Franklin’s experiments

Benjamin Franklin s experiment is mentioned in the opening paragraphs of this chapter. Estimate, from his results, an approximate value for Avogadro s number make your calculation clear. The answer is a little off explain whether more accurate measurements on Franklin s part would have helped. 

Franklin mentioned Pliny s account of fisherman pouring oil on troubled waters in ancient times, a practice that survives to the present. (Franklin s experiment was reenacted by the author at the pond on Clapham Common with a teaspoon of olive oil. The spreading oil covered a surface not larger than that of a beach towel-it appears that technique and/or choice of oil is important. The olive oil quickly spread out in circular patterns of brilliant prismatic colors, but then dissolved from sight. Indeed, the pond itself has shrunken considerably over the intervening 230 years.)... 

An engaging discussion of the history of Benjamin Franklin s experiment and a relatively nontechnical treatment of monolayers and bilayers of surfactants and their implications to biochemistry and biology are presented by Tanford, a pioneer of what is known as the hydrophobic effect and the biological applications of mono- and multilayers (Tanford 1989). Almost all of the material discussed in this highly readable volume is relevant to the focus of this chapter. 

Benjamin Franklin, author and renowned statesman, was also an inventor and a scientist. Every schoolchild knows of Franklin s experiment with a kite and a key, demonstrating that lightning is electricity. Less well known is that his measurement of the extent to which oil spreads on water makes possible a simple estimate of molecular size and Avogadro s number. 

Estimate the area per molecule (in A2) in Franklin s experiment on Clapham pond. 

Cavendish was fascinated by such stories. He read also about Franklin s experiments with atmospheric electricity—how he had flown a kite in the summer of 1752 and felt the electric shock of the thunderstorm. This force must be a powerful weapon, thought Cavendish, for a year later Dr. Georg Rich-mann who tried the same experiment had been killed. Here was a potent instrument which the chemist might use to solve great mysteries. 

One of the earliest studies of insoluble films was conducted by Benjamin Franklin in 1765 on a pond in Clapham Common in London. Surprisingly Franklin s experiment was sufficiently controlled to establish that olive oil formed a film of monolayer thickness (quoted... 

I. Bernard Cohen (ed.), "Benjamin Franklin s Experiments" (Harvard University Press, Cambridge, MA, 1941). 

Amide ions have been used for many years to induce proton abstraction reactions and therefore might be expected to react with the tetramethylammonium ion in a similar way. In 1935, the decomposition of tetramethylammonium amide in liquid ammonia was initially reported by Franklin 44> to give trimethylamine and methylamine but no experimental details were given. Later, Hazlehurst, Holliday, and Pass 63> repeated Franklin s experiment 44> and noted that a trace of ethylene was evolved. During later attempts to prepare solid tetramethylammonium amide, a... 

Percy Shelley had long been interested in electricity and galvanism. He had constructed a large-scale battery and repeated Franklin s experiment (Hohnes 1976, pp. 44f). 

Experimental Researches and Observations on Electricity made at Philadelphia and communicated in several letters to Mr. Collinson in LondoUy London, 1751 1752 (with Second Communication)y 1754 (with Third Communication) New Edition of the Whole, 4°, 1766 with Additions, 1769,117 f. The Complete Works, London, 1806, i, 165-440 new ed. by I. B. Cohen, Benjamin Franklin s Experiments, Cambridge, Mass., 1941. The letters run from 1747 to 1754. 

One of Benjamin Franklin s experiments was to pour olive oil (oleic acid CH3(CH2)tCH=CH(CH2)7COOH), density = 0.895 g mL i) on the surface of a pond in London and observe the oil forming a surface film. If the pond was 0.50 ac in area and 1.0 teaspoons of oil were used, calculate the area of each oleic acid molecule assuming a monolayer film was formed. 

Lord Charles Cavendish might not have been wealthy, but he was a natural philosopher and experienced experimentalist. Indeed his research on heat, electricity, and magnetism earned him praise from Benjamin Franklin. Henry must have learned a lot from his father, because he, too, became a meticulous experimenter. Some of Henry s experiments in physics and most of his chemical experiments were performed while he was still living under his father s roof. 

Adding to the source of conflicts, McGrayne contends that the social life at King s was far different to Franklin s previous experience ... 

At a lecture delivered in Philadelphia s Franklin Institute on March 17, 1949, Pauling reported some of the results from Dickey s experiments [23]. Silica gels had been prepared by procedures analogous to the formation of antibodies , i.e. in accordance with the selective theory, and the study was published later the same year [24]. The method described involved polymerisation of sodium silicate in the presence of a dye. Four different dyes were used, namely methyl, ethyl, /i-propyl and -butyl orange (Fig. 1.3). As much as possible of the dye was subsequently removed, and in rebinding experiments it was found that silica prepared in the presence of any of these pattern moleeules would bind the pattern molecule in preference to the other three dyes. Table 1.2 shows the selective increase in pattern dye sorption capacities of the gels as related to a control gel, prepared in the absence of dye. 

International recognition Many scientists held Lavoisier in high esteem. Benjamin Franklin made a point to observe experiments by Lavoisier when he was in France soliciting support for the cause of the American Revolution. Lavoisier s experiments were also followed closely by Thomas Jefferson. 

Although the law of conservation matter is strongly and quite properly associated with Lavoisier, its chemical consequences were stated explicitly at least a century earlier and, indeed, the concept dates back to antiquity. Nonetheless, Franklin s views on this matter are not widely known and his statement even suggests a specific experiment to verify the law. Franklin also reports witnessing the flammability of swamp gas (methane), in New Jersey, no less, over a decade be-... 

Figure 1—1. Benjamin Franklin s first experiments with the atmospheric plasma phenomenon of lightning.

The scientific approach of interfacial phenomena started in the second half of the eighteenth century with B. Franklin s reports in 1765 on the amount of oil needed to cover the surface of Clapham Pond in England. Later, in the nineteenth century. Lord Rayleigh pursued these experiments and A. Pockels and I. Langmuir did the first quantitative studies on the properties of monolayers of surface-active substances at liquid/air interfaces. 

Lord Brougham, who attended one of Black s last lecture courses, described in his memoirs how Black s experiments were often like Franklin s, performed with the simplest apparatus.. .. 1 remember his pouring fixed air from a... 

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