YREPARATIOK AND PROPERTIES OF SOLID AMMONIUM CYANATE:. 21 llI.-The Prxparation and Propevties of Solid Ammo&in~ Cyanate. By JAMES WALICER and JOHN K. WOOD. WHEN a solution of ammonium cyanate (prepared by the double decomposition of silver cyanate and ammonium chloride) is evaporated to dryness, either on a water-bath or in a vacuum at the ordinary22 WALKER AND WOOD : THE PREPARATION AND temperature, the residue is found t o consist entirely of urea, the transformation of the cyanate into urea taking place at an ever- increasing rate as the concentration of the solution becomes greater (Walker and Hambly, Trans., 1895, 67, 746). I n alcoholic and other solutions, the conversion of ammonium cyanate into urea is still more rapid (Walker and Kay, Trans., 1897, 71, 489), so that, in order t o obtain pure ammonium cyanate, it is necessary to prepare i t directly in the solid state.Liebig and Wijhler (Ann. Phys. Chem., 1830, 20, 393) attempted t o prepare it by direct union of ammonia and cyanic acid, both sustances being in the form of gases. They describe their experiments as follows : “When the vapour of the acid was passed into dry ammonia gas contained in a wide glass tube over mercury, the tube became warm and the gases condensed t o a cloud which soon settled on the inner wall of the vessel as a microcrystalline, very voluminous, woolly mass. I n order to obtain it in larger quantity and free from the impurity of mercury, we brought the gases into contact in a dry flask. The cloud which was formed with simultaneous heating of the flask was deposited as a loose, snow-white powder, and a t the mouth of the tube which delivered the cyanic acid gas there was produced a thick woolly vegetation, which, on account of the heat; evolved, soon melted t o clear drops which fell from the tube.” They showed that the loose powder gave the reactions of a cpnate, the clear drops being urea produced from the cyanate by the heat of the reaction.The powder, when left over mercury in presence of ammonia, remained unchanged for n week. Left in a vessel loosely covered with paper, it con- tinuously gave off ammonia, and in two days was almost entirely con- verted into urea. Both the freshly prepared cyanate and the urea formed by its transformation left a residue of much “insoluble cyanuric acid ” (cyamelide) when treated with water.“ From these facts it appears then that ammonium cyanate is a basic salt, which undergoes transformation in to urea with loss of ammonia.” It seemed t o us likely that if we could prevent the heat produced by the union of the ammonia and the cyanic acid vapour from raising the temperature to a point a t which ammonium cyanate was decom- posed or transformed, we might be able to obtain the normal cyanate in the pure state, and free from any admixture of urea or cyamelide. The method we a t first adopted was to mix ethereal solutions of the reacting substances a t the temperature of a good freezing mixture, and this we found t o be successful. A wide glass tube was bent at a n obtuse angle, and the horizontal portion charged with anhydrous cyanuric acid.The other limb passed downwards through a cork closing the mouth of a wide test- tube, and dipped beneath the surface of anhyclrous ether which thePROPERTIES OF SOLID AMMONIUM CYAN ATE. 23 test-tube contained. This ether was kept at a temperature not exceeding - 17O by means of a freezing mixture, The cyanuric acid in the horizontal limb was gradually heated with a Ramsay burner, a moderately rapid stream of hydrogen being at the same time passed through the tube in order to carry over the resulting cyanic acid vapour into the ether, in which the bulk of it dissolved. It is impossible to avoid the condensation of a considerable portion of the cyanic acid vapour t o form cyanuric acid or cyamelide, so that, unless the tube chosen is a t least half an inch in diameter, it is apt to become blocked before the experiment is completed. We now freed the ethereal solution of cyanic acid from cyamelide and other solid matters by filtration through a dry filter, and mixed it with a solution of ammonia in anhydrous ether in such proportions that the acid remained in slight excess.As a rule, the ethereal solution of ammonia was also cooled to the temperature of the freezing mixture, but experiments showed that this was not absolutely necessary. A flocculent, semi- gelatinous precipitate separated as soon as the solutions were mixed, and the temperature did not rise more than a few degrees, the heat of the reaction being mostly absorbed in warming the solvent. The precipitate was collected as rapidly as possible with the aid of a filter-pump, and freed from ether in an exhausted desic- cator over sulphuric acid.I n the case of some samples used for