Tuesday, January 17, 2017

Smokeless Powders: Further Developments by Abel and Schultze

In our last post, we studied some discoveries by Baron Von Lenk, who succeeded in developing a process to manufacture gun cotton in larger quantities. The Austrian empire adopted his gun cotton as a propellant to replace black powder and supplied thirty howitzer batteries with gun cotton cartridges, as well as a new model of the Lorenz rifle (the M1862 model) to use gun cotton. Two factories in Austria started to manufacture gun cotton based on his process.

The gun cotton, as made by Von Lenk's process, retained the fibrous nature of the original cotton. The Austrians spun it into threads and braided them together, or wound them on wooden or paper bobbins, and arranged them in cartridges, so as to secure the desired air gaps in between and insure proper ignition. The Austrians found that this propellant was not affected by dampness, only required a charge of 1/4th to 1/3rd of the amount of black powder previously used, left less residue inside the barrel, produced less smoke and the gases evolved were also less harmful to the weapons and the men around them. France and England got interested in his discoveries and sent scientists to study the Austrian process as much as they were willing to reveal and Von Lenk also lent his expertise to scientists from both countries.

Unfortunately, there was an accident in 1862 in the factory at Hirtenberg, Austria, which blew up for some unknown reason. Soon after this, a British company called Thomas Prentice & Co. started to manufacture gun cotton in 1863, in a town called Stowmarket in England. Shortly thereafter, Sir Frederick Abel also began to research producing nitrocellulose safely at the Royal Gunpowder Mills at Waltham Abbey, England. His process was based on Von Lenk's process as described in our previous post, but he effected a more complete purification of the gun cotton by pulping it before the final washing process, thereby cutting the tubular fibers into short lengths and rendering it possible to remove the last traces of acid retained within the tubes by capillary action. Traces of acid remaining in the gun cotton was what caused it to decompose over time. He patented this method in 1865, just around the time that the second Austrian factory also blew up. The Austrians had also had some accidents with their guns and after the second factory blew up, they decided to stop using gun cotton in their military. Meanwhile, Abel continued to experiment in England with his pulped, purified gun cotton, which he could compress into various shapes and in 1867 and 1868, he got some very promising results when used with field artillery. However, the British military were still very wary of gun cotton and military authorities were concerned about safety issues more than the advantages of the smokeless powder technologies. Also, the Thomas Prentice & Co. factory in Stowmarket blew up in 1871 and this was another reason why the British military discontinued further research for artillery and small arms for about twenty years. Instead, the compressed gun cotton was used in naval mines and for filling torpedoes and this is where the entire gun cotton production at the Waltham Abbey factories went to for the next couple of decades.

While military interest in gun cotton had decreased, civilians were very interested in this new technology. In particular, sportsmen who liked to hunt, appreciated the lack of smoke combined with higher velocities and lack of fouling and the next few years of developments were largely done in response to their demands. Naturally, the goal was to reduce the force of the explosion, so that barrels would not rupture, as had happened in the previous years. Around 1863, a Prussian artillery officer, Captain Johann Edward Schultze, invented a powder made from well purified and partially nitrated wood. His process started by sawing the wood into thin sheets about 1/16th of an inch in thickness, which was then passed through a machine that punched out disks or grains of uniform size. The next step was to remove the resinous matter from the disks, which was done by boiling the disks in sodium carbonate solution, washing them, steaming them, bleaching them with chloride of lime and then drying them. After this, the cellulose was nitrated in an acid mixture similar to the Von Lenk process. After this, the nitrated wood was then steeped in a solution of potassium nitrate and barium nitrate and then dried, which completed the process of manufacturing process. Using this process, the nitrocellulose that was produced was diluted with unconverted cellulose and metallic nitrates, which allowed for an even rate of combustion.

The advantage of using nitrates and organic substances as diluents was soon copied by other people and many other powders were soon on the market, using potassium, sodium and barium nitrates, and potassium nitrate (saltpeter), while sugar, cellulose, charcoal, sulfur, starch, gums, resins and paraffin were all used as combustible diluents and cementing agents.

