No. 3, one made with unguentum paraffini mixed with 3 per cent. of lard.
All three vials were then suspended in beakers filled with water. After
standing twenty-four hours at the ordinary temperature, the contents of
none of the beakers gave any iodine reaction. After having been placed
into a warm temperature, between 25-37° C., all three showed iodine
reactions after three hours, Nos. 2 and 3 very strongly, No. 1 (with
lard alone) very faintly.
The same experiment was now repeated, with the precaution that the
bladder was previously washed completely free from chlorine. Each vial
was suspended, at a temperature of 25-27° C., in 50 grammes of distilled
water. After three hours, the contents of No. 1 (containing the ointment
made with _lard_) gave _no_ iodine reaction; the contents of the other
two, however, gave traces. After eight hours no further change had taken
place. The temperature was now raised to 30-35° C., and kept so for
eight hours. All three beakers now gave a strong iodine reaction, 0.2
c.c. of normal silver solution being required for each 15 grammes of the
contents of the beakers.
In addition to the iodide, some of the fatty base had osmosed through
the membrane in each case.
The next experiment was made by substituting a piece of the skin (freed
from chlorine by washing) of a freshly killed sheep for the bladder. The
ointment in No. 3 in this case was made with 10 per cent. of lard. No
reaction was obtained, at the ordinary temperature, after twelve hours,
nor after eight more hours, at a temperature of 25-30° C. After letting
them stand for eight hours longer at 30-37° C., a faint reaction was
obtained in the case of the ointment made with unguentum paraffini; a
still fainter with No. 3; but no reaction at all with No. 1 (that made
with lard). None of the fats passed through by osmosis. After eight
hours more, the iodine reaction was quite decisive in all cases, but no
fat had passed through even now. On titrating 20 grammes of the contents
of each beaker,
No. 1 required 0.5 c.c. of silver solution.
No. 3 " 0.5 c.c. "
No. 2 " 0.7 c.c. "
showing that the most iodine had osmosed in the case of the ointment
made with unguentum paraffini (equivalent to vaseline).
* * * * *