analysis, moisture was carefully excluded during the process of filtration, and the temperature was kept below zero by means of a freezing mixture surrounding the frlter-tube. When the ether had been entirely removed from the precipitate, the latter presented the appearance of a pure white mass, caked together and very friable. It dissolved completely in water, the solution having a perfectly neutral reaction to litmus, so that neither cyamelide nor free ammonia could be present. On the addition of strong nitric acid, there was a copious evolution of gas, and no precipitate of urea nitrate was obtained. Silver nitrate gave a pure white precipitate, soluble in nitric acid, and also in boiling water, from which crystals were deposited on cooling.These reactions all tended to show that the substance was ammonium cyanate free from admixture of the impurities met with by Liebig and Wohler, and analysis served to confirm this conclusion. 0.0607 gave 0,0441 CO, and 0.0382 H,O. 0.0351 C: = 19.8 ; H = 7.0. ,, 13.80 C.C. moist nitrogen at 11.5" and 760mm. N = 46.8. CH,ON, requires C = 20.0 ; H = 6.7 ; N = 46.7 per cent. The ammonia in the ammonium radicle of the substance was estimated by adding a weighed portion to excess of silver nitrate (whereby silver cyanate and ammonium nitrate were produced),24 WALKER AND WOOD : THE PREPARATION AND filtering, and distilling the filtrate with caustic soda, the ammonia evolved being collected in a known quantity of hydrochloric acid, and determined by titration in the ordinary way.0.1026 yielded ammonia which neutralised 17.08 C.C. of N/10 acid. NH,CNO requires NH, = 30.0 ; found 30.0 per cent. The amount of the cyanate radicle was estimated by adding a known weight of the substance to excess of decinormal silver nitrate, silver cyanate being precipitated. Although silver cyanate is perceptibly soluble in water, it is almost insoluble in water containing silver nitrate (Walker and Hambly, Zoc. cit., 747). The precipitate was there- fore washed in a Gooch crucible, first with water containing a little silver nitrate, and then with absolute alcohol until the filtrate gave no reaction for silver.The silver cyanate was then dried a t 120' and weighed. 0.1235 gave 0.3126 AgCNO. NH,CNO requires CNO = 70.0 per cent. These analyses show that the substance obtained by mixing ammonia and cyanic acid in ethereal solution at a low temperature is normal ammonium cyanate free from admixture with other substances, In order to ascertain if it were not possible to prepare pure ammonium cyanate without the medium of a liquid solvent, the gaseous sub- stances were brought together at the ordinary temperature in a diluted state, so that heating might be avoided as far as possible. A current of dry hydrogen was led through a cooled et.herea1 solution of cyanic acid, and then by means of a glass tube to the bottom of a large globe. Into the same globe was led a stream of air which had bubbled through strong aqueous ammonia, and had then been dried by passing over quicklime and solid caustic potash.These gases there- fore carried into the globe gaseous cyanic acid and ammonia re- spectively in a dilute condition. The currents mere so regulated that the reacting substances were delivered slowly, and as they entered at different parts of the large globe, the process of mixing was very gradual, the ammonium cyanate falling as a sort of snow at the bottom of the globe, and forming vegetative growths round the mouths of the delivery tubes. After a sufficient quantity had collected, the substance was a t once transferred to a desiccator, which was rendered vacuous in order t o remove any excess of ammonia or cyanic acid which might cling to the salt.The substance was found, as before, to dissolve in water without residue, and to yield a perfectly neutral solution. It there- fore contained neither cyamelide nor free ammonia,, and analysis showed that it was free from urea. CNO= 70.9.PROPEHTI ES OF SOLID AMMONIUM CYANATE. 25 0.1818 gave 0.4496 AgCNO. CNO = 69.3. 0.1823 ,, 0.451 7 AgCNO, CNO = 69.4. NH,CNO requires CNO = 70.0 per cent,. That the precipitdte obtained by the addition of the substance to the silver nitrate solution was in reality silver cyanate, was proved by converting the silver salt in the Gooch crucible directly into chloride by means of hydrochloric acid, and weighing the silver chloride thus produced. 