Schultze started manufacturing his smokeless powder in a factory in Potsdam, near Berlin, around 1864. His powder soon gained popularity among civilian hunters. However, in 1868, there was a major fire in his factory and it burned to the ground. Shortly after this event, over in England, near a town called Fritham in the New Forest area, at a site called Eyeworth Lodge, a new factory called the Schultze Gunpowder Factory was established by two businessmen, Clement Dale and William Bailey. There was already an earlier attempt about 7 years previously to establish a black powder factory at the same site, which was not successful. The new owners hoped to capitalize on smokeless powder technology as well as the name of Captain Schultze, from whom they obtained a license to manufacture the powder. It must be noted that while Captain Schultze was not really directly involved with the new Schultze Gunpowder Factory, they did use his original manufacturing process and subsequently improved it over the years as well.

Click on the image to enlarge.

Initially, the factory was not very successful and in 1871, they only had four employees. The November 1872 edition of Popular Science had this to say about the factory and its production process:

"Here and there at intervals wide apart are various buildings of light structure from one of which rises a tall chimney instrumental in raising steam to drive a 10HP sawing machine which rapidly creates the "wood powder". This is subjected to chemical washing leaving hardly anything behind save pure woody material, known as lignine or cellulose. The next operation involves the conversion of these cellulose grains into a sort of gun cotton material by digestion with a mixture of sulphuric and nitric acids. Next it is washed with carbonate of soda and dried. The resultant grains are stored away until the time of packaging and dispatch when they are charged with a definite percentage of a nitrate powder -- nitrate of baryta is preferred.  All the buildings requisite for manufacturing this explosive are cheap and flimsy so that if they did catch fire no loss would ensue. The plant and machinery is of small cost in comparison to that used for making black gunpowder and Schultze wood powder is sold at a price commensurate with its cheap production."

In 1874, a talented self-taught chemist named R.W.S. Griffiths was appointed as the general manager and he refined the production process. Soon after this, the company began to become famous for the quality of its powder, particularly after samples of powder were successfully tried out in a series of trials organized by The Field magazine. By 1878, it became a leader in the world's sporting powder market. Many of the famous cartridge manufacturers, such as Eley Brothers, Kynoch and Union Metallic Cartridge Co. (UMC), used Schultze powder in their cartridges. The company rapidly expanded and the population of the local village of Fritham expanded with it, causing a reservoir, a new church, a store and workers houses to be built. Nevertheless, powder manufacturing remained a dangerous process and therefore, the wages for workers at that factory were around double that of those working in agriculture at that time.

At its peak, the Schultze Gunpowder Factory also opened offices in Gresham Street, London and had agents in various cities around the world. They became the largest manufacturer of smokeless powder for sporting use and produced about 75% of the world's supply. In 1897, they formed an American branch in conjunction with E.C. Gunpowder Co. and called it American E.C. & Schultze Gunpowder.

One of the most famous users of Schultze powders was the legendary American exhibition shooter, Annie Oakley, who was the star of Buffalo Bill's Wild West Show.

The legendary Annie Oakley. Click on the image to enlarge. Public domain image.

Annie Oakley had mentioned in several interviews, that she only used Schultze powder for her performances. Interestingly, when the Wild West Show toured France in 1889, she brought along fifty pounds of Schultze powder with her and then discovered at the dock that there was a French law that forbade the import of foreign gunpowders! At that time, the quality of French powders was not as good, because of a government monopoly on powder manufacturing and she didn't have the time to experiment with a new brand anyway. Fearing that her accuracy would be affected, there was only one thing she could do: smuggle the powder in! She obtained five hot-water bottles and enlisted four other lady riders with the show as co-conspirators. They filled the hot-water bottles with Schultze powder and each woman wore a dress with a bustle, hiding the bottles within. In fact, Annie had never worn a bustle in her life before that day, but she admitted that on this occasion she was glad to do so. She led the women safely through the customs line and into France. As she later admitted, "We sure did attract some attention when we went down the gang plank, for although the bustle originated in France, it was going out of fashion at that time". Even then, as the tour went on in France, her supply of powder eventually ran out and her shooting accuracy was affected because she had to use French powder. In fact, the French powder exploded one of her best guns and gave her a big bruise and her husband noted that no matter how carefully one loaded French powder into cartridges, no two ever fired alike. Luckily for her, in Marseilles, she received a notice to go to the Customs House to pick up a box mailed to her by some friends in England. The box was rather large and inside it were two dozen fresh eggs and an unsigned note telling her that she should try the packing material out in her gun before throwing it away. The eggs were packed in Schultze powder! She gladly paid the 40 cent import duty on the eggs and as she reported, "I never shot better in my life than I did the next three days, either winning or dividing every event. It may be that I was in better form, but I'm sure my Schultze load had a great deal to do with my good scores."

