1164 FOODS AND FOOD ADULTERANTS. 



ON THE OCCUKHKNCK OF TIN IN ARTICLES OF FOOD AND DRINK, AND ON THE PHYSIO- 

 LOGICAL ACTION OF TIN COMPOUNDS. 1 



[Abstract.] 



The method of analysis adopted was as follows: About 30 grams of the article to 

 be examined were incinerated in a platinum dish and the ash heated with strong 

 hydrochloric acid, the acid for the most part boiled off, about 30 or 40 cc. of water 

 added, boiled and filtered. This alternate treatment with water and acid was re- 

 peated until sulphuretted hydrogen no longer indicated the presence of tin. The 

 clear and, as a rule, colorless solution thus obtained was precipitated by the hydro- 

 gen sulphid in the usual manner. The following vegetable foods all gave abundant 

 yellow precipitate of stannic sulphid: French asparagus, American asparagus, peas, 

 tomatoes, peaches (3 brands), pineapples (2 brands), white cherries, red cherries, 

 and marmalade. In several cases the inner surface of the canister w,as found much 

 corroded. So considerable is the proportion of tin in most of the acid fruits that, 

 tin reactions can be obtained from 2 or 3 grams of the substances. A metallic taste 

 is sometimes perceptible. The following animal foods were examined: Corned beef 

 (5 brands), ox cheek, ox tongue (3 kinds), collared head, tripe, oysters, sardines in 

 oil, salmon, salmon cutlets, lobster, shrimps, curried fowl (2 kinds), boiled rabbit, 

 boiled mutton, roast chicken, roast turkey, ox cheek soup, gravy soup, sausages, 

 condensed milk (3 brands). 



With the exception of the sausages, the whole of these samples contained more or 

 less tin. One soup contained 35 mg of tin in a 1-pound can. A can of condensed 

 milk contained 8 mg, and a can of preserved oysters 45 mg, besides a considerable 

 quantity of copper. The metal is to be found throughout the mass of liquid soups 

 and pasty curries, but resides chiefly on the outer surface of hard meats, such as 

 corned beef. In many cases the canisters were much discolored and blackened on 

 the inner surface, but in others the surface of the metal was perfectly bright, al- 

 though there was an abundance of tin in solution. From the results given it appears 

 beyond doubt that tin is readily acted upon by articles of food, vegetable and ani- 

 mal. Vegetable acids dissolve it abundantly, even if the contact is only of very 

 short duration. Several samples of ginger ale and lemonade which were tested gave 

 distinct tin reactions. Even C0 2 attacks the metal. Metallic tin readily precipi- 

 tates lead from its solution, and from tin containing lead acids do not extract the 

 lead until much of the tin has dissolved and the proportion of lead in the residue 

 has become considerable. From solder lead can be dissolved simultaneously with 

 the tin. It follows that there is little danger to be apprehended from the employ- 

 ment of impure tin for the manufacture of tin plates, the tin effectually preventing 

 theleadfrom being dissolved. Itisfromthe solder that contamination withlead might 

 ensue. Regarding the physiological effects of tin salts, the following experiments 

 were made: A half grown, apparently healthy guinea pig was given, together with 

 its ordinary food, 25 mg of tin in the form of stannous hydrate. This had been 

 freshly precipitated and had not been dried, but was given shaken up with water. 

 There was no apparent effect. The solid excreta contained much tin after a few 

 hours, while the metal could not be detected in the urine. Two days afterward the 

 animal took 50 mg of tin as stanmms hydrate. After three hours it appeared ill, 

 and next morning it was dead. The quantity of feces passed since the administra- 

 tion of the second dose was very small, and the size of the feces had diminished 

 extremely, about to that of those of a mouse. On dissection the stomach was found 

 practically empty, the colon distended with food, the small intestines empty. The 

 liver, kidneys, lung, and heart were separately examined. They all ronlaincd 

 traces of tin, the largest quantity being apparently in the liver. The main part of 

 the dose given, however, remained in the food contained in the colon, so that com- 



O. Hehiier, Analyst, 1880, 5, 218. 



