Sir James Dewar
Ri = Royal Institution
Trivia: Inventor of the Thermos which is also known as a Dewar Flask.
Below is a collection of articles to illustrate Dewar's interest in bubbles.
Interesting to note: His discoveries came in many fields, some of which involved elaborate and expensive apparatus. It seems when funding got tight Dewar would detour back to studying bubbles.
1879 Report of Ri Christmas Lecture On A Soap Bubble by Dewar.
Flintshire Observer Mining Journal and General Advertiser, January 3, 1879
On Saturday afternoon, in London, Professor Dewar gave the first of a series 0! Christmas lectures on “A Soap Bubble," at the Royal Institution, Albermarle‐street. The lectures are specially intended for a juvenile audience, but half of those who attended on the present occasion were certainly considerably removed from that category.
The Professor began by observing that there were very few of his auditors who had not at some time or other indulged in the blowing of soap-bubbles. He wanted them to go back to their childhood‐ not, however, to play, but to think. They all remembered how a soap bubble was made; water, soap, and a pipe were brought into requisition, and then the fleeting, elastic, and beautifully coloured bubble was cast adrift. The lecturer here made a bubble, somewhat after the old fashion, using a glass air-pipe instead of the breath, and ended by depositing it on a iron ring in a square glass box. Placing a piece of cardboard on an opening in the upper side of the box so as to exclude the air, he by this means succeeded in preserving the bubble until he had exhibited on the screen all the changes in its colours, Gradually the bubble assumed the most beautiful and delicate hues, and when placed under a limelight looked like a transparent globe of the most dazzling and varied tints. The lecturer assured the audience it was quite possible to keep the bubble thus imprisoned for hours if it were made of the right material. He then proceeded to explain the nature of the soap, air, and water - the ingredients composing the bubble. Soap, he said, was a salt, though made from fatty oils. These oils, when treated to an infusion of a certain alkali, were broken up and afterwards combined, and made the substances called soap. The Professor illustrated this by an experiment. He poured some fatty substances into a dish, added the alkali, and in about forty seconds had a piece of solid soap, having previously strained off the excessive fluid. The best substance, however, with which to make a soap bubble was that commonly known as glycerine, which was obtained from stearine and olein, the chemical names of the common fats. It was necessary that the glycerine should be carefully added, and in proper proportions, for this was a most remarkable agent, inasmuch as dynamite and gun‐cotton, the most terrible of all explosives, were produced from glycerine. This same substance had the curious property of absorbing water from the air contained in the bubble, and so kept the bubble from breaking. The professor next practically illustrated
the separation of metals from salts, raising burning metal globules with an electric rod from a crucible. in which both the metals and the salts were melted. He also showed, by means of a number of connected glass tubes, the combustion of a candle, and how everything that came from the candle was seized and separated‐in other words, resolved into its primary elements. Having explained the nature of air, the lecturer concluded by a description of the properties of water, and, illustrating the mode in which the latter may be tested, had a ray of light passed through a tube containing distilled water. The reflection passing through a powerful magnifier at the end of the tube on to the screen. The lecture, which was entirely free from scientific phraseology, and therefore all the more easily understood, was frequently interrupted by applause.
Report about Dewar's Long Lasting Bubbles:
Scientific American April 7 1917
Soap Bubbles of Long Duration
The season of the Royal Institution evening discourses was opened by Sir James Dewar, F.R.S., Fullerian Professor of Chemistry, who delivered a lecture on Longevity, he remarked, could only be demonstrated by registers, and he pointed to the bulky notes in which his observational records were entered. Last year he had dealt with the finest soap films, which, when produced in an atmosphere containing nothing but water vapour——no air-- could easily be preserved for many months. The large glass bottle containing the horizontal films shown in
January, 1916, was on the lecture table; the "black" film, only visible in reflected light, was still intact.
The study of soap bubbles introduced further difficult problems; there were the difficulties of internal gas pressure and of the transference of gas from the in side of the bubble, in addition to the primary difficulty of isolating one particular bubble for the examination to which he had submitted films. Why had he taken up these studies, Sir James asked. Years ago he had lectured on soap bubbles, and he had then been fascinated by the wonderful work of Joseph A. F. Plateau, of Brussels, Professor of Physics at Ghent, who had entered upon the investigation of soap bubbles in 1842, when 40 years old, and practically blind owing to his experiments on the action of intense light on the retina. Plateau was also a painter, and that had helped him to continue his researches with the aid of assistants till he died, when nearly 80 years of age.
