FOBTER ON PIPERIC AND HYDROPIYERIC ACIDS. IV.-On Piperic and Hydrcpiperic Acids. By G. C. FOSTER,B.A. PIPERIC acid was first described in 1857 byv. Babo and Keller.+ Their analyses led them to represent its composition by the for-mula C26H1208 C50H240,6 or C,,H2,016 the last formula they considered the most probable. The analysis of the acid and of its silver-salt was soon afterwards repeated by St 1:ecker t who gave the formula C24H,,08 for piperic acid and the formula C,,H,MO for the piperates and showed that many of Babo and Keller’s own analyses agreed with these expressions. If the accuracy of Strecker’s formula be admitted it seems to indicate that piperic acid is a triatomic acid analogous to glyceric acid C3H604f; otherwise it is difficult to reconcile its monobasic character with the high proportion of oxygen it contains.These considerations induced me to make a few experiments on piperic acid in the hope of obtaining some knowledge of the relation in which it stands to bo-dies whose constitution is better understood. * J. pr. Chem. lxxii 53; Jebresber. 1867,p. 413. + Ann. Ch. Pharm. cv 317; Jahreaber. 1857 p. 414. $ Here and hereafter in this paper C=12 H =1 0=16. VOL. xv. C 18 FOSTER ON PIPERIC AND HYDROPIPEHIC ACIDS. The piperic acid cmployed wa.s obtained by decomposing piperino with alcoholic potash according to 13abo and Keller’s proccss; but I foulid that by employing a closed vessel in which thc matcrials could bc heated above the boiling point of alcohol much time might be saved 100 grms.piperine mixed with an equal weight of solid potash and as much strong alcohol aa will dissolve both is completely decomposed when heated for five or six hours to 100°C; The ailalpis of pipcric acid and of its potassium- and barium- salts gavc me numbers which agree with Strecker’s formula m is shown by the following statement of results. Piperic acid C12Hl,0,. 0.517 grm. acid gave 1.248 grm. carbonic acid and -229 grm. water. 0443 grm. acid gave 1.074 grm. carbonic acid and *197 grm. water. Calculated. Found. ... \ / -14% 66.05 65-83 66.12 c12 10 4.59 4-92 4.94 % 04 6% 29.36 , ,> C12H1004 218 100.00 Piperate of potassium C,2H9K04. 0.4371 grm. salt gave ,147 grm. sulphate of potassium.425 grm. salt gave ,144 grm. sulyhate of potassium. -7325grm. salt gave 1.502 grm. carbouic acid and -232grm. water. Calculntcd. Found. -7-C12 144 5625 > , 55-92 9 3.52 3-52 2 39 15-23 15’bS 16’19 , 04 64 25-00 ,f 9 >> C,,H-,KO 256 100.00 Piperate of barium C,,H,FaO,.-This salt wi1s prepared by adding chloride of barium to a solutiou of yiperate of potassium arid purified by crystallizatim from boiliug water in which it is somevliat more soluble than in cold water and subsequent wwh- POBTER ON PIPEBIC AND UYDBOPIPERIC ACIDS. ing with boiling alcohol. A current of carbonic acid passea through a solution of this salt in hot water decomposes it into carbonate of barium and piperic acid. Air-dry it does not lose weight at looo 03082 grm.salt gave *I251grm.aulphate of barium. ,3406p.salt gave 01388grm. eulphate of barium. Mculated. Found. Barium per cent. 23.99 23-86 23.98 My first experiment with piperic acid was an attempt to reduce it by means of hydriodic acid in the hope of obtaining a mona-tomic acid (C12Hl,-,0,$ which should bear the same relation to'it as propionic acid (C,H,O,) bears to glyceric acid (C,H,O,). In this attempt I was unsuccessful. At 100°C. and even below piperic acid is converted by hydriodic acid into a black uncrystal- lizable substance carbonic acid being formed at the same time but no iodine set free. The only crystalline .substance which I SUC-ceeded in separating from the black carbonaceous product of this reaction was a small quantity of what appeared to be unaltered piperic acid.Having failed to reduce piperic acid by hydriodic acid I hoped to be more successful iik employing uascent hydrogen. This re- agent however instead of giving a product containing less oxygen gives rise to a new acid containing two atoms of hydrogen more than yiperic acid which I have named hydropiperic acid. This substance is best obtained by allowing sodium-amalgam to act for some hours upou a solution of piperate of potassium kept at a gentle heat and frequently stirred. The piperate of potassium which is obtained as a direct product of the action of alcoholic potash on piperiue may be employed for this preparation after hav-ing been once recrystallized. The hydropiperic acid is separated from the alkaline solution by the addition of hydrochloric acid in the form of oily drops which gradually solidify when allowed to stand.It may be purified by solution in a large quantity of boiling water which deposits it ou cooling in exceedingly thin silky needles sometimes as much as an inch long; or by solution in alcohol and treatment af the solution with animal charccal. Pure hydropiperic