A 2iEW ANTISEPTIC. 681 



University of Lei.psic. Salicylic acid exists ready-formed in the flow- 

 ers of Spircea ulmaria (meadow-sweet), and as methyl-salicylic acid in 

 oil of wiutergreen. It is also prepared from indigo and from salicin, 

 a substance found in the bark of several species of willow and poplar. 

 But the best mode of preparing it is that proposed by Kolbe and 

 Lautemann, which is thus described by Watts : 



Dry carbonic anhydride is passed into warm phenol, with addition 

 of small pieces of sodium. The metal then dissolves, with evolution 

 of hydrogen, and a stiff paste is formed, containing the isomeric salts, 

 salicylate and phenyl-carbonate of sodium, together with unaltered 

 phenol. On acidulating with hydrochloric acid, the phenyl-carbonic 

 acid is decomposed, with evolution of carbonic anhydride, and the sali- 

 cylic acid which is set free may be separated from the phenol by solu- 

 tion in strong aqueous carbonate of ammonium. The solution, boiled 

 down till it acquires a slight acid reaction, filtered from separated 

 resin, and mixed with hydrochloric acid, yields salicylic acid, to be 

 purified by recrystallization with the aid of animal charcoal. 



Reasoning from the fact that salicylic acid can thus be prepared 

 from phenol and carbonic acid, and from the further fact that on the 

 application of heat it again splits up into those two acids, Kolbe was 

 led to inquire whether it possessed the antiseptic properties of phenol. 

 The value of the latter substance as an anti-ferment is well known, but 

 its poisonous properties, as well as its disagreeable smell and acrid 

 taste, render it unsuitable as a means of preserving articles of food, or 

 as a medicinal agent. It was evident, therefore, that if salicylic acid, 

 which is odorless, almost tasteless, and, when taken in small quanti- 

 ties, innocuous, possessed antiseptic properties equal to those of phenol, 

 one of the most urgent wants of modern life would be at once sup- 

 plied. Experiment proved the conjecture to be correct, and thus 

 many years of theoretical investigation were crowned by practical 

 results of the highest value. 



Among the experiments made with this substance we may mention 

 the following: Brewer's yeast (quantity not stated), which causes al- 

 coholic fermentation of sugar, was found to have no effect upon 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 on 120 grammes of sugar dis- 

 solved in a litre of water. Experiments made by Neubauer show 

 that 100 grammes of salicylic acid suffices to absolutely prevent fer- 

 mentation 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 to it. So, too, this acid prevents the action 

 of emulsin (the ferment contained in almonds) upon amygdalin, and 

 the conversion of the latter into oil of bitter-almonds. Milk treated 

 with 0.04 per cent, of salicylic acid remained uncoagulated for thirty-six 