0.4517 silver salt gave 0,4297 AgCl. Ag = 71.6. AgCNO requires Ag = 72.0 per cent.It thus appears that pure ammonium cyanate may be prepared by the union of gaseous ammonia and cyanic acid, if care be taken t h a t the heat produced by their combination does not raise the temperature of the product to the point a t which i t is transformed into urea. The solid cyanate, when prepared from the gases, presents under the microscope the aspect of very fine needles which show double refraction when examined witah a polarising apparatus. It is very readily soluble in water, and the solution, when evaporated, leaves a residue of urea. On heating in a capillary melting point tuhe, it contracts visibly a t a temperature somewhat above 60° and melts suddenly at a temperature in the neighbourhood of 80°, the exact point depending on the rate of heating and on the tightness with which the substance is packed in the tube. The fused mass, however, speedily resolidifies, and does not melt again until a temperature of 128--130° has been reached.The contraction a t 60' indicates incipient conversion into urea. A t 80°, the transformation takes place so rapidly that enough heat is evolved t o fuse the urea produced, the second melting point of 130' being that of urea. During the first fusion, a small quantity of gas is invariably evolved, and when the experiment was repeated on a larger scale the gas was found to be ammonia. It was noted also that although the original ammonium cyanate was completely soluble in water, the product after transformation left a slight insoluble residue which was apparently cyamelide. This production of small quantities of ammonia and cyamelide constantly accompanies the transformation of solid ammonium cyanate into urea, and sufficiently explains the origin of the impurities obtained by Liebig and Wohler, as well as their inference that the substance produced by the union of gaseous ammonia and cyanic acid is a basic ammonium cyanate.A quantitative experiment was made in order to determine the amount of ammocia given off during the conversion of the solid cyanate into urea. A Lunge nitrometer was filled with dry mercury up to the Greiner aad Priedricb stopcock with which it was provided.26 WALKER AND WOOD : THE PREPARATION AND There was then connected directly to the capillary tube, by means of a small piece of thick-walled rubber tubing, a bulb-tube which contained 1 gram of solid ammonium cyanate.By raising and lowering the mercury reservoir, with suitable manipulation of the stopcock, the bulb was rendered vacuous, and the mercury finally permitted to run back so as to fill it. The bulb was then heated in water at 95O, and after about a minute gas was vigorously evolved. When the trans- formation mas complete, the mercury levels were adjusted and the volume of gas read off, tho capacity of the bulb and capillary having previously been determined ; 1 C.C. of water was then introduced into the nitrometer, and in this the gas dissolved completely. The volume of ammonia obtained in this experiment and reduced to normal con- ditions was 11.4 c.c., corresponding to 0.0086 gram. The quantity of drj7 cyanate which mould produce this amount of ammonia is 0.030 gram, so that me may say that 3 per cent.of the cyanate on trans- formation is decomposed with production of ammonia, the rest of the molecule being probably converted into cyanuric acid and cyamelide. For purposes of comparison with the ammonium cyanate prepared i n aqueous solution by Walker and Hambly, a determination of the rate of transformation into urea mas made. A decinormal solution of the pure ammonium cyanate was prepared, and the progress of its con- version into urea followed by means of silver titration as previously described (Trans., 1895, 6'7, 746). The temperature of experiment was 50.2'. l a t A - x ' t. X. A -x. 55 4.94 17.96 0*00500 97 7.44 14.46 0.00496 186 10.74 12.16 0.00475 298 13.64 9.26 0.00494 -.- Mean ... ... ... ... 0.00491 1 x t ' A - x The mean value for the expression - - here observed is identical with that calculated for the same temperature from the formula used to express the results of all the experiments in aqueous solution (Walker and Hambly, Zoc. cit.). Thennochenzistry of Anzmonium Cycmate. From the displacement by change of temperature of the point of equilibrium between ammonium cyanate and urea in aqueous solution, Walker and Kay (Zoc. cit., p. 507) were able to calculate roughly the heat of transformation into urea of the cyanate in the form of ions,PROPERTIES OF SOLID AMMONIUM CYANATE. 