13 V1II.-New Vohtile Organic Acids of the Mountai?L Ash Berry. BY A. W. HOFMANN. WHOEVER has been engaged in the preparation of malic acid from the juice of the unripe berry of the mountain ash cannot have failed to perceive the peculiar pungent odour evolved during the evaporation of the liquid partially saturated with lime. Nobody however seems to have paid any attention to the body to which this odour belongs until my friend and former pupil lh.George Merck of Darmstadt when preparing malic acid on a large scale had the happy idea of performing the evaporation of the liquid in a distilling apparatus. He obtained in this manner an acid aqueous distillate from which an oily body of distinctly acid pro-perties could be extracted. Under the name of Vogelbeer-oel (mountain ash berry oil) a specimen of this remarkable oil was transmitted to me by Dr.Merck; and since the properties of this substance appeared of such interest as to invite a more minute examination my friend anxious to assist in the further elucidation at' this matter undertook the preparation of a larger quantity of the oil. To his kindness I owe the whole of the material em-ployed in the experiments which I am going to describe. I have received from Dr. Merck the following account of the process by which he has produced the new oil :-The juice of the unripe berries had been boiled with a quantity of milk of lime insufficient for the saturation of the acid which it contained and the solution on cooling had deposited the bimalate of calcium.The liquid separated from the crystals mas int'roiluced into a copper still and distilled over an open fire. The condensed vapours furnished a powerfully acid distillate and when after some time the acid reaction of the liquid which distilled over ceased it could be renewed by pouring a quantity of dilate sulphuric acid into the still. In order to coiicentratc the acid the aqueous dis-tillate was saturated with carbonate of sodium and evaporatcd on the water bath. The residuary semi-solid mass was decomposed in a tall glass cylinder by moderately concentrated sulphuric acid vrhen tlle oil rose as abrown layer on the surface of thc colourleas saline solution. It was dissolved in cther separated €IV~Ithe IIOFMANN ON NEW aqueous liquid and reetified after the ether had been allowed to evaporate.Several specimens of the mountain ash-berry oil which Dr. Merck had prepared at different periods exhibited some discre-pancies in their properties. Several were of mobile fluidity and scarcely coloured ; others brown nearly black and considerably resinified. On rectification however the oil was Obtained colour- less. Ebullition commenced at a temperature but little higher than 100°C; the distillate at this stage of the operation separated into two layers,- oil which still contained \.T ater floating upon an aqueous solution of the acid. On continuing the distillation the temperature rose rapidly to 20OoC then more slowly until it reached 225°C. There remained in the retort more or less of a yellowish brown transparent resinous matter.A few distillations soon convinced me that by far the greater bulk of the oil consists of a homogeneous substance which is however very apt to change under various influences. Freshly distilled the mountain ash-berry oil constitutes a trans- parent colourless liquid of a peculiar aromatic odour not unplea- sant when dilute but rather disagreeable and almost overpowering when concentrated. The oil has a sp. gr. 1,0681 and boils con- stantly at 221OC under a pressure of 0.755 m. It is appreciably soluble in water soluble in all proportions in alcohol and ether. Thc solutions are strongly acid. The mountain ash-berry oil has the characters of an acid. It dissolves with facility in the fixed caustic alkalies and in ammonia also in baryta-and lime-water.Even in carbonate of sodium the oil dissolves without however expelling the carbonic acid. The solutions thus obtained yield on evaporation dry resinous residues which indicate no signs of cry stallisation. Addition of hydro-chloric acid to these residues separates the original oil unchanged. The ammonia-solution furnishes with nitrate of silver a white gelatinous precipitate which slightly changes colour when exposed to the light. 