Edward Frankland - Scientific Work

Scientific Work

From an early age, Frankland engaged in original research with great success. Analytical problems, such as the isolation of certain organic radicals, attracted his attention at first, but he soon turned to chemical syntheses, and he was only about twenty-five years of age when an investigation, doubtless suggested by the work of his master, Robert Bunsen and Hermann Kolbe, on cacodyl, yielded the interesting discovery of organometallic compounds. After his return to England he achieved the synthesis of diethylzinc and dimethylzinc by the reaction of ethyl iodide and methyl iodide with metallic zinc.

The theoretical deductions Frankland drew from considering these bodies were even more interesting and important than the bodies themselves. Perceiving a molecular isonomy between them and the inorganic compounds of the metals from which they may be formed, Frankland saw their true molecular type in the oxygen, sulphur or chlorine compounds of those metals, from which he held them to be derived by the substitution of an organic group for the oxygen, sulphur, &c. In this way they enabled him to overthrow the theory of conjugate compounds, and they further led him in 1852 to publish the conception that the atoms of each elementary substance have a definite saturation capacity, so that they can only combine with a certain limited number of the atoms of other elements. The theory of valency thus founded has dominated the subsequent development of chemical doctrine, and forms the groundwork upon which the fabric of modern structural chemistry reposes.

In applied chemistry Frankland's great work was in connection with water-supply. Appointed a member of the second royal commission on the pollution of rivers in 1868, he was provided by the government with a completely equipped laboratory, in which, for a period of six years, he carried on the inquiries necessary for the purposes of that body, and was thus the means of bringing to light an enormous amount of valuable information respecting the contamination of rivers by sewage, trade-refuse, &c., and the purification of water for domestic use. In 1865, when he succeeded August Wilhelm von Hofmann at the School of Mines, he undertook the duty of making monthly reports to the registrar-general on the character of the water supplied to London, and these he continued down to the end of his life. At one time he was an unsparing critic of its quality, but in later years he became strongly convinced of its general excellence and wholesomeness.

Frankland's analyses were both chemical and bacteriological, and his dissatisfaction with the processes in vogue for the former at the time of his appointment caused him to spend two years in devising new and more accurate methods. In 1859 Frankland passed a night on the very top of Mont Blanc in company with John Tyndall. One of the purposes of the expedition was to discover whether the rate of combustion of a candle varies with the density of the atmosphere in which it is burnt, a question which was answered in the negative. Other observations made by Frankland at the time formed the starting-point of a series of experiments which yielded far-reaching results. He noticed that at the summit the candle gave a very poor light, and was thereby led to investigate the effect produced on luminous flames by varying the pressure of the atmosphere in which they are burning. He found that pressure increases luminosity, so that hydrogen, for example, the flame of which gives no light in normal circumstances, burns with a luminous flame under a pressure of ten or twenty atmospheres, and the inference he drew was that the presence of solid particles is not the only factor that determines the light-giving power of a flame, Further, he showed that the spectrum of a dense ignited gas resembles that of an incandescent liquid or solid, and he traced a gradual change in the spectrum of an incandescent gas under increasing pressure, the sharp lines observable when it is extremely attenuated broadening out to nebulous bands as the pressure rises, till they merge in the continuous spectrum as the gas approaches a density comparable with that of the liquid state. An application of these results to solar physics in conjunction with Sir Norman Lockyer led to the view that at least the external layers of the sun cannot consist of matter in the liquid or solid forms, but must be composed of gases or vapours.

Frankland and Lockyer were also the discoverers of helium, along with Pierre Jules César Janssen. In 1868 they noticed, in the solar spectrum, a bright yellow line which did not correspond to any substance then known. It was this line which they attributed to the then hypothetical element, helium. This was the first time an element was discovered on an extraterrestrial world before being found on the earth.