Diphenylamine test

The older technique for this purpose (Ref 8), variously referred to as the paraffin test, the paraffin-glove test, the dermal nitrate test, and the diphenylamine test, had been abundantly shown to be unreliable, was no longer accepted in most US courts, and was now seldom used by good crime investigation laboratories... 

In 1922, F. Benitez recorded this technique as a method for revealing the presence of propellant particles on the hands of a firer.112 114 In Mexico in 1931, T. Gonzales performed a modified version of Iturrioz s test using molten paraffin wax on the hands of a firer and in 1933 demonstrated the test in the United States. The test has also been referred to as the dermal nitrate test, the diphenylamine test, and the Gonzales test.115,116... 

After the isolation of DNA, we will probe its identity by using the diphenylamine test. The blue color of this test is specific for deoxyribose and the appearance of a blue color can be used to identify the deoxyribose-containing DNA molecule. 

Ethchlorvynol—diphenylamine test. Sprinkle a few mg of diphenylamine sulphate on to the surface of 2 ml of urine in a test-tube, incline the tube, and carefully trickle in 1 ml of sulphuric acid. A red colour forms on the surface of the crystals if ethchlorvynol is present. 

Oxidising agents—diphenylamine test. Filter a portion of the sample md add 2 (hops of the filtrate to 1 ml of a 1% solution of diphenylamine in sulphuric acid. A deep blue colour, appearing immediately, indicates tiie presence of an oxidising agent. The test will detect hypochlorite (from domestic bleach), bromates, chlorates, iodates, nitrates, and nitrites. Tests to distinguish between certain anions will be foimd imder Metals and Anions (p.64). 

S.Ethchlorvynol—diphenylamine test. Carry out the test as described for urine (above) using a suitable volume of the filtered sample. 

Diphenylamine test for oxidising a nts which covers about 50% of the group Not available... 

In addition, many odier tests described on pp. 129-147 may be used for pesticides, especially Aromat-icity (Method 2), Diphenylamine Test, Fujiwara Test, Koppanyi-Zwikker Test, Liebermann s Test, Marquis Test, Methanolic Potassium Hydroxide, Palladiiun Chloride, Sodium Nihoprusside (Method 2), md Sulphuric Acid. Certain pesticides are included in die Tables of colours, where appropriate. A test for the presence of cholinesterase inhibitors... 

Diphenylacetylindandione, 557 Diphenylamine Test, 132 Diphenylamine test, on stomach contents, 5 on urine, 5... 

Diphenylamine Test. Much difficulty was encountered in this test, because of the low concentration of the oxidizing substances (nitric acid) and also because of the dilution of the blue color when a positive test was obtained therefore the following modification was developed and adopted by at least one government as official. 

Diphenylamine test Suspend 0.1 g diphenylamine in 30 ml water and then add carefully 100 ml concentrated sulfuric acid. (Note The acid should be added slowly.) Add a drop of the fresh reagent to the plastic sample on a plate a dark blue coloration indicates cellulose nitrate. 

Cellulose nitrates (Celluloid) may be recognized by the above reactions and by the sensitive diphenylamine test. Heat a sample with 0.5 N aqueous potassium hydroxide (2.8 g potassium hydroxide in 100 ml water) or 0.5 N sodium hydroxide (2.0 g NaOH in 100 ml water) for a few minutes and then acidify this with dilute sulfuric acid. Separate the supernatant liquid from the residue. Layer a solution of 10 mg diphenylamine in 10 ml concentrated sulfuric acid on top of that. A blue ring at the interface indicates cellulose nitrate. In order to identify nitrocellulose lacquers on cellophane, dissolve a few crystals of diphenylamine in 0.5 ml concentrated sulfuric acid and add a few drops of this to the sample. A blue color is a positive test. 

Coxon (1993) has recommended a spot test to identify the presence of acetates present in cellulose acetate and poly (vinyl acetate). Four pre-mixed reagents in turn are applied to a sample of the unknown plastic. One millilitre of a 6 per cent solution by weight potassium hydroxide in methanol is added to the sample. Next, 1 to 2 drops of a saturated solution of hydroxylamine hydrochloride in methanol are added and the mixture is either left to stand for at least 3 minutes or warmed gently. One drop 1 per cent ferric chloride in water is added and the mixture shaken. Finally, a 10 per cent solution of hydrochloric acid is added dropwise with shaking until a colour develops. Burgundy red indicates the presence of cellulose acetate or poly (vinyl acetate). Pale purple-red colouration is said to indicate cyanoacrylate or cellulose nitrate, but the diphenylamine test should be carried out if cellulose nitrate is suspected. 

On the other hand, mechanisms differing from the above in the order of dehydration have been proposed by Hurd and Isenhour, by Isbell (68), and by Wolfrom, Schuetz, and Cavalieri (69). The mechanism of the latter involves in the first two dehydrations the production of adouble bonds in a manner generally characteristic of jS-hydroxy carbonyl compounds. To be noted also is the apparent greater ease of dehydration (indicated by the Dische diphenylamine test, presumably a measure of the hydroxylevulinic aldehyde formed) of arabinal and xylal as compared to 2-deoxyribose (70), although the former are known to have pyranose rings. 

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