By the early 1900s, Schultze Gunpowder Company expanded so much that they had to move to Redbridge in Southampton, which was more suitable for transportation of its products. However, the company really suffered during the World War I period due to anti-German sentiment. In fact, the company had to take out newspaper advertisements declaring that despite their German-sounding name, all the owners, management and workers were British! Soon afterwards, a bunch of British powder manufacturers all combined together to form Nobel Industries, which later combined with three other companies in 1920 to form ICI (Imperial Chemical Industries),which was Britain's largest manufacturer for most of its history. This was around the time that the Schultze factory at Eyeworth Lodge was closed. All that remains there today are a few buildings and a farm.

In our next post, we will how gun cotton started to attract the interest of militaries once again.

Monday, January 16, 2017

Smokeless Powders: The Von Lenk Process

In our last post, we learned that an Austrian officer, Wilhelm Freiherr Lenk von Wolfsberg, had come up with a method to produce gun cotton efficiently. We will study more about his exact process in today's post:

Baron von Lenk in 1866. Click on the image to enlarge. Public domain image.

The Von Lenk process involves the following general guidelines:
  1. The cotton should be cleansed and perfectly dessicated (i.e. dried out) previous to its immersion in acids.
  2. The acids used should be the strongest available.
  3. The steeping of the cotton in a fresh strong mixture of acids after the first immersion and partial conversion into gun cotton.
  4. The steeping should be continued for 48 hours.
  5. The gun cotton should be thoroughly purified afterwards and every trace of free acid should be removed.
The process started by spinning the cotton into hanks of about 85 grams (about 3 oz.) each, suspended on hooks in a hot solution of potash. An under-heated iron boiler was used for this purpose, the water in the boiler containing sufficient potash to give it a specific gravity of about 1.022. The cotton was immersed in the boiling potash solution for about 2 to 3 minutes, according to the amount of grease contained in the cotton strands. The potash solution acts as a soap and removes the grease. Then the cotton hanks were put in a centrifugal machine and spun around at high speeds to drive out some of the potash solution (the same idea is used in modern washing machines as well). Then the cotton hanks were put in perforated zinc baskets and swung to-and-fro in pure water to remove any remaining traces of soap, after which they were wrung out again and allowed to completely dry out. This completed the stage 1 of the process, cleaning out the cotton and drying it.

The acid mixture was prepared by taking strong nitric acid of specific gravity 1.48 to 1.49 (at 17.5° C or 63.5° F) and strong sulfuric acid of 1.835 specific gravity and streaming them from two taps into an earthenware vessel. The proportion was usually 1 part of nitric acid to three parts of sulfuric acid. The process of mixing the two acids produces heat, so the mixture was allowed to cool in the earthenware jars and stored until ready for use.

The nitration process was done in cast-iron dipping pans divided into three compartments, with a grating fitted over the middle one. Two hanks of cotton at a time were put into 300 times their weight of acid mixture in the first two compartments of a dipping pan. The hanks were turned over and squeezed with spatulas until the acid had completely penetrated through the cotton hanks. Next, they were transferred to the grating and squeezed again to free out most of the excess acid, the cotton being allowed to retain about 9.5 parts of acid. When about 2 kg. (4.4 lbs.) of cotton had been treated this way, the acid mixture was emptied out and fresh acid was put into the dipping pan. When six hanks of cotton had been nitrated, they were put into another earthenware pot standing in the third compartment of the dipping pan. A weighted disk was put into the pot to make sure that the cotton was completely submerged in the acid and then the pot was closed with a lid and allowed to stand for between 24 to 48 hours in a special temperature-controlled room, where the temperature was not allowed to fall below 5° C (41° F) or go above 25° C (77° F). In order to maintain the temperature within these limits (remember that air-conditioning technology wasn't really well developed yet), the room had to be heated during winter and the exterior of the pots was cooled by running water in the summer. During the first two to six hours, the pots had to be watched carefully and the heating was prevented either by adding some fresh acid or passing cold water around the pots.

