6 



TIN SALTS IN CANNED FOODS OF LOW ACID CONTENT. 



the vegetables which are recognized as strongly attacking tin con- 

 tainers are asparagus, spinach, string beans, and pumpkin. Samples 

 of these substances of unknown history were procured and the acidity 

 to phenolphthalein, the measure of amino acid by titration after add- 

 ing formaldehyde (Sorensen's method), alkalinity to methyl orange, 

 and total volatile alkali were determined in each case. The results 

 are given in the following tabular statement calculated for 100 grams 

 of sample. It is suggested that these volatile alkalis and amino acids 

 are responsible to a great degree, if not entirely, for the solvent action 

 on tin exerted by foods of very low acidity. 



Volatile 



in canned goods. 



1 Corrected for the acidity of formaldehyde. 



It is evident that the volatile alkalis and amino acids which occur 

 in these vegetables probably have an effect on the tin container 

 analogous to that of the methylamin found in shrimp. Further 

 work on this subject is in progress, but, considering the number of 

 chemists who are studying the content of tin salts in canned goods, 

 it seemed best to offer this preliminary statement for the purpose of 

 bringing to the attention of other workers certain phases of tin cor- 

 rosion which seem to be of considerable importance and which have 

 not been recognized heretofore. Acknowledgment is made to F. W. 

 Liepsner and C. W. Clark for much of the analytical work done in 

 connection with the investigation. 



