5 86 
Journal of Agricultural Research 
Vol. XXI, No. 8 
strength. Had the experiment been continued long enough it is pos¬ 
sible that the strength of the solution would have been increased suffi¬ 
ciently to injure the potatoes, as sweet potatoes are very susceptible to 
mercuric-chlorid injury. It was found that 6 pounds of washed sweet 
potatoes removed slightly more than i per cent of the mercuric chlorid 
from 2 gallons of the solution. A pound of dirt in 2 gallons of solution 
removed from 1.8 to 18 per cent of the mercuric chlorid, the variation 
being due to the type of soil used. Aside from the potatoes, dirt is 
probably responsible for a greater change in the strength of the solution 
than any other single substance. However, sacks used as containers 
reduced the concentration very rapidly, a gunny and a grain sack in 2 
gallons of solution decreasing the strength 16.7 and 14.2 per cent, re¬ 
spectively, in 10 minutes. On the other hand, a bushel hamper removed 
the mercury less rapidly. In view of these facts it would seem best 
whenever possible to use hampers or other wooden containers for the 
treatment. However, if it is necessary to use sacks the amount of mer¬ 
curic chlorid added from time to time should be slightly increased. The 
oak barrel as well as the concrete blocks weakened the strength of the 
solution. 
The foregoing facts show that the factors involved in disinfecting 
sweet potatoes are so many and varied that it is unwise to make any 
sweeping generalizations. However, if it is assumed that the average 
of approximately 5 per cent is removed by each 5 bushels of potatoes 
reasonably free from soil and treated in hampers in a clean barrel con¬ 
taining 32 gallons of solution, then the following recommendations may 
be made: After each 10 bushels of potatoes treated, add from % to y 2 
ounce of mercuric chlorid and add water to make the solution up to 
its original volume. It is further recommended that the solution be 
discarded after* the treatment of 50 bushels. 
Since the dirt and other foreign matter remove some of the mercuric 
chlorid, it is important that the barrel be thoroughly cleaned out before 
a fresh solution is made up. It is impossible to state that a given 
number of potatoes under known conditions will remove a definite 
amount of mercuric chlorid. The results of experiments 1 and 2 given 
in Table II illustrate this point, since in both cases 6 pounds of washed 
sweet potatoes of the same variety and from the same source were 
treated in 2 gallons of solution and in the former case 1 per cent and 
in the latter 2 per cent of the mercuric chlorid was removed in 1% 
hours. No doubt the surface area of the potatoes governs to a certain 
extent the quantity removed. It is impossible to know the type or 
quantity of dirt and refuse that will find its way into the solution, and 
these are both important in reducing the concentration. All of these 
facts show how unreliable any sweeping generalizations may be. Nev¬ 
ertheless, there is need for some definite method of procedure in treating 