27 They found that the heat of transformation was positive, and of the dimensions of 50 K per gram-molecule, R being equal to 100 cal.It was of interest, therefore, to determine directly, if possible, the heat of transformation of solid ammonium cyanate, and also its heat of solu- tion, for from these data and the known heat of solution of urea the heat of transformation of the dissolved cyanate can be calculated. The accurate determination of the heat of transformation of the solid cyanate into urea presents considerable difficulty, inasmuch as the conversion only takes place readily a t about 80°, and therefore necessitates somewhat complicated apparatus. Since, however, the actual transformation is always accompanied by secondary decompo- sitions, an accurate determination for the pure reaction is plainly impos- sible, so that we contented ourselves with experiments made by means of simple apparatus, which afforded numbers probably within 5 per cent., and certainly within 10 per cent., of the real value.The calorimeter consisted of' two beakers, one within the other, the inner one being supported on cork prisms, and kept from contact with the outer beaker by means of cardboard rings. These beakers were introduced into a double-walled steam oven and rested on a piece of asbestos, which was in turn supported by a stage made of glass tubing. Through the hole in the top of the oven were introduced a ther- mometer, a stirrer, and a wide glass tube for delivering the experi- mental substances, all three projecting into the inner vessel after passing through corresponding apertures in the cover of the outer beaker. The most suitable calorimetric liquid we found to be melted paraffin wax, about 50 grams of which were contained in the inner vessel.The thermometer employed was divided into tenths of a degree, so that hundredths of a degree could be estimated. To perform an experiment, the water in the walls of the steam oven was kept at a constant level and in steady ebullition until the temperature registered by the thermometer in the pa-raffin became constant, which it usually did in the neighbourhood of 96" after about 5 hours, A weighed quantity of mercury of known temperature was then rapidly introduced through the wide glass tube into the inner vessel, and the course of the thermometer was followed for about 10 minutes. From the readings, the weight, specific heat, and original temperature of the mercury, the amount of heat taken up by the latter could be easily calculated.Thus 60 grams of mercury at 14-70", when introduced into the beaker containing 49 grams of paraffin wax, lowered the temperature from 95.SO" to a minimum of 92.12'. The mercury had therefore absorbed 154 cal. from the calorimeter and had thereby lowered the temperature 3*6S0, or making due allowance for the rate of heating, 3*S6". A similar experiment28 WALKER AND WOOD: THE PREPARATION AND made with the same weight of paraffin showed that 152 cal. absorbed by the mercury lowered the temperature of the calorimeter 3.88". After preliminary experiments had shown the approximate value of the heat of transformation of ammonium cyanate, a quantity of this material was chosen so that, by its conversion into urea, it would give to the calorimeter about as much heat as the mercury had absorbed in the previous experiments, all other conditions remaining the same.The weighed quantity of cyanate was compressed into the form of a short cylinder in order that it might be easily introduced through the glass tube into the calorimetric vessel. After the cyanate had entered the paraffin, the thermometer at first fell, owing to the heat required to raise the temperature of the cyanate to the transformation point ; thereafter, the rise was rapid, a maximum temperature being soon reached. By making use of the previous experiments with mercury, the total amount of heat supplied to the calorimeter could be easily calculated, allowance being made for the rate of cooling from the thermometric observations.The heat of transformation was greater than this amount by the quantity of heat necessary to raise the temperature of the cyanate, or its transforma- tion products, from the atmospheric temperature to the maximum temperature observed. I n calculating this quantity, it was assumed that the cyanate had the same specific heat as its chief transformation product, urea. From the experiments, i t appears that the molecwlur h a t of tyansfownation of solid ammonium cyanate into solid urea is 49 K, the chief source of uncertainty lying in the unknown thermal change which accompanies the decomposition of 3 per cent, of the cyanate with formation of ammonia. Another set of experiments made with a modified apparatus in which a Victor Meyer toluene bath was used instead of a steam oveu, yielded a mean value of 48 K as the molecular heat of transformation of the cyanate. I f we accept 49 K as the heat of conversion of the cyanate into urea, it follows that the molecular heat of formation of solid ammonium cyanate from its elements is 738 K, since 787 K is the molecular heat of formation of solid urea, and this must be greater than that of the cyanate by the observed heat of transformation.I n determining the heat of solution of ammonium cyanate, the calorimeter chosen mas of the simple form described by Nernst (Zed. p?hysikaZ. Chem., 1888, 2, 23). The amount of water employed was 200 grams, the water equivalent of the calorimeter being 11.8 grams, as calculated from the weight of materials, and 11 grams as found by direct experiment.The substance whose heat of solution was to be investigated was enclosed in a thin-walled glass bulb weighted withPROPERTIES OF SOLID AMMONIUM CYANATE. 