TIN SALTS IN CANNED FOODS OF LOW ACID CONTENT. 



tained a volatile alkaline substance, apparently monomethylamin, 

 which attacks tin quite markedly and which also attacks the skin of 

 the hands. From the volatile nature of the alkali it seems possible 

 that the portion of it on the surface of the shrimp may escape when 

 the shrimps are preserved on ice for a time and so explain the fact 

 that shrimps so treated do not attack the skin. Even when so 

 treated, however, special precautions must be taken to protect cans 

 in which shrimps are preserved. Ordinary tin containers employed 

 for the preservation of shrimps are rapidly corroded and the lining 

 completely removed. To prevent this the cans are lined with parch- 

 ment paper and corrosion is then only noted at the junction of the 

 papers and at points where for some reason the paper is pressed 

 against the tin coating. As the points of junction of the paper leave 

 a free opening the reason for the attack there is self-evident. The 

 attack at places where the paper is pressed against the can is be- 

 lieved to be due to surface action. The liquor separated from the 

 shrimps was found to be alkaline to litmus. The alkalinity was 

 measured as follows: 



50 grams of this liquor required 8.1 cc of tenth-normal hydrochloric acid to 

 make it neutral to azolitmin ; 



50 grams of this liquor required 44.5 cc of tenth-normal hydrochloric acid 

 to make it neutral to methyl orange ; 



50 grams of this liquor required 15 cc of tenth-normal sodium hydroxid 

 to make it neutral to phenolphthalein. 



These results show that this liquor contains quite a large quantity 

 of a moderately weak base partlyl combined with a weak acid, and 

 hence largely hydrolyzed to contain considerable numbers of hy- 

 droxyl ions. 



Some shrimps were extracted with alcohol and the volatile alkali 

 distilled over as given below. This alkali was just neutralized with 

 hydrochloric acid and the resulting solution evaporated to dryness 

 on a steam bath. In the white, crystalline, deliquescent salt so ob- 

 tained chlorin and nitrogen were determined with the following 

 results : 



TABLE 3. Analysis of the volatile alkali. 



The chlorplatinate of this amin was found to consist of bright 

 yellow crystals containing 41.9 per cent of platinum. The theo- 

 retical amount in (N(CH 3 )H 3 ) 2 PtCl 6 is 41.3 per cent. 