When soap bubbles were blown in air the air should be free of dust. The part played by the impurities of the air in putrefaction had been discovered by Pasteur, and Tyndall had later demonstrated the gross impurity of the air and its purification in very valuable ways. The lecturer concentrated the beam of an arc lamp by a lens; a whitish cone of light was seen in the impure air of the lecture theatre, but when the many organic particles in that dust were burnt by placing a burner under the beam, peculiar black shadows of "optically pure" air were noticed moving in the beam. Tyndall had further purified the air in glass boxes by smearing the glass with glycerin; in Tyndall's box exhibited, into which air was admitted through cotton-wool filters, no putrefaction had taken place, and the Tyndall effect test for dust-free air—invisibility of a strong beam of light—-was well known. He further demonstrated it by some novel experiments. He sent a beam of light upward through a glass bottle containing ordinary air; when a blast of air which had been strongly compressed (for subsequent condensation and liquefaction), and thus been heated, was passed through the bottle, the beam became much fainter. He also placed the electrode of a Wimshurst machine axially in the beam, the bottle in this case having been filled with smoke from some burnt bituminous matter; after the machine had been worked for a few minutes the air clarifier and shadows of black were seen to develop in the beam.
Illuminated by the arc, the space inside a big soap bubble, blown in pure air, within a glass case, looked dark. Ordinary London air contained about 100,000 particles of organic and inorganic matter, often greasy, per cubic centimeter. A speck of grease on a soap bubble would, of course, affect the surface tension of the bubble and make it break down. It was astonishing that people should have blown bubbles for 54) years after Plateau, in the open air, without suspecting the air; but he had not particularly referred to this point last year because he had not known it himself then.
As regards the soap solution, Plateau had used a 2 per cent solution of olive-oil soap containing 30 percent of glycerin. For his own experiments, in which he measured and weighed and tested, he sometimes used high percentages of glycerin, and he preferred the purest oleic acid (tested by the iodine number) and ammonium (not potassium or sodium) soap, because there was a very sensitive reagent for ammonia (Nessler’s—mercuric iodide gives, with a trace of ammonia, a reddish-brown precipitate or color, as demonstrated), with the aid of which the disappearance of ammonia from the film could be followed. The bubbles were blown in purified air, by opening a stop-cock in the air supply tube, or with the mouth. Liquid air might be used, of course, but it would have to be heated up first; ordinary air used for blowing was filtered through cotton wool; several devices for this purpose were shown.
Bubbles could be blown hanging or resting (upon a wide ring, for example). The little bubble or sac of liquid at the bottom of a bubble could be removed by suction through tubes applied from outside (the tubes used in blowing), or tubes passed from above axially into the bubble. Properly drained, the bubbles lasted a long time; but bubbles were more sensitive to tremors than films. Some of the bubbles exhibited were nearly 1,1; m. in diameter; they were blown in cubical or oval glass vessels containing pure air at atmospheric pressure. Some water was always kept in the bottom of the containing vessel.
The experiments which Sir James then briefly out lined with the aid of slides concerned the life of bubbles, the changes in the diameter of the bubble (spontaneous contraction) and in the liquid forming it, and the transference of gas through the skin of the bubble from the inside to the outside of the bubble. His first bubble by the improved processes had only lived three days, but the life had soon been prolonged; a bubble 20 cm. in diameter had held out 95 days, one of 4-0 dia meters 63 days, smaller bubbles nearly a year. A uniform cool temperature (about 10 deg. C.) favored longevity. The freshly blown bubble, we might perhaps interpose, shows, of course, an irregular streaming of the liquid in the film; as the excess of liquid drains 0d the visible motion ceases, the bubble thins out and becomes black in the upper portion, while colored rings appear near the bottom, in which streaming may still be observed.
At the same time the “condensation" sets in, water vapor was absorbed by the glycerin of the bubble; the bubble solution was thereby diluted, but the film still remained thick enough to display colors. This condensation was watched by periodic analyses of the drops falling from the bubble, which were collected in a graduated tube leading out from the containing vessel. The condensation amounted, for example, to 0.412 milligrams on the first day and decreasing rapidly, to 0.003 milligrams on the 20th day, the weights named being per square centimeter per day. Only 2 or 3 per cent of the glycerin originally in the solution might be left in a fortnight, and in this way 90 per cent of the soap had been washed out in 20 days.
Owing to the surface tension in the film there was further contraction of the bubble, accompanied by the transference of gas through the film outward. The rate of the contraction and transference varied with the gas; it was much more rapid with hydrogen than with air; a hydrogen bubble would be blown in hydrogen at atmospheric pressure. The contraction of the diameter increased more rapidly as the time advanced and the diameter became smaller, the curve, diameter plotted against time, being parabolic. The internal pressure varied inversely as the diameter. In a diagram exhibited the diameter of a bubble diminished from the .value 1 to 0.2 in 24 days; in the case of a black bubble the diameter had been reduced from 38 to 1.5 cm. in five weeks.
Black bubbles best showed this contraction, which depended upon the thinness of the film and the dilution of the solution ;‘ but it was very well observable also in colored bubbles. The gas transference amounted to 0.023 cub. cm. per square centimetre per day in one case quoted. Finally, the
speaker exhibited a series of colored photographs which brought out well the gradual color changes and the beautiful colors displayed; in some of these photographs the sharp boundary lines of the black zone and of the silvery zone and the colored rings were quite distinct; others exemplified more the gradual transition of pink into green, etc. Peculiar color effects were seen in the bubbles and in these photographs when the illumination was by mercury-vapor lamps.