Picric acid test

Picric acid tested herein is of the A, C. S. reagent grade (98 % picric acid) and was got from Aldrich chemical Co., Inc. as moist picric acid containing 35 % water. The moist picric acid was dehydrated before testing in accordance with directions described under the heading of Section 9.5. 

At all events, it is certain that, when confined in the closed cell and subjected to the isothermal storage test performed at a T, below 163 °C, 2 g of picric acid tested herein does not start the exothermic decomposition reaction at all. 

Nevertheless, Merrifield and his co-workers introduced the picric acid test into a commercial peptide synthesizer to refine it into an almost fully automatic system controlled by a spectrophotometric unit, which determines the concentration of picrate released from the polymer support [137]. Though the machine performs the physical measurements with the highest accuracy available in this connection to date, the best analytical device cannot compensate inherent variable chemical deviations of a test reaction employed on polymer phase. 

Picric acid is usually stored damp for safety, and acetone is therefore a better solvent than benzene or this test the solutions musi be almost saturated, however. 

Place a mixture of 0-5 g. of finely powdered thiourea, 0-5 g. of the alkyl halide and 5 ml. of alcohol in a test-tube or small flask equipped with a reflux condenser. Reflux the mixture for a j)eriod depending upon the nature of the halide primary alkyl bromides and iodides, 10-20 minutes (according to the molecular weight) secondary alkyl bromides or iodides, 2-3 hours alkyl chlorides, 3-5 hours polymethy lene dibromides or di-iodides, 20-50 minutes. Then add 0 5 g. of picric acid, boil until a clear solution is obtained, and cool. If no precipitate is obtained, add a few drops of water. RecrystaUise the resulting S-alkyl-iso-thiuronium picrate from alcohol. 

Eor the selective pre-concentration of deactivated phenols a new silica-based material with the grafted 2,3,5-triphenyltetrazole was proposed. This method is based on the formation of molecular chai ge-transfer comlexes of 2,3,5-triphenyltetrazole (7t-acceptor) with picric acid (7t-donor) in the phase of the sorbent. Proposed SPE is suitable for HPEC analysis of nitrophenols after their desorption by acetonitrile. Test-system for visual monitoring of polynitrophenols under their maximum concentration limits was developed using the proposed adsorbent. 

VIII. Explosive Characteristics. Picric Acid is generally considered to be a relatively insensi tive but brisant expl. On a qualitative sensitivity scale of comparing common expls, PA would be judged to be more sensitive than TNT but appreciably less sensitive than Tetryl. Its power and brisance are also similar to those of TNT (112% TNT in the Ballistic Mortar 101% of TNT in the Trauzl Block and 107% in the plate dent test (Ref 48). In this section we will consider the steady detonation parameters. initiation characteristics and potential hazards of PA... 

Tait24 was determined as 189°C by adiabatic Dewar tests, with an apparent energy of activation of 144 kJ/mol. Dinitrophenol is now classified as an explosive in the UK, and is normally available from laboratory suppliers wetted with 15% water, as is picric acid. 

More recently, explosives have been tested for impact sensitivity by an impact machine in which 40 mg of explosive on sandpaper are placed between an anvil and a steel cylinder. A 2.5 kg weight is dropped from different heights and the sound produced serves to indicate a go or no go . The result from 25 drops is calculated to give a height at which the probability of explosion is 50%. Results from a compilation104 are presented in Table 12 and show that the relative values of TNT and picric acid are reversed from the previous table. TNT is relatively more sensitive on the Type 12 impact machine than in the FI impact test. TATB is so insensitive that it fails to explode at the maximum drop height of the machine. 

A special type of ISE is used in the two-phase titration [ 17, 50, 51, 52], in which the titrant (for example picric acid) is added to the aqueous phase containing the test ion (for example the trioctylethylammonium ion), which is in contact with a nitrobenzene phase containing picrate ions and functioning as an ISE. 

Falling Weight (Impact) Test. Ten tests with 0.05 to 0.1 Og samples, using an apparatus having an anvil 1.27cm(0.5") in diameter, should show that the explosive is less sensitive than Picric Acid (PA)... 

Pentryl is less sensitive to impact than tetryl (according to Clark, the maximum height causing no explosion in the drop test is 50 cm for pentryl, whereas for tetryl it is 27.5 cm and for picric acid 42.5 cm). 

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. 

Sauer (Ref 9) stabilized Dinitrodiaminomethane at a temp below its mp by coating with 0.1 to 2.0% polynitrophenol or polynitro aromatic carboxylic acid by means of absorption, recrystn or evapn from a non solvent. Thus, 98% of the pure compd 8C 2% Picric Acid were mixed 8t benz added to form a slurry. After the mixt was dried under vacuum, tests at 75° showed improved stabi-... 

International Heat Test at 75°, 0.4% loss in 48hrs reported by British no loss reported in tests conducted at Picatinny Arsenal Power by Trauzl Pb Block, 146 vs 100 for Picric Acid... 

Its Impact Sensitivity with 2kg wt app is 115cm vs 40cm for Picric Acid. Power by Trauzl Test — 111% of TNT (Refs 7 St 8)... 

Impact Sensitivity — FI 92% Picric Acid Power by Trauzl Test — 87% Picric Acid Refs 1) Beil 12, 180, (166) St [1053... 

N 21.96% crysts, mp 295-300°(dec) si sol in hot ale Sc benz very low expin temp. It was prepd by nitrating oxanilide. Its power Sc brisance are comparable with those values of TNT Pb block expansion test — 70% Picric Acid. It is reported to be chemically unstable or reactive with moisture (Refs 6, 7, 8 8t 9) Refs 1) Beil 12, 284, (207) Sc [l65]... 

It is an expl which was examined during WWII in GtBritain and the USA and found to be less powerful than TNT or Picric Acid (75% of PA by Trauzl Test) andmore sensitive to impact (FI 117% PA) (Ref 10, p 74)... 

In the test described in Ref 2, the pellets were made of TNT instead of PA (Picric Acid) of original test (Ref 1), because TNT is less sensitive and more uniform. They were not phlegmatized with oil, as only a limited quantity can be incorporated with.the expl, the excess being driven aut again on pressing. Most of the reported experiments were carridd out with TNT incorporated with 4 to 14% paraffin wax pressed at 400 kg/cm2 to pellets of 25mm... 

Urea nitrate is insensitive to friction and to impact. The density of the substance subjected to a pressure of 1500 kg/cm3 is 1.59 g/cm3. In the lead block test it caused an expansion of 260 (Kast) or 270 cm3 (T. Urbanski, Kapuscinski, Wojcie-chowski [59]). It detonates somewhat better than ammonium nitrate and guanidine nitrate, but a No. 8 detonator did not provoke complete detonation. Medard [59a] reported that urea nitrate gives a relative figure of the lead block expansion 79.6 (picric acid = 100) and the rate of detonation of 30 mm dia. charges is ... 

---