended use of the powder. Note that the blasting powders vary in proportion much more than the rest. This is because blasting powder's requirements were that it should be cheap and develop as much gas as possible at a high temperature. Actually, blasting powders were more varied than the table indicates because powders with different rates of burning were used for rocks of different hardness. So even though the table above suggests that the French were manufacturing blasting powder with the ingredients in 72%, 13% and 15% ratio, that was only one grade and the French Government factories actually made 3 grades of blasting powder:

	Saltpeter	Sulfur	Charcoal
Ordinary Powder	62	20	18
Slow Powder	40	30	30
Strong Powder	72	13	15

Similarly, some blasting powders in England were made of different proportions (e.g.) 65% saltpeter, 20% sulfur, 15% charcoal.

Powders manufactured in Belgium had the following compositions depending on the purpose:

	Saltpeter	Sulfur	Charcoal
Rifle Powder	75	12.5	12.5
Cannon Powder	75	12.5	12.5
Sporting Powder	78	10	12
Blasting Powder	75	12	13
Slow Powder or Pulverin	70	13	14 & 3% wood meal
Slow Powder in cartridges	70	13	14 & 3% dextrine
Export Powder	68	18	22

In France, "pulverin" was also manufactured for use in fireworks and contained 75% saltpeter, 12.5% sulfur and 12.5% charcoal mixed together.

In the next couple of posts, we will study the grain sizes of black powder in the 19th century.

Manufacture of Sulfur - IV

In our last post, we saw how Sicily was slowly losing dominance in the sulfur trade and how Britain became a major sulfur producer using the Claus process. In today's post, we will look at how the United States started dominating the business of sulfur production.

In the mid-1800s, the United States was producing sulfur, but only in small quantities. There were sulfur mines found in the Western United States, in Wyoming, Colorado, Texas, Utah, Nevada and California, but the total production of these mines couldn't keep up with demand and therefore, the US also imported a lot of sulfur from Sicily. Then, in 1867, a large sulfur deposit was discovered in Calcaseiu Parish, Louisiana by workers employed by the Lousiana Petroleum and Coal Oil Company (LPCO). Unlike the other places in the US, where the sulfur was found on the surface or close to it, this particular sulfur deposit was buried deep underground in a salt dome, covered by a layer of quicksand. Two years later, a geologist, Professor Eugene Hilgard, from the University of Mississippi, was brought in to study this deposit and he realized that this deposit was large enough to offer an alternative to sulfur imported from Sicily, although mining it would be a challenge. Professor Hilgard later moved to the University of California, Berkeley in 1875 and became Professor of Agricultural chemistry there, where he later studied wine making and his research was responsible for California becoming a major wine maker in the world today.

Meanwhile, LPCO officials decided to go ahead and try to mine the sulfur out of their discovery, but they could not do it because they only had licenses to mine coal and oil, not sulfur. Therefore, they sold their rights to another company, which sold it to another and so on. The problem was that while everyone knew that the sulfur deposit was there, no one knew how to get it out of the ground. Unlike the other sulfur mines, this one was located deep underground and there was a layer of quicksand in between and pockets of deadly hydrogen sulfide gas, that made mining the sulfur underneath impossible. Numerous attempts made in the 1870s and 1880s failed with the loss of many lives.

The solution to getting to this deposit was discovered in 1890 by Herman Frasch, a German-born American chemist.

Herman Frasch
Click on the image to enlarge. Public domain image.

Herman Frasch was born in Oberrot bei Gaildorf, Wurttemberg, Germany in 1851. At the age of sixteen, he migrated to the United States in 1868 and arrived in Philadelphia, where he joined the College of Pharmacy and began increasing his knowledge of chemistry. One of his first inventions was discovering how to separate tin from steel cans. Previously, tin had to be imported from Britain and the cost was passed down to anyone who bought a tin can. Later, he got interested in the field of industrial chemistry, specifically driven by the oil industry. He came up with a process of purifying paraffin wax, which was a waste by-product in oil refining until then, and after his invention, it could be used in many industries, such as waterproofing, candle manufacturing, preserving food etc. 