29 mercury so as to sink in the water of the calorimeter. When the temperature had become constant, the bulb was broken and the course of the thermometer observed. In order to test the apparatus, the heat of solution of urea was first determined. The values obtained were -36.1, - 36.6, and - 3 6 . 3 Kfor the gram-molecule, in good accordance with Rubner's number of For the rnokcula~ heat of solution of ammonium cyanate, the mean of two concordant experiments WiLS - 62.3 X, the strength of the resulting solution being about one-twentieth normal. This number is somewhat greater than me had anticipated, being in excess of the corresponding value for potassium cyanate, namely, -52 K, in opposition to the general rule that the potassium salts have greater heats of solution than the ammonium salts of l;he same acids.The divergence cannot be explained by the assumption that a portion of the cyanate is trans- formed into urea during the progress of the experiment. The portion so transformed could a t most have reachedonly 2 per cent. of the total, and the thermal effect of the transformation would have been to diminish the heat of solution instead of to increase it. The heat of transformation of the cyanate into urea in aqueous solu- tion may be calculated from the corresponding value for the solid sub- stance as follows.We may pass from solid ammonium cyanate to dissolved urea in two ways, namely, by transforming the cyanate in the solid state and then dissolving the urea, or by dissolving the cyanate and then transforming it in aqueous solution. The total heat effect must be the same in both cases, so that we obtain the equation : Heat of transformation of solid cyanate + heat of solution of Heat of solution of cyanate + heat of transformation in solution, -36.8 K. urea = or, substituting the numerical values for the gram molecular weight, whence x = 75 K. 4 9 K + ( - 3 6 Zi) = - 6 2 K + X, This value for the heat of transformation of the gram-molecule of ammonium cyanate in aqueous solution is considerably in excess of the value 50 K calculated from the displacement of the equilibrium point with change of temperature.This latter value, however, can only be taken as indicating the sign and dimensions of the heat change, since in the calculation it mas assumed that the transformation was pure, instead of being complicated, as is actually the case, with subsidiary actions which affect the accuracy of the deduction, and, secondly, that the cyanate was fully dissociated at the dilutions considered, an assumption which is only approximate. The number 75 K must there-30 WAT,KER AND WOOD : THE PREPARATION AND fore be accepted as a considerably closer approximation to the true value than the number 50 K, since it is affected by much smaller sources of error. It may be noted that the value observed for the heat of transforma- tion of the solid cyanate is sufficiently great to account for the fusion of the urea which occurs when the transformation takes place suddenly at about SOo.At this temperature, the transformation proceeds at such a rate that the heat evolved cannot all escape by conduction; the temperature therefore rises and the action is accelerated until it pro- ceeds almost instantaneously, with sudden evolution of so much heat that the temperature is raised above the melting point of urea, the heat of fusion of urea being probably less than - 25 K. Rute of Dansformation into Urea. It has been already stated that the substance obtained by Liebig and Wohler remained unchanged for a week in an atmosphere of dry ammonia, whilst in the course of two days it was almost entirely con- verted into urea when exposed t o the air, ammonia being continually evolved during the transformation.Liebig and Wohler were appar- ently of opinion that the presence or absence of ammonia was the determining circumstance in the conversion. This, however, is not the case, as we have found that moisture plays the chief part in determining the rate of transformation at moderate temperatures. Exposed to a moist atmosphere, the cyanate, as Liebig and Wohler observed, is converted into urea in the course of a few days. If left in a desiccator over sulphuric acid, the cyanate in the same length of time remains practically unchanged; and in an exhausted tube in presence of phosphoric oxide the cyanate shows little sign of altera- tion even after several months.Two tubes were prepared, one with