acid is colourless; it melts at 63" or 64"C. and solidifies at about 56'; it may sometimes be cooled still lower FOSTGIL ON PIPERIC AND FIYDROPIPEIIIC ACIDS. without solidifying but then solidi fics suddenly when touchetl with a glass rod ; it docs riot appcar to bc volatile without dccom- position but wlicii hcatcd in a tcst-tiih it creeps up thc sides of the tulle lcaviiig only a very alight residue at the bottom.It is very slightly solulde in cold watcr biit sufficicntly so ta give a faint acid rcwtion to the solution and to cause it to give a preci-pitate with acetate of lead; it is somewhat more but still only sparingly soluhle in hot watcr and givcs a solution having a strong acid rcnction. It separatcs on cooling partly as an oil partly in very fine crystals. Alcohol dissolvcs hyclropiperic acid in all proportions ;in cthcr also it is wry soluhlc and it crystnl- lizes hy the spontaricous evaporation of its cthcrcal solution in largc but confusedly formcd hard crystals apparently belonging to thc iiionoclinic system and many of them hemitropic (2.1724grm. acid gave 4124 grm.carbonic acid arid ,0877 gym. water. *4883grin. acid ;saw 1,1715 grm. carhonic acid and 02495 grm. water. 4GG grm. acid xavc 1.116 grin. carbonic acid and .235 grni. water. Calculntctl. Found. 7'-. Cl2H12 144 12 (i;i*4fi 5-43 r G 5 5.65 - 4 4 547 G5-31 5.60 04 6 l! 29-09- .>> ,> 99 C,2Hl,0 220 100.00 The first mid sccoiid analyses werc made witli the products of two diffcrciit preparations ; tlic third analysis is of the product obtaiiicct by trcntirig sonic of tlic satlie siil)stwcc ns scrvcti for thc sccoiid analysis a second time with sodium-amdgani. Stroiig sulpliuric acicl givcs il 1h)cl-rerl colour with hydro-pipcric wid ; filming nitric acid acts in tlic snmc way; nitric acid ilililtcrl witli its owti bulk of water acts viol(tnt1y 011 1iydrol)il)cric acid WIACI~ sliglitly licntcd giving a soltitioil f'rorn whicli wntcr prccil)itatcs a scmi-fluid nitro-acid.IVhcn hytlropiperic acid is licntctl with cxyccss of' alkali a good deal of gas is givcii off and the rcsitluc csliihits thc rcactioiis of tlic acid Cj€I6O4,obtairicd by Ur. X at tliiesseii aid myself* by distilling hemipixiic acid with * I'ro:.. Coy. SOC.,xi 58. FOSTER ON PIPERIC AND EYDROPIPEBIC ACXD8. 2& hydriodic acid and sul~scqucntly obtained by S trecker* by heating pipcric acid with excess of potash. With hydriodic acid it behaves in the same way as piperic acid. Hydropir,erct!e of nrn~~io)iiu~n, C12H (NIX,)O,.-This salt ww prepared by nciltralizi~~g tlic acid with ammonia.It crystallizee easily from hot watcr iii small shining scales For analysis a portion was dissolved in :ilittlc waster ; the acid was precipitated by hydrochloric acid collcctcd on a wcighed filter and washed with as small a quantity of water as possible; the filtrate was evapo-rated ; the residue dissolyccl in very little water; the small additional quantity of acid thus separated was collected on the same filter as before and the whole quantity *eighed after being dried in vacuo; the second filtrate arid wash-waters were then again evaporated and the ammonia was determined in the residue aa chloro-platinate. 0.4813 grm. aalt gave .4469 grm. hydropiperic acid and 04126 grm. chloroplatinate of ammoaium. 05147grm. salt gave -4787 grm. hydropiperic acid and *2146 grm.platinum. Calculated. Found. 0-F /-,-, c1211,,0 220 92.83 92-85 93.01 H3 N 17 7.1 7 6.55 7.16 C12€11204113N 237 100.00 99.40 100.17 A strong solution of hydropipcrate of ammonium can dissolve a considerable quantity of hydropiycric acid the addition of strong aqueous ammonia to such a solution saturated with acid gives an almost solid maw of hydropiperate of ammonium ; by the addition of water it is decomposed into hydropiperate of ammonium which dissolves arid hydropipcric acid which is prccipitatcd. HydropQi&ate of potassium with excess of 'ucid Cl,HllKO + C,,H,,O,.-Tllis salt mas obtained by boiling it soliltion of hydro-piperic acid in nearly absolute alcohol with excess of dry carbonate of potassium filtering the solutiori while still hot and allowing it to cool the salt was thus obtaiiicd crystallized in hemispherical clunips of radiating needles.It was analysecl after being once recrystallized from alcohol and dried at 100°C. Ann. Ch. Pharm. cviii 280. FOSTER ON ?IPEBIC AND RYDROPIPERIC ACIDS. 0.316 grm. salt gave -688 grm. carbonic acid and *1455grm. water. 0.261 grm. salt gave -050 grm. sulphate of potassium. Calculated. Fonnd. C, / 288 h 4/-60.125 h 5938 7 >) H23 23 4.81 5.1 1 K 39 8.16 9 8'59 08 128 26.78 9 99 C,,H=KO 478 100.00 The deficiency of carbon and excess of potassium shown by the analysis were no doubt caused by the presence of a small quan- tity of neutral hydropiperate of potassium (cnlc. carbon 55.81 per cent.;potassium 15.12 per cent.) ;indeed the acid salt appears to he decomposed by repeated crystallization from alcohol into hydro- piperic acid and the neutral potassium-salt at least a portion which 'had been recrystallized three times from alcohol gave on analysis 12-63 per cent. potassium. The acid salt is imme-diately decomposed by water with precipitation of hgdropiperic acid. HIidropiperate of calcium C,,H ,CaO,( +H,O ?).