CALVERT ON A CRYSTALLISED HYDRATE XII1.-On a Crystallised Hydrate of Phenylic Alcohol. By F. CRACECALVERT.F.R.S. F.C.S. I OBSERVED some time since that when four parts of carbolic acid were well agitated with one part of water and the whole exposed to a temperature of 4"C. the sides of the containing vessel became lined with fine large crystals which proved on more carefiil ex- amination to be six-sided prisms of the rhombic system. This new substance was found to be soluble in water alcohol and ether and to melt at a temperature of 16OC. To ascertain its composition some of the crystals were taken and carefully dried betmeeu folds of blotting paper and then submitted to analysis when the following results were obtained :-0.435 of substance gave 0.260 of water or 6-67 of hydrogen and 1.112 of carbonic acid or 69.65 of carbon.In a second analysis 0.488 of substance gave 0.301 of water or 6.85 hydrogen and 1.243 of carbonic acid or 69.5 of carbon. These results correspond in composition to a bihydrate of phenyl or to the ordinary hydrate of phenyl + 1eq. water as seen by the following formulae :-C,2H60.H0 C12H50.2H0 C12H50.3H0. Found. Carbon....,....... 76-59 69.90 64-29 69.13 Hydrogen .... Oxygen ,...,. . . 6.38 17-03 6.80 23.30 7.14 28.57 6.72 24.15 - -I -7- 100~00 m.00 100~00 100~00 The above figiires show that the substance analysed is ordinary phenylic alcohol which has taken an equivalent of water to form a new crystalline compound and what further substantiates this opinion is that when it has been liquified by a temperature above 16"C.and heat is applied it gradually loses water and the boiling point of the liquid rises until it reaches 187"C. the boiling point of phenylic alcohol. This is I believe the first instance of an alcohol uniting with one equivalent of water to form a crystallized hydrate. The only apparent exception with which I am acquainted is the hydrate of propyl-alcohol discovered by Erlenmeyer. I say apparent OF PHENYLTC ALCOHOL. 67 because from the short extracts I have been able to read of his paper it does not appear that he has separated the water which forms the hFdrate of the alcohol obtained by him; in fact the product appears to distil without decomposition. The neutrality of bihydrate ofphenyl on litmus paper as well as that of the ordiuary hydrate led me to enquire if the ordi- nary hydrate should be considered an acid as stated in most of our text-books (as carbolic or phenic acid) or as an alcohol or as a body having some similar properties to glycerin.To decide this point I made the following series of experiments 1 took 100 cub. cent. of solutions of caustic potash having the following specific gravities-1-08 1.03 1-04,1.06 and added successively to ertch of them 25 cub. cent. of the ordinary hydrate of phenyl perfectly pure and having a melting point of 34'C. The following table gives the results observed :-*$363 25 c. c. On adding 25 c. c. of the ordinary hydrate of phenyl to 100 c. c. of solution caustic potash of the above strength the mixtwe 5%a separated into txo layeta-the upper layer consisting of 104 c.c. a GS ...( solution of carbolic acid in alkali and the lower layer of 21.c. c. 88 carbolic acid which has taken up a certain amount of water. 1.02 25 C. C. 25 C. C. On adding aa before hydrate of phenyl to mlution of caustic potash of the above d strength it was not until the addition of the .r( .d 3rd measure of 25 c. c. that the mixture sepa- rated into two layers; the upper layer = 45 c. c., PI and the lower om = I30 c. c. I I 25 c. c. II 25 c. c. In thia instance it required 100 c. c. carbolic acid before Feparation took place when the following results were obtained:-Higher layer = 13 c. c. of alkaline aolution and lower layer = 187 c.c. of acid solution. 26 c. c. 25 c. c. 25 c. c. 11 CALVERT ON A CRYST-4LLISED HYDRATE The above experiments clearly show that the solubility of phenic acid in the alkaline solution is not due to a combination of the acid with the alkali for in that case the quantity of phenylic acid which would have entered into solution would have increased in ratio to the quantity of potash in solution whilst no such ratio exists ad therefore no combination. What further substantiates this view is that if to 100 c. c. of alkaline solution of sp. gr. 1.03 is added successively 25 C.C. of carbolic acid the first two enter into solution but on a further addition of 25 cub. cent not only do they remain undissolved but they separate or carry down with them nearly their own bulk of acid which had been previously held in solution This novel fact of the separation of a substance already held in solution by the simple addition of a further quantity of the same compound proves beyond all doubt that