Picric acid properties

Reactions of Picric Acid, (i) The presence of the three nitro groups in picric acid considerably increases the acidic properties of the phenolic group and therefore picric acid, unlike most phenols, will evolve carbon dioxide from sodium carbonate solution. Show this by boiling picric acid with sodium carbonate solution, using the method described in Section 5, p. 330. The reaction is not readily shown by a cold saturated aqueous solution of picric acid, because the latter is so dilute that the sodium carbonate is largely converted into sodium bicarbonate without loss of carbon dioxide. 

The fact that all ligands failed to transfer Fe " ion from the aqueous into the organic phase was not unexpected, since this ion prefers to bind with picric acid more than the other ligands. This property is typical only for the Fe " ion [54]. Yet, our previous observations [49] indicated that, when FelNO.ala was used instead of metal picrate, it was possible to efficiently extract Fe " into the organic phase by utilizing ligands 1, 3, and 4. 

Le Roux (Ref 19) examined the expl properties of Nitrostarch of 13.52% N, At a density of 0.90g/cc, a charge of 30mm diam in a cardboard tube detonated at the rate of 497Qm/sec. The relative lead block expansion was 117% of Picric Acid... 

Sowinski M. Warman, Lead Salts of Trinitro Phenols. I. Preparation and Properties of Methoxy Picric Acid and Lead Methoxy Picrate , PATR 3344(1966)... 

The view then prevailed, supported by such an authority as Abel, that Picric Acid itself is not an explosive, but only its salts are. Nevertheless in 1873 Sprengel (Ref 11) proved that Picric Acid could be brought to explosion by a detonator and Turpin (Ref 12) proposed applying this property of Picric Acid by utilizing it for... 

The powdered oxidant functions as an explosive when mixed with finely divided metals, organic materials or sulfur, which increase the shock-sensitivity up to that of picric acid [1]. The hazardous properties of such mixtures increase as the particle size of the oxidant salt decreases [2],... 

Cl Sulphur Black 1, which is produced from the relatively simple intermediate 2,4-dinitrophenol and aqueous sodium polysulphide. A similar product (Cl Sulphur Black 2) is obtained from a mixture of 2,4-dinitrophenol and either picric acid (6.148 X = N02) or picramic acid (6.148 X = NH2). A black dye possessing superior fastness to chlorine when on the fibre (Cl Sulphur Black 11) can be made from the naphthalene intermediate 6.149 by heating it in a solution of sodium polysulphide in butanol. An equivalent reaction using the carbazole intermediate 6.150 gives rise to the reddish blue Cl Vat Blue 43 (Hydron blue). This important compound, which also possesses superior fastness properties, is classified as a sulphurised vat dye because it is normally applied from an alkaline sodium dithionite bath. Interestingly, inclusion of copper(II) sulphate in the sulphurisation of intermediate 6.150 leads to the formation of the bluish black Cl Sulphur Black 4. 

Turpin (1848-1927) of detonating properties of PA (Picric Acid), was followed by its adoption for filling HE shell of his design (See next item) Note Accdg to Marshall (Ref 11, p 44), H. Sprengel was the first to draw attention to the fact that PA by itself could be initiated by a powerful detonator and was a very powerful expl, but no practical use was made of his discovery (See year 1873)... 

Explosifs 6 I aluminium. Fr for Aluminized Explosives. Several Fr formulations are listed in Vol I of Encycl under ALUMINUM CONTAINING EXPLOSIVES, on p A146-L. Examination in 1902 by CSE (Commission des Substances Explosives) showed that some of these exp Is, as, for example, Formula. 226 (p A146 L)> were more powerful than PA (Picric Acid). More recently (1948 1950), Medard (p A148-L) determined the properties of die following Fr aluminized explosives ... 