Then in 1885, he came up with a process to remove excess sulfur from oil. Oil with a large amount of sulfur in it was called "skunk oil" or "sour oil" because of its smell and poor burning characteristics, which made it unusable and very hard to sell. As it happened, the Standard Oil Company owned by John D. Rockefeller had found a large oil field in Ohio, where the oil had a lot of sulfur content in it, therefore he brought Herman Frasch in to solve the issue. The Frasch process he developed in 1888 to extract the sulfur from the oil was a huge success on an industrial scale. Previously, Rockefeller could only get about 16 cents per barrel, but after using the process developed by Frasch, he could sell it for over $1 per barrel. Considering that there were millions of barrels of oil sold, this made Rockefeller very rich. As Herman Frasch was also paid in shares of Standard Oil, he became very rich as well!

Incidentally, as modern laws for automobiles mandate using unleaded gasoline, oil refineries use sulfur extraction units to remove sulfur from crude oil to produce unleaded gasoline.

However, Herman Frasch wasn't done yet. He set his sights on the sulfur deposit that was found in Louisiana back in 1867 and bought some land there. But as luck would have it, the area containing the sulfur was not on his property. He took out multiple patents for his newly developed Frasch process in 1890 and 1891, formed the Union Sulfur Company in 1892 and then signed a contract with his neighbors to mine sulfur from their land. In 1894, the sulfur was successfully brought to the surface for the first time.

The Frasch Process. Click on the image to enlarge. Public domain image.

The Frasch process consists of using three concentric tubes, which are drilled through the earth into the sulfur deposit. The walls of the outer tube keep the quicksand from collapsing into the hole. Water is heated under pressure to produce superheated water (about 340 °F or 171 °C), which is then pumped in through the outer tube under high pressure. This heat is enough to melt the sulfur, which has a melting point of around 240 °F (or 115 °C). The molten sulfur flows through the middle tube, but since sulfur has a greater density than water, the water pressure is often insufficient to bring the sulfur to the surface. Therefore, hot air is pumped through the inner tube, which causes the molten sulfur to form a froth and reduces its density, which allows it to be pushed up towards the surface. All other substances have a higher melting point and remain underground. The sulfur obtained by this method is very pure (99.7% or greater) and needs no further refinement. The molten sulfur is then pumped into large containers and allowed to solidify in open air and the blocks are then broken up and directly loaded onto rail cars.

One major problem with this method was the cost of fuel for heating the water, but this problem was overcome in 1901 when oil was discovered a short distance away in Spindletop, Texas, which provided cheap fuel oil for the entire region and made the production of sulfur economically competitive with other sources. Due to the booming growth of sulfur mining, a small town was formed in the area around where Frasch built his mine, appropriately named Sulphur, Louisiana! The town of Sulphur still exists today and an elementary school there is named after Herman Frasch.

As a result of this process, the Union Sulfur Company became one of the top sulfur producing companies in the world and the United States displaced Italy as the world's leading sulfur producer. In 1903, Sicily had exported over 157,000 tons of sulfur to the US and 106,000 tons in 1904, but by 1906, they only exported 7000 tons, as the rest was made up by the Union Sulfur Company in America! The mighty Anglo-Sicilian Sulfur Company (ASSC) demanded that Union Sulfur stay out of Europe and demanded a share of the US market, but they didn't know Herman Frasch very well. His process gave him a huge manufacturing cost advantage over ASSC and Union Sulfur started dropping their price to the point where ASSC could not compete any more. By 1907, ASSC was out of business. In 1911, Frasch's patent for his process expired and other American companies in Texas and Louisiana started producing sulfur from salt domes all over the Gulf Coast of the United States.

The Frasch process dominated the world markets until about 1970 or so, when sulfur recovered as a by-product of oil refining and natural gas production (the Claus process we studied in our previous post) became significant again. The last US Frasch sulfur mine closed in 2000, but the process is still used in Mexico and Poland today.

Manufacture of Sulfur - III

In our last post, we saw how sulfur was extracted and purified in Italy (mainly Sicily) and then further purified in England for the purposes of manufacturing gunpowder. Up to the end of the nineteenth century, Italy was the main source of sulfur for both Europe and America. Therefore, both the British and the French tried to secure their supplies from Italy. In particular, the British managed to secure very favorable trading rights with Sicily in the early 1800s, thanks to rescuing their ruler from Napoleon Bonaparte's invasion. Soon, British, French and American merchants were all trying to get a piece of the Sicilian export market, with British merchants having the most control generally. Many of these British merchants were originally wine merchants, who got into the sulfur trade since they already had well-established transport networks and marketing connections with other regions of the world. There was a brief hiccup in 1839, when a French company named TAC (Taix, Aycard & Company, named after its two founders, Aime Taix and Arsene Aycard) managed to convince the ruler of Sicily, Ferdinand II, to grant them a monopoly and thereby increase the price of sulfur worldwide. This action caused many countries to manufacture sulfur from pyrites and import from other sources (such as Iceland) and nearly caused a war in 1840, before diplomatic efforts succeeded in negotiating a settlement. Nevertheless, sulfur produced from pyrites took a share of the market.

