342 ON A DIRECT METHOD OF OBTAINING IODINE. 
in cells between the external cortical and central medullary 
portions. An important step has now been made in the in- 
vestigation, and hopes were at first entertained that the ob- 
ject sought after would at once be arrived at, by exposing 
the stem of the plant to pressure, and from the liquid ob- 
tained, which it was presumed would contain the greater 
portion of iodides in solution, without further trouble liber- 
ating the iodine itself. Great physical difficulties however 
presented themselves; and so condensed was the cellular 
tissue found, that on exposing a portion, not exceeding the 
dimensions of a cubic inch, to the pressure of a ton weighty 
but a very small portion of fluid was obtained, although 
Professor Forchhammer* estimates this at 75 per cent., a 
quantity far less than has been found at different times by 
my friend Mr. Waldie of Liverpool, and myself. It was 
determined, therefore, in the next experiment, to break up 
the cellular tissue as completely as possible, by rubbing the 
stem on an ordinary domestic grater. The result was per- 
fectly satisfactory, and the iodine liberated, by ordinary 
chemical operations, with the greatest ease ; but it was ne- 
cessary to modify the plan, so as to adapt it for application 
on a large scale. A turnip-cutter was therefore furnished 
with a small band-wheel of 6 inches in diameter, and this 
connected by means of a band with a wheel 5 feet in diame- 
ter, which in working was caused to revolve eighty times 
per minute, thus communicating to the smaller wheel a 
velocity of 800 revolutions per minute ; and the machine 
being supplied with the stem divested of roots and terminal 
leaves it was cut into small slices with great rapidity. The 
original intention was to pass these slices through another 
* " At the point of Kronborg, near Elsingor, about 30,000 two- 
horse loads of sea-weed are annually thrown on shore in the months 
of November and December, which, calculated at 500 lbs. dry plants 
each, are equal to 15 millions of pounds. " — Forchhammer on the 
Metamorphosed Fucoid Schists in Scandinavia ; Report of British As- 
sociation for 1844, p. 163. 
