Issued September 11, 1911. 



United States Department of Agriculture, 



BUREAU OF CHEMISTRY Circular No. 79. 

 H. W WILEY, Chief of Bureau. 



TIN SALTS IN CANNED FOODS OF LOW ACID CONTENT, WITH SPECIAL 

 REFERENCE TO CANNED SHRIMP. 



By W. D. BIGELOW and R. F. BACON, 

 Division of Foods. 



INTRODUCTION. 



It is customary to attribute the presence of tin salts in canned foods 

 to the action of the acids of those foods on the tin of the container. 

 We usually think of the action of a food upon the tin as propor- 

 tional to the acidity of the food. 



The acidity of many products ordinarily preserved in cans is so 

 high and their effect on the tin lining of the container so marked 

 as to offer a sufficient explanation of the amount of tin salts they 

 contain, and until recently the high tin content of certain vegetables 

 and other products of low acidity was overlooked or regarded as 

 accidental. The interest lately awakened in the subject of tin salts 

 has led to a more careful study of the question than has been given 

 it before and it is now recognized that several articles such as cer- 

 tain varieties of fish, beets, lima beans, asparagus, and pumpkin, 

 though being almost without acidity, have a marked solvent action 

 upon the tin lining of the container in which they are preserved. As 

 far as we are aware, however, no explanation of this fact has been 

 offered. 



TIN CONTENT OF CANNED GOODS VARYING IN ACIDITY AND AGE. 



The relation of the acid to the tin content of a series of canned 

 goods, examined about six months after they were packed, is well 

 shown by the following table in which the acidity is expressed as 

 acetic acid and the amount of tin is stated in milligrams per kilogram 



6012 Cir. 79 11 