'I'wo combustions of the oil gave the following results :-I 0.2280grm. oil gave 0.5352 grrn. carbonic acid and 0.1449 grm. water. II. 0.1926 grrn. oil gavc 0.4546 grm. carboriic acid arid 0.1280 grm. water. 45 In the analysis of the silver-compound just mentioned- 0.2465 grrn.silver-salt left 0.1209 grm. silver. The simplest expression for the acid suggested by these data is the formula- C 2HB04J the theoretical values of' which I subjoin with the experimental percentages. Theory. Experiment. Mean 12 equiv. of Carbon 72 64.28 64.01 64-27 64.14 8 , Hydrogen 8 7-14 7.06 7-38 7-22 4 , Oxygen 32 28.58 28.93 28.35 28.64 --_^__-1 equiv. of Oil 112 100~00 100~00100~00 100*00 In the silver-compound one equivalent of hydrogen of the acid is replaced by one equivalent of silver. The formula is supported by the silver-determination above quoted Theory. Experiment Percentage of Silver 49-31 49-05 I should have endeavoured to obtain additional compounds of the oil in order to gain if possible further data in favour of the formula which I propose had not any effort in that direction become superfluous by the observation of the remarkable deport- ment of the oily acid under the influence of powerful bases and acids.I have stated that the solution of the oil in potassa furnishes on addition of a mineral acid the unchanged oily acid; the alkaline solution may even be boiled for some time without altering the nature of the substance. But on gently heating the oily acid with solid hydrate of potassa an unexpected transformation takes place. The product of the reaction dissolved in water and saturated with hydrochloric acid furnishes an oil which rapidly solidifies into a hard crystallhe compound possessing the characters of a well defined acid.This observation at once suggested the idea of alde-hyde and acid but it was found that the transformation takes place without the evolution of a trace of hydrogen. Several grammes of the oil were heated for two or three hours in a sealed tube with hydrate of potassa in a water-bath. Not a trace of gas was clis. engaged when after cooling the tube was opened under water but the oil mas almost entirely converted into the crystalline acid. The same molecular transformation as might have been expected is produced by the action of acids. On boiling the oil for a short time with concentrated hydrochloric acid it becomes more and more viscid and ultimately solidifies. A similar result is produced by sulphuric acid.The oily acid dissolves in concentrated sulphuric acid the oil which is reprecipitated by addition of water gradually becomes a solid crystalline mass. The mode of forming the new acid suggested the probability of its being isomeric with theoriginal oil. This suggestion has been fdy borne out by experiment. I propose to designate this beau- tiful body by the name of sorbic acid reviving thus a name once used for malic acid. The oily acid may then conveniently be called parasorbic acid; for although more directly related to the moun-tain ash its character is less defined and salient than that of its derivative. Sorbic acid is readily purified ; being nearly insoluble in cold and moderately soluble in boiling water this substance is chemi- cally pure after two or three crystallisations from boiling water.It dissolves with great facility in alcohol or ether. The most appropriate solvent is a mixture of 1vol. of alcohol and 2 vol. of water. From this liquid the acid separates on cooling in magni- ficent white needles often several inches in length. Sorbic acid is inodorous. When in contact with a quantity of water insufficient for its solution the acid fuses at the temperature of boiling water. The fusing point of dry sorbic acid is 134.5OC; at a higher tern. perature the acid distils without decomposition. Sorbic acid is a powerful acid expelling carbonic acid from all the carbonates. The composition of sorbic acid was fixed by the following experiments :-For experiment I. the acid had been dried over sulphuric acid for experiments 11.and 111.in the water-bath.I. 0.3331 grm sorbic acid gave 0.7877 grm. carbonic acid and 0*2160grm. water 11. 