TIN SALTS IN CANNED FOODS OF LOW ACID CONTENT. 



of the canned food and as milligrams of tin for each 100 mg of 

 acid. In the table those foods having the highest amount of tin 

 in relation to their acidity are given first, and it is seen that the fruits 

 whose action on tin is most familiar to us because of their high 

 acidity come last in the list with from 1 to less than 5 mg of tin 

 per 100 mg of acid. 



TABLE 1. Acidity and tin content of canned goods about six months after 



packing. 



In some of the A^egetables considered in this table the ratio of tin 

 to acid is a little higher than in the case of some of the fruits shown. 

 It is distinctly higher in all cases, however, especially if the pears, 

 which are somewhat anomalous in one other respect, are excluded. 

 Moreover, in the fish and in a number of the vegetables the ratio of 

 tin to acid is strikingly higher than in the fruit. In a general way 

 the ratio of tin to acid in the fruits appears to depend on the variety 

 of the acid the fruit contains, the solvent action of citric acid, to 

 which the acidity of raspberries and tomatoes is due, being less than 

 that of malic acid. Pears appear to be an exception to this rule, 

 however, since, notwithstanding the fact that their characteristic acid 

 is malic, they contain a greater amount of tin in proportion to their 

 acidity than any of the other fruits. 



It is obvious that in data of this kind conclusions must be drawn 

 from the data as a whole rather than from the analyses of individual 

 cans. For instance, one of the samples of tomatoes has 7.4 mg of 

 tin for each 100 mg of acid, whereas the second sample, put up at the 

 same time and from exactly the same batch of tomatoes, but in a dif- 

 ferent kind of plate, contains but 3.7 mg of tin for each 100 mg of 

 acid. A wide difference is shown also among the samples of corn and 

 of pumpkins examined. The general trend of the results is so strik- 

 ing, however, as to indicate that individual differences may be over- 



