164 THE ANALYST. METHODS OF SEPARATING SALICYLIC ACID. BY A. WJNTER BLYTH, M.R.C.S. Rend bPfore the Xocicty of Pu6lic AnaZyysts on 14th November, 1877. SALICYLIC ACID can be separated by (1) dialysis, (2) sublimation, (3) ether acting 011 an acid solution. Dr. Muter has already described this method, and ha3 also gii-cn n process for the colorimetric estimation% of salicylic acid. On placing a little of the pure acid between two watch gltlsscs, and heating for even a few minutes on the water bath at 100QC, the upper giass is clouded by silky crystals, which she-s that solutions containing the acid must not be evaporated to dryness at that temperature.Placed in the subliming cell I have already described? salicylic acid begins to give n sr:nnty sublimite as low as 60.5 C, whilst at 100pC sublimation is rapid.Sublimation at these low temperaturea does not, however, take place in flasks, closed tubes, or the like vessels. I have not succeeded in getting a decided sublimate at lOOoC i n a closed tube. Struck, however, with its low subliming temperature I have attempted t o distil it over from beer. A milligramme was dissolved in 100 C.C. of beer, and the beer distilled t o dryness, 110 salicylic acid came over until the residue was apparently dry; then the drops from the delivery tube gave a distinct colouration with ferric chloride, but the whole of It was uot obtained.On using, however, a globular flask without a neck, furnished with n very short jvide delivery tube, and the whole immersed almost entirely in a spermaceti bath, and towards the end of the operation passing a stream of purificd coal gas through the flask, most of the salicylic acid distilled over at a temperature approaching 149OC.Salicylic acid is very soluble in ether, it does not take tile acid up from an aqueous, alkaline solution, but if the solution be strr>ngly acidified by ClH, the removal is complete. A simple experiment will show this; if t o a solution of salicylic acid in a test tube C1H is added, then shaken up with ether, alld lastly tested with ferric chloride ; the lower stratum of liquid will not show a trace of the well-known purplish colour.Advantage of this fact can be taken in the testing of' yarious fluids, such as beer, &c. The beer is first concentrated to a small bulk acidified with C1H and shaken up with ether, the latter removed and evaporated in the usual way.(1) Dialysis. (2) Sublimation. (3) Extraction by EtJw. * Analyst p. 193. 1877. .t- Analyst, p. 38. 1877.THE ANALYST. 165 - Milk cannot be manipulated so simply, and merely shaking up with ether, after adding ClH, will scarcely succeed. I find it best to concentrate the milk first at 100°C, and then at GOOC, until it is in a pasty condition. Repeated treatment with ether will now dissolve out both fat and salicylic acid, and after evai2oration of the ether the salicylic acid is separated from the fat by obvious methods.