CONSTITUTION OF LACTIC ACID. V.-Conversion of Lactic Acid into Propionic Acid. BY Dr. C. ULRICH. THEfollowing experiments were undertaken at the suggestion of Professor XColbe with the view of testing the correctness of tlic supposition that the compound recently obtained by Wint z from lactic acid and described by him as chloride of lactyl C6H40,.C1 is the chloride of chloropropioxyl (c,{ Ef) c,o,,c~. If t~iis view be correct the supposed chloride of chloropropioxyl may lie expectea to decompose with water into chloropropionic and hydro-chloric acids and the product of the action of alcohol on tlmt compound described by W ur t z as chlorolactic ether will exhibit the characters of cbloropropionate of ethyl Chloride of chloropropioxyl. Chloropropionic acid.(C4 (cHi)c,O,,cI+ c4H50,H0 =C,H,O(C {Ff)C202,0 +HCI Chloride of chloropropioxyl. Chloropropionate of ethyl. The assumption that the compound formed from the so-called chloride of lactyl by the action of water is chloropropionic acic? is opposed to the statement of Wur t z that the acid produced in this reaction is lactic acid. I have however repeated the experi- ment and found as I expected that the re-production of lactic ULRICH ON THE CONVERSiON OF LACTIC AClD acid by the action of water OLI chloride of lactyl takes placc oiily when an alkali or other strong basc is lilreivise present; and that when the decomposition is produced by the action of water alone the resulting conipound is not lactic but cliloropropionic acid. The colourless fuming liquid (the mixture of chloride of chloro- propioxyl and oxychloride of phosphorus) obtained by heating dry lactate of lime with pentachloride of phosphorus was added by small portions to a.largc quantity of water and the acid liquid containing considerable quantities of phosphoric and hydrochloric acid was distilled to about half its bulk. The distillate contained lipctrochloric acid and as I shall presently show chloropropionic acid. The residue in the retort which should have contained lactic acid if that acid had been formed was further evaporated in thc water-bath in order to expel the remaining chloropropionic acid as coniplctely aspossible and then tested for lactic acid; it did not liowerer afford any ilidicntion of tlie presence of that ucid.The acid distillate containing the chloropropio~~ic acid was iieutralised in the cold with recently precipitatcd carbonate of silver ; the filtered saline solution mas evaporated to dryness over sulpI~uric acid in racuo ; aiid the chloropropionate of silver which crj-stallised from it in beautiful colourless square prisms was ana- lysed. I had found by a preliminary esperimeut that the salt when heated gave off acid vapours aid left a rcsidue consisting cliiefly of cliloride of silver but containing also a certain quantity of metallic silver ; in fact a small portion of the chloropropionic acid evaporates undecomposed when the silver- salt is heatcd as shown by the odonr of thc acid vapours; if this were not the case the residue would consist entirely of chloride of silver.0.478 grm. dried in V~CUO gave aftcr being heated 0.299 grm. of a mistnre of chloride of silver and nietallic silver. This resi-due after being heated to a temperature short of its melting point was warmed with nitric acid and the liquid evaporated to dryness after addition of hydrochloric acid. On ignition there remained 0.319 grin. of fnserl chloride of silver corresponding to 50.2 per cent. of silvcr. 0.710 grm. burnt with oxide of copper yielded 0.430grm. of carbonic acid and 0.121 grm. of water (= 16.5 p. c. carbon and 1.9 p. c. hydrogen). These numbers agree very nearly with the calculated composition of chloropropioaate of silver. Cslculltted. Ponnd. 6C . . 36.0 16.7 16.5 4H b * 4.0 1.9 1.9 c1 .355 16.5 --4g . 108.0 50.1 50.2 40. . 32.0 14.8 -C6H,Clhg0 . 215.5 100.0 Chloropropionate of silver is much more soluble in water thau the propionate. It is but little blackened by light. On boiling the aqueous solution chloride of silver is dcposited and lactic acid is doubtless formed. The same decomposition takes place during the evaporatioir of the aqueous solution on the water-bath. Chloropropionic acid is much less volatile than propionic acid and has an odour like that of terchloracetic acid. As it seemed desirable to adduce still further proof that the acid obtained as above is really chloropropionic acid I endeavoured to convert it directly into propionic acid. This was effected as follows The crude chloride of chloropropioxyl still containing oxy-chloride of phosphorus was made to flow gradually into water contained in a vessel well cooled from without and having at bottom a tolerably large quantity of finely granulated zinc.The hydrogen evolved by the mutual action of thc water the zinc and the phosphoric and hydrochloric acids was expected to replace the chlorine in the chloropropionic acid produced by the action of the water on the chloride of chloropropioxyl. An abundant evolution of gas immediately took place; and when at length the drops of oil had disappeared and the odour of chloride of chloropropioxyl and oxychloride of phosphoriis mas uo longer perceptible the acid liquid was decanted from the zinc diluted with water and dis- tilled.The watery distillate contained besides traces of hydro-chloric acid a considerable quantity of pure propionic acid. This liquid was neutralised with carbonate of soda ; the saline solution evaporated to dryness; and the dry nims distilled with dilute sul- phuric acid. A portion of the strongly acid distillate which smelt distinctly of propionic acid was boiled with carbonate of silver and the solution filtered while hot. It theu on cooling deposited pure propionate of silver in fine crystals which slowly blackened when exposed to light. ULRICH ON CONVERSION OF LACTIC ACTD &C. 0.331 grm. of these crystals dried over sulphuric acid left on ignition 0.198 grm. of metallic silver. 0.4495 grm. burnt with oxide of copper gave 0.330 grm.car-bonic acid and 0,116 grrn. water. Calculated. Found. 6C. . 86 19.9 19.6 5H . 5 2.7 2.8 Ag . 108 59.6 59.8 40 . 32 17.8 C6H,Ag0 . 181 100.0 I have also prepared the potassium-salt and decomposed 0.3985 grm. of it with strong sulphuric acid. After strong and continued ignition this quantity of the salt left 0.314 grm. sulphate of potassium corresponding to 35.3 p. c. potassium. The formula K0.C6H,0 requires 34.8 p. C. The ahove-described method of preparing propionic acid is so productive and yields so pure an acid that it is perhaps to be preferred to all other methods. Lastly I have treated chloroyropionatc of ethyl (TVurtz’s chlo- rolactic ether) boiling constantly at 143°C. with zinc and dilute sulphuric acid with the hope of converting it into propionate Gf ethyl.The liquid soon exhibited a considerable amourit of hydro.. chloric acid but in the subsequent distillation yielded only traces of propionic ether with considerable quantities of propionic acid. 0.4635 grm. of propionate of silver prepared therefrom yielded 02755 grm. metallic silver = 59.441 p. c. (calculated quantity 59.66 p. c.). Propionate of ethyl appears therefore at the moment of its formation from chloropropionate of ethyl to be resolved into pro-pionic acid and alcohol perhaps in consequence of the decomposing action of the free sulphuric acid present.