0.4065 grm. sorbic acid gave 0.9561 grm. carbonic acid and 05?705 grm. water. 111. 0.3593 grm. sorbic acid gave 0%600 grm. carbonic acid and 0.2264grm. water These results lead to the formula previously established for parasorbic acid. Theory. Experiment Mean. I. 11. 111. 12 eq. of Carbon 72 64.28 64-49 64-14! 64.51 64-38 8 , Hydrogen 8 7.14 7.20 7*39 7-00 7.20 4 7 Oxygen 32 28-58 28.31 28.47 28.49 28.42 1 eq. of Sorbic Acid 112 100.00 100.00 100*00 200.00 100*00 The composition of sorbic acid receives additional support from the analysis of several of its salts and derivatives.Sor6ate of SiZver. White insoluble pulverulent precipitate obtained on adding nitrate of silver to sorbate of ammonium. I. 0.6288grm. silver-salt gave 0.7488 grrn. carbonic acid and 0.1807 grm. water. 11. 0.4635 grm. silver-salt gave 0.3012 grm. chloride of silver. 111. 0.6546 grm. silver-salt gave 0.4275 grm. chloride of silver. To the formula Cl [H,*glO* correspond the following values :-Theory. Experiment. I. XI. JI I. 12 equiv. of Carbon 72 32-88 32-48 - - 7 , Hydrogen 7 3-19 3.19 - - 1 , Silver 108 49*31 - 48.90 49.15 4 - 9 Oxygea 32 14.62 - 3 - 1 ey. of Silver-salt 219 lo000 Sorbate of Barium. On boiling carbonate of barium with an aqueous solution of sorbic acid a neutral solution of the barium- compound is obtained which yields a crystalline residue on IIOFMANN ON NEIV evaporation.The salt is not much less soluble in cold than in boiling water. It is however less soluble in alcohol. The best mode of obtaining it in the pure state consists in adding alcohol to the boiling aqueous solution; on cooling the sorbate of barium crystallises in scales of silver-white lustre. The salt is anhydrous. I. 0.4144 grm. of sorbate of barium dried at 125" C. gave 0.6135 grm. of carbonic acid and 0.1502 grm. of water. 11. 0.2863grm. of sorbate of barium treated with sulphuric acid left 0.1846 grm. sulphate of barium. The formula Cn [H,BalO requires Theory. Experiment. I. TI. 12 equiv. of Carbon 72 40.11 40.37 -7 , Hydrogen 7 3-90 4.02 -1 , Barium 68.5 38.16 -37.89 4 > Oxygen 32 17.83 -1 eq.of Barium-salt 179.5 100.00 Xorbate of CaZcium. Preparation and properties perfectly similar to those of the preceding salt. The formula was controlled by a calcium-determination. 0.2463 grm. of the salt dried at lMoC. and treated with sulphuric acid left 0.1260 grm. sulphate of calcium. Theory. Experiment. Percentage of Calcium 15.26 15.05 I have not analysed any of the other metallic sorbates; but have made some qualitative observations which may be recorded as contributions to the history of the acid. The sorbates of potassium and of sodium arc very solixhle salts crystallisirig with difficulty ; the ammonium-compound is likewise very soluble but crystallises beautifully in long slender needles which are apt to lose part of the ammonia by exposure to the air.A concentrated solution of the ammonium-compound shows the following deportment with reagents Chloride of calcium . White crystalline precipitate appearing after a short time. Chloride of barium Chloride of strontium No precipitate. Chloridc of magnesium 11 Aluminium -alum . . White precipitate which dissolves in ether and is therefore nothing but the acid. On ebullition a precipitatc is formed which is insoluble in ether and is probably the sorbate. Chromium-alum . . White precipitate of the acid. On ebullition a green amorphous preci- pitate of sorbate of chromium. Sulphate of iron . . Yellowish dingy amorphous precipi- tate.Iron-alum . . Yellow amorphous precipitate. Sulphate of nickel . . Greenish amorphous precipitate. Nitrate of cobalt . . No precipitate. Sulphate of manganese . Granular crystalline white precipitate appearing after a few minutes. Sulphate of zinc . . White acicular precipitate which ap- pears after a short time. Insoluble in ether. Acetate of lead . Nitrate of mercury curosum) . White copious amorphous precipitate. Chloride of (Mercuricum) . Sulphate of copper. Light bluish green amorphous precipi- tate. The analytical results obtained in the analyses of the acid itself and of the silver- barium- and calcium-compounds are sufficient to VOL XII. E HOFMANN ON NEW cstshlish the conipositioii of sorbic acid. It remttiiiq now bi~t twiefly to mention a few cvyerimcnts miiadc respecting the deriva- tives of sorbic acid; they are rather fi-agmentsry but may serve to complete the picture of the acid.Sorbic ether.