A more general application of the same principle has been described by E. E. Reid.3

Alcohols when heated with phthalic anhydride yield phthalic esters; and the sodium salts of these, heated with para-nitrobenzyl bromide, give mixed phthalic esters which have definite melting

1 "Poisons," p. 147. 2 Chem. Weekblad., 1914, 11, 26.

3 J, Amer, Chem. Soc, 1917, 39, 1249, points. These reactions may be used for the identification of many different alcohols.

A moderate excess of the alcohol to be tested is heated for one hour with 1 gram of phthalic anhydride For a primary alcohol, the temperature employed is 100°, for a secondary, 140°. In the case of the lower alcohols, the mixture is sealed up in a tube and heated in a boiling water-bath, whilst with the less volatile alcohols the mixture may be heated in an open tube. The product is then mixed with 10 c.c. of water and shaken with 15 c.c. of ether and 5 c.c. of normal sodium hydroxide solution; the aqueous- layer drawn off, and evaporated to dryness. The residue thus obtained is heated for one hour under a reflux condenser with 5 c.c. of water, 10 c.c. of 95 per cent. alcohol, and 1 gram of p-nitrobenzyl bromide, and the product is recrystallised from 63 per cent. alcohol, and its melting point determined.

Ethyl-p-nitrobenzyl phthalate melts at 80°. The corresponding methyl compound has the melting point 105.7°, the propyl compound 53°, the isopropyl 74°, the normal butyl 62°, and the allyl 61.5°.

The method may be used for the detection of ethyl alcohol in admixture with ethyl benzoate or menthol, and also of borneol in camphor.

Another general reaction for the lower alcohols of the aliphatic series has been described by E. de Stoecklin.1 Iron tannate, prepared by the interaction of tannin and a ferric salt, acts as a peroxydase; and in the presence of hydrogen peroxide it serves as a convenient means of oxidising the lower alcohols. The aldehyde produced is then detected by the violet colour given with rosaniline bisulphite solution (Gayon or Schiff's reagent). Glycerol, if present, is also oxidised, and yields a colour Some other iron combinations act in a similar manner as oxygen carriers.

One c.c. or less of the liquid to be tested is made faintly acid with acetic acid; or, if already acid, is made almost neutral to phenolphthalein. Two drops of an iron solution (made by adding a ferric salt to a saturated solution of hydroquinone and diluting it to contain 1 mg. of iron per c.c.) are then added, followed immediately by 4 drops of hydrogen peroxide solution. After shaking for a few seconds, the liquid is treated with a little of the rosaniline bisulphite solution. If alcohols were originally present, a violet colour is produced. The test is repeated with an iron tannin solution containing 1 mg. of iron per c.c, made by adding a ferric salt to a 3 per cent. aqueous solution of tannin.

A positive result indicates the presence of methyl, ethyl, propyl, or butyl alcohols in the original liquid. If the latter has not been distilled, glycerol may also be a cause of the colour produced; and hence if the volatile alcohols are expelled by boiling, and the liquid still shows the reaction, the presence of glycerol is indicated.

1 Compt. rend., 1908, 147, 1489; 1910, 150, 43.