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SALICYLIC ACID (ortho-hydroxybenzoic ...

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Originally appearing in Volume V24, Page 70 of the 1911 Encyclopedia Britannica.
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SALICYLIC See also:

ACID (ortho-hydroxybenzoic acid)  , an aromatic See also:acid, See also:C6H4(OH)(See also:CO2H), found in the See also:free See also:state in the buds of Spiraea Ulmaria and, as its methyl ester, in gaultheria oil and in the essential oil of See also:Andromeda Leschenaultii . It was discovered in 1838 by Piria as a decomposition product of See also:salicin . It may be obtained by the oxidation of saligenin and of salicylic aldehyde; by the See also:distillation of See also:copper benzoate; by the decomposition of anthranilic acid with nitrous acid; by See also:fusion of ortho-chlor or ortho-brom benzoic acid with potash; by See also:heating orthocyanphenol with alcoholic potash; by heating a mixture of phenol, See also:carbon tetrachloride and alcoholic potash to zoo° C . (F . Tiemann and K Reimer, Ber., 1876, 9, p . 1285); and by the See also:action of See also:sodium on a mixture of phenol and chlorcarbenic ester (T . Wilm and G . Wischin, Zeit. f . Chemie, 1868, 6) . It is manufactured by See also:Kolbe's See also:process or by some modification of the same . Sodium phenolate is heated in a stream of carbon dioxide in an See also:iron See also:retort at a temperature of 18o-22o° C., when See also:half the phenol distils over and a basic sodium salicylate is See also:left . The sodium See also:salt is dissolved in See also:water and the free acid precipitated by hydrochloric acid (H .

Kolbe, See also:

Ann., 186o, 115, p . 201) . R . Schmitt (Jour. See also:peak . Chem., 1885 (2), 31, p . 407) modified the process by saturating sodium phenolate at 13o C. with carbon dioxide, in an See also:autoclave, sodium phenyl carbonate C6H6O•CO2Na being thus formed; by continuing the heating under pressure this carbonate gradually changes into mono-sodium salicylate . S . Manasse (See also:German patent 73,279) prepared an intimate mixture of phenol and See also:potassium carbonate, which is then heated in a closed See also:vessel with carbon dioxide, best at 130-16o° C . The Chemische Fabrik vorm . See also:Hofmann and Schotensack decompose a mixture of phenol (3 molecules) and sodium carbonate (4 moll.) with carbonyl chloride at 140-200° C . When 90 % of the phenol has distilled over, the See also:residue is dissolved and hydrochloric acid added, any phenol remaining is blown over in a current of See also:steam, and the salicylic acid finally precipitated by hydrochloric acid . The acid may also be obtained by passing carbon monoxide over a mixture of sodium phenolate and sodium carbonate at 200° C .

: Na2COa+ C6H2ONa+CO = C7H4O2Na2 + HCO2Na;and by heating sodium phenolate with See also:

ethyl phenyl carbonate to 200° C.: C6HSO•CO2C2H +CsH5ONa = HO•C6H4COiNa+CiHs•C2Hs . It is to be noted in the Kolbe method of See also:synthesis that potassium phenolate may be used in See also:place of the sodium salt, provided that the temperature be kept See also:low (about 15o° C.), for at the higher temperature (220° C.) the isomeric See also:para-oxybenzoic acid is produced . Salicylic acid crystallizes in small colourless needles which melt at 155° C . It is sparingly soluble in See also:cold water, but readily dissolves in hot . It sublimes, but on rapid heating decomposes into carbon dioxide and phenol . It is volatile in steam . Ferric chloride See also:colours its aqueous See also:solution See also:violet . Potassium bichromate and sulphuric acid oxidize it to carbon dioxide and water; and potassium chlorate and hydrochloric acid to chloranil . On boiling with concentrated nitric acid it yields picric acid . When heated with See also:resorcin to zoo° C. it gives trioxybenzophenone . See also:Bromine water in dilute aqueous solution gives a See also:white precipitate of tribromophenol-bromide C6H2Br3.OBr . Sodium reduces salicylic acid in boiling amyl See also:alcohol solution to n-pimelic acid (A .