Then in 1883, Carl Friedrich Claus, working in London, patented a process called the Claus process, that allowed recovering sulfur from hydrogen sulfide gas. By 1887, Alexander Chance and C.F. Chance modified his process to process sulfur from the left over waste of the Leblanc process (which was used to manufacture soda ash (sodium carbonate), useful for glass, textile and soap industries). Until then, the waste product of the Leblanc process, which is calcium sulfide, was simply thrown into heaps outside the plant. The Claus-Chance process first converts the calcium sulfide to hydrogen sulfide, using water and carbon dioxide, and then extracts the sulfur from the hydrogen sulfide gas using the Claus process. Therefore, all those heaps of waste calcium sulfide that were thrown out earlier, could be used to extract the sulfur from them.

A pile of Sulfur produced by the Claus process in Vancouver, Canada. Click on the image to enlarge.

Image licensed under Creative Commons Share Alike 1.0 License by LeonardG.

Using the Claus-Chance process, England became the second largest sulfur producer in the world by the early 1890s.

The British also attempted to form a cartel to control the Sicilian industry, almost 55 years after the attempt made by the French Company TAC. The Anglo-Sicilian Sulfur Company (ASSC) was formed in 1896, which gained control of about 2/3rd of Sicily's export. In particular, they made some huge sales in the American marketplace, shipping it to many well known companies in the US.

However, there was danger to the Anglo-Sicilian Sulfur Company from an American invention that we will study about in our next post: the Frasch process. Sicily was exporting over 177,000 tons to the American market in 1902, 106,000 tons in 1904, and two years later, it dropped to 7000 tons thanks to the new process invented in America! In fact, in 1906 Sicily was no longer the global dominant producer of sulfur, being replaced by sulfur produced in Louisiana and Texas, which was cheaper and purer, and the Anglo-Sicilian Sulfur Company was out of business a couple of years later.

However, while the Claus-Chance process went into decline, the Claus process did not go away entirely. In fact, it is still around today and is the dominant method of producing sulfur today, as there is plenty of hydrogen sulfide gas from other sources, especially from oil and natural gas fields and from crude oil refineries.

We will study the Frasch process in our next post.

Manufacture of Sulfur - II

In our last post, we saw how the Chinese extracted sulfur from pyrites (fool's gold) and used it in gunpowder. In some parts of the world though, particularly in regions containing hot springs and volcanoes, elemental sulfur occurs naturally on the surface of the earth. Some famous locations are Sicily in southern Italy, the Romagna region in northern Italy, some islands in Japan (Iwo Jima, for one), the Ijen volcano complex in Indonesia etc. Today, we will study how sulfur was extracted from these regions in the past centuries.

Naturally occurring sulfur at the edge of a crater on Vulcano Island, Sicily, Italy.

A miner carrying away blocks of sulfur on Kawah Ijen, Indonesia. Click on the image to enlarge.
Image licensed under a Creative Commons license
By Jean-Marie Hullot - originally posted to Flickr as Kawah Ijen, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=8753232

Mining for sulfur from Sicily and Romagna regions in Italy dates back to at least Roman times. After the 14th century, as gunpowder technology began to develop throughout Europe, the demand of sulfur began to increase. Several gunpowder mills began to appear near the sulfur mines. In the 19th century, 75% of the world's sulfur production came from Sicily alone, and 5% more from the Romagna region. This meant that Italy accounted for both the 1st and 2nd largest producers of sulfur in the world in the 19th century.

The traditional way of extracting sulfur during the Roman times to the middle ages was to melt it in open pits. Sulfur from Sicilian deposits generally contained from 12% to 50% sulfur, with the other impurities being mainly gypsum and limestone. However, to melt the sulfur, fuel is needed and wood was a luxury in those volcanic regions. Hence, sulfur was used as a fuel as well and was used to melt itself! The earliest recovery technique consisted of placing the crude sulfur in conical mounds over and open pit and covering it with earth. The bottom of the sulfur was set on fire, melting the rest of what remained on the pile, which could be extracted. However, this process wasted a good portion of the sulfur (about 33% was recovered and 67% was wasted) and over the centuries, miners exhausted the sulfur deposits on the surface and had to start digging tunnels into the hillsides to extract the sulfur deposits.

