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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 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.

(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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