through the whole mass, but proceeds from definite points or nuclei, the rate increasing as the surface of contact between the two phases increases, as it does in the crystallisation of an over-cooled liquid, or the conversion of one crystalline modification into another.

So far as we have observed, there is no tendency to the reverse transformation of urea into ammonium cyanate in the solid state. After being heated for a long time in a vacuous tube at 110°, dry urea was found to be unchanged, dissolving completely in water with formation of a perfectly neutral solution which gave no precipitate with silver nitrate. After heating for 6 hours at 129°, that is, just below its melting point, it was found to have slightly decomposed with production of ammonia, but the presence of cyanate could not be proved in the residue. Whether the ammonia and cyanuric acid produced by heating urea to a still higher temperature are entirely the decomposition products of urea and biuret, or are in part derived from ammonium cyanate into which a portion of the urea may have been transformed, is a point to which we can at present give no definite answer.

Waddell (J. Physical Chem., 1898, 2, 525) has shown that solid ammonium thiocyanate does not suffer transformation into thiourea below a temperature of 110°. When fused, however, at temperatures of 150° and over, it is gradually converted into thiourea, the rate of transformation rising rapidly with the temperature. In this case, the transformation is not complete, equilibrium being attained when the fused mass contains 80 per cent. of thiourea and 20 per cent. of thiocyanate. The existence of a similar state of equilibrium between urea and ammonium cyanate cannot be ascertained, owing to the decomposition which these substances suffer when in the fused state. There can of course be no such equilibrium between the solids, for when two mutually convertible solids are in contact with each other, there is no real equilibrium between them except at one definite temperature, the transition or inversion point, at which temperature they may be brought together in any proportion without either undergoing change. In the fused state, on the other hand, the substances are miscible, and thus form but one phase instead of two, the system thereby gaining an additional degree of freedom, so that equilibrium may be attained at any temperature, the composition of the system changing according as the temperature varies. What the transition point of ammonium cyanate and urea may be, we are not in a position to determine. All that can be said is that it is above 80°, and in all probability very far above that temperature.

Substituted Ammonium Cyanates.

When dry ethylamine was gradually mixed with the vapour of cyanic acid, the two substances united to form a light, colourless powder, the solution of which, in water, gave a precipitate of silver cyanate when brought into contact with silver nitrate solution. The white powder, therefore, consisted, in part, at least, of ethylammonium cyanate. On standing for some time, it showed indications of lessening in bulk, and eventually it liquefied. The liquid, however, soon set to a solid mass, which, when dissolved in water, gave no precipitate with silver nitrate. The phenomena encountered here are consequently similar to those met with in the case of ammonium cyanate, the only difference being that the ethylammonium cyanate is rapidly converted into ethylurea at a much lower temperature than suffices for the rapid transformation of ammonium cyanate.

An ethereal solution of aniline, when mixed with an ethereal solution of cyanic acid, gave no immediate precipitate, but the solution deposited a crystalline substance on standing for some time. The crystals, which separated, however, did not behave as phenylammonium cyanate, but as phenylurea. A similar result was obtained with p-toluidine as base; the crystalline substance which separated from the ethereal solution on standing proved to be p-tolylurea, and not p-tolylammonium cyanate.

These substituted ammonium cyanates therefore pass much more readily into the corresponding ureas than ammonium cyanate itself. UNIVERSITY COLLEGE,

DUNDEE.

IV.-Etherification of Derivatives of B-Naphthol.
By WILLIAM A. DAVIS.

In the following pages, an account is given of the etherification of derivatives of B-naphthol by heating the naphthol with a mixture of alcohol and sulphuric acid (Henriques, compare Gattermann, Annalen, 1887, 244, 72). It is shown that, whereas ẞ-naphthol yields an almost theoretical amount of ether, most of its derivatives can only be very partially etherified.

As no action occurs at the ordinary temperature, in the first series of experiments a mixture of 2 grams of purified naphthol with 2 grams of the alcohol and 0.8 gram of sulphuric monohydrate was gently boiled during 6 hours on the sand-bath in a test-tube attached to a condenser.

VOL. LXXVII.

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To free the ether from unchanged naphthol, an excess of dilute caustic soda was then added, and the mixture gently warmed, a preliminary experiment having shown that this could be done without hydrolysis or dissolution of the ether taking place. The ether was collected on a tared filter-paper, which had previously been exposed in a weighing bottle in a vacuum until its weight was constant, and after being thoroughly washed, was dried in a vacuum desiccator and weighed. The results obtained are given in Table I.

Owing to a considerable proportion of the alcohol being converted into ethyl ether by the action of the sulphuric acid at the temperature at which the mixture boiled, it was generally observed that the latter separated, after about 3 hours, into two layers, of which the upper contained the alcohol and sulphuric acid, whilst the lower consisted of the naphthyl ether and unchanged naphthol. Owing to this separation, little etherification occurred after the third hour. It was found, however, that at 100°, whilst the formation of ethyl ether was largely prevented, that of the naphthyl ether was not interfered with ; in addition, the disturbing influence which is undoubtedly exercised on the etherification by varying the rate of ebullition was entirely excluded. Table II gives the results obtained at 100°. In these experiments, the mixture was heated during a much longer period than in the experiments recorded in Table I, and a definite limit of etherification was attained; it is doubtful whether this limit had been reached in the first series of experiments, as will appear on comparing the two sets of results. The method of heating at first adopted was to surround the tube containing the etherification mixture with boiling water, but the results obtained were, in some cases, vitiated by moisture permeating the cork; subsequently the lower portion only of the tube was heated by passing it through a cork fitted into the neck of a steam-bath constructed from a sheet-iron can by soldering six short tubes 1 inch in diameter round the central neck. A condenser, fitted to the central neck, served to keep the volume of water in the can practically

constant.

Table III gives the results of experiments carried out at 100°, using methyl instead of ethyl alcohol; these values are probably not quite so trustworthy as those of Table II, for two reasons. First, the mixture used boiled below 100°, and a considerable decrease in its amount occurred owing to the formation of methyl ether; secondly, a small proportion of the naphthyl ether sublimed, and thus a change in the condition of equilibrium was introduced. The latter circumstance probably accounts for the fact that the amounts of ether obtained with methyl are higher than those obtained with ethyl alcohol; in experiment 2, especially, much sublimation occurred. The results obtained with 3'-bromo-2-naphthol are possibly slightly higher than the true

values, owing to the fact that 3'-bromo-2-methoxynaphthalene does not melt below 100° when warmed with dilute caustic soda, so that small quantities of unchanged naphthol probably remained occluded; moreover, much of the product sublimed. The alcohol used boiled at 66.0-66.5° under 759 mm. pressure.

Similar experiments were made with propyl alcohol (b. p. 96·25—97° under 747-5 mm. pressure); the results are given in Table IV. In the case of 1:3'-dibromo-2-naphthol, resinous substances insoluble in caustic soda were formed owing to the occurrence of secondary change.

=

In all experiments except those marked * and †, the proportions in grams were-naphthol : ethyl alcohol: sulphuric acid 2: 2:08; in those marked with an asterisk, the molecular proportions were the same as in the etherification of B-naphthol, namely, 1 mol. naphthol : 3·12 mols. alcohol: 0.59 mol. acid. In two experiments, Nos. 21 and 22,

the proportion of sulphuric acid was the same as in the experiments with B-naphthol, but 2 grams of alcohol were used. Unsatisfactory results were obtained in experiments 5, 6, 7, 14, 15, and 16 with 1-bromoand 1:3'-dibromo-2-naphthol, owing to the fact that the mixture was boiled too rapidly, this giving rise to compounds insoluble in dilute caustic soda, which seriously interfered with the purity of the ether. Moreover, on filtering the dilute, alkaline solution of the unchanged naphthol, oxidation apparently occurred, and the solution became purple in colour, depositing a finely-divided purple or brownish powder in the pores of the filter paper, thus preventing further filtration. In the later experiments (Nos. 8, 9, 10, 17, 18, 19), the ebullition was careful regulated and the filtration hastened by using a filter-pump; under these conditions, the ether weighed was nearly pure. The melting points given in the table serve to indicate the degree of purity of the products weighed.

TABLE II.-Etherification at 100°.

Proportions:-Naphthol : ethyl alcohol: sulphuric acid 2: 2:08

=

In the experiments marked, the mixture was heated in boiling

water; in all others, the steam-bath was used.