During the Middle Ages, a better technique emerged, using clay pots to distill the sulfur. There was at least two pots employed, called Doppioni (which means "double" in Italian), which were connected by a clay pipe. The crude sulfur was placed in one pot, which was heated on a fire using wood or coke as a fuel. The sulfur would evaporate and the fumes would be led into the other pot via the pipe, where it would condense and be poured into wooden moulds. Meanwhile, the slag remaining in the first pot would be unloaded. Later on, the pots were produced using cast iron. This technique was mainly used in the Romagna region and not in Sicily, because of the way that land mining rights laws were in the two regions.

Instead, in 19th century Sicily, they simply improved on the melting techniques and came up with melting furnaces called Calcarelli and Calcaroni. The main difference between these two was that the Calcaroni was a larger furnace and soil was added to the top of the sulfur heap inside it, to control the combustion.

It consists of a round open-topped furnace, lined with firebrick, with an inclined floor. Calcarelli furnaces tended to be smaller and were typically about 2 meters (6.6 feet) in diameter, whereas Calcaroni type furnaces were larger and about 10-30 meters (about 33-100 feet) in diameter. A cone-shaped pile of sulfur was built up, and in the case of the Calcaroni furnace, a cover plug of soil was put on top of the sulfur. A flame was applied from the top and part of the sulfur burned away, which produced enough heat to melt the rest, which would then flow down the sloping floor and could be collected from a hole in the bottom (appropriately called morte, the Italian word for "death"). The Calcarelli type furnaces would yield about 1/3rd of the sulfur from the ore and took about 2 days to finish the process, only processing a few tons at a time. The larger Calcaroni type furnaces could extract about 50-65% of the sulfur and took about 60-90 days to complete, producing about 200 tons of sulfur per batch. Nevertheless, these were highly polluting furnaces and the sulfur dioxide fumes would destroy any vegetation in the neighborhood, which is why Italian laws prohibited building these furnaces less than 3 km. (2 miles) from any town and only allowed these furnaces to run at certain times of the year so that they wouldn't interfere with growing crops. These furnaces were more inefficient than the Doppioni, but were widely used in Sicily because they allowed large scale processing for cheap.

An improved kiln was invented in 1880 by Robert Gill, a British engineer working for the Gibellini Sulphur Company. A Gill kiln consists of a series of cone shaped chambers (typically two to six chambers) which are connected sequentially and the heat from the first chamber is used to preheat and set fire to the second one and the heat from the second one is used to preheat and set fire to the third one and so on. Each chamber has an inclined floor and is provided with several openings: one for adding the crude sulfur, another for a pipe to bring in the hot gases, another for a pipe to take out the combustion gases to a main chimney, a tap hole at the bottom to extract the molten sulfur and another adjustable hole to adjust the airflow needed for combustion.

The main innovation of this type of furnace was to reuse the combustion gases from one chamber to heat the next chamber and so on, which reduced the amount of sulfur fumes, allowing a Gill furnace to work continuously through the year. Typical wastage was only around 7-10% of the sulfur and this furnace was widely adopted in Italy -- by 1890, Gill's furnace was used in about 12% of Sicily's production, but by 1905, it was used for about 65% of the sulfur produced by Sicily.

The sulfur produced varied in quality and was generally exported to other distilleries, primarily to Marseilles, France, but also to smaller refineries owned by gunpowder mills, such as Waltham Abbey, where it could be further refined. At Waltham Abbey, best quality Sicilian sulfur came in with about 3-5% of impurities. It was distilled in a large iron pot, provided with two tubes at right angles to each other: The larger tube (about 15 inches diameter) communicated to a large dome-shaped subliming chamber, the smaller tube (about 5 inches diameter) entered an iron pot, which received the distilled sulfur. This tube was surrounded a jacket cooled with water. Valves could be opened or closed in the tubes to connect to or cut off the distilling vessel. The distilling vessel was heated till the sulfur boiled and the valves were initially manipulated so that vapors were sent to the subliming chamber, where the sulfur would deposit on the interior surface as small crystals (called the "flowers of sulfur"). After a while, the other valve would be opened and the vapors sent through the condenser, which would then liquify the sulfur. The liquid sulfur would be allowed to cool a bit, but not enough to solidify. Then it would be ladled into moist wooden molds to solidify into "stick sulfur". The "flowers of sulfur" contained a small percentage of sulfuric acid, formed by the action of the air on the sulfur and therefore, wasn't suitable for the manufacture of gunpowder. The "stick sulfur", on the other hand, was very pure and only needed to be ground up into powder to be used in gunpowder.

