CHEMISTRY. 



105 



advantages of being tasteless, inodorous, and 

 non-poisonous. 



Salicylic acid exists ready formed in the 

 flowers of Spiraea ulmaria (meadow-sweet), 

 and as methyl-salicylic acid in oil of winter- 

 green. It may also be prepared from indigo, 

 and from salicine, a substance found in the 

 bark of several species of willow and poplar. 

 Kolbe's mode of preparing it is thus described 

 by himself. 



After many months' trial, I have at last succeed- 

 ed in gaining the clew which has led me to the dis- 

 covery of a new, simple, and productive method of 

 making salicylic acid. In dissolving sodium in hot 

 phenol in the presence of a stream of carbonic acid 

 there is always found, besides sodic sulicylate, more 

 or less sodic carbonate and phenylate. And I ob- 

 served that the more of the. former salt there was, 

 the less was found of the two latter. I further ob- 

 served that a product rich in sodic phenylate and 

 relatively poor in sodic salicylate yielded richly of 

 the latter salt when further heated in a stream of 

 carbonic acid. 



The method of manufacturing salicylic acid, up- 

 on which I finally settled and by which I have al- 

 ready prepared about fifty pounds, is the following: 

 Saturate exactly commercial crude soda lye of known 

 strength with crystallized carbolic acid previously 

 fused, and evaporate in a shallow iron vessel. The 

 sticky, dough-like mass is now heated moderately, 

 with constant stirring, being finally powdered with 

 a heavy pestle. This dried product is sodic pheny- 

 late. It is always reddish-yellow in color, perhaps 

 on account of partial decomposition by the oxygen 

 of the air during the evaporation, is very hygrosco- 

 pic, and must while yet hot be bottled and kept well 

 stoppered. If the sodic phenylate is moist, or con- 

 tains either free alkali or carbolic acid, the results 

 are not good. 



The sodic phenylate thus prepared is heated slow- 

 ly in a metal retort in an oil or air bath. When the 

 contents of the retort are about 100 C., begin to lead 

 into the mass a moderate stream of carbonic acid. 

 Let the temperature slowly rise, till after some hours 

 it stands at 180. After further action of the car- 

 bonic acid, phenol begins to distill over, toward the 

 last in greater abundance. Finally raise the tem- 

 perature to from 220 to 250. The operation is fin- 

 ished when at this temperature, under the continued 

 influence of carbonic acid, no more phenol distills 

 over. 



When the reaction is finished the residue in the 

 retort is (if the operation has been conducted prop- 

 erly) a grayish-white mass of sodic sodium-salicylate. 

 The following equation represents the reaction : 



C 6 H 5 ONa ) nrk H 4 I ^x T , n TT OTT 



cXoNa \ +CO ' = C 6 COONa f ONa + C eH 6 OH. 



The salt dissolves easily in water, to a dark-brown 

 fluid. Upon the addition of hydrochloric acid the 

 whole forms a thick paste of salicylic acid, which 

 contains only traces of phenol. It may be perfected 

 by the usual methods. Curiously enough, upon re- 

 peating the experiment with potassic hydrate, not 

 salicylic acid, but its isomer, peroxybenzoic acid, was 

 formed. 



Knowing that salicylic acid may be easily made 

 from phenol and carbonic acid, and on the other 

 hand that it is decomposed into phenol and carbonic 

 acid on heating it above its boiling-point, I came to 

 suppose that like carbolic acid it would retard or en- 

 tirely prevent fermentation and putrefaction. Prof. 

 Thiersch and myself, having experimented in this 

 direction, find surprising confirmation of my con- 

 jecture. 



The crude acid is a yellowish powder, and in 

 this state it may be used for many of the coarser 

 forms of disinfection. For other purposes it re- 



quires to be purified, and this Rautert accom- 

 plishes in the following way : 



The salycylic acid is heated, in a retort, to 170 C., 

 and a current of superheated steam of the same teYn- 

 perature is then thrown in. The acid distills at once 

 in a colorless state, leaving behind it in the retort, at 

 the end of the operation, a small quantity of black- 

 ish impurities. The apparatus must be arranged in 

 such a way that the neck of the retort may be kept 

 free from crystals, which may be done by inserting 

 a movable wire. 



The valuable properties of this substance as 

 an antiseptic and disinfectant have been demon- 

 strated by numerous experiments, made by dif- 

 ferent investigators. A few will suffice for il- 

 lustration : 



Brewer's yeast, which causes alcoholic fermenta- 

 tion of sugar, was found to have no efi'ect on a solu- 

 tion of glucose containing the one-thousandth part 

 of salicylic acid. Half a gramme of the acid suffices 

 to check the fermentation produced by five grammes 

 of beer-yeast acting upon 120 grammes of sugar in a 

 litre of water. Neubauer showed that 100 grammes 

 of salicylic acid is sufficient to absolutely prevent 

 fermentation in 1,000 litres of must, or fresh-pressed 

 juice of grapes. Flour of mustard, which, when 

 mixed with lukewarm water, gives out the pungent 

 oil of mustard, is perfectly odorless when a small 

 quantity of salicylic acid is added. So, too, this acid 

 prevents the action of emulsine (the ferment con- 

 tained in almonds) upon amygdaline, and the con- 

 version of the latter'into the oil of bitter almonds. 

 Milk treated with 0.09 per cent, of salicylic acid re- 

 mained uncoagulated for thirty-six hours longer than 

 milk not so treated. In like manner a litre of beer 

 containing one gramme of the acid, and exposed to 

 the air, did not become sour after standing a con- 

 siderable time, nor was there the slightest trace of 

 movement. Godeffroy, in a series of careful experi- 

 ments, has proved that, as an anti-ferment, salicylic 

 acid is three times as powerful as carbolic acid. Eggs 

 immersed for an hour in a solution of salicylic acid 

 were at the end of three months as fresh as at first. 

 Flesh-meat dusted over with the acid keeps its fresh- 

 ness for weeks. When about to be used, the meat 

 may be dipped into water, to remove the acid. 



Dr. Thiersch, of the Leipsic Hospital, has 

 used this substance u with very favorable re- 

 sults " in his surgical practice. Kolbe has em- 

 ployed it as a wash for the teeth and mouth, 

 and asserts that it is very effectual in purifying 

 the breath. In a communication published in 

 the Journal fur praktische Cliemie, he says : 



As a medicine for internal use salicylic acid does 

 not seem to have been much employed hitherto, and 

 yet, owing to its antis-eptic properties, it is indicated 

 in all diseases of the blood, especially in those which 

 are developed by contagion. 



Dr. Karl Fontheim, writing to the same jour- 

 nal, says: 



This new remedy has been found of very special 

 benefit in treating diphtheria ; I have employed it in 

 thirty-two cases; of these none have proved fatal, 

 and the worst case recovered in eight days. 



Dr. Ogilvie "Will, writing in the Lancet, 

 speaks of it in the very highest terms as an 

 antiseptic in surgical practice. He relates sev- 

 eral cases where, by reason of its non-irritant 

 action, it was possible to apply it directly to 

 the surface of wounds, with, in each case, most 

 excellent results. Prof. Ziirn, of Leipsic, has 

 employed salicylic acid in veterinary practice, 