After the nitration was finished, the crude gun-cotton was then put into centrifugal machines and spun around again to remove some of the excess acid. Then they were washed with a large quantity of water in copper drums and then finally treated in running water in special washing boxes for six weeks. The gun-cotton was then wrung out  again in a centrifugal machine, treated with a boiling potash solution, then again through the centrifugal machine, washed with pure water, through the centrifugal machine once more and then dried. After this, it was dipped into a solution of sodium silicate of 1.072 specific gravity, then a spin cycle through a centrifugal machine again and then finally exposed to the air for three days. During this time, the sodium silicate was decomposed by the action of carbonic acid in the air and silica (or an insoluble silicate) would precipitate on the fibers of the gun-cotton. After three days, the product was again washed in pure water, passed through another spin cycle in the centrifugal machine and then dried in open air, or in a drying house, at a temperature not exceeding 35° C (95° F) and making sure to avoid direct exposure to the sun's rays. While all of this washing and wringing the cotton in the centrifugal machines may seem excessive, it was necessary to do this to ensure that even minute traces of acid were removed from the treated gun-cotton, in order to ensure its stability.

This process would yield about 165-167 parts of gun-cotton for every 100 parts of dry untreated cotton. The structure of the gun cotton threads were carefully examined and hanks containing torn threads were discarded. Then, a small portion of the gun cotton was tested for strength and if found satisfactory, the batch was packed.

Unlike the processes of previous inventors such as Schonbein, Otto etc., which could only be used to manufacture small quantities at a time, Von Lenk's process could be scaled up to produce large quantities.

Baron Von Lenk patented his process and was invited to give lectures in France and England detailing his methods. While in France, he was personally awarded the Commander's Cross of the Legion of Honor from Emperor Napolean III and was also given a box studded with diamonds for his discoveries.

In Austria, another army officer, Ritter von Lorenz (Joseph Lorenz) was working on the design of a rifle which was first approved in 1854 and subsequently updated in the following years. The version that was manufactured in 1862 used a steel barrel instead of a cast-iron one, in order to use gun-cotton cartridges. The gun-cotton cartridges and the M1862 Lorenz rifle model came to the attention of Dr. Theodore Canisius, the US consul to Austria at that time. Dr. Canisius saw the advantages of gun-cotton over black powder and began to send back regular reports to the State Department about various Austrian experiments with gun-cotton propellants. In August 1863, Dr. Canisius returned to the US with an M1862 Lorenz rifle and some Austrian ammunition samples, and arranged meetings with several key officials (including then Secretary of State, William Seward, Secretary of War, Edwin Stanton and some military officers) to try and convince them to adopt this new technology. While the military were not entirely convinced, the Austrian military had decided to switch to gun-cotton entirely and therefore, a lot of their Lorenz rifles designed for black powder were now available for sale. As a result of this, a large number of Lorenz rifles were purchased by both the Union and Confederate sides during the US Civil war, with the Union purchasing over 225000 rifles and the Confederates buying 100,000 rifles. In fact, the Lorenz rifle was the third most used rifle during the Civil war.

However, Von Lenk's process was abandoned by Austria around the end of 1865, due to explosions in two factories and a fear about the stability of gun-cotton. Nevertheless, scientists in other countries were hard at work trying to improve on his processes. The next breakthroughs were by a Prussian artillery officer, Johann Edward Schultze, a French scientist, Paul Vielle and a British scientist, Sir Frederick Abel, and we will study about their discoveries in the next few posts.