Trinitrotoluene (TNT) was the most commonly used conventional military explosive during the twentieth century. Although it had been used extensively in the dye industry during late 1800s, it was not adopted for use as a military explosive until 1902, when the German army used it to replace picric acid. TNT was first used in warfare during the Russo-Japanese War (1904-1905). The US Army began its use in 1912. After an economical process was developed for the nitration of toluene, TNT became the chief artillery ammunition in World War I (1914—1918). The most valuable property of TNT is that it can be safely melted and cast alone or with other explosives as a slurry. 

The presence of nitro groups in phenol and resorcinol enhances their acidic properties and that is why trinitrophenol is commonly known as picric acid while trinitroresorcinol is known as styphnic acid. 

Cyclonite is a very important explosive. The outstanding properties of RDX as an explosive are high chemical stability, not much lower than aromatic nitro compounds and high explosive power which considerably surpasses that of aromatic nitro compounds such as TNT and picric acid. RDX has a detonation velocity of8600 ms"1 and a detonation pressure of 33.8 GPa at a density of 1.77 gem"3. RDX is used in mixtures with TNT (Hexotols, Cyclotols, Compn. B) wax (Composition A) aluminum (Hexals) aluminum and TNT (HBX, Hexotonal, Torpex) etc. 

The substance possesses quite uncommon and valuable explosive properties. It is more powerful than tetryl, and considerably less sensitive to impact (as sensitive as picric acid). However, its acidic properties limit its use to a great extent. In this respect it resembles picric acid. Even so ethylenedinitramine, under the name of Haleite, has been accepted in the United States as a military explosive. During World War II, production in that country was carried out by the method outlined above according to eqn. (17)... 

Romburgh [3] was the first to prepare this substance both by nitrating ethyl-aniline and by nitrating diethylaniline. It is comparable to tetryl in its physical and chemical properties. As an explosive it is weaker than tetryl. Its sensitiveness to impact and its explosive power, measured in the lead block, are somewhat greater than those of picric acid. 

The explosive properties of hexanitrodiphenyl-/ -hydroxynitraminoethyl nitrate are similar to those of pentryl. It is slightly more stable on heating its ignition temperature lies between 390 and 400°C. It is somewhat less sensitive to impact than pentryl and rather more powerful (by 3%) in the lead block test. It requires a stronger initiator than pentryl, tetryl or picric acid, but a weaker one than trinitrotoluene. 

A number of salts of picric acid have been described already (Vol. I). Some salts of polynitrophenols and of heavy metals have initiating properties. One of the earliest known substances of this kind is lead picrate. Its high sensitiveness to the action of mechanical impact, however, raised difficulties in its practical utilization. 

The molecular composition of picric acid was established in the early ninteenth century when it was the only highly-nitrated aromatic compound then known. It was evident that its oxygen content was insufficient for complete combustion (to C02 and H20). This was considered to be an adequate foundation for the erroneous theory that, because of its insufficient oxygen content, the substance has no explosive properties. It was believed that explosive properties are achieved only by mixing picric acid with oxidizing agents such as chlorates, or sodium or potassium nitrates. 

To achieve the necessary stability he used its ammonium salt, which has no acidic properties instead of picric acid. 

With the development of the organic chemical industry, aromatic nitro compounds of the TNT type were introduced as ingredients of composite explosives. TNT is preferable to picric acid since it has no acidic properties and hence is much less reactive. Mixtures with TNT and similar nitro compounds showed an excellent chemical stability. 

The explosive properties of mixtures with ammonium nitrate depend on the quantitative relationship between the oxidizing agent and the explosive or combustible substance. According to Parisot and Laffitte s [9, 47] investigations the explosive properties of mixtures of aromatic nitro compounds with ammonium nitrate vary with the change in composition of the system in an almost rectilinear manner. The graph in Fig. 69 shows how the rate of detonation depends on the composition of mixtures of tetryl or picric acid with ammonium nitrate. T. Urbanski et al. [48] also obtained a rectilinear relationship for nitrostarch mixtures with ammonium or sodium nitrate (Fig. 71, p. 265). 

