306 FOOD AND FOOD ADULTERANTS. 



The acid may also be extracted by treatment with successive portions 

 of chloroform, which is carefully decanted, the solution evaporated, and 

 the crystallized salicylic acid weighed. 1 



A. Bemout 7 published in 1881 a method for the colorimetric estima- 

 tion of salicylic acid, which was modified by Pellet and De Grobert 3 in 

 the following manner: 



A series of uniform test-tubes are prepared about 20cm. in height and 

 15mm. in caliber, to which are added, successively, Ice., 0.75cc., O.Scc., 

 0.4cc., 0.3ec., 0.2cc., O.lcc. of a solution of 1 gram of salicylic acid in 1 

 liter of distilled water, and the volume in each tube brought to lOcc. 

 with distilled water. To the first tube is added three drops of a di- 

 lute solution of ferric chloride (1005 to 1010 specific gravity), in the 

 second and third two drops, in the others one drop. The last tube may 

 be simply stirred with a glass rod which has been dipped into the iron 

 solution. One hundred cubic centimeters of the beer or wine to be tested 

 are now taken and shaken up with lOOcc. of ether, and five drops H 2 SO 4 

 of 30 B., allowed to stand, carefully separated, and this operation re- 

 peated twice. The ether is quickly evaporated off in the water bath, the 

 residue brought into a porcelain evaporating dish of about 6-8 cm. di- 

 ameter, the flask washed out with a few cc. of ether and the dish placed 

 in an air bath heated to about 50 C. to drive off the ether completely; 

 1.5cc. of a solution of soda is then added, of such strength that lOcc. con- 

 tain 0.4 grains Na 2 O, which is sufficient to saturate about 0.2 grams 

 of salicylic acid, equal to a content in the sample of 2 grams per liter. 

 J f the residue is still acid after this addition, it is due to acetic acid. By 

 evaporating to dryness this excess can be driven off while the salicylic 

 acid is retained, as it is able to displace acetic acid from its salts. The 

 residue is now treated with five drops of n 2 SO 4 of 30 B., and then with 

 20cc. of benzine, and the whole filtered ; lOcc. of the filtered benzine so- 

 lution is brought into a test-tube of similar dimensions to those men- 

 tioned above; lOcc. distilled water and one or two drops of the dilute 

 ferric chloride solution added, and the contents well shaken. If sal 

 icylic add is present it is all taken up by the lower watery portion and 

 the color may be compared with that of the standard tubes. If it agrees 

 in intensity with one of these, the calculation is very simple. Suppose, 

 for example, it agrees with the fourth tube, which contains in the lOcc. 

 of liquid 0.0004 grams salicylic acid, then the lOcc. of benzine solution 

 also contained 0.0004 grams, and the 20cc. from which it was taken 

 contained 0008 grams in lOOcc. of the wine, or .008 grams to the liter. 

 The authors of this method found on applying it to wine to which a 

 known quantity of salicylic acid had been added, that only 93 per cent. 

 of the amount added was found, so their results were divided by 93 on 

 that basis. With this modification they obtained from two samples of 



1 These two methods arc employed in tho Municipal Laboratory of 1'aris. 



.lour, riiarm. Cliim. [.">], 4, III, Cliein. ( 'cut ., 1*81, 77;}. 

 3 Compt. IJoml. It:?, 278, Cbeui. Cent., 1881, 711. 