Friday, December 30, 2016

Smokeless Powders: Productionizing Gun Cotton: Early Experiments

In our last post, we saw how gun cotton was accidentally discovered. As was mentioned in our previous post, some early researches were done by French scientists, namely Henri Braconnot in 1832 and Theophile-Jules Pelouze in 1838, but the Swiss scientist Christian Schönbein in 1845, was the first to realize its potential to be used in firearms as a replacement for black powder. Schönbein sent out samples of his discovery to friends in England in 1846 and published details about his discovery, but kept his method of preparation a secret until he received a patent for his discovery. Schönbein also worked with a German scientist from the University of Frankfurt named Rudolf Böttger, who had discovered the same process independently during 1845, to improve the manufacturing process. By a strange coincidence, another German, a professor from the town of Braunschweig, Dr. F. J. Otto also made a similar discovery and published his process details in 1846 before Schönbein and Böttger,

The discoveries of Schönbein soon attracted the attentions of many other chemists (mostly French and German), who investigated the properties and chemical composition and came up with different variants. Some of these names include the above mentioned Pelouze (who revisited his earlier research and came up with a new process in 1846), Dr. Knopp, Dr. Bley, Von Kirchoff & Reuter, Porret, Teschemacher, Walter Crum and Dr. J.H. Gladstone.

In England, a company called John Hall & Sons Co. bought the patent rights to manufacture gun cotton from Schönbein in 1846 and built a new factory to do so at Faversham in early 1847. Unfortunately for them, the process and its associated dangers was not fully understood and a few months later, on 14th July 1847, there was a huge explosion that destroyed the factory and killed many workers, leading to the factory being closed soon afterwards. The manufacture of gun cotton was not attempted in Faversham again until 1873, when a different company opened a new plant at a new location outside town. But this was not the only tragedy -- only a year later, on 17th July 1848, 1600 kg. of gun cotton exploded in a factory at Bouchet near Paris. This explosion was so powerful that walls from 18 inches to a yard in thickness were reduced to powder, and heavy weights were hurled to great distances. These and other accidents, caused the French and German governments to appoint committees to study whether manufacturing of gun cotton was worthwhile or not. After 6 years of experiments, the French Commission reported that, "In the present condition of things, there is no use in continuing the experiments in relation to employment of gun-cotton in warlike arms."

However, all was not lost. Over in Austria, an officer named Wilhelm Freiherr Lenk von Wolfsberg (also known as Baron von Lenk and Von Lenk) was conducting his own experiments in 1849 on behalf of the Austrian military. Von Lenk was serving in a Field Artillery regiment when he began his experiments and he discovered the cause of the previous failures. He came up with a process of manufacture that was both safer and profitable. Due to his researches, a factory "K. K. Ärarische Schießwollanstalt" was set up in Hirtenberg to manufacture gun cotton in 1851. This factory was later absorbed into a larger artillery arms company that still exists today, Hirtenberger AG.

Major General Baron Von Lenk in 1865. Click on the image to enlarge. Public domain image.

The developments in Austria naturally attracted the attention of several European governments, and from England, a Major Young was sent over to Austria to learn everything that the Austrians were willing to disclose. In 1862, a committee was appointed by the British Association to inquire into the application of the new explosives for war purposes. The committee consisted of 3 chemists, the previously mentioned Dr. J.H. Gladstone, Professor W.A. Miller and Professor Frankland, and 6 engineers, William Fairbairn, J, Whitworth, James Nasmyth, J. Scott Russell, J. Anderson and Sir W.G. Armstrong. In case you think some names sound familiar, J. Whitworth is the gent that invented the Whitworth rifle and W.G. Armstrong invented the Armstrong gun and they later co-founded Armstrong, Whitworth & Co., a major armaments, shipbuilding, aircraft and engineering company. James Nasmyth is known for inventing the steam hammer, while John Scott Russell was an engineer who built the Great Eastern steamship, which was the largest ship in the world for 40 years. This superstar committee talked to General Von Lenk and presented a report in 1863 at Newcastle, with some details of the Von Lenk process which will be described below:

In the manufacture of gun-cotton, the end-goal is to produce a product that is as highly nitrated as possible. Von Lenk found that, in order to ensure the production of this, it was necessary to adopt several procedures, the most important of which were specified as:

  1. The cotton should be cleansed and perfectly dessicated (i.e. dried out) previous to its immersion in acids.
  2. The acids used should be the strongest available.
  3. The steeping of the cotton in a fresh strong mixture of acids after the first immersion and partial conversion into gun cotton.
  4. The steeping should be continued for 48 hours.
  5. The gun cotton should be thoroughly purified afterwards and every trace of free acid should be removed. This was done by washing the product in a stream of water for several weeks; subsequently a weak solution of potash could be used as a final wash, but this wasn't essential.
We will study more details about the Von Lenk process in our next post.

