10 BULLETIN 449, U. S. DEPARTMENT OF AGRICULTURE. 
low the boiling point, although the tarnish was removed, the cleaned 
silver had a somewhat dull appearance. From the results of these 
tests it is evident that the cleaning solution should be kept at the 
boiling point, since the tarnish is more quickly removed and the 
silver has a much brighter appearance than when cleaned in cooler 
solutions. In cases where it is not possible to boil the articles to be 
cleaned very hot cleaning solutions can be used with fairly satisfac- 
tory results. 
RELATIVE MERITS OF THE ELECTROLYTIC AND POLISHING METHODS OF 
CLEANING SILVER. 
From the theory of the cleaning process as formulated earlier in 
the paper it would appear that there is practically no loss in weight 
of the silver cleaned by the electrolytic method, since the tarnish of 
silver sulphid is merely reduced to metallic silver. In order to verify 
this, however, three sterling silver and three silver-plated spoons 
were weighed, tarnished and cleaned 50 times, and weighed after the 
final cleaning, zinc being used in a solution of 1 teaspoonful of 
sodium carbonate in 1 quart of water at the boiling temperature. 
During the 50 cleanings the three sterling silver spoons lost 0.0043, 
0.0034, and 0.0034 grams and the three plated spoons lost 0.0026, 
0.0019, and 0.0021 grams, or an average of 0.00006 grams in each 
cleaning. This loss is insignificant when compared with the loss in 
polishing with an abrasive silver polish which actually cuts away 
the tarnish, as was shown by the following test. One sterling silver 
and one silver-plated spoon were weighed, tarnished and cleaned 
six times by rubbing with a paste of finely powdered whiting and 
water, and weighed after the last cleaning. The spoons lost 0.0091 
and 0.008T grams, respectively, or an average of 0.0015 grams in each 
cleaning, about 25 times as much as by the electrolytic method. For 
a further comparison three sterling silver spoons were weighed, tar- 
nished, and cleaned six times with a 5 per cent solution of potassium 
cyanid. By this method the spoons lost in weight 0.0135, 0.0129, 
and 0.0123 grams, respectively, an average of 0.0022 grams in each 
cleaning, a greater loss than by either of the other methods. 
While the electrolytic method removes the tarnish effectively and 
with practically no loss of metal, it gives the articles cleaned a satin 
finish rather than the bright burnished appearance obtained when 
abrasive polishes are used. After the spoons used in these experi-- 
ments had been cleaned a number of times by the electrolytic method 
it was found necessary to rub them with the paste of whiting and 
water to restore their original bright polish. In practice, therefore, 
it may be found desirable to use the electrolytic method as frequently 
as is necessary to remove the tarnish and to rub the silver with some 
