XI. A. 4 



Heise and Clemente: Tin Plate 



197 



completed after an hour or two. Doubtless the presence of 

 much lead in a tin coating would lessen the accuracy and ap- 

 plicability of this method. 



Other salts of lead yield similar results, but the reaction is 

 by no means confined to lead salts. Aluminium nitrate, made 

 alkaline with sodium hydroxide, will strip tin, although the 

 action is extremely slow. A solution of copper sulphate and 

 tartaric acid, made alkaline with sodium hydroxide, has a sim- 

 ilar effect. Chromium nitrate solution attacks both tin and 

 iron, but the same solution with enough sodium hydroxide added 

 to make a clear liquid will dissolve only the tin. The data 

 secured with typical solutions are given herewith, the tables 

 showing the results obtained with two different samples of tin 

 plate. Lead salts are the only ones listed to be recommended 

 for analytical work. 



Table V. — Detinning by immersion. 



PLATE A." 



No. 



16-19 

 20 

 21 



22 



23 



24 

 25 



Solution used. 



Lead acetate and sodium hydroxide 



Lead chromate and sodium hydroxide. 



Chromium nitrate and sodium hy- 

 droxide 



Aluminium nitrate and sodium hy- 

 droxide 



Copper sulphate, tartaric acid, and 

 sodium hydroxide -. 



Nitric acid, concentrated 



do 



Weight 

 of, sam- 

 ple. 



Grams. 

 4.261 

 4.351 



4.401 



4.321 



bl. 224 

 4.272 

 4.299 



Loss on immersion. 



Grams. 

 0.075 

 0.071 



0.067 



0.065 



0.022 

 0.069 

 0.066 



Per cent. 

 1.76 

 1.63 



1.61 



1.52 



1.79 

 L61 

 L54 



Weight of coating. 



Per 



square 

 deci- 

 meter. 



Grams. 

 0.300 

 0.284 



0.268 



0.260 



0.303 

 0.276 

 0.264 



Per 



square 



foot. 



Ounces. 

 0.098 

 0.093 



0.088 



0.086 



0.099 

 0.090 

 0.086 



PLATE B.« 



5.202 



0.064 



1.23 



0.248 



0.081 



5.314 



0.066 



1.24 



0.256 



0.084 



5.341 



0.066 



1.24 



0.256 



0.084 



5.420 



0.071 



1.31 



0.275 



0.090 



5.526 



0.063 



1.14 



0.244 



0.080 



5.452 



0.065 



1.19 



0.252 



0.083 



5.374 



0.071 



1.32 



0.275 



0.090 



Lead acetate and sodium hydroxide . . 

 ....do 



Lead nitrate and sodium hydroxide .. 

 ...-do ^ 



Lead chromate and sodium hydroxide. 



do 



Aluminium nitrate and sodium hy- 

 droxide 



• Size of samples, 5 by 5 centimeters, except as noted. 



•> Size of sample, 1.45 by 5 centimeters. 



•^ Size of samples, 2 by 2 inches (5.08 by 5.08 centimeters). 