The Sicilian monopoly on sulfur production slowly started to decrease at the end of the 19th century, due to an invention by a German-born American chemist in Louisiana. We will study his process in our next post.

Manufacture of Sulfur - I

In our last couple of posts, we looked at some historical methods used to produce charcoal, one of the key ingredients of black powder. In today's post, we will look at some methods used to extract the third ingredient of black powder, namely sulfur (also spelled as "sulphur" if you speak British English).

As we've seen previously, the saltpeter (potassium nitrate) provides the oxygen needed for the gunpowder to burn rapidly, and the charcoal (carbon) provides the fuel. So what's the role of sulfur then? The sulfur helps to reduce the ignition temperature of gunpowder. Strictly speaking, it is possible to manufacture gunpowder using only saltpeter and charcoal, but the result needs sparks at a higher temperature to ignite. This is why sulfur was added to black powder to increase the reliability of ignition on early firearms such as matchlocks, wheellocks, flintlocks etc. If there is no sulfur in the black powder, then the chance of misfiring on these early firearms increases quite a bit. However, the presence of sulfur is also responsible for most of the smoke produced by burning black powder.

 Interestingly, a mixture of saltpeter and sulfur, but no charcoal, does not burn at all, although sulfur alone burns well in air and saltpeter is an oxidizer.

Sulfur has been known since ancient times and has been mentioned in texts of ancient Egypt, Greece, India, China, Italy etc. It is even mentioned in the Bible as "brimstone". Sulfur is a pretty common element and occurs in many minerals, as well as in natural state (elemental sulfur). When it occurs in natural state, this is typically around hot springs and volcanic regions in many parts of the world (e.g. Sicily, Indonesia, Japan, etc.) It also occurs in minerals such as pyrites (fool's gold). One more source of elemental sulfur is salt domes in many regions of the world. 

Sulfur found naturally on the ground from the island of Vulcano in Italy.

Click on the image to enlarge. Public domain image.

In China, the common source of sulfur in ancient times was from pyrites. This is a mineral that contains both iron and sulfur and commonly occurs in various places around the world. It was known since ancient times because of its property of giving off sparks, when struck with a piece of flint or a steel rod. This is why pyrites were also used in early wheel lock firearms. Even before firearms were invented, travelers would carry a small piece of pyrite and one of flint with them and strike them together to start a fire. There is evidence that using pyrite and flint as a portable fire-starter has been in use since at least the Upper Paleolithic era. In fact, the word "pyrite" derives from the Greek word for fire (pyr)

Three samples of pyrites. Click on the image to enlarge.

Pyrites are also known as "fool's gold", since their shiny nature has fooled many people into believing that they have found some mineral containing gold in it.

We have good accounts of how sulfur was extracted from pyrites in China. One book by Song Yingxing in 1637, describes the process: About 250 kg. (550 lbs.) of pyrites was surrounded by 500 kg. (1100 lbs.) of coal in a brick kiln, and a hole was left on top of the pile. The pile was then ignited at the base and left to burn for 10 days. The sulfur would form a yellow vapor that came out of the top of the pile and this could be condensed into solid sulfur crystals by covering the top of the pile with a simple earthenware bowl, as seen in the image below.

Ancient Chinese process to make sulfur from pyrites. Click on the image to enlarge. Public domain image.

There is evidence that the technique of extracting sulfur from pyrites was known to the Chinese, since at least the 3rd century. This process was somewhat wasteful in the amount of sulfur extracted from the pyrites, but since pyrites were plentiful in China, it was very commonly used there. 

In Europe, the main source of sulfur for many centuries was the island of Sicily, where sulfur occurs in its natural state (we will study its extraction in the next post) and was mined since Roman times at least. However, in 1839, the Sicilian deposits came under the control of a French company, which raised the price about three-fold. This led to a number of countries reverting back to extracting sulfur from pyrites, until the price dropped again.

In the next post, we will look at how sulfur was extracted in Europe since ancient times until the middle of the nineteenth century.