All these electrolytes are neutral in Bronsted acid-base properties. Although rather exceptional, an acid, a base, or a pH buffer may be added to the supporting electrolyte of neutral salts. The acid-base system to be selected depends on the purpose of the measurement. We often use trifluoromethanesulfonic acid (CF3S03F1) as a strong acid acetic acid, benzoic acid, or phenol as a weak acid an amine or pyridine as a weak base and tetraalkylammonium hydroxide (ILtNOH) as a strong base. Examples of buffer systems are the mixtures of picric acid and its R4N-salt and amines and their PlCl04-salts. Here, we should note that the acid-base reactions in aprotic solvents considerably differ from those in water, as discussed in Chapter 3. 

Picric acid was used in grenade and mine fillings and had a tendency to form impact-sensitive metal salts (picrates) with the metal walls of the shells. The filling of mines and grenades was also a hazardous process, since relatively high temperatures were needed to melt the picric acid. Some of the properties of picric acid are presented in Table 2.9. 

RDX has a high chemical stability and great explosive power compared with TNT and picric acid. It is difficult to dissolve RDX in organic liquids but it can be recrystallized from acetone. It has a high melting point which makes it difficult to use in casting. However, when it is mixed with TNT, which has a low melting temperature, a pourable mixture can be obtained. Some of the properties of RDX are presented in Table 2.15. 

Trinitrophenetol or ethyl picrate, m.p. 78°, is prepared by the same methods as trinitroanisol. The explosive properties of the two substances have been studied by Desparmets and Calinaud, and by Desvergnes,72 who has reported the results of the earlier workers together with data of his own and discussions of methods of manufacture and of the explosive properties of mixtures with picric acid, ammonium nitrate, etc. Drop test with a 5-kilogram weight were as follows ... 

At present nitration is one of the most widely applied direct substitution reactions. This is due to several factors. For example nitration usually proceeds easily, its products can readily be separated from the spent acid, said there is a wide range of possibilities in the practical use of nitro compounds, both as intermediates and end products. The presence of a nitro group in the starting product made it possible to obtain a number of basic organic intermediates such as aniline said benzidine. Dyes with more than one nitro group, such as picric acid were obtained. It has been found that higher nitrated nitro compounds and nitric acid esters have explosive properties and are of practical importance. Some nitro compounds are used in perfumes. Medicinal properties have lately been discovered in certain nitro compounds, eg. chloramphenicol. 

This property of nitro compounds was first observed by Foord [78] with regard to o- nitrophenol, 2,4-dinitrophenol, picric acid, m- dinitrobenzene, 2,4-dinitro-toluene, 1,3,8-trinitronaphthalene, 2,4-dinitroaniline and other higher nitrated aromatic compounds. 

The ability to form addition compounds, especially with aromatic hydrocarbons composed of condensed rings, is one of the specific properties of aromatic poly-nitro compounds. For example, compounds of trinitrobenzene or picric acid with naphthalene, as well as with other hydrocarbons with condensed rings, are very characteristic. Generally they are intensely coloured. 

While for picric acid a value K = 0.164 had been found by this method (Rothmund Mid Drucker [76]), for trinitrotoluene Farmer found K = 2.0 x 10 14, which means that trinitrotoluene is mi acid 1013 times weaker than picric acid. In effect it has virtually no acidic properties. 

Chemical properties. The chlorine atom in a picryl chloride molecule is exceptionally reactive. Besides hydrolysis to picric acid when heated with water, as mentioned above, picryl chloride can yield picric acid when boiled with alcohols, according to the equation ... 

The presence of nitro groups enhances the acidic properties of the phenol group. This is why the trinitro derivatives are also called acids, e.g. trinitrophenol is known as picric acid and trinitroresorcinol as styphnic acid. These compounds readily form salts with metals or bases. Polynitro derivatives of phenols also form addition compounds with hydrocarbons, e.g. naphthalene. 

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