See also:

Einhorn and R . Willstatter, Ber., 1893, 26, pp . 2, 913; 1894, 27 p . 331) . Potassium persulphate oxidizes it in alkaline solution, the product on boiling with acids giving hydroquinone carboxylic acid (German Patent 81,297) . When boiled with See also:calcium chloride and See also:ammonia, salicylic acid gives a precipitate of insoluble basic calcium salicylate, C6114 <C82> Ca, a reaction which serves to distinguish it from the isomeric See also:meta-and para-hydroxybenzoic acids . It yields both See also:esters and See also:ethers since it is an acid and also a phenol . Methyl Salicylate, C6H4(OH)•CO2CH6, found in oil of See also:wintergreen, in the oil of See also:Viola tricolor and in the See also:root of varieties of Polygala, is a pleasant-smelling liquid which boils at 222° C . On passing dry ammonia into the boiling ester, it gives salicylamide and dimethylamine . When boiled with See also:aniline it gives methylaniline and phenol . Ethyl salicylate, C6H4(OH)•CO2C2H6, is obtained by boiling salicylic acid with alcohol and a little sulphuric acid, or by dropping an alcoholic solution of salicylic acid into 13-See also:naphthalene sulphonic acid at a temperature of 140-150° C . (German Patent 76,574) .

It is a pleasant-smelling liquid which boils at 233° C . It is practically unchanged when boiled with aniline . Phenyl salicylate, C6H4(OH)•C•02C6H6, or salol, is obtained by heating salicylic acid, phenol and See also:

phosphorus oxychloride to 120-125° C.; by heating salicylic acid to 220° C.; or by heating salicyl metaphosphoric acid and phenol to 140-150° C . (German Patent 85,565) . It crystallizes in rhombic plates which melt at 42° C. and See also:boil at 172° C . (12 mm.) . Its sodium salt is transformed into the isomeric C6H4(OC6H5) CO2Na when heated to 300° . When heated in See also:air for many See also:hours it decomposes, yielding carbon dioxide, phenol and See also:xanthone . Acetyl-salicylic acid (salacetic acid), See also:C5H4(O•000H3)•CO2H, is obtained by the action of acetyl chloride on the acid or its sodium salt (K . Kraut, Ann., 1869, 15o, p . 9) . It crystallizes in needles and melts at 132° C .

Phoenix-squares

(with decomposition) . See also:

Hydrolysis with baryta water gives acetic and salicylic acids . It is used in See also:medicine under the names aspirin, acetysal, aletodin, saletin, xaxa; &c . It has the same action as salicylic acid and salicylates, but is said to be much freer from objectionable secondary effects . Salicylo-salicylic acid O•(C6H4CO2H)2 Is obtained by continued heating of salicylic acid and acetyl chloride to 130-140° C . It is an amorphous yellow See also:mass which is easily soluble in alcohol . Applications.—The addition of a little of the acid to See also:glue renders it more tenacious; skins to be used for making See also:leather do not undergo decomposition if steeped in a dilute solution; See also:butter containing a small quantity of it may be kept sweet for months even in the hottest See also:weather . It also prevents the mouldiness of preserved fruits and has been found useful in the manufacture of See also:vinegar . The use of salicylic acid as a See also:food preservative, was, however, condemned in the findings of the See also:commission appointed by the See also:government of the See also:United States of See also:America, in 1904 . Medicine.—The pharmacopeial dose of the acid is 5-2o grains, but it is so unrelated to experience and practice that it may be ignored . The See also:British Pharmacopeia contains only one preparation, an ointment containing one See also:part of acid to 49 of white See also:paraffin ointment . Salicylic acid is now never given internally, being replaced by its sodium salt, which is much cheaper, more soluble and less irritating to mucous membranes .

The salt has a sweet, mawkish See also:

taste . Salicylic acid and salicin (q.v.) See also:share the properties See also:common to the See also:group of aromatic acids, which, as a group, are antiseptic without being toxic to See also:man—a See also:property practically unique; are unstable in the See also:body; are antipyretic and analgesic. and diminish the See also:excretion of See also:urea by the kidneys . As an antiseptic salicylic acid is somewhat less powerful than carbolic acid, but its insolubility renders it unsuitable for See also:general use . It is much more powerful than carbolic acid in its inhibitory action upon unorganized ferments such as See also:pepsin or ptyalin . Salicyclic acid is not absorbed by the skin, but it rapidly kills the cells of the epidermis, without affecting the immediately subjacent cells of the dermis (" true skin ") . It has a very useful See also:local anhidrotic action . Salicylic acid is a powerful irritant when inhaled or swallowed in a concentrated See also:form, and even when much diluted it causes See also:pain, See also:nausea and vomiting . When salicin is taken internally no irritant action occurs, nor is there any antisepsis . Whatever See also:drug of this group be taken, the product absorbed by the See also:blood is almost entirely sodium salicylate . When the salt is taken by the mouth, absorption is extremely rapid, the salt being See also:present in the peripheral blood within ten minutes . Sodium salicylate circulates in the blood unchanged, decomposition occurring in the See also:kidney, and probably in tissues suffering from the Diplococcus rheumaticus of Poynton and See also:Paine . It used to be stated that these drugs are marked cardiac depressants; and the See also:heart being invariably implicated in rheumatic See also:fever, it is supposed that these drugs must be given with See also:great caution .

It has now been established that, provided the kidneys be healthy, natural salicylic acid, sodium salicylate prepared from the natural acid, and salicin, are not cardiac depressants . Of the two latter, 300 grains may begiven in a dose and 1y oz. in twenty-four hours, without any toxic symptoms . The artificial acid and its salt contain ortho-, para- and meta-cresotic acids, which are cardiac depressants . The See also:

vegetable product—which is extremely expensive—must be prescribed or the synthetic product guaranteed " physiologically pure," i.e. tested upon animals and found to have no toxic properties . Salicylates are the next safest to See also:quinine of all antipyretics, whilst being much more powerful in all febrile states except See also:malaria . Sodium salicylate escapes from the blood mainly by the kidneys, in the secretion of which sodium salicylate and salicyluric acid can be detected within fifteen minutes of its See also:administration . After large doses haematuria has been observed in a few cases . The rapid excretion by the kidneys is one of the See also:cardinal conditions of safety, and also necessitates the very frequent administration of the drug . See also:Therapeutics.—Salicylic acid is used externally for the removal of corns and similar epidermic thickenings . It causes some pain, so that a sedative should be added . A common See also:formula has II parts of the acid, 3 of See also:extract of See also:Indian See also:hemp, and 86 of See also:collodion . There is probably no better remedy for corns .

See also:

Perspiration of the feet cannot be attacked locally with more success than by a See also:powder consisting of salicylic acid, See also:starch and See also:chalk . These drugs are specific for acute See also:rheumatism (rheumatic fever) . The drug is not a true specific, as quinine is for malaria, since it rarely, if ever, prevents the cardiac damage usually done by rheumatic fever; but it entirely removes the agonizing pain, shortly after its administration, and, an See also:hour or two later, brings down the temperature to normal . In See also:thirty-six hours no symptoms are left . If the drug be now discontinued, they will return in over 9o% of cases . In acute gonorrhoeal See also:arthritis, simulating rheumatic fever, salicylates are useless . They may thus afford a means of diagnosis . In rheumatic hyperpyrexia, where the See also:poison has attacked the central See also:nervous See also:system, salicylates almost always fail . The mode of their administration in rheumatic fever is of the utmost importance . At first 20 grains of sodium salicylate should be given every hour: the See also:interval being doubled as soon as the pain disappears, and extended to three hours when the temperature becomes normal . The patient should continue to take about See also:loo grains a See also:day for at least a fortnight after he is apparently convalescent, otherwise a recrudescence is very probable . Sahcylate of soda may occasionally be of use in cases of'gallstone, owing to its action on the bile .

It often relieves See also:

neuralgia, especially when combined with See also:caffeine and quinine . Salicylism, or salicylic poisoning, occurs in a See also:good many cases of the use of these drugs . Provided the kidneys be healthy, the symptoms may be ignored . If nephritis be present, it may be seriously aggravated, and the drug must therefore be withheld . The headache, deafness, ringing in the ears and even See also:delirium of salicylism, are practically identical with the symptoms of cinchonism . The drug must be at once withheld if haemorrhages (subcutaneous, retinal, &c.) are observed . As in the See also:case of quinine, the administration of small doses of hydrobromic acid often relieve the milder symptoms .

End of Article: SALICYLIC ACID (ortho-hydroxybenzoic acid)
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