Biology Reference
In-Depth Information
marble table, it did not spread, indicating the importance of both oil and water. Franklin's
observations were not published in a formal scientific paper written by him, but instead
appeared as extractions of personal letters written to friends in 1774. These letters appeared
the same year in Philosophical Transactions of the Royal Society of London. Unfortunately
Franklin missed a golden opportunity when he failed to estimate how thin the oil slick
must have been. He knew the volume of the olive oil as well as the lake area it covered.
This simple calculation would have estimated the oil layer at about 10
˚
, a good estimate
of the molecular length of triolein. This would have been the first correct measurement of
molecular size, a parameter that would have to wait another 120 years until Lord Rayleigh
repeated Franklin's experiment.
Benjamin Franklin's work on oils on water was extracted from a letter to a friend, Dr. Wil-
liam Brownrigg, dated November 7, 1773. The extract was published in Philosophical Transac-
tions of the Royal Society of London, in 1774
[6]
. A quote from this letter follows:
'At length being at Clapham where there is, on the common, a large pond, which I observed to be one
day very rough with the wind. I fetched out a cruet of oil, and dropt a little of it on the water. I saw it
spread itself with surprising swiftness upon the surface;
. the oil, though not more than a teaspoonful,
produced an instant calm over a space several yards square, which spread amazingly, and extending itself
gradually till it reached the lee side, making all that quarter of the pond, perhaps half an acre, as smooth
as a looking glass.'
.
Lord Rayleigh: (1890)
Lord Rayleigh (real name John William Strutt) was a well educated, very high profile
gentleman scientist at the turn of the 19
th
century (
Figure 2.3
). In 1904 he became one of
the first Nobel Prize winners for his discovery of the noble gas argon and was the first to
explain the age-old question of why the sky is blue
[7]
. During his long and prolific career,
he published more than 500 papers, primarily on optics and sound, and all were personally
hand written! Although, as his title implies, he was quite wealthy, he did not use a secretary.
In 1890 Rayleigh repeated the Franklin experiment, but took it a step farther. He precisely
measured both the volume of olive oil added to his experimental water bath and the surface
area over which it spread. From these measurements he calculated the molecular size of tri-
olein, the major component of olive oil, to be 16
˚
.
Agnes Pockels: (1891)
Perhaps the most compelling of the major players in the colorful history of membranes
was Agnes Pockels (
Figure 2.4
). Miss Pockels, as she was always referred to, overcame almost
insurmountable odds to become one of the earliest women to make a lasting impact on
science. She lived in Braunschweig, in north central Germany and, as was typical of girls
in the late 19
th
century, had no formal education. Her job was to cook, sew, and take care
of the house. However, she had a keen interest in science and dabbled in her kitchen with
pots and pans, sewing threads, and buttons to study the phenomena of oil on water. Her
now famous kitchen experiments began in 1880 when Miss Pockels was only 18. In these
primitive conditions she worked out the basic methods of making and measuring lipid
monolayers. Her basic methods are still in practice today. The Langmuir Troughs used today