-Obtained by boiling the acid with milk of lime filtering hot and separating the excess of lime by carbonic acid; or by precipitating a rather strong solution of hydropiperate of ammonium with chloride of cal.. cium. Tbis salt is partially decomposed by solution in hot water but may be purified by crystallization from a mixture of about 2 parts water and 1 part alcohol which deposits it in bunches of tine needle-shaped crystals.It is only slightly soluble in cold water. The crystals effloresce in the air but do not lose all their water below about 100"C.; they melt together to a sticky mass at lo", which may be powdered when quite dry pnd then docs not again become soft on heating. Hydropiperate of calcium dried at loo",does not further diminish iu weight at 120".* Hydropiperate of calcium appear8 to cqstallizc with one atom of water. A calciumdetermination in the airdry salt gave 7.53per cent. calciitm (the formula CI,HIICa04+ H,O requires 7.78 per cent. calciam) ; after the =me salt had stood two days longer over sulphiiric acid it contained 4.2 per cent.water ; in other prepa- rations of tbc salt (airdry) I found 4 94 4.88. and 4.87 pcr cent. water ; niimbere which do not agree with any simple atomic proportion. The percentage of water calculated for the above formula is 7.00 I can only explain the results oldnincd by ascribing them to the rapidity with which the salt effloresces. After drying very quickly by pressure between paper and exposure to the air the crystals were found te have partially effloreeced when examined under the microscope. FOSTER ON PtPERIC AND HYDROPIPERIC ACIDS. 0.595 grm. kalt (dried at 105') gave -170 grm. sulphate of calcium. -3348grm. salt (dried at 100") gave *095 grm. sulphate of calcium. Calculated. Found. -CI 1 144 60.25 99 9 11 4-60 9 ¶, HI1 Ca 20 8.37 8.30 8.35 64 26.78 , 9, 04 Cl,HllCaO 239 -100.00 Hydropiperate of barium C12HllBaO+,resembles the calcium- salt and may be obtained in a similar way.(Found 23.2 per cent. barium; calculdted 23.8 per cent.) Hydropiperate of silver Cl,H Ago,.-A crystalline precipitate almost insoluble in cold water; it dissolves in hot water but is partially decomposed at the same time. It can hardly be dried without undergoing slight decomposition. 0.2933grm.gave -0985 grm. metallic silver'. Calculated. Found. Silver per cent. . . 33.03 -33-58 A solution of hydropiperate of ammooium gives a whitish brown precipitate with perchloride of iron and white precipitates with corrosive sublimate mercurow nitrate and acetate of lead all of them soluble in hot water.Hydropiperate of ethyl.-A solution of hydropiperic acid in absolute alcohol was saturated with hydrochloric acid gas and heated to 130' for four or five hours; the product was then evaporated on a water-bath and the residue washed with dilute potash. In this may a neutral brown liquid was obtained which was heavier than and insoluble in water. By solution in ether treatment of the ethereal solution with animal charcoal and sub- sequent evaporation it mas obtained as a brownish yellow liquid. It was not altered by dilute potash or ammonia but gave a half-solid mass probably hydropiperamide when saturated with gaseous ammonia. Hydropiperic acid heated with an excess of monohydrated acetic - A. OPPENHEIM ON THE acid to 160OC.during 30 houre appears to be unaltered. The product of this experiment was poured into water which caused a precipitate of a solid acid; this precipitate was washed to remove acetic acid ; about two-third3 of it were then neutrdizcd by lime the other third added and the whole evaporated to dryness on a water-bath. The residhe was well washed with strong alcohol the remaining salt crystalhd from very dilute alcohol and then decomposed by hydrochloric acid. The acid thus separated was dried over sulphuric acid and analysed. 0.3394grm.acid gave 810 grm. carbonic acid and -1724 grm. water. These numbers show that the substance was nearly pure hydropiperk acid of which it had all the external properties. Found. Hydropiperic acid.Carbon . . 6512 6546 Hydrogen . . 5-64 5.45 The deficiency of carbon may perhaps indicate that a small quantity of aceto-hydropiperic acid C,,H, (C,H,O)O, (carbon 69-12per cent.) had been formed. Hydropiperic acid heated to 150"C. with chloride of acetyl gives a neutral oil insoluble in water and dilute alkalis ;probably accto- hydropipcric anhydride ; I do not know whether aceto-hydro- piperic acid was formed at the same time or not.