TIN PLATE AND ITS VARIETIES. 1035 



Alex. Fries & Bros., 92 Eeade St., New York," was sent in by Mr. 

 H. E. Taylor, of 152 Clifton Place, Brooklyn, N. Y. The accompany- 

 ing letter stated that this sweetener was used largely in the canneries 

 of this country as an addition to canned corn, and was claimed by 

 Fries & Bros, to be a good antiseptic, but perfectly harmless. On 

 examination it proved to be a 12.8 per cent solution of saccharin . 



As to the physiological action of saccharin little definite is known, 

 although there is already a large literature pertaining to the subject. 

 It seems probable, however, that in most cases it is not particularly 

 deleterious to the human system. 



BENZOIC ACID. 



Benzoic acid was not found in any instance. The methods for its 

 detection, however, are far too imperfect to allow the conclusion to be 

 drawn that it is never used to preserve vegetable foods. 



HYDRONAPHTHOL. 



"Hydronaphthol" or beta-naphthol was not found in any sample. 



BOBIO ACID. 



Neither boric, acid nor borax was found in any sample. Both flame 

 test and turmeric test were used. It is not probable that either anti- 

 septic is used for canned vegetables. 



TIN PLATE IN CANS. 



Commercially tin plate is divided into two classes, known respectively 

 as "bright" and " terne " plate, the former being covered with more 

 or less pure tin and the latter with a varying mixture of lead and tin. 

 " Bright " plate is, or should be, the kind used in canning food, terne- 

 plate being intended for roofing. Inasmuch, however, as the price of 

 tin is between four and five times that of lead, plate containing a little 

 lead is somewhat cheaper, and there is a constant tendency among 

 cauners to use these cheap grades. In tinning iron plate with a mix- 

 ture of lead and tin, the coating may be regarded as composed of two 

 layers, the undermost being an alloy of iron and tin containing little 

 lead and a surface layer of tin richer in lead than was the original 

 metal used for plating. This concentration of lead on the surface is 

 due to the fact that iron and lead have little affinity for one another. 



Metallic tin placed in a weakly acid solution containing a small 

 amount of lead throws down the latter in the metallic form, becoming 

 itself oxidized. Similarly, if an alloy of lead and tin containing a 

 small amount of lead is exposed to such an acid solution the tin dis- 

 solves first. 1 This play of affinities, however, does not hold good in 

 the case of alloys containing large .amounts of lead, such as solders, 



O. Hehner, Analyst, 1880,5, 218; G. Wolff hiigel, Chem. Centrbl., 1887, 592. 



