HEAVY METALS IN FOOD. 1163 



COPPKK IN PRESEKVKD GREEN PEAS. 1 



The method ejnployed for copper was : Weigh 1,000 grains of peas and the 

 liquor with which they were mixed into a porcelain basin, dry and ignite over the 

 flame of a Buusen hurner. When the mass has burned down to a gray ash, it is 

 cooled, moistened with H^SO.,, and reignited. The treatment with HiSO 4 prevents 

 the loss of copper which would occur from the presence of NaCl in the ash at the 

 temperature necessary to burn off the last portion of carbon. Unless carbon be 

 wholly removed from the ash copper can not be completely dissolved from it. The 

 ash is then boiled with acid and the copper electrolytically deposited from the solu- 

 tion. 



The presence of copper may be beautifully shown by placing a quantity of the 

 peas themselves in a platinum dish, acidifying with HC1, and electrolysing. In 

 about twenty-four hours an abundant deposit of copper is obtained, but the whole 

 of it can not be thus separated. 



ANALYSIS OF CANNED PEAS.' 2 



The juice around the peas contained 1.11 per cent of dry matter. The total water 

 was 58.3 per cent, so that, as ripe peas contain about 14 [per cent, about 45 per cent 

 had been added for cooking purposes. The albuminoids calculated in the sample 

 with 14 per cent of water were 21 per cent. 



RUBBER RINGS IN THE PRESERVING INDUSTRY. 3 



Cans for preserving purposes are now made which are closed by tops made tight 

 by rubber rings, and which have another ring pressed tightly against the solder 

 seam at the bottom. The German law prohibits the use of solder containing more 

 than 10 per cent of lead where it can come in contact with food, but as lead-poor 

 solder is difficult to use, the manufacturers have adopted the rubber ring system. 

 Foods thus preserved, however, show astonishingly high amounts of lead. This was 

 finally explained by the analysis of the rubber rings, which showed 60 to 66 per cent 

 of minium (red lead). 



METAL VESSELS FQR CULINARY PURPOSES. 4 



The results of a series of investigations led the royal health office (Prussia) to 

 conclude : 



(1) That vessels of tinware without exception give up more or less lead to fluid 

 contents. 



(2) That upon the whole this vulnerability diminishes with increasing lead con- 

 tent of the alloy. 



(3) That the amount given up depends on the nature of the attacking fluid, upon 

 the mechanical condition of the metal surfaces, as well as of exterior influences (tem- 

 perature and air), and also upon the kind of use made of the vessels. 



(4) That the amount given Tip by the contents does not increase proportionally 

 with the time of action as the dissolved lead is again precipitated partially by the 

 tin in the course of time, and as some of the lead is also precipitated in the form of 

 insoluble combinations with the components of the fluid. 



(5) That besides vinegar other substances used for food purposes (wine, beer r 

 solutions of salt and sugar, milk, tea, etc.) can take up lead from tinning alloys. 

 Against all expectation in thesaexperiments weak vinegar attacked the vessels more 

 than stronger. 



1 Charles H. Piesse, Analyst, 1878, 2, 27. 



2 G. W. Wigner, Analyst, 1880, 15, 102. 



3 W. Reuss, Chem. Ztg., 1891, 15, 1522; abs, Chem. Centrbl., 1892, 1,63. 



4 Gustav Wolffhugel, Arbeiten aus der Kais. Gesundheits Amt. 1887, 2, 112 (Berlin) j 

 abs. Chem. Centrbl., 1887, 592. 