-Colourless liquid boiling at 195.5' C. lighter than water possessing an aromatic oclour similar to that of benzoic ether. It is conveniently obtained by saturating the alcoholic solution of the acid with dry hydrochloric gas. The action of chloride of sorbyl upon alcohol produces the same compound. Sorbatc of ethyl contains C16H1204 = Cl C~~,(C*H,)IO* as proved by the combustion of the ether. 0.2136 grm. of sorbic ether gave 0.5342 grm. of carbonic acid and 0.1644grm. of water. Theory. Experiment. 16 eyuiv. of Carbon . 96 68.5'7 68.21 12 4 , , Hydrogen Oxygen .. 12 32 8.57 22.86 8.55 - - __I- 1 , Sorbic Ether 140 100.00 Chloride of Sorbyl is obtained by the usual processes; by the action of pentachloride of phosphorus upon the acid or of the trichloride upon the potassium-compound. The limited amount of acid at my disposal did not permit me to procure this substance in a state of purity and to establish analytically the formula (C12W2) c1 assigned to it by theory. But this formula is indirectly proved by the deportment of the crude product still containing chloride of phosphorus with water,-when sorbic acid is at once reproduced,- with alcohol,-when sorbic ether is obtained,-vith ammonia and phenylamine,-when respectively sorbamide and phenyl-sorbamide are generated. The chloride is not volatile without considerable decomposition.Sorbamide.-This substance is formed by the action of dry car- bonate of ammonium upon the crude chloride. It is also pro-duced by digesting sorbic ether with aqueous ammonia in a sealed tribe at a temperature of 120°C. At too high a temperature however or by protracted digestion the amide absorbs the ele- ments of water and regenerates sorbate of ammonium. Sor- VOLATILE ORGANLC ACIDS kC. bainidc forms white readily fusible needles soluble in water and in alcohol. I liad scarcely a sufficient quantity for analysis at my disposal but the following numbers although exhibiting a slight deficiency in hydrogen establish the composition of sorbamide 0.0942 grm. of' sorbamide gave 0*2230grm of carbonic acid and 0.0665 grm.of water. The formula C,,H9N02 = H requires Theory. Experiment. 12 equiv. of Carbon . 72 64.86 64.55 9 , Hydrogen . 9 8-10 7.84 i , Nitrogen . 14 12.61 -2 , Oxygen . 16 14.43 -1 , Sorbamide 111 100*00 Phenyl-sorbamide (Sorbanilide) is obtained by replacing the am- monia in the previous process by phenylamine. After treatment ~bith water an oily liquid remains which gradually soliciifies into a crystalline mass. I have not analysed it its composition being sufficiently characterised by theory. When distilled with an excess of hydrate of baryta sorbic acid cxhibits the deportment of the acids with 4 equivalents of oxygen; carbonate of barium being produced whilst an aromatic hydro- carbon distils over.The limited amount of material has pre- cluded for the present the possibility of a more minute examina- tion of this body. Sorbic acid is obviously the first term of a new series of well characterised organic acids closely allied with the ordinary fatty arid aromatic acids occupying in fact a sort of intermediate position between the two. On comparing sorbic acid with the terms of the fatty and aromatic acid series containing an equal number of carbon-equivalents the hydrogen of sorbic acid stands in the middle C12H 1204 c,$804 C12H404 Caproic acid. Sorbic acid. Lox er homologue of Benzoic acid. E% BARRAT AiYAT,YSIS OF THE The same remark applies to the carbon if sorbic acid l)c COH-. trasted with the fatty and aromatic acids containing an cqiial number of hydrogen-equivalents C8H804 C,,HP4 C16H804 Butyric acid. Sorbic acid. Toluic acid.