KaMenberg—Osmosis and Osmotic Pressure. 243 
The vegetable septa employed consisted of the rinds of Cali¬ 
fornia oranges and grape frnit and Florida grape fruit. The 
grape fruit, also called shaddock, is the fruit of Citrus 
decumana. In each case the fruit was carefully cut in two 
transversely with a sharp knife, so that the halves after careful 
removal of the pulp formed two cups. Each half rind was 
filled to about half of its capacity with the liquid to be tested 
and then suspended in pure water so that the latter was about 
on a level with the liquid in the rind. The suspension of the 
rind was accomplished by means of fine aluminum wire run 
through small holes pricked through the upper edges of the 
rind. Each experiment was continued for twenty-four hours, 
unless otherwise stated. It was found to be impracticable to 
continue the experiments much longer, for the rinds after be¬ 
ing immersed in water for a considerable time undergo alter¬ 
ation, becoming soft and loosing their waxy outer coating. 
With the arrangement as just described and employing water 
as the outer liquid and an aqueous solution as the inner liquid, 
it was found that sodium chloride readily passes through 
orange skins, but sodium sulphate very much less readily. In¬ 
deed, only traces of the latter salt were found in the outer 
liquid even when strong solutions were employed. Again, urea 
readily goes through the orange rinds, but sugar passes through 
only in very small amounts. When an aqueous solution of 
potassium alum w T as used it was found that a slight amount 
of potassium sulphate appeared in the outer water, but no alu¬ 
minum sulphate, showing that the latter ingredient is left be¬ 
hind during the time of the experiment at least. 
In the upper half of the rind of a Florida grape fruit was 
placed 100 cc. of a solution containing 10 grams sodium chloride 
plus 10 grams of sodium sulphate. The rind so charged was 
suspended in distilled water as above described. The outer 
water had a volume of 500 cc. Tests of the outer liquid showed 
that the NaCl was passing through much faster than the 
Na 2 S0 4 . This experiment was run for seven days; the rind 
did not seem to be altered much. 
The lower half of the rind of a California grape fruit con¬ 
taining 70 cc. of an aqueous solution, which contained 10 grams 