Tuesday, December 27, 2016

Smokeless Powders: The Invention of Gun Cotton

In today's post, we will study one of the earliest developments in smokeless powder technology: the invention of gun cotton.

In 1832, a French chemist named Henri Braconnot found that mixing nitric acid and wood fibers would produce a very explosive material. A few years later in 1838, another Frenchman, Theophile-Jules Pelouze, produced explosive materials by treating paper and cardboard with nitric acid. However, both these discoveries very highly unstable and could not be used for practical explosives. It was left to a Swiss chemist named Christian Schönbein to discover a more practical solution. The discovery of gun cotton was actually the result of an accident:

Christian Schönbein. Public domain image.

Schönbein was a professor of chemistry at the University of Basel in Switzerland. His wife laid down an order to not conduct any chemical experiments at home, but he didn't always obey her and would do his experiments at home when she was not around. One day in 1845, his wife went out for some time and he went into the kitchen and mixed up a combination of nitric acid and sulfuric acid. Due to careless handling, he spilled the mixture onto the kitchen table. He quickly grabbed his wife's cotton apron and wiped the mess up and then hung her apron over the stove to dry, so she would not find out that he'd been doing experiments at home when she was away. To his surprise, the apron suddenly ignited and burned very rapidly, leaving almost no ash behind. What he had done was accidentally create nitrocellulose (gun cotton).

Let us understand the chemistry behind what he'd accidentally invented. The manufacture of guncotton (and other nitro compounds) consists of immersing the material (cotton, wood fibers, paper etc.) in a mixture of nitric and sulfuric acids and allowing the nitric acid to act upon it for a certain amount of time. The explosive material that is formed is then separated from the acids and washed until it loses all traces of acid. For example, in the case of gun cotton, the following reaction happens:

C12H20O10 + 6HNO3 = C12H14O4(O.NO2)6 + 6H2O

The cellulose combines with the nitric acid forming nitrocellulose and water (H2O). It would appear from this above equation that only nitric acid is needed for this reaction. However, note that one of the other byproducts of this reaction is water, which would end up diluting the remaining nitric acid and cause it to form other nitro-compounds instead. This is where the sulfuric acid comes in. The sulfuric acid takes care of the water formed by this reaction and also acts as a catalyst to form the NO2 ions.

In the original version of his process, Schönbein mixed three parts of sulfuric acid to one part of nitric acid by weight. Then, he would take twenty to thirty parts of this acid mixture into a porcelain vessel and dip one part of cotton at a temperature of around 10° to 15° C for an hour. After that, the liquid was poured out and the gun cotton was thoroughly washed in water and then in a dilute potash solution to eliminate acids. It was then again washed in water to dissolve any salts formed from the previous washing, then squeezed out to remove the water, then soaked in 0.6% solution of saltpeter, squeezed out again and finally dried at 65° C. Later on, Schönbein modified this process to use 14 parts of a mixture of equal volumes of nitric and sulfuric acids, to each part of cotton.

Gun cotton produces about six times the amount of gas than the same volume of black powder, while producing far less smoke and heat.

Now that we've studied the reaction at a high level, we will look at some of the machinery used for this process in the next few posts.

Friday, December 23, 2016

Smokeless Powders: Introduction

In the last several months, we have studied the production of various forms of black powder in depth. The next series of posts will deal with an in-depth study of smokeless powders. We had studied about this some years ago, but not really in detail.