an alkaline solution acts only as a solvent for the hydrate of phenyl and is therefore not a combination of carbolic acid with oxide of potassium.The above table also illustrates another interesting fact viz. that if to a solution of alkali of sp. gr. 1.06 is added successively 25 c. c. of pure carbolic acid no separation takes place; for we were able to add 200 c. c. of hydrate of phenyl without any of it separating. This is due probably to the fact that the hydrate of phenyl takes up a certain amount of water which reduces its specific gravity until it is almost identical with that of the alkaline solution.Further. Two volumes of liquified hydrate of pheriyl were mixed with one volume of concentrated caustic ley and the mix- ture distilled in a retort when 98 O? of the original acid passed over into the receiver whilst the 2 o/o left in the retort was decom- posed into a resinous matter due to the oxidizing action of the alkali upon the carbolic acid. I may state that these experiments were repeated with the bihy-drate of phenyl when precisely similar results were obtained if the quantity of water it contains is taken into account leaving no douht that they are identical bodies with the exception that the new hydrate contains 1 eq.more water not of composition but simply of crystallization. It is stated in our text-books that phenic acid is prepared by mixing the oils of tar which distil between 150°C. and 200' C. with a highly concentrated solution of caustic potash and that the whole on cooling forms a white crystalline mass If we repeat OF PHENYLIC ALCOHOL. this process substituting for the oil of tar pure hydrate of phenyl a white solid mass is also obtained which on being pressed a great number of times between folds of blotting paper so as to remove as neax as possible the whole of the excess of alkali a white crystalline mass is obtained which proves on examination to be crystals of hydrate of phenyl contaminated with a little alkali. Carbolic acid absorbs with great avidity dry ammoniacal gas but no combination takes place for if the mixture is heated the ammonia gas is expelled not a trace remaining in combination with the acid.It is barely necessary to add that if the ammoniacal carbolic acid ia heated in a closed tube water and aniline are produced. Both the hydrates of phenyl when heated with oxide of lead dissolve it and both form a solid compound. These on being well washed with water to remove all excess of phenic acid and dried are found on analysis to have an identical composition viz. C,,H60 + 2Pb0. This compound is slightly soluble in hot alcohol and deposits on cooling. As a solution of both the hydrates of phenyl give with a solu- tion of subacetate of lead a white bulky precipitate (which con-tracts on drying in a remarkable manner remaining as a white amorphous powder) I made the following series of experiments to ascertain if the precipitates which are produced under these cir-cumstances have a constant composition.For this purpose I mixed 200 c. c. of a saturated solution of the ordinary hydrate with 10 c. c. of a solution of subacetate of lead containing 1.614 of oxide of lead. The precipitate produced was collected washed slightly and dried at 110' C, when 1.090 grm. of it gave on cal-cination 0.698 grm. of oxide of lead or 64 % PbO. In another experiment I took the same quantity of carbolic acid dution and added to it double the quantity of subacetate of lead. In this instance the quantity of oxide of lead in 100 parts of the precipitate was equal to 68.2 % showing that in this preci- pitate there was 4 "/o more oxide of lead than in the preceding one and therefore that there is no definite compound formed ; in fact there is so little affinity between hydrate of phengl and oxide of lead that if one of the above precipitates is washed several times with boiling water it loses a large proportion of the hydrate of phenyl.In one instance for example 0470 grm. of the above CALVERT ON TBE ACTION OF SILICATE washed precipitate (dried again of' course at 110 C.) gave on cal-cination 0.393 grm. of oxide of lead; consequently the precipi- tate contained 83.6 % of oxide. There can therefore be no doubt that the hydrate of phenyl like many other organic substances does not give any well-defined compound with oxide of lead.Lastly. Carbolic acid does not decompose alkaline carbonates even under the influence of heat. The small amount of cnrbonate which disappears is not decomposed but merely enters into solution. From the above facts I conclude that what has been called carbolic or phenic acid is a neutral compound and must be re- garded as the hydrate of an alcohol and the new substance de- scribed by me is the bihydrate of the same radical.