Sometimes, when discussing ammunition, in particular, cartridges, one can come across the assertion that the lead azide used in primers is such a more powerful and modern initiating explosive compared to mercury fulminate, better known as mercury fulminate. This is usually presented as truth beyond doubt.
However, when comparing the properties of both types of initiating explosives, it can be seen that the parameters of lead azide are somewhat lower than those of detonating mercury. For lead azide, the heat of explosion is 1.6 MJ / kg, for explosive mercury - 1.8 MJ / kg, the volume of gases for lead azide is 308 liters / kg, for explosive mercury - 315 liters / kg, the detonation velocity for lead azide, in depending on the density, it ranges from 4630 to 5180 m / s, for explosive mercury - 5400 m / s. The sensitivity to impact of explosive mercury is higher; in terms of explosiveness, they are the same. In general, comparable substances, with some advantage in mercury.
In addition, lead azide, obtained in the form of needle-like crystals, has a much lower flowability and compressibility than powder detonating mercury, and this is important for the accurate composition of the mixture for the primer charge. However, to initiate TNT, 0.36 grams of explosive mercury is required, and 0.09 grams of lead azide is required. These substances have their advantages and disadvantages.
The reason for the replacement was clearly different and was rooted in military and economic considerations. Mercury is difficult to obtain, and it is not possible to obtain it everywhere, while lead is mined in volumes of thousands and even tens of thousands of tons. It is easier to produce lead azide.
The emergence and use of lead azide
Lead azide, as you might guess, appeared in Germany. It was first obtained in 1891 by the German chemist Theodor Curtius. This discovery was quickly noticed by the military, and already in 1907 the first initiating charge with lead azide was patented in Germany. In 1910, the Rhine-Westphalian Explosives Company patented a mixture of lead azide, nitrogen sulfide and diazolbenzene nitrate for detonator caps.
Work on lead azide was also carried out in France, the USA, Russia and other countries. By the way, lead azide was studied in Russia, but it did not go into widespread use, for the reason that there was a lot of mercury in Russia. Its production began in the 18th century in Transbaikalia. In 1879, the Nikitovskoye deposit was discovered in Ukraine, and the production of metallic mercury began in 1887. From 1887 to 1913, about 6762 tons of mercury were mined, of which 5145 tons were exported, which gives an average annual production of 260 tons and an export of 197 tons. In addition, there was also an import of cinnabar and mercury, in 1913 56 tons of cinnabar and 168 tons of mercury. That was such an interesting economy, import and export, most likely, the refining of primary mercury was carried out abroad. In general, there was enough raw material for the production of explosive mercury, and there was no particular need for lead azide.
In Germany, the situation was the opposite. Germany's own resources were small and produced at best 4-5 tons of mercury per year. Germany in 1913 imported 961 tons of mercury, mainly from Italy, buying up almost all Italian production. With the outbreak of the First World War and the transition of Italy to the Entente camp, this source disappeared. But the ally, Austria-Hungary, which had the second largest cinnabar mine in the world, in Idrija, Slovenia, had a lot of mercury. It was one of the most important businesses in the empire. However, fighting between the Austrian and Italian armies put this source in serious jeopardy. In the summer of 1917, the Italian army approached only about 12 miles away from Idrija. This circumstance forced the German command to promptly help the Austrian army in organizing an offensive, during which the Italians were driven back.
In view of the possibility of the loss of mercury in Germany, lead azide began to be produced and put into use during the First World War. Although it cannot be said that everywhere and everywhere the replacement of explosive mercury with lead azide was good. For example, in shells for anti-aircraft guns, lead azide led to frequent explosions in the barrel. In March 1918, 43% of anti-aircraft guns on the Western Front were disabled by explosions of a shell in the barrel. The reason was that the manufacturing process for lead azide was changed, and it became so sensitive to impact that it exploded when fired. The Germans were forced to replace the entire stock of shells for anti-aircraft guns.
After the end of the war, when the world market for mercury collapsed, production fell to 2,100 tons in 1923 (in 1913 there were 4,000 tons), lead azide began to take over. Coal mines needed detonators now and cheaper for mining. The Rhine-Westphalian Society has established a very large-scale production of this substance. One plant in Troisdorf produced 750 tons of lead azide until 1932.
During World War II, Germany did not pay much attention to lead azide, because by the beginning of the war the largest producers of mercury, Spain and Italy, were on the side of Germany. Especially Italy, which was in dire need of German equipment and German coal. In 1938, Italy produced 3,300 tons of mercury, which would be enough for every imaginable need. By the way, the former Austrian mercury mine ended up in the region of Slovenia occupied by the Italians and included in the Venezia Giulia region of Italy.
As far as can be judged, lead azide played a slightly different role in the war economy of Nazi Germany. Its use, especially in a mixture with lead trinitroresorcinate, made it possible to save the consumption of scarce copper for the production of fuses. Lead azide with copper forms copper azide, which is very unstable and prone to spontaneous explosion; therefore, the fuse bodies were made of aluminum. On the other hand, detonating mercury requires a copper tube, since it forms an amalgam with aluminum. On a production scale of tens and hundreds of millions of ammunition, replacing copper with aluminum gave very tangible savings.
What does it mean to lose mercury?
On October 29, 1941, a disaster struck - the Germans captured Gorlovka in Ukraine. Next to it was Nikitovka, where there was the only combine in the USSR for the extraction and smelting of mercury. In 1940, he produced 361 tons of mercury, and in January-September 1941 - 372 tons. The plant was technically advanced (which was noted even by the Germans), it processed ore with a very low mercury content. True, it did not cover all the country's needs for mercury, which reached 750-800 tons, and before the war the USSR bought mercury abroad, primarily in Italy.
Now all sources have disappeared. Meanwhile, according to the data of the Glavredmet of the People's Commissariat of Nonferrous Metallurgy of the USSR, consumption in the 4th quarter of 1941 by military commissariats was 70 tons (including the People's Commissariat of ammunition - 30 tons), and by civilian commissariats - 69 tons (RGAE, f. 7794, op. 5, d.230, l.36). The estimated annual consumption in the production of ammunition alone was 120 tons; total military consumption per year - 280 tons, total - 556 tons.
Of course, all the mercury that was possible was sent to the military industry, up to the removal of mercury in laboratories and at civilian enterprises. We were approaching mercury switches and gold mining by amalgamation.
The equipment and workers of the Nikitovskiy mercury plant was hastily transferred to Kyrgyzstan, to the Khaidarkan mining deposit, explored in the early 1930s. This is a huge deposit of fluorspar mixed with mercury and antimony. There, a new mercury plant was built at an accelerated pace, on the basis of an already existing pilot plant. In 1941, Khaidarkan gave 11.6 tons of mercury, and the plan for 1942 was delivered to him 300 tons. Of course, the new plant has not smelted that much. Even in 1945, the smelting of mercury amounted to 193.7 tons. But still, Khaidarkan's mercury made it possible to hold out in 1942-1943, in the most difficult period. And there the allies already helped (according to Lend-Lease, 818.6 tons of mercury were delivered before January 1, 1945), and on September 5, 1943, Gorlovka was liberated, and specialists from the USSR People's Commissariat of Nonferrous Metallurgy rushed to Nikitovka.
The data on mercury production was a very interesting archival find, which allows us to say that the acute shortage of ammunition, especially artillery shells, which was noted from the end of 1941 and around the spring of 1943, was associated not only and not so much with the relocation of the industry, but with an acute lack of raw materials for the production of explosive mercury.
Under these conditions, lead azide, of course, had to be used as a substitute for explosive mercury. Only information about this has to be mined approximately like gold in Kolyma, in the placers of information. For example, there is information that at the plant number 5 named. I. I. Lepse in Leningrad (also known as the Okhta shipyard) used to have a shell production for naval artillery, and with it there was a workshop for the production of lead azide. Therefore, this workshop was closed in connection with the separation of shell production in a separate plant. In September 1941, part of the plant was evacuated, but in connection with the expansion of the production of weapons and ammunition in Leningrad, the former workshop was remembered and restored.
Now there is little mercury
Apparently, the Soviet leadership learned a lesson from the epic of the loss of the Nikitovsky mercury plant and after the war paid the most serious attention to the mercury industry: it began to grow. The extraction of primary mercury in the USSR in the early 1980s was about 1900-2200 tons per year, and in 1966 a special decree was issued obliging enterprises to send all mercury-containing waste to the Nikitovsky Combine for processing. The plant received about 400 tons of secondary mercury per year. Domestic consumption of mercury in the 1980s ranged from 1000 to 1250 tons per year (in 1985 even 1307 tons), exports fluctuated in the range of 300-450 tons per year, and the remainder was added to the stock.
About 20% of domestic consumption went to military needs, including for the production of explosive mercury, that is, from 200 to 250 tons per year. And another 500-600 tons of mercury a year was added to the reserve, apparently also for military needs, in case of a major war. In principle, 1000-1500 tons of mercury in the warehouse could meet the needs of the production of ammunition for two or three years of war.
Lead azide is a substitute for explosive mercury in conditions of its lack. The current prevalence of lead azide is due to the fact that mercury production has declined sharply. In the 1970s, the world market for primary mercury was about 10 thousand tons per year, now production has decreased to about 3 thousand tons per year. This is significant, since a significant part of the mercury is consumed irretrievably. At the same time, the Minamata Convention on Mercury was signed in October 2013, which aims to drastically reduce the use of mercury and bans the production of mercury switches, lamps, thermometers and pressure measuring devices from 2020.
With the decline in mercury production, the sale of stocks (Russia also sold its stocks of mercury in the 1990s) and the prospects for an even greater drop in mercury production, of course, the spread of lead azide is not surprising. If the UN decided to strangle the world mercury industry, then something must be done for democracy or against it, and lead azide will replace the explosive mercury.