So why smokeless powder?? First, let's go over some disadvantages of black powder:

  1. It is very flammable. Black powder can easily be ignited by a single stray spark, hard impact or a hot object and therefore, it requires careful handling.
  2. It leaves a lot of residue behind, which can cause fouling problems inside the firearm. The residue is also caustic, which can cause corrosion issues if it is not removed quickly. What this means is that firearms that use black powder need to be cleaned after firing just a few shots. 
  3. Black powder also produces a lot of smoke upon ignition. In fact, many infantry troops using black powder weapons faced a problem on the battlefield in that after firing a few shots, they would no longer be able to see the enemy due to the clouds of smoke produced by their own weapons.
  4. Black powder is hygroscopic (i.e.) it absorbs water from the atmosphere. This causes two problems: the first is that presence of water makes the powder less efficient and may even spoil it to the point where it doesn't ignite reliably. The second problem is that remnants of black powder in a firearm can cause the metal to rust rapidly. Due to this, it was necessary to clean firearms thoroughly immediately after use, especially in humid areas, in order to prevent the formation of rust.
  5. Black powder does not ignite when wet. This caused many soldiers to have their firearms rendered useless during rainstorms. This is the reason why many soldiers also carried a sword or a spear as a backup weapon.
By contrast, smokeless powders offer more propulsive power than the same weight of black powder and leave a lot less smoke and residue behind. This makes it possible to not only increase the range of firearms, but also shoot for longer periods of time without cleaning the weapon -- this is what made it possible to develop semi-automatic and automatic firearms. Early smokeless powders were somewhat unstable, but as technology improved, they became a lot more stable than black powder and don't require as much careful handling. They are also not affected by rainy weather and can even ignite underwater. 

With that said, there are a few misnomers about smokeless powder that we should clear up before we go in-depth with our study. First, the name is misleading: smokeless powder is not actually 100% smokeless. There is some smoke produced, but it is much less than that produced by black powder. The second misnomer is that there is no single formula for smokeless powder. In fact, there are multiple types of smokeless powders, each made with different chemicals. This is unlike black powder, where the three ingredients are always carbon, sulfur and potassium nitrate (albeit with different proportions of the ingredients and different grain sizes).

In our next post, we will study the first development in the family of smokeless powders: guncotton.

Sunday, December 4, 2016

Black Powder - Chemical Examination

In our last few posts, we saw how people would determine the quality of black powder by measuring the physical properties of the powder, such as color, size, shape, density, hygroscopic properties etc. In today's post, we will study some of the chemical properties that people would examine to determine the quality of powder.

The first type of test was the Qualitative Examination test, which was done if the ingredients of the powder were not known (e.g. some powders did not have sulfur, others may have sodium nitrate instead of potassium nitrate, still others may have charcoal made of wood, wood pulp, bark, straw etc.).

Recall a few months ago, we had stated that black powder is a mixture and not a compound at room temperature. It only forms various chemical compounds when it starts to burn. Therefore, since it is a mixture, it retains properties of its component parts.

Therefore, to determine the kind of nitrate contained in the powder, a small quantity of powder would be put in a filter and then hot water poured over it, which dissolves the nitrate salt. The filtered liquid was then chemically analyzed to determine the type of nitrate. Next, to determine if the powder contains sulfur or not, a small quantity was placed in a beaker and carbon disulfide was poured on top and allowed to stand for a little while. The solution was then poured out and evaporated. If any sulfur was present in the powder sample, it would crystallize out. To determine the type of charcoal used, they would first remove the sulfur from the sample using the carbon disulfide solution, then they would filter it and then wash with hot water to extract the saltpeter out, then they would dry out the remaining residue and examine it under a microscope, which would show whether the carbon was made from charcoal, wood pulp, wood bark, straw etc.

Of course, the above qualitative tests would show the presence of the ingredients in the powder, but not the proportions of the ingredients. To do that, they would do quantitative analysis tests, which determine the percentages of the ingredients. To do this, they would first dry a sample of powder as much as possible. Then, they would take a known quantity of powder, run hot water through it several times to dissolve all the saltpeter and then evaporate the solution to recover the saltpeter crystals, which could then be weighed.

