484 



INFLUENCE OF FOOD PRESEKVATIVES ON HEALTH. 



cent alcohol, decant the alcohol on a filter paper and repeat the extrac- 

 tion five or six times. Transfer the precipitate to a filter and wash 

 until no test for salicylic acid can be obtained by evaporating 10 cubic 

 centimeters of the extract to dry ness, taking up with petroleum spirit 

 and testing in the usual way. 



Evaporate the extracts to free them from alcohol, take up with 

 water, acidify, extract with ether, and evaporate until free from ether. 

 Dissolve the salicylic acid in hot water and make up to a definite 

 volume at room temperature and make up aliquot portions of this 

 solution to 100 cubic centimeters in Nessler's jars. 



Add 5 cubic centimeters of a 0.5 per cent ferric alum solution to 

 one of these jars and mix thoroughly, noting the depth of color. 

 Make up a set of standards from a solution containing 0.1 milligram 

 per cubic centimeter of salicylic acid so that they approximately match 

 the color developed in the test just described. That is, if the color 

 developed approximates 1.2 milligrams make up the standards so that 

 they will contain 1.18, 1.20, and 1.22 milligrams of salicylic acid. 

 Then compare a new solution of the sample with these samples, mak- 

 ing the comparisons immediately after adding the ferric alum solution, 

 as the color fades rapidly. The comparisons should be made in tripli- 

 cate and are accurate to 0.02 of a milligram. 



Blanks run by adding salicylic acid to normal urines averaged 95 

 per cent of the acid recovered. Extracts of urines passed during the 

 preservative period were heated to 156 to volatilize the salicylic acid 

 and the residues weighed as salicyluric acid. In every case the residues 

 were so small as to be negligible. 



The samples of feces tested gave no indication of the presence of 

 salicylic acid. 



TABLE III. Salicylic acid ingested and recovered in urine, Series VI. 



