TIN SALTS IN CANNED FOODS OF LOW ACID CONTENT. 5 



Twenty cans of shrimps were ground up, covered with alcohol, 

 and allowed to extract for two days. The extract was passed through 

 muslin and the filtrate made slightly acid with sulphuric acid and 

 evaporated to a small volume. To this extract magnesium oxid was 

 added in excess and the volatile alkali distilled. The distillate, 

 which smelled much like ammonia, was just neutralized with sul- 

 phuric acid and alcohol was added, causing the separation of a 

 crystalline precipitate. 



This was dissolved in water and re-precipitated with alcohol, giv- 

 ing 6 grams of dry salt. Some of this salt was distilled with sodium 

 hydrate, the distillate (marked Solution I) w r as made up to such a 

 volume that it was a deci-normal alkali, and its solvent action on 

 tin was determined. When this solution was boiled for one hour 

 with two plates of thin block tin, each 2 by 3 inches, 6 mg; went 

 into solution from each plate. Another portion of the solution, 

 after neutralization with hydrochloric acid, was boiled in the same 

 manner and dissolved 5.8 mg from each plate. A tenth-normal 

 solution of methylamin treated in the same manner dissolved 5.7 mg 

 of tin from each place. Similar plates were boiled for one hour in 

 dilute solutions of other alkalis, amins, and ammo acids, including 

 one of the purin bases, with the following results : 



Mg per plate. 



Sodium hydroxid, tenth-normal 5. 



Potassium hydroxid, tenth-normal- 7. 5 

 Ammonium hydroxid, tenth-nor- 

 mal 1. 3 



Sodium hydroxid, fourth-normal 6. 2 



Acetamid, 2 per cent 6. 5 



Asparagin, 3 per cent 4. 4 



Asparagin, 0.3 per cent 4.3 



Mg per plate. 



Aspartic, 0.3 per cent 3. 7 



Alanin, 0.3 per cent 2. 4 



Glycocoll, 0.3 per cent 3. 3 



Sarkosin, 0.3 per cent 5.0 



Tyrosin. 0.3 per cent 2. 4 



Hypoxanthin, 0.3 per cent 4. 2 



Creatin, 0.3 per cent 2. 9 



Lencin. 0.3 per cent 1. 7 



DETERMINATION OF VOLATILE BASES IN OTHER COMPARA- 

 TIVELY NONACID FOODS. 



It appears, therefore, that monomethylamin exists to a considerable 

 extent in shrimps, and explains largely their corrosive action on tin 

 containers. The thought suggests itself that the solvent action of 

 certain other nonacid or slightly acid foods may be explained in the 

 same manner, and that amins and amino acids as a class may have a 

 marked solvent effect on tin. These bodies are known to be present in 

 practically all fish. According to Schreibler, 1 beets contain 0.25 per 

 cent of betain and ripe beets 0.10 per cent. Asparagin has been found 

 in asparagus, several vetches, beets, beans, and sometimes in peas. 

 Although asparagin is formed especially during the germination of 

 these products, it is also present in the unripe vegetables. Among 



Ber. d. chem. Ges., 1870, 3 : 155. 