After the saltpeter had been removed from the sample of powder, the next was to determine the amount of sulfur in the remaining sample. This could be done either directly, or by converting the sulfur into sulfuric acid. The direct method was due to Berzilius: The sample of powder after the saltpeter was extracted, was dried and weighed and then transferred into one of the bulbs of a double bulbed tube. A current of dry hydrogen was passed over the mixture while it was gradually heated. This heat would cause the sulfur to vaporize and the sulfur fumes would be carried along with the current of hydrogen into the second bulb, where it would cool down and crystallize in the second bulb. The decrease in weight in the first bulb and the increase in weight in the second bulb could be measured and this would show the amount of sulfur in the sample. Another technique was to dissolve the sulfur in a carbon disulfide solution and then evaporate it to recover the sulfur crystals, which could then be weighed to determine the percentage of sulfur in the sample.

After the saltpeter and sulfur have been removed, the remainder was dried and weighed to determine the amount of carbon in the sample.

It is also possible to determine all the components of black powder simultaneously, using special apparatus, such as that invented by Linck in the 19th century.

Click on the images to enlarge. Public domain images.

This involves using various pieces of equipment to precisely extract the components of the powder, using carbon disulfide, hot water, barium chloride, lead acetate etc. to determine the exact quantities of the various ingredients in the sample.

Friday, November 25, 2016

Examining Black Powder Quality - III

In our last post, we studied one physical property (density) that was used by people to judge black powder quality. Today we will study another technique that people used to judge the quality of black powder: the hygroscopic properties of powder.

The term "hygroscopy" refers to the phenomenon of certain substances attracting water molecules from the surrounding air and absorbing it. Examples include table salt, sugar, honey etc. This is why they are usually kept in sealed containers, otherwise they tend to absorb water from the atmosphere and spoil.

In the case of black powder, two of its three components have hygroscopic properties: saltpeter and charcoal. The saltpeter is usually hygroscopic due to the presence of impurities such as calcium salts and sodium chloride. In general, calcium sulfates or calcium oxide can react with the sodium chloride to form calcium chloride, which is very hygroscopic in nature. The calcium chloride on the surface absorbs enough water to become a liquid and dissolves some saltpeter and the solution spreads itself through all the grains by capillary action. This causes the saltpeter to be no longer evenly distributed in the powder grains. Therefore, keeping the saltpeter as pure as possible helps keep the hygroscopic properties of the powder down.

Charcoal also influences the hygroscopic properties of black powder. As a general rule of thumb, the more charcoal that the powder contains, the more water it will tend to absorb. One more interesting factor has to do with the temperature that the charcoal is manufactured at. The lower the temperature at which it was manufactured, the more water it can absorb. As a result of this, red charcoal will generally absorb more water than black charcoal.

If the powder becomes damp, it may be restored by drying in the sun or in a dry, well-ventilated room. As a general rule, if the powder does not show an efflorescence of white crystals of saltpeter on its surface, it may be possible to dry it. Powder of smaller gravimetric density will absorb more moisture than a powder of a greater one, and a glazed powder will absorb less moisture than an unglazed one, all other things being equal. Powder that has become damp can be easily recognized by its unequal distribution of color and by the grains crushing more easily between the fingers. However, if it manages to absorb a large amount of moisture. the powder will form hard black lumps and if is reaches this state, the powder is generally useless and cannot be serviced.

To determine the moisture content of a sample of powder, a standard amount (usually 100 grains or 50 grams, depending on country) would be carefully weighed onto a glass plate. Then the glass plate would be placed in an oven and heated for a few hours at a specified temperature that depended upon the country (160 °F for England, 190 °F for Germany etc.) and then placed in a dessicator to cool for 20-30 minutes, after which they would weigh the sample again. The difference in weight is the amount of water absorbed by the powder sample.

To determine the tendency of a particular powder sample to absorb moisture, the powder sample was put alongside a sample of standard powder over a layer of water in a tub, which was closed air-tight and left for a period of time. The two powder samples would then be removed and the amount of water absorbed by each sample would be compared. This test would let people know how much their particular powder differed from the standard sample powder.

In the next few posts, we will look at some of the chemical properties that people would look at to judge powder quality.

Note: I trust my American readers had a happy Thanksgiving holiday so far. Your humble editor was temporarily hospitalized for a little while, but I recovered just in time to spend the holiday at home with family and friends, just as it should be :-).