dry (but not specially dried) cyanate, the other with the same material and a minute trace of moisture introduced from the end of a fine capillary. These tubes were sealed off and heated at the same temperature for the same length of time. I n the tube containing the added moisture, 27 per cent. of the cyanate had been transformed into urea, whilst in the other tube only 2 per cent. had undergone transformation. As might be expected, temperature has a great influence on the rate of transformation. It has already been indicated that the transforma- tion proceeds at a noticeable rate when the temperature reaches 60' for then a distinct diminution in volume is visible when the substance is contained in a, capillary tube. An experiment with ordinary dry cyanate showed that in the course of two hours 80 per cent.of the cyanate was converted into urea at that temperature.PROPERTIES OF SOLID AMMONIUM CYANATE. 31 I n order t o ascertain the effect of temperature on the rate of trans- formation of carefully dried cyanate, the following experiment was made. Four small tubes were charged with weighed quantities of cyanate and placed in tubes which were slightly wider than themselves and contained a layer of phosphoric oxide on the bottom. These outer tubes were then rendered vacuous and sealed off, After ten days, the tubes, without being opened, were heated at various temperatures, either in thermostats or in boiling liquids, for such lengths of time as preliminary experiments had shown would bring about approximately the same extent of transformation. The times required for the con- version of 3.5 per cent.of the cyanate into urea are exhibited in the following table : Temperature. Time in hours. 3 3" 50 40 19 45 7 57 1.1 The dried cyanate, like the freshly prepared material, passed rapidly into urea, with fusion when the temperature was raised to a little over 80". The rate of transformation we found to be by no means proportional t o the amount, of cyanate present, as the following figures indicate. The cyanate used was contained in vacuous tubes and dried for five days over phosphoric oxide in the manner desciibed above, the tem- perature of transformation being 57". Time in hours. Percentage traiisforined. 1 5.4 2 1914 5 58.6 10 95.1 I n the first hour, only 5-4 * per cent.was converted into urea, whilst in the second hour 14 per cent. of the original amount, or 14.7 per cent, of the amount remaining after the first hour, underwent transforma- tion. Between the second and fifth hours there was transformed hourly, on the average, 16 per cent. of the amount of cyanate which remained at the beginning of the time, and in the last period of five hours there was an hourly average transformation of 18 per cent. of the amount of cyanate present at the commencement of the period. There are thus evidences of a gradual acceleration of the action as it progresses. This we might expect, since the transformation is one in a condensed two-phase system. The action is probably not uniform * This number is greater than the corresponding number in the temperature experiments quoted above, on account of less perfect drying.32 PREPARATION AND PROPERTIES O F SOLID AMMONIUM CYANATE, 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 l l O o , dry urea was found to be unchanged, dissolving completely in water with forma- tion 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, i t was found to have slightly decomposed with pro- duction 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.I n 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 thio- cyanate. The existence of a similar state of equilibrium between urea and ammonium cyanate cannot be ascertained, owing to the decom- position 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 a t one definite temperature, the transition or inversion point, a t which temperature they may be brought together in any proportion without either undergoing change.I n 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.DAVIS : ETHERIFICATION OF DERIVATIVES OF ,B-NAPHTHQL. 33 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, a t 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 ethyluren at a much lower temperature than suffices €or the rapid transformation of ammonium cyanate. An ethereal solution of aniline, when mixed with an ethereal solu- tion of cyanic acid, gave no immediate precipitate, but the solution deposited a crystalline substance on standing for Mome 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 ths ethereal solution on standing proved to be p-tolylurea, and not ptolplammonium cyanate, These substituted ammonium cyanates therefore pass much more readily into the corresponding ureas than ammonium cyanate itself. UNIVERSITY COLLEGE, DUNDEE.