8 
BULLETIN 449, U. S. DEPARTMENT OF AGRICULTURE. 
minum was the active metal, in others zinc was used, and in a few 
cases an alloy, which was prepared in the laboratory by melting to- 
gether zinc and aluminum. Two cleaning solutions were used : One 
contained 1 teaspoonful of washing soda per quart of water, and the 
other was made up of 1 teaspoonful each of washing soda and salt to 
every quart of water. The results obtained are given in Table II. 
Table II. 
-The effect of varying the concentration of the electrolyte by the 
addition of sodium chlorid. 
Solution. 
Time required for 
cleaning. 
Remarks. 
Observed. 
Average. 
Series IS. 
Washing soda 
Do 
Seconds. 
3 
5 
3 
2 
1 
1 
10 
4 
6 
3 
3 
3 
3 
2.5 
2.5 
1.5 
1 
1 
3 
2.5 
3 
2.5 
1 
2 
160 
15 
15 
140 
12 
10 
Seconds. 
1 4 
I 1 
r 3 
f 3 
I i 
i 3 
i 2 
r 15 
\ n 
Do 
Washing soda+salt . 
Do 
Do 
Series U- 
Washing soda 
Do 
/In series 14, 15, and 16 zinc was the active metal, which was 
\ cleaned frequently with dilute HC1. 
Do 
Washing soda+salt . 
Do 
Do 
Series 15. 
Washing soda 
Do 
Do 
Washing soda+salt . 
Do 
Do 
Series 16. 
Washing soda 
Do 
Do 
Washing soda+salt . 
Do 
. 
Do 
Series 17. 
Washing soda 
Do 
(The alloy of zinc and aluminum was used in series 17. The 
1 exceptionally long time observed in two instances was neces- 
Do 
Washing soda+salt . 
Do 
Do 
1 sary to clean two parts of the same silver buckle, badly tar- 
l nishedbyuse. 
The data recorded in Table II indicate that the average time re- 
quired for cleaning the silver was less when sodium chlorid was added 
to the solution. For all practical purposes, however, the difference 
is so slight as to be of little or no consequence. It is reasonable to 
assume that by increasing the concentration of the electrolyte, as is 
the case when sodium chlorid is added, the cleaning reaction will take 
place somewhat more rapidly. This conclusion is strengthened by 
further experiments carried out to study the